Statum/js/statum.js

/*!
 * Statum - client-side state library.
 *
 * An HTMX-inspired state layer. The library manages signed "snapshots" of
 * application state (one per slot type), keeps them fresh via the server's
 * `transmit_after` / `invalid_after` timestamps, and binds them to the DOM
 * through `stm-*` attributes. See model.md for the full specification.
 *
 * Distribution: a single IIFE that attaches `window.statum` (no dependencies,
 * no build step). Targets modern evergreen browsers (uses fetch,
 * BroadcastChannel, queueMicrotask, URLSearchParams, FormData).
 */
(function () {
  'use strict';

  /** Content-Type used by every Statum directive response. */
  var STATUM_CONTENT_TYPE = 'application/vnd.statum+json';
  /** Request/response header carrying one slot's reference (or base64 frame). */
  var SLOT_HEADER = 'X-Statum-Slot';
  /** Request header carrying an action's opaque `private` blob. */
  var PRIVATE_HEADER = 'X-Statum-Private';
  /** Session-cookie marker used to detect a fresh browser session. */
  var SESSION_COOKIE = '_statum_sdc';
  /** BroadcastChannel name used to sync session/device state across tabs. */
  var CHANNEL_NAME = 'statum';
  /** localStorage / sessionStorage key prefix for persisted frames. */
  var STORAGE_PREFIX = 'statum:';

  // ---------------------------------------------------------------------------
  // Configuration
  // ---------------------------------------------------------------------------

  /**
   * Endpoint URLs. These defaults may be overridden per-page with the
   * `stm-entrypoint` and `stm-slots` attributes on the `<body>` element.
   *
   * @type {{entrypointUrl: string, slotsUrl: string}}
   */
  var config = {
    entrypointUrl: '/_statum/entrypoint',
    slotsUrl: '/_statum/slots',
    channelUrl: '/_statum/channel',
    // The realtime worker is embedded in the library as a default resource
    // (served at /_statum/resource/statum-worker.js); override with stm-worker.
    workerUrl: '/_statum/resource/statum-worker.js'
  };

  // ---------------------------------------------------------------------------
  // State store
  // ---------------------------------------------------------------------------

  /**
   * In-memory store, keyed by slot type. Each value is `{frame, snapshot}`
   * where `snapshot` is the parsed `frame.content`. This map is the single
   * source of truth for rendering; persistent backends merely hydrate it.
   *
   * @type {Map<string, {frame: object, snapshot: object}>}
   */
  var store = new Map();

  /** Listeners, keyed by type name. @type {Map<string, Set<Function>>} */
  var listeners = new Map();

  /**
   * Idempotency tracking: slot key -> last-applied frame `signature`. Held in
   * memory only (per tab), so a frame already persisted by another tab still
   * re-draws a tab whose tracking lags. Entries are dropped on clear so a
   * replayed frame re-applies.
   * @type {Map<string, string>}
   */
  var signatures = new Map();

  /** Optional UI handlers (set via `statum.on*Handler`). */
  var handlers = { onConfirm: null, onNotify: null, onError: null };

  /** @type {BroadcastChannel|null} */
  var channel = null;

  /** Whether {@link init} has already run. */
  var initialized = false;

  /** Whether the entrypoint has been fetched (guards without pre-entrypoint
   *  only evaluate after this). */
  var entrypointLoaded = false;

  /** Set when a guard has triggered a redirect, so further work is skipped. */
  var guardRedirected = false;

  // ---------------------------------------------------------------------------
  // Small utilities
  // ---------------------------------------------------------------------------

  /**
   * Parse an ISO 8601 timestamp to epoch millis, or `undefined`.
   * @param {string|undefined} s
   * @returns {number|undefined}
   */
  function parseTime(s) {
    if (!s) return undefined;
    var t = new Date(s).getTime();
    return isNaN(t) ? undefined : t;
  }

  /**
   * Base64-encode a UTF-8 string (safe for frames containing non-Latin1 data).
   * @param {string} str
   * @returns {string}
   */
  function b64encode(str) {
    var bytes = new TextEncoder().encode(str);
    var bin = '';
    var chunk = 0x8000;
    for (var i = 0; i < bytes.length; i += chunk) {
      bin += String.fromCharCode.apply(null, bytes.subarray(i, i + chunk));
    }
    return btoa(bin);
  }

  /** Read a cookie value, or `null` if absent. @param {string} name */
  function getCookie(name) {
    var escaped = name.replace(/([.$?*|{}()[\]\\/+^])/g, '\\$1');
    var match = document.cookie.match(new RegExp('(?:^|; )' + escaped + '=([^;]*)'));
    return match ? decodeURIComponent(match[1]) : null;
  }

  /** Set a session cookie (no expiry => cleared when the browser closes). */
  function setCookie(name, value) {
    document.cookie = name + '=' + encodeURIComponent(value) + '; path=/; SameSite=Lax';
  }

  // ---------------------------------------------------------------------------
  // Expression evaluation
  // ---------------------------------------------------------------------------

  /**
   * Compiled-expression cache. Expressions are evaluated as JavaScript against
   * a scope object (the page's HTML is trusted, per the model).
   * @type {Map<string, Function>}
   */
  var exprCache = new Map();

  /**
   * Wrap a scope for expression evaluation so bare identifiers resolve in a
   * controlled order: names on the scope (slot types, loop variables,
   * `stm-def-*` locals) win; names missing from the scope but present on
   * `globalThis` (`Math`, `parseInt`, `String`, …) forward to that global;
   * anything else resolves to `undefined` instead of throwing a
   * `ReferenceError` or leaking an unintended global. The `has` trap claims
   * every name so `with` never falls through around the proxy, and the inner
   * try/catch of the compiled expression still turns property access on a
   * resolved `undefined`/`null` into `undefined` for that expression alone.
   * @param {object} scope
   * @returns {Proxy<object>}
   */
  function evalScope(scope) {
    return new Proxy(scope, {
      has: function () { return true; },
      get: function (target, name) {
        if (name in target) return target[name];
        if (typeof name === 'string' && name in globalThis) return globalThis[name];
        return undefined;
      }
    });
  }

  /**
   * Compile (and cache) an expression string into a function of `scope`.
   * Uses `with` so that arbitrary type names and loop variables are resolved
   * as bare identifiers. Returns a function that yields `undefined` on any
   * runtime or compile error.
   * @param {string} expr
   * @returns {Function}
   */
  function compileExpr(expr) {
    var cached = exprCache.get(expr);
    if (cached !== undefined) return cached;
    var fn;
    try {
      // Function-constructor bodies are non-strict by default, so `with` is
      // permitted. The inner try/catch turns runtime errors (property access
      // on an unset slot's `undefined`) into `undefined` so a missing path
      // simply yields no value; missing identifiers already resolve to
      // `undefined` via the evalScope proxy.
      fn = new Function('scope', 'with(scope){try{return (' + expr + ');}catch(e){return undefined;}}');
    } catch (e) {
      fn = function () { return undefined; };
    }
    exprCache.set(expr, fn);
    return fn;
  }

  /**
   * Evaluate an expression against a scope.
   * @param {string} expr
   * @param {object} [scope]
   * @returns {*} `undefined` if the expression is empty or fails.
   */
  function evalExpr(expr, scope) {
    if (expr == null || expr === '') return undefined;
    try {
      return compileExpr(expr)(evalScope(scope || {}));
    } catch (e) {
      return undefined;
    }
  }

  /**
   * Build a child scope that inherits the parent (so type bindings remain
   * visible) and adds one own loop variable.
   * @param {object} parent
   * @param {string} name
   * @param {*} value
   * @returns {object}
   */
  function childScope(parent, name, value) {
    var scope = Object.create(parent || null);
    scope[name] = value;
    return scope;
  }

  // ---------------------------------------------------------------------------
  // StatumError
  // ---------------------------------------------------------------------------

  /**
   * Error type thrown for HTTP failures and `error` directives.
   * @param {string} [message]
   * @param {string} [code]
   * @param {object} [data]
   */
  function StatumError(message, code, data) {
    this.name = 'StatumError';
    this.message = message || '';
    this.code = code || undefined;
    this.data = data || undefined;
  }
  StatumError.prototype = Object.create(Error.prototype);

  // ---------------------------------------------------------------------------
  // UI handlers (confirm / notify / error)
  // ---------------------------------------------------------------------------

  /**
   * Run the `notify` directive's default behaviour or the custom
   * `statum.onNotifyHandler`. The default surfaces the message via `alert()`.
   * @param {string} [kind] Application-defined category (freeform).
   * @param {string} [message]
   */
  function triggerNotify(kind, message) {
    var fn = handlers.onNotify;
    try {
      if (fn) fn(kind, message);
      else if (message != null) window.alert(message);
    } catch (e) { console.error('[statum] notify handler error', e); }
  }

  /**
   * Run the `stm-confirm` gate: the custom `statum.onConfirmHandler` if set,
   * otherwise `window.confirm`. Supports async handlers (custom modals).
   * @param {string} message
   * @param {HTMLElement} element
   * @returns {Promise<boolean>} truthy if the action should proceed.
   */
  async function triggerConfirm(message, element) {
    var fn = handlers.onConfirm;
    try {
      if (fn) return !!(await fn(message, element));
      return !!window.confirm(message);
    } catch (e) {
      console.error('[statum] confirm handler error', e);
      return false;
    }
  }

  /**
   * Run the custom `statum.onErrorHandler`, if set. Returns whether the default
   * behaviour (promise rejection + `stm-on-error` classes) should proceed: the
   * handler suppresses the default by returning (or resolving) `false`.
   * @param {StatumError} error
   * @param {HTMLElement|null} element
   * @returns {Promise<boolean>}
   */
  async function triggerError(error, element) {
    var fn = handlers.onError;
    if (!fn) return true;
    try {
      var suppress = await fn(error, element);
      return suppress !== false;
    } catch (e) {
      console.error('[statum] error handler error', e);
      return true;
    }
  }

  /**
   * Surface a failure: run `triggerError`, and if the default is not
   * suppressed, apply `stm-on-error` classes (when an origin element exists)
   * and re-throw so the originating promise rejects.
   * @param {StatumError} error
   * @param {HTMLElement|null} element
   */
  async function reportFailure(error, element) {
    if (await triggerError(error, element)) {
      if (element) applyErrorClasses(element, true);
      throw error;
    }
  }

  // ---------------------------------------------------------------------------
  // Persistence
  // ---------------------------------------------------------------------------

  /**
   * Pick the storage backend for a scope.
   * @param {string} scope
   * @returns {Storage|null} `null` for in-memory scopes.
   */
  function storageFor(scope) {
    if (scope === 'device' || scope === 'session') return localStorage;
    if (scope === 'flow') return sessionStorage;
    return null; // page / transient
  }

  /**
   * Persist a slot's frame to the backend matching its scope, removing any
   * stale copy from the other backend first (in case the scope changed).
   * @param {string} type
   * @param {{frame: object, snapshot: object}} entry
   */
  function persistEntry(type, entry) {
    var scope = entry.snapshot.slot && entry.snapshot.slot.scope;
    removePersisted(type);
    var storage = storageFor(scope);
    if (!storage) return;
    try {
      storage.setItem(STORAGE_PREFIX + type, JSON.stringify(entry.frame));
    } catch (e) {
      /* storage full or unavailable; remain in-memory only */
    }
  }

  /** Remove a persisted frame from both backends. @param {string} type */
  function removePersisted(type) {
    try { localStorage.removeItem(STORAGE_PREFIX + type); } catch (e) {}
    try { sessionStorage.removeItem(STORAGE_PREFIX + type); } catch (e) {}
  }

  /** Load every persisted frame from a backend into the in-memory store. */
  function loadFrom(storage) {
    for (var i = 0; i < storage.length; i++) {
      var key = storage.key(i);
      if (!key || key.indexOf(STORAGE_PREFIX) !== 0) continue;
      try {
        var frame = JSON.parse(storage.getItem(key));
        var snapshot = JSON.parse(frame.content);
        var type = snapshot.slot && snapshot.slot.type;
        if (type && !store.has(type)) store.set(type, { frame: frame, snapshot: snapshot });
      } catch (e) {
        /* corrupt entry: ignore */
      }
    }
  }

  /** Hydrate the store from localStorage and sessionStorage. */
  function hydrate() {
    try { loadFrom(localStorage); } catch (e) {}
    try { loadFrom(sessionStorage); } catch (e) {}
  }

  // ---------------------------------------------------------------------------
  // Session-cookie initialization
  // ---------------------------------------------------------------------------

  /**
   * Detect a fresh browser session using the `_statum_sdc` session cookie.
   * On a fresh session, clear all `session`-scoped persisted frames, then set
   * the marker. Session cookies are shared across tabs, so a tab opened
   * mid-session sees the marker and leaves session data intact.
   */
  function initSession() {
    if (getCookie(SESSION_COOKIE) !== null) return;
    clearSessionSlotsFromStorage();
    setCookie(SESSION_COOKIE, '1');
  }

  /** Remove all `session`-scoped frames from localStorage. */
  function clearSessionSlotsFromStorage() {
    var toRemove = [];
    for (var i = 0; i < localStorage.length; i++) {
      var key = localStorage.key(i);
      if (!key || key.indexOf(STORAGE_PREFIX) !== 0) continue;
      try {
        var frame = JSON.parse(localStorage.getItem(key));
        var snapshot = JSON.parse(frame.content);
        if (snapshot.slot && snapshot.slot.scope === 'session') toRemove.push(key);
      } catch (e) {}
    }
    for (var j = 0; j < toRemove.length; j++) localStorage.removeItem(toRemove[j]);
  }

  // ---------------------------------------------------------------------------
  // Listeners & cross-tab broadcast
  // ---------------------------------------------------------------------------

  /**
   * Fire all listeners for a type. (Renamed from `notify` to avoid confusion
   * with the `notify` directive.)
   * @param {string} type
   * @param {object|null} frame
   * @param {object|null} snapshot
   */
  function fireListeners(type, frame, snapshot) {
    var set = listeners.get(type);
    if (!set) return;
    var event = { type: type, frame: frame, snapshot: snapshot };
    set.forEach(function (cb) {
      try { cb(event); } catch (e) { console.error('[statum] listener error', e); }
    });
  }

  /**
   * Broadcast a state change to other tabs. Only `session`/`device` scopes are
   * shared (flow/page/transient are per-tab).
   * @param {object} message
   * @param {string} [scope]
   */
  function broadcast(message, scope) {
    if (!channel) return;
    if (scope !== 'session' && scope !== 'device') return;
    try { channel.postMessage(message); } catch (e) {}
  }

  /**
   * Broadcast a message to other tabs regardless of slot scope. Used to relay
   * realtime (live) events so they reach every tab, not just session/device
   * ones.
   */
  function broadcastAlways(message) {
    if (!channel) return;
    try { channel.postMessage(message); } catch (e) {}
  }

  /** Open the BroadcastChannel and wire inbound messages. */
  function setupChannel() {
    if (typeof BroadcastChannel === 'undefined') return;
    try {
      channel = new BroadcastChannel(CHANNEL_NAME);
    } catch (e) {
      channel = null;
      return;
    }
    channel.onmessage = function (ev) {
      var msg = ev.data;
      if (!msg) return;
      if (msg.kind === 'set' && msg.frame) {
        try {
          var snapshot = JSON.parse(msg.frame.content);
          var type = snapshot.slot && snapshot.slot.type;
          if (type && commitSet(msg.frame, snapshot, type, false)) renderAll();
        } catch (e) { /* ignore malformed */ }
      } else if (msg.kind === 'clear') {
        var t = msg.type;
        if (!t && msg.key != null) {
          store.forEach(function (entry, type) {
            if (entry.snapshot.slot && entry.snapshot.slot.key === msg.key) t = type;
          });
        }
        if (t) clearType(t, { broadcast: false });
        else if (msg.key != null) signatures.delete(msg.key);
        renderAll();
      }
    };
  }

  // ---------------------------------------------------------------------------
  // State mutation
  // ---------------------------------------------------------------------------

  /**
   * Remove a type from the store, un-persist it, drop its idempotency entry,
   * fire listeners, and (optionally) broadcast the clear to other tabs.
   * @param {string} type
   * @param {{broadcast?: boolean}} [opts]
   */
  function clearType(type, opts) {
    var entry = store.get(type);
    if (!entry) return;
    var scope = entry.snapshot.slot && entry.snapshot.slot.scope;
    var key = entry.snapshot.slot && entry.snapshot.slot.key;
    store.delete(type);
    removePersisted(type);
    if (key) signatures.delete(key);
    fireListeners(type, null, null);
    if (opts && opts.broadcast) broadcast({ kind: 'clear', key: key, type: type }, scope);
  }

  /**
   * Resolve a slot key to its type and clear it. Used by the `clear` directive
   * (keyed) and by live `clear` events.
   * @param {string} key
   * @param {boolean} [broadcast]
   */
  function clearByKey(key, broadcast) {
    var typeToRemove = null;
    store.forEach(function (entry, type) {
      if (entry.snapshot.slot && entry.snapshot.slot.key === key) typeToRemove = type;
    });
    if (typeToRemove) clearType(typeToRemove, { broadcast: !!broadcast });
    else if (key) signatures.delete(key);
  }

  /**
   * Resolve a frame signature to its slot type and clear it. Used by the
   * `invalidate` directive, which references a signature (not a key) because the
   * server reports a bad signature without trusting the frame's content.
   * @param {string} signature
   * @param {boolean} [broadcast]
   */
  function clearBySignature(signature, broadcast) {
    var typeToRemove = null;
    store.forEach(function (entry, type) {
      if (entry.frame && entry.frame.signature === signature) typeToRemove = type;
    });
    if (typeToRemove) clearType(typeToRemove, { broadcast: !!broadcast });
    else if (signature) signatures.delete(signature);
  }

  /**
   * Commit a `set` to the in-memory store, persist it, and fire listeners.
   * Idempotent: if the frame's `signature` matches the last-applied signature
   * for this slot (tracked in {@link signatures}), nothing happens and `false`
   * is returned. When `doBroadcast` is true the set is forwarded to other tabs
   * via the scope-gated broadcast (session/device only).
   * @param {object} frame
   * @param {object} snapshot
   * @param {string} type
   * @param {boolean} doBroadcast
   * @returns {boolean} `true` if state changed.
   */
  function commitSet(frame, snapshot, type, doBroadcast) {
    var key = snapshot.slot && snapshot.slot.key;
    var sig = frame.signature;
    if (key && sig !== undefined && signatures.get(key) === sig) return false;
    var entry = { frame: frame, snapshot: snapshot };
    store.set(type, entry);
    persistEntry(type, entry);
    fireListeners(type, frame, snapshot);
    if (key && sig !== undefined) signatures.set(key, sig);
    if (doBroadcast) {
      var scope = snapshot.slot && snapshot.slot.scope;
      broadcast({ kind: 'set', frame: frame }, scope);
    }
    return true;
  }

  /**
   * Apply a `set` directive: store/refresh a slot's snapshot (idempotently),
   * broadcasting to other tabs.
   * @param {object} directive `{ snapshot_frame }`
   */
  function applySet(directive) {
    var frame = directive.snapshot_frame;
    if (!frame || !frame.content) return;
    var snapshot;
    try { snapshot = JSON.parse(frame.content); } catch (e) { return; }
    var type = snapshot.slot && snapshot.slot.type;
    if (!type) return;
    commitSet(frame, snapshot, type, true);
  }

  /**
   * Apply a `clear` directive. The directive carries a slot key, so the type
   * holding that key is resolved and removed.
   * @param {object} directive `{ key }`
   */
  function applyClear(directive) {
    if (directive.key == null) return;
    clearByKey(directive.key, true);
  }

  /**
   * Apply a live `set` event received over the realtime channel. The frame is
   * committed (idempotently) and, when new, broadcast to sibling tabs via the
   * scope-agnostic {@link broadcastAlways} so every tab sees it regardless of
   * which (or how many) tabs hold a subscription.
   * @param {object} frame
   */
  function applyRemoteSet(frame) {
    try {
      var snapshot = JSON.parse(frame.content);
      var type = snapshot.slot && snapshot.slot.type;
      if (!type) return;
      if (commitSet(frame, snapshot, type, false)) {
        broadcastAlways({ kind: 'set', frame: frame });
        renderAll();
      }
    } catch (e) { /* malformed frame */ }
  }

  /** Apply a live `clear` event received over the realtime channel. */
  function applyRemoteClear(key) {
    if (key == null) return;
    signatures.delete(key);
    clearByKey(key, false);
    broadcastAlways({ kind: 'clear', key: key });
    renderAll();
  }

  // ---------------------------------------------------------------------------
  // Snapshot freshness & request headers
  // ---------------------------------------------------------------------------

  /**
   * Categorize a held snapshot relative to the current time.
   * @returns {'silent'|'always'|'invalid'|'stale'|'fresh'}
   *   - `silent`: unidirectional (`transmit_after` undefined) - never sent.
   *   - `always`: `transmit_after === as_at` - send the base64 frame each time.
   *   - `invalid`: past `invalid_after` - drop and refetch.
   *   - `stale`: past `transmit_after` but not yet invalid - pre-flight first.
   *   - `fresh`: still cached server-side - send the `as_at` reference.
   */
  function entryCategory(entry) {
    var snap = entry.snapshot;
    var transmit = snap.transmit_after;
    if (transmit === undefined || transmit === null) return 'silent';
    if (transmit === snap.as_at) return 'always';
    var now = Date.now();
    var invalidAt = parseTime(snap.invalid_after);
    var transmitAt = parseTime(transmit);
    if (invalidAt !== undefined && now >= invalidAt) return 'invalid';
    if (transmitAt !== undefined && now >= transmitAt) return 'stale';
    return 'fresh';
  }

  /**
   * Drop locally-invalid snapshots and pre-flight any stale ones. Pre-flighting
   * posts the stale frames to the slot endpoint and applies the returned `set`
   * directives, refreshing their `as_at` values before the real request runs.
   *
   * Single-flight: concurrent callers share one in-flight preparation.
   * @returns {Promise<void>}
   */
  var preparePromise = null;
  function prepareSlots() {
    if (preparePromise) return preparePromise;
    preparePromise = doPrepareSlots().then(function () {
      preparePromise = null;
    }, function () {
      preparePromise = null;
    });
    return preparePromise;
  }

  async function doPrepareSlots() {
    var stale = [];
    store.forEach(function (entry, type) {
      var cat = entryCategory(entry);
      if (cat === 'invalid') {
        clearType(type, { broadcast: false });
      } else if (cat === 'stale') {
        stale.push(entry.frame);
      }
    });
    if (stale.length) {
      var directives = await postSlots(stale);
      var pfResult = applyDirectives(directives, { originElement: null });
      executeTerminal(pfResult);
    }
  }

  /**
   * Build the `X-Statum-Slot` header values for every held slot, using the
   * freshness rules. Assumes {@link prepareSlots} has just run.
   * @returns {string[]}
   */
  function buildSlotHeaders() {
    var headers = [];
    store.forEach(function (entry) {
      var snap = entry.snapshot;
      var cat = entryCategory(entry);
      if (cat === 'silent' || cat === 'invalid') return;
      if (cat === 'always') {
        headers.push(b64encode(JSON.stringify(entry.frame)));
      } else {
        headers.push('key=' + snap.slot.key + '; as_at=' + snap.as_at);
      }
    });
    return headers;
  }

  /**
   * Collect the current frames held for the given slot keys, in the order the
   * keys are first supplied. Used by the `transmit` directive (which forces a
   * slot's frame to be posted as if its `transmit_after` had elapsed). Keys the
   * client does not currently hold are skipped.
   * @param {string[]} keys
   * @returns {object[]}
   */
  function collectFramesForKeys(keys) {
    var keySet = Object.create(null);
    for (var i = 0; i < keys.length; i++) keySet[keys[i]] = true;
    var frames = [];
    store.forEach(function (entry) {
      var key = entry.snapshot.slot && entry.snapshot.slot.key;
      if (key && keySet[key]) {
        frames.push(entry.frame);
        delete keySet[key];
      }
    });
    return frames;
  }

  // ---------------------------------------------------------------------------
  // HTTP helpers
  // ---------------------------------------------------------------------------

  /** True if a response is a Statum directive response. */
  function isStatum(res) {
    return (res.headers.get('Content-Type') || '').indexOf(STATUM_CONTENT_TYPE) !== -1;
  }

  /**
   * POST an array of frames to the slot endpoint (the pre-flight target) and
   * return its directive array. This request intentionally carries no slot
   * headers (it is itself the refresh).
   * @param {object[]} frames
   * @returns {Promise<object[]>}
   */
  async function postSlots(frames) {
    var headers = new Headers();
    headers.set('Accept', STATUM_CONTENT_TYPE);
    headers.set('Content-Type', 'application/json');
    var res = await fetch(config.slotsUrl, {
      method: 'POST',
      headers: headers,
      body: JSON.stringify(frames),
      credentials: 'same-origin'
    });
    if (!isStatum(res)) return [];
    try { return await res.json(); } catch (e) { return []; }
  }

  /**
   * Apply the non-terminal directives from a response (set/clear/subscribe/
   * unsubscribe/notify/transmit-collection), then `render`.
   *
   * Terminal directives (`navigate`, `post`), error directives, and any
   * transmit/retry intent are collected on the returned result rather than
   * executed here: {@link handleResponse} performs the asynchronous
   * transmission (and optional retry) and then runs terminal navigation, so
   * that a `transmit` with `retry` can re-issue the request before the page is
   * navigated away.
   * @param {object[]} directives
   * @param {{originElement?: HTMLElement}} [ctx]
   * @returns {{errors: StatumError[], transmitKeys: string[], retry: boolean, navigate: object|null, post: object|null}}
   */
  function applyDirectives(directives, ctx) {
    var result = { errors: [], transmitKeys: [], retry: false, navigate: null, post: null, formSubmits: [], formResets: [] };
    var list = Array.isArray(directives) ? directives : [];

    for (var i = 0; i < list.length; i++) {
      var d = list[i];
      if (!d || typeof d !== 'object') continue;
      switch (d.type) {
        case 'set': applySet(d); break;
        case 'clear': applyClear(d); break;
        case 'invalidate':
          if (d.signature != null) {
            console.warn('[statum] server could not verify slot frame ' + d.signature + '; clearing it');
            clearBySignature(d.signature, true);
          }
          break;
        case 'subscribe': channelSubscribe(d.key); break;
        case 'unsubscribe': channelUnsubscribe(d.key); break;
        case 'notify': triggerNotify(d.kind, d.message); break;
        case 'transmit':
          if (d.key != null) {
            if (result.transmitKeys.indexOf(d.key) === -1) result.transmitKeys.push(d.key);
            if (d.retry) result.retry = true;
          }
          break;
        case 'error':
          {
            var err = new StatumError(d.message, d.code, d.data);
            var detail = d.code ? (d.message + ' [' + d.code + ']') : d.message;
            console.error('[statum] error directive: ' + (detail || '(no message)'));
            result.errors.push(err);
          }
          break;
        case 'navigate': result.navigate = d; break;
        case 'post': result.post = d; break;
        case 'form-submit': result.formSubmits.push(d); break;
        case 'form-reset': result.formResets.push(d); break;
      }
    }

    renderAll();
    return result;
  }

  /** Execute the terminal directives collected by {@link applyDirectives}. */
  function executeTerminal(result) {
    result.formResets.forEach(doFormReset);
    result.formSubmits.forEach(doFormSubmit);
    if (result.navigate) doNavigate(result.navigate);
    if (result.post) doPost(result.post);
  }

  /** Execute a `form-submit` directive: optionally override action/method, then submit. */
  function doFormSubmit(d) {
    var form = document.getElementById(d.form);
    if (form) {
      if (d.action) form.setAttribute('action', d.action);
      if (d.method) form.setAttribute('method', d.method);
      form.submit();
    }
  }

  /** Execute a `form-reset` directive. */
  function doFormReset(d) {
    var form = document.getElementById(d.form);
    if (form) form.reset();
  }

  /** Execute a `navigate` directive as a full page load. */
  function doNavigate(d) {
    if (d.uri) window.location.href = d.uri;
  }

  /** Execute a `post` directive as a real (navigating) form POST. */
  function doPost(d) {
    if (!d.uri) return;
    var form = document.createElement('form');
    form.method = 'POST';
    form.action = d.uri;
    form.style.display = 'none';
    var data = d.data || {};
    Object.keys(data).forEach(function (name) {
      var input = document.createElement('input');
      input.type = 'hidden';
      input.name = name;
      input.value = data[name] == null ? '' : String(data[name]);
      form.appendChild(input);
    });
    document.body.appendChild(form);
    form.submit();
  }

  /**
   * Handle a fetch response: if it is a Statum response, apply its directives;
   * otherwise throw on HTTP errors and no-op on other successful responses.
   *
   * Directive ordering: non-terminal directives are applied and the page
   * rendered; then any `transmit` directives force their slot frames to be
   * posted (applying the directives the slot endpoint returns); then, if a
   * transmit requested a retry, the originating request (`ctx.retry`) is
   * re-issued and this response's terminal directives and errors are skipped.
   * Otherwise terminal navigation runs, then error directives are surfaced.
   * @param {Response} res
   * @param {{originElement?: HTMLElement, retry?: Function}} [ctx]
   */
  async function handleResponse(res, ctx) {
    var el = ctx && ctx.originElement;
    if (!isStatum(res)) {
      if (!res.ok) await reportFailure(new StatumError('HTTP ' + res.status), el);
      return;
    }
    var directives;
    try { directives = await res.json(); } catch (e) { directives = []; }
    var result = applyDirectives(directives, ctx);

    if (result.transmitKeys && result.transmitKeys.length) {
      var frames = collectFramesForKeys(result.transmitKeys);
      if (frames.length) {
        var txDirectives = await postSlots(frames);
        applyDirectives(txDirectives, { originElement: el });
      }
    }

    if (result.retry && ctx && typeof ctx.retry === 'function') {
      await ctx.retry();
      return;
    }

    executeTerminal(result);

    var errors = result.errors || [];
    for (var i = 0; i < errors.length; i++) {
      await reportFailure(errors[i], el);
    }
  }

  // ---------------------------------------------------------------------------
  // Entrypoint & action requests
  // ---------------------------------------------------------------------------

  /**
   * Fetch the entrypoint for the current URL, applying its directives. Carries
   * slot headers (and pre-flights) like any other request. The request is
   * wrapped in an `attempt` closure passed as the response `retry` callback, so
   * a `transmit` directive with `retry` can re-issue it after transmission.
   * @returns {Promise<void>}
   */
  function loadEntrypoint() {
    if (guardRedirected) return Promise.resolve();
    // From this point on guards are "post-entrypoint" (all of them evaluate).
    entrypointLoaded = true;
    var attempt = async function () {
      await prepareSlots();
      var headers = new Headers();
      headers.set('Accept', STATUM_CONTENT_TYPE);
      buildSlotHeaders().forEach(function (v) { headers.append(SLOT_HEADER, v); });
      var url = config.entrypointUrl + '?uri=' + encodeURIComponent(window.location.href);
      var res = await fetch(url, { headers: headers, credentials: 'same-origin' });
      await handleResponse(res, { originElement: null, retry: attempt });
    };
    return attempt();
  }

  /**
   * Perform an action request.
   *
   * The request is wrapped in an `attempt` closure passed as the response
   * `retry` callback, so a `transmit` directive with `retry` can re-issue the
   * same action after the transmission (rebuilding headers from current state).
   *
   * @param {object} action `{ uri, method, private }`
   * @param {object} [data] Key/value parameters. Encoded as query string for
   *   GET/HEAD, otherwise as `application/x-www-form-urlencoded`.
   * @param {HTMLElement} [originElement] Element that triggered the action, so
   *   that `stm-on-error` classes can be applied on an `error` directive.
   * @returns {Promise<void>} Resolves once the request completes and its
   *   directives have run; rejects on HTTP failure or an `error` directive.
   */
  function performAction(action, data, originElement) {
    var attempt = async function () {
      await prepareSlots();
      var headers = new Headers();
      headers.set('Accept', STATUM_CONTENT_TYPE);
      buildSlotHeaders().forEach(function (v) { headers.append(SLOT_HEADER, v); });
      if (action.private) headers.set(PRIVATE_HEADER, action.private);

      var method = (action.method || 'GET').toUpperCase();
      var params = data || {};
      var init = { method: method, headers: headers, credentials: 'same-origin' };
      var url = action.uri;

      if (method === 'GET' || method === 'HEAD') {
        var qs = new URLSearchParams(params).toString();
        if (qs) url += (url.indexOf('?') !== -1 ? '&' : '?') + qs;
      } else {
        init.body = new URLSearchParams(params).toString();
        headers.set('Content-Type', 'application/x-www-form-urlencoded');
      }

      var res;
      try {
        res = await fetch(url, init);
      } catch (networkErr) {
        await reportFailure(new StatumError('Network error'), originElement);
        return;
      }
      await handleResponse(res, { originElement: originElement, retry: attempt });
    };
    return attempt();
  }

  // ---------------------------------------------------------------------------
  // Realtime channel (subscribe/unsubscribe directives)
  // ---------------------------------------------------------------------------

  /**
   * Per-tab fallback engine, used when `SharedWorker` is unavailable. Owns an
   * `EventSource`, reads the channel id from the first `event: channel`,
   * reference-counts slot keys within this tab, PATCHes subscription changes,
   * applies incoming set/clear events (broadcasting them to siblings), and
   * closes the stream once it has no subscriptions.
   */
  function createFallbackEngine() {
    var es = null;
    var channelId = null;
    var refs = new Map(); // slotKey -> count
    var pending = { subscribe: [], unsubscribe: [] };
    var patchScheduled = false;

    function openStream() {
      if (es) return;
      try { es = new EventSource(config.channelUrl); }
      catch (e) { es = null; return; }
      es.addEventListener('channel', function (ev) { channelId = ev.data; flushPatch(); });
      es.addEventListener('set', function (ev) {
        try { applyRemoteSet(JSON.parse(ev.data)); } catch (e) {}
      });
      es.addEventListener('clear', function (ev) { applyRemoteClear(ev.data); });
      es.onerror = function () { /* EventSource auto-reconnects */ };
    }

    function closeStream() {
      if (es) { try { es.close(); } catch (e) {} es = null; }
      channelId = null;
    }

    function schedulePatch() {
      if (patchScheduled) return;
      patchScheduled = true;
      Promise.resolve().then(function () { patchScheduled = false; flushPatch(); });
    }

    function flushPatch() {
      if (!channelId) return;
      var sub = pending.subscribe, uns = pending.unsubscribe;
      if (!sub.length && !uns.length) return;
      pending = { subscribe: [], unsubscribe: [] };
      var body = {};
      if (sub.length) body.subscribe = sub;
      if (uns.length) body.unsubscribe = uns;
      try {
        fetch(config.channelUrl + '/' + encodeURIComponent(channelId), {
          method: 'PATCH',
          headers: { 'Content-Type': 'application/json' },
          credentials: 'same-origin',
          body: JSON.stringify(body)
        }).catch(function () {});
      } catch (e) {}
    }

    return {
      subscribe: function (key) {
        var c = refs.get(key) || 0;
        refs.set(key, c + 1);
        if (c === 0) { openStream(); pending.subscribe.push(key); schedulePatch(); }
      },
      unsubscribe: function (key) {
        var c = refs.get(key) || 0;
        if (c <= 0) return;
        if (c - 1 <= 0) {
          refs.delete(key);
          pending.unsubscribe.push(key);
          schedulePatch();
          if (refs.size === 0) setTimeout(function () { if (refs.size === 0) closeStream(); }, 0);
        } else {
          refs.set(key, c - 1);
        }
      }
    };
  }

  /**
   * Channel manager. Prefers a `SharedWorker` (which owns the single SSE
   * connection, reference-counts subscriptions across tabs, and relays events
   * through the cross-tab `BroadcastChannel`); falls back to a per-tab
   * `EventSource` engine when `SharedWorker` is unavailable or the worker
   * script fails to load. Tracks the true per-slot subscription count so it can
   * replay active subscriptions into the fallback on a mid-session switch.
   */
  function createChannelManager() {
    var port = null;
    var workerObj = null;
    var fallback = null;
    var mode = null; // 'worker' | 'fallback' | null
    var counts = new Map(); // slotKey -> count (true subscription state)

    function switchToFallback() {
      if (mode === 'fallback') return;
      mode = 'fallback';
      port = null;
      workerObj = null;
      fallback = createFallbackEngine();
      counts.forEach(function (c, key) {
        for (var i = 0; i < c; i++) fallback.subscribe(key);
      });
    }

    function ensure() {
      if (mode !== null) return;
      if (typeof SharedWorker !== 'undefined') {
        try {
          workerObj = new SharedWorker(config.workerUrl);
          port = workerObj.port;
          port.start();
          port.postMessage({ op: 'init', url: config.channelUrl });
          // The worker delivers events via the BroadcastChannel, so nothing is
          // required on this port beyond command messages.
          port.onmessage = function () {};
          workerObj.onerror = function () {
            console.warn('[statum] realtime worker failed; falling back to per-tab channel');
            switchToFallback();
          };
          window.addEventListener('pagehide', function () {
            if (mode === 'worker' && port) {
              try { port.postMessage({ op: 'disconnect' }); } catch (e) {}
            }
          });
          mode = 'worker';
          return;
        } catch (e) { workerObj = null; port = null; }
      }
      switchToFallback();
    }

    return {
      subscribe: function (key) {
        if (key == null) return;
        ensure();
        counts.set(key, (counts.get(key) || 0) + 1);
        if (mode === 'worker') { try { port.postMessage({ op: 'subscribe', key: key }); } catch (e) {} }
        else fallback.subscribe(key);
      },
      unsubscribe: function (key) {
        if (key == null) return;
        var c = (counts.get(key) || 0) - 1;
        if (c <= 0) counts.delete(key); else counts.set(key, c);
        ensure();
        if (mode === 'worker') { try { port.postMessage({ op: 'unsubscribe', key: key }); } catch (e) {} }
        else fallback.unsubscribe(key);
      }
    };
  }

  var channelManager = createChannelManager();

  function channelSubscribe(key) { channelManager.subscribe(key); }
  function channelUnsubscribe(key) { channelManager.unsubscribe(key); }

  // ---------------------------------------------------------------------------
  // Rendering: loops, conditionals, bindings
  // ---------------------------------------------------------------------------

  /** Templates captured from loop holders. @type {WeakMap<Element, Element>} */
  var templates = new WeakMap();
  /** Instance nodes managed by a loop holder. @type {WeakMap<Element, Element[]>} */
  var instancesByHolder = new WeakMap();
  /** Loop instance nodes; skipped by the render walk (owned by their holder). */
  var instanceNodes = new WeakSet();
  /** Elements whose `stm-action` has been wired, to avoid double-binding. */
  var wired = new WeakSet();

  /**
   * Find a `stm-for-{name}-in` attribute on an element.
   * @returns {{varName: string, expr: string}|null}
   */
  function getStmFor(el) {
    var attrs = el.attributes;
    for (var i = 0; i < attrs.length; i++) {
      var match = attrs[i].name.match(/^stm-for-(.+)-in$/);
      if (match) return { varName: match[1], expr: attrs[i].value };
    }
    return null;
  }

  /** Remove any `stm-for-*` and `stm-key` attributes from an element. */
  function stripLoopAttrs(el) {
    var toRemove = [];
    for (var i = 0; i < el.attributes.length; i++) {
      var name = el.attributes[i].name;
      if (/^stm-for-(.+)-in$/.test(name) || name === 'stm-key') toRemove.push(name);
    }
    toRemove.forEach(function (n) { el.removeAttribute(n); });
  }

  /**
   * Evaluate an `stm-if` / `stm-else-if` / `stm-else` chain beginning at `el`,
   * showing the matching branch and hiding the rest.
   *
   * Branches are toggled with the `hidden` attribute rather than detached, so
   * every branch stays in the DOM and is re-evaluated on each render. (Detaching
   * the `stm-if` element would remove it from the render walk, leaving an
   * already-attached `stm-else` branch skipped and never refreshed.)
   * @returns {Element|null} The active branch element (or `null`).
   */
  function handleIfChain(el, scope) {
    var branches = [{ el: el, expr: el.getAttribute('stm-if') }];
    var cur = el.nextElementSibling;
    while (cur) {
      if (cur.hasAttribute('stm-else-if')) {
        branches.push({ el: cur, expr: cur.getAttribute('stm-else-if') });
        cur = cur.nextElementSibling;
      } else if (cur.hasAttribute('stm-else')) {
        branches.push({ el: cur, expr: null });
        break;
      } else {
        break;
      }
    }
    var activeEl = null;
    for (var i = 0; i < branches.length; i++) {
      var b = branches[i];
      if (b.expr === null || !!evalExpr(b.expr, scope)) { activeEl = b.el; break; }
    }
    branches.forEach(function (b) {
      if (b.el === activeEl) b.el.removeAttribute('hidden');
      else b.el.setAttribute('hidden', '');
    });
    return activeEl;
  }

  /** Toggle `stm-class.{name}` classes from their predicate expressions. */
  function handleClass(el, scope) {
    var attrs = el.attributes;
    for (var i = 0; i < attrs.length; i++) {
      var attr = attrs[i];
      if (attr.name.indexOf('stm-class.') === 0) {
        var cls = attr.name.slice('stm-class.'.length);
        if (cls && !!evalExpr(attr.value, scope)) el.classList.add(cls);
        else el.classList.remove(cls);
      }
    }
  }

  /**
   * Bind `stm-attribute.{name}`: a boolean result toggles the attribute, any
   * other defined value sets it, and `undefined` removes it.
   *
   * For booleans, prefer the element's IDL property when one exists (e.g.
   * `checked`, `disabled`, `hidden`) — setting the content attribute is
   * unreliable for these once the control is "dirty".
   */
  function handleAttribute(el, scope) {
    var attrs = el.attributes;
    for (var i = 0; i < attrs.length; i++) {
      var attr = attrs[i];
      if (attr.name.indexOf('stm-attribute.') === 0) {
        var name = attr.name.slice('stm-attribute.'.length);
        if (!name) continue;
        var value = evalExpr(attr.value, scope);
        if (value === undefined) {
          el.removeAttribute(name);
        } else if (typeof value === 'boolean') {
          if (name in el && typeof el[name] === 'boolean') el[name] = value;
          else if (value) el.setAttribute(name, '');
          else el.removeAttribute(name);
        } else {
          el.setAttribute(name, value === null ? '' : String(value));
        }
      }
    }
  }

  /**
   * Apply `stm-disabled`: when the predicate is truthy, disable the element and
   * its descendant form controls; otherwise enable them.
   */
  function handleDisabled(el, scope) {
    if (!el.hasAttribute('stm-disabled')) return;
    setDisabledCascade(el, !!evalExpr(el.getAttribute('stm-disabled'), scope));
  }

  /** Set the `disabled` attribute on an element and its descendant controls. */
  function setDisabledCascade(el, on) {
    var nodes = [el].concat(Array.prototype.slice.call(
      el.querySelectorAll('button,input,select,textarea,fieldset')));
    nodes.forEach(function (n) {
      if (on) n.setAttribute('disabled', ''); else n.removeAttribute('disabled');
    });
  }

  // ---------------------------------------------------------------------------
  // Markdown rendering (CommonMark 0.31.2)
  // ---------------------------------------------------------------------------
  //
  // A two-pass CommonMark engine: block structure first (paragraphs, ATX and
  // setext headings, thematic breaks, indented and fenced code blocks, block
  // quotes with lazy continuation, lists with tight/loose rendering and link
  // reference definitions), then inline parsing inside the leaf blocks
  // (delimiter-run emphasis, links and images, code spans, autolinks,
  // backslash escapes, entity references, hard/soft line breaks).
  //
  // SECURITY: the markdown source is untrusted text. Raw HTML is never passed
  // through — inline HTML and HTML-block-looking constructs render as escaped
  // text, which intentionally diverges from the CommonMark HTML output for
  // those examples. Link and image destinations are scheme-filtered by
  // safeMarkdownUrl() and everything is escaped before it reaches the output.


  function safeMarkdownUrl(url) {
    var u = url.trim();
    var m = u.match(/^([a-zA-Z][a-zA-Z0-9+.-]*):/);
    if (!m) return u;
    var scheme = m[1].toLowerCase();
    if (scheme === 'http' || scheme === 'https' || scheme === 'mailto' || scheme === 'ftp') return u;
    return '#';
  }

  /**
   * Packed HTML5 named-entity table (WHATWG `entities.json`, 2125 entries).
   * Each record is "name cp[,cp...]" on one line; multi-codepoint entities
   * carry comma-separated codepoints. Line breaks are escaped so the whole
   * table stays one string literal. Parsed lazily into a name -> text map the
   * first time an entity reference is looked up.
   */
  var MD_ENTITIES_PACKED = ''
    + "AElig 198\nAMP 38\nAacute 193\nAbreve 258\nAcirc 194\nAcy 1040\nAfr 120068\nAgrave 192\n"
    + "Alpha 913\nAmacr 256\nAnd 10835\nAogon 260\nAopf 120120\nApplyFunction 8289\nAring 197\n"
    + "Ascr 119964\nAssign 8788\nAtilde 195\nAuml 196\nBackslash 8726\nBarv 10983\nBarwed 8966\n"
    + "Bcy 1041\nBecause 8757\nBernoullis 8492\nBeta 914\nBfr 120069\nBopf 120121\nBreve 728\n"
    + "Bscr 8492\nBumpeq 8782\nCHcy 1063\nCOPY 169\nCacute 262\nCap 8914\n"
    + "CapitalDifferentialD 8517\nCayleys 8493\nCcaron 268\nCcedil 199\nCcirc 264\nCconint 8752\n"
    + "Cdot 266\nCedilla 184\nCenterDot 183\nCfr 8493\nChi 935\nCircleDot 8857\n"
    + "CircleMinus 8854\nCirclePlus 8853\nCircleTimes 8855\nClockwiseContourIntegral 8754\n"
    + "CloseCurlyDoubleQuote 8221\nCloseCurlyQuote 8217\nColon 8759\nColone 10868\n"
    + "Congruent 8801\nConint 8751\nContourIntegral 8750\nCopf 8450\nCoproduct 8720\n"
    + "CounterClockwiseContourIntegral 8755\nCross 10799\nCscr 119966\nCup 8915\nCupCap 8781\n"
    + "DD 8517\nDDotrahd 10513\nDJcy 1026\nDScy 1029\nDZcy 1039\nDagger 8225\nDarr 8609\n"
    + "Dashv 10980\nDcaron 270\nDcy 1044\nDel 8711\nDelta 916\nDfr 120071\nDiacriticalAcute 180\n"
    + "DiacriticalDot 729\nDiacriticalDoubleAcute 733\nDiacriticalGrave 96\n"
    + "DiacriticalTilde 732\nDiamond 8900\nDifferentialD 8518\nDopf 120123\nDot 168\n"
    + "DotDot 8412\nDotEqual 8784\nDoubleContourIntegral 8751\nDoubleDot 168\n"
    + "DoubleDownArrow 8659\nDoubleLeftArrow 8656\nDoubleLeftRightArrow 8660\n"
    + "DoubleLeftTee 10980\nDoubleLongLeftArrow 10232\nDoubleLongLeftRightArrow 10234\n"
    + "DoubleLongRightArrow 10233\nDoubleRightArrow 8658\nDoubleRightTee 8872\n"
    + "DoubleUpArrow 8657\nDoubleUpDownArrow 8661\nDoubleVerticalBar 8741\nDownArrow 8595\n"
    + "DownArrowBar 10515\nDownArrowUpArrow 8693\nDownBreve 785\nDownLeftRightVector 10576\n"
    + "DownLeftTeeVector 10590\nDownLeftVector 8637\nDownLeftVectorBar 10582\n"
    + "DownRightTeeVector 10591\nDownRightVector 8641\nDownRightVectorBar 10583\nDownTee 8868\n"
    + "DownTeeArrow 8615\nDownarrow 8659\nDscr 119967\nDstrok 272\nENG 330\nETH 208\nEacute 201\n"
    + "Ecaron 282\nEcirc 202\nEcy 1069\nEdot 278\nEfr 120072\nEgrave 200\nElement 8712\n"
    + "Emacr 274\nEmptySmallSquare 9723\nEmptyVerySmallSquare 9643\nEogon 280\nEopf 120124\n"
    + "Epsilon 917\nEqual 10869\nEqualTilde 8770\nEquilibrium 8652\nEscr 8496\nEsim 10867\n"
    + "Eta 919\nEuml 203\nExists 8707\nExponentialE 8519\nFcy 1060\nFfr 120073\n"
    + "FilledSmallSquare 9724\nFilledVerySmallSquare 9642\nFopf 120125\nForAll 8704\n"
    + "Fouriertrf 8497\nFscr 8497\nGJcy 1027\nGT 62\nGamma 915\nGammad 988\nGbreve 286\n"
    + "Gcedil 290\nGcirc 284\nGcy 1043\nGdot 288\nGfr 120074\nGg 8921\nGopf 120126\n"
    + "GreaterEqual 8805\nGreaterEqualLess 8923\nGreaterFullEqual 8807\nGreaterGreater 10914\n"
    + "GreaterLess 8823\nGreaterSlantEqual 10878\nGreaterTilde 8819\nGscr 119970\nGt 8811\n"
    + "HARDcy 1066\nHacek 711\nHat 94\nHcirc 292\nHfr 8460\nHilbertSpace 8459\nHopf 8461\n"
    + "HorizontalLine 9472\nHscr 8459\nHstrok 294\nHumpDownHump 8782\nHumpEqual 8783\nIEcy 1045\n"
    + "IJlig 306\nIOcy 1025\nIacute 205\nIcirc 206\nIcy 1048\nIdot 304\nIfr 8465\nIgrave 204\n"
    + "Im 8465\nImacr 298\nImaginaryI 8520\nImplies 8658\nInt 8748\nIntegral 8747\n"
    + "Intersection 8898\nInvisibleComma 8291\nInvisibleTimes 8290\nIogon 302\nIopf 120128\n"
    + "Iota 921\nIscr 8464\nItilde 296\nIukcy 1030\nIuml 207\nJcirc 308\nJcy 1049\nJfr 120077\n"
    + "Jopf 120129\nJscr 119973\nJsercy 1032\nJukcy 1028\nKHcy 1061\nKJcy 1036\nKappa 922\n"
    + "Kcedil 310\nKcy 1050\nKfr 120078\nKopf 120130\nKscr 119974\nLJcy 1033\nLT 60\nLacute 313\n"
    + "Lambda 923\nLang 10218\nLaplacetrf 8466\nLarr 8606\nLcaron 317\nLcedil 315\nLcy 1051\n"
    + "LeftAngleBracket 10216\nLeftArrow 8592\nLeftArrowBar 8676\nLeftArrowRightArrow 8646\n"
    + "LeftCeiling 8968\nLeftDoubleBracket 10214\nLeftDownTeeVector 10593\nLeftDownVector 8643\n"
    + "LeftDownVectorBar 10585\nLeftFloor 8970\nLeftRightArrow 8596\nLeftRightVector 10574\n"
    + "LeftTee 8867\nLeftTeeArrow 8612\nLeftTeeVector 10586\nLeftTriangle 8882\n"
    + "LeftTriangleBar 10703\nLeftTriangleEqual 8884\nLeftUpDownVector 10577\n"
    + "LeftUpTeeVector 10592\nLeftUpVector 8639\nLeftUpVectorBar 10584\nLeftVector 8636\n"
    + "LeftVectorBar 10578\nLeftarrow 8656\nLeftrightarrow 8660\nLessEqualGreater 8922\n"
    + "LessFullEqual 8806\nLessGreater 8822\nLessLess 10913\nLessSlantEqual 10877\n"
    + "LessTilde 8818\nLfr 120079\nLl 8920\nLleftarrow 8666\nLmidot 319\nLongLeftArrow 10229\n"
    + "LongLeftRightArrow 10231\nLongRightArrow 10230\nLongleftarrow 10232\n"
    + "Longleftrightarrow 10234\nLongrightarrow 10233\nLopf 120131\nLowerLeftArrow 8601\n"
    + "LowerRightArrow 8600\nLscr 8466\nLsh 8624\nLstrok 321\nLt 8810\nMap 10501\nMcy 1052\n"
    + "MediumSpace 8287\nMellintrf 8499\nMfr 120080\nMinusPlus 8723\nMopf 120132\nMscr 8499\n"
    + "Mu 924\nNJcy 1034\nNacute 323\nNcaron 327\nNcedil 325\nNcy 1053\n"
    + "NegativeMediumSpace 8203\nNegativeThickSpace 8203\nNegativeThinSpace 8203\n"
    + "NegativeVeryThinSpace 8203\nNestedGreaterGreater 8811\nNestedLessLess 8810\nNewLine 10\n"
    + "Nfr 120081\nNoBreak 8288\nNonBreakingSpace 160\nNopf 8469\nNot 10988\nNotCongruent 8802\n"
    + "NotCupCap 8813\nNotDoubleVerticalBar 8742\nNotElement 8713\nNotEqual 8800\n"
    + "NotEqualTilde 8770,824\nNotExists 8708\nNotGreater 8815\nNotGreaterEqual 8817\n"
    + "NotGreaterFullEqual 8807,824\nNotGreaterGreater 8811,824\nNotGreaterLess 8825\n"
    + "NotGreaterSlantEqual 10878,824\nNotGreaterTilde 8821\nNotHumpDownHump 8782,824\n"
    + "NotHumpEqual 8783,824\nNotLeftTriangle 8938\nNotLeftTriangleBar 10703,824\n"
    + "NotLeftTriangleEqual 8940\nNotLess 8814\nNotLessEqual 8816\nNotLessGreater 8824\n"
    + "NotLessLess 8810,824\nNotLessSlantEqual 10877,824\nNotLessTilde 8820\n"
    + "NotNestedGreaterGreater 10914,824\nNotNestedLessLess 10913,824\nNotPrecedes 8832\n"
    + "NotPrecedesEqual 10927,824\nNotPrecedesSlantEqual 8928\nNotReverseElement 8716\n"
    + "NotRightTriangle 8939\nNotRightTriangleBar 10704,824\nNotRightTriangleEqual 8941\n"
    + "NotSquareSubset 8847,824\nNotSquareSubsetEqual 8930\nNotSquareSuperset 8848,824\n"
    + "NotSquareSupersetEqual 8931\nNotSubset 8834,8402\nNotSubsetEqual 8840\nNotSucceeds 8833\n"
    + "NotSucceedsEqual 10928,824\nNotSucceedsSlantEqual 8929\nNotSucceedsTilde 8831,824\n"
    + "NotSuperset 8835,8402\nNotSupersetEqual 8841\nNotTilde 8769\nNotTildeEqual 8772\n"
    + "NotTildeFullEqual 8775\nNotTildeTilde 8777\nNotVerticalBar 8740\nNscr 119977\nNtilde 209\n"
    + "Nu 925\nOElig 338\nOacute 211\nOcirc 212\nOcy 1054\nOdblac 336\nOfr 120082\nOgrave 210\n"
    + "Omacr 332\nOmega 937\nOmicron 927\nOopf 120134\nOpenCurlyDoubleQuote 8220\n"
    + "OpenCurlyQuote 8216\nOr 10836\nOscr 119978\nOslash 216\nOtilde 213\nOtimes 10807\n"
    + "Ouml 214\nOverBar 8254\nOverBrace 9182\nOverBracket 9140\nOverParenthesis 9180\n"
    + "PartialD 8706\nPcy 1055\nPfr 120083\nPhi 934\nPi 928\nPlusMinus 177\nPoincareplane 8460\n"
    + "Popf 8473\nPr 10939\nPrecedes 8826\nPrecedesEqual 10927\nPrecedesSlantEqual 8828\n"
    + "PrecedesTilde 8830\nPrime 8243\nProduct 8719\nProportion 8759\nProportional 8733\n"
    + "Pscr 119979\nPsi 936\nQUOT 34\nQfr 120084\nQopf 8474\nQscr 119980\nRBarr 10512\nREG 174\n"
    + "Racute 340\nRang 10219\nRarr 8608\nRarrtl 10518\nRcaron 344\nRcedil 342\nRcy 1056\n"
    + "Re 8476\nReverseElement 8715\nReverseEquilibrium 8651\nReverseUpEquilibrium 10607\n"
    + "Rfr 8476\nRho 929\nRightAngleBracket 10217\nRightArrow 8594\nRightArrowBar 8677\n"
    + "RightArrowLeftArrow 8644\nRightCeiling 8969\nRightDoubleBracket 10215\n"
    + "RightDownTeeVector 10589\nRightDownVector 8642\nRightDownVectorBar 10581\n"
    + "RightFloor 8971\nRightTee 8866\nRightTeeArrow 8614\nRightTeeVector 10587\n"
    + "RightTriangle 8883\nRightTriangleBar 10704\nRightTriangleEqual 8885\n"
    + "RightUpDownVector 10575\nRightUpTeeVector 10588\nRightUpVector 8638\n"
    + "RightUpVectorBar 10580\nRightVector 8640\nRightVectorBar 10579\nRightarrow 8658\n"
    + "Ropf 8477\nRoundImplies 10608\nRrightarrow 8667\nRscr 8475\nRsh 8625\nRuleDelayed 10740\n"
    + "SHCHcy 1065\nSHcy 1064\nSOFTcy 1068\nSacute 346\nSc 10940\nScaron 352\nScedil 350\n"
    + "Scirc 348\nScy 1057\nSfr 120086\nShortDownArrow 8595\nShortLeftArrow 8592\n"
    + "ShortRightArrow 8594\nShortUpArrow 8593\nSigma 931\nSmallCircle 8728\nSopf 120138\n"
    + "Sqrt 8730\nSquare 9633\nSquareIntersection 8851\nSquareSubset 8847\n"
    + "SquareSubsetEqual 8849\nSquareSuperset 8848\nSquareSupersetEqual 8850\nSquareUnion 8852\n"
    + "Sscr 119982\nStar 8902\nSub 8912\nSubset 8912\nSubsetEqual 8838\nSucceeds 8827\n"
    + "SucceedsEqual 10928\nSucceedsSlantEqual 8829\nSucceedsTilde 8831\nSuchThat 8715\n"
    + "Sum 8721\nSup 8913\nSuperset 8835\nSupersetEqual 8839\nSupset 8913\nTHORN 222\n"
    + "TRADE 8482\nTSHcy 1035\nTScy 1062\nTab 9\nTau 932\nTcaron 356\nTcedil 354\nTcy 1058\n"
    + "Tfr 120087\nTherefore 8756\nTheta 920\nThickSpace 8287,8202\nThinSpace 8201\nTilde 8764\n"
    + "TildeEqual 8771\nTildeFullEqual 8773\nTildeTilde 8776\nTopf 120139\nTripleDot 8411\n"
    + "Tscr 119983\nTstrok 358\nUacute 218\nUarr 8607\nUarrocir 10569\nUbrcy 1038\nUbreve 364\n"
    + "Ucirc 219\nUcy 1059\nUdblac 368\nUfr 120088\nUgrave 217\nUmacr 362\nUnderBar 95\n"
    + "UnderBrace 9183\nUnderBracket 9141\nUnderParenthesis 9181\nUnion 8899\nUnionPlus 8846\n"
    + "Uogon 370\nUopf 120140\nUpArrow 8593\nUpArrowBar 10514\nUpArrowDownArrow 8645\n"
    + "UpDownArrow 8597\nUpEquilibrium 10606\nUpTee 8869\nUpTeeArrow 8613\nUparrow 8657\n"
    + "Updownarrow 8661\nUpperLeftArrow 8598\nUpperRightArrow 8599\nUpsi 978\nUpsilon 933\n"
    + "Uring 366\nUscr 119984\nUtilde 360\nUuml 220\nVDash 8875\nVbar 10987\nVcy 1042\n"
    + "Vdash 8873\nVdashl 10982\nVee 8897\nVerbar 8214\nVert 8214\nVerticalBar 8739\n"
    + "VerticalLine 124\nVerticalSeparator 10072\nVerticalTilde 8768\nVeryThinSpace 8202\n"
    + "Vfr 120089\nVopf 120141\nVscr 119985\nVvdash 8874\nWcirc 372\nWedge 8896\nWfr 120090\n"
    + "Wopf 120142\nWscr 119986\nXfr 120091\nXi 926\nXopf 120143\nXscr 119987\nYAcy 1071\n"
    + "YIcy 1031\nYUcy 1070\nYacute 221\nYcirc 374\nYcy 1067\nYfr 120092\nYopf 120144\n"
    + "Yscr 119988\nYuml 376\nZHcy 1046\nZacute 377\nZcaron 381\nZcy 1047\nZdot 379\n"
    + "ZeroWidthSpace 8203\nZeta 918\nZfr 8488\nZopf 8484\nZscr 119989\naacute 225\nabreve 259\n"
    + "ac 8766\nacE 8766,819\nacd 8767\nacirc 226\nacute 180\nacy 1072\naelig 230\naf 8289\n"
    + "afr 120094\nagrave 224\nalefsym 8501\naleph 8501\nalpha 945\namacr 257\namalg 10815\n"
    + "amp 38\nand 8743\nandand 10837\nandd 10844\nandslope 10840\nandv 10842\nang 8736\n"
    + "ange 10660\nangle 8736\nangmsd 8737\nangmsdaa 10664\nangmsdab 10665\nangmsdac 10666\n"
    + "angmsdad 10667\nangmsdae 10668\nangmsdaf 10669\nangmsdag 10670\nangmsdah 10671\n"
    + "angrt 8735\nangrtvb 8894\nangrtvbd 10653\nangsph 8738\nangst 197\nangzarr 9084\n"
    + "aogon 261\naopf 120146\nap 8776\napE 10864\napacir 10863\nape 8778\napid 8779\napos 39\n"
    + "approx 8776\napproxeq 8778\naring 229\nascr 119990\nast 42\nasymp 8776\nasympeq 8781\n"
    + "atilde 227\nauml 228\nawconint 8755\nawint 10769\nbNot 10989\nbackcong 8780\n"
    + "backepsilon 1014\nbackprime 8245\nbacksim 8765\nbacksimeq 8909\nbarvee 8893\nbarwed 8965\n"
    + "barwedge 8965\nbbrk 9141\nbbrktbrk 9142\nbcong 8780\nbcy 1073\nbdquo 8222\nbecaus 8757\n"
    + "because 8757\nbemptyv 10672\nbepsi 1014\nbernou 8492\nbeta 946\nbeth 8502\nbetween 8812\n"
    + "bfr 120095\nbigcap 8898\nbigcirc 9711\nbigcup 8899\nbigodot 10752\nbigoplus 10753\n"
    + "bigotimes 10754\nbigsqcup 10758\nbigstar 9733\nbigtriangledown 9661\nbigtriangleup 9651\n"
    + "biguplus 10756\nbigvee 8897\nbigwedge 8896\nbkarow 10509\nblacklozenge 10731\n"
    + "blacksquare 9642\nblacktriangle 9652\nblacktriangledown 9662\nblacktriangleleft 9666\n"
    + "blacktriangleright 9656\nblank 9251\nblk12 9618\nblk14 9617\nblk34 9619\nblock 9608\n"
    + "bne 61,8421\nbnequiv 8801,8421\nbnot 8976\nbopf 120147\nbot 8869\nbottom 8869\n"
    + "bowtie 8904\nboxDL 9559\nboxDR 9556\nboxDl 9558\nboxDr 9555\nboxH 9552\nboxHD 9574\n"
    + "boxHU 9577\nboxHd 9572\nboxHu 9575\nboxUL 9565\nboxUR 9562\nboxUl 9564\nboxUr 9561\n"
    + "boxV 9553\nboxVH 9580\nboxVL 9571\nboxVR 9568\nboxVh 9579\nboxVl 9570\nboxVr 9567\n"
    + "boxbox 10697\nboxdL 9557\nboxdR 9554\nboxdl 9488\nboxdr 9484\nboxh 9472\nboxhD 9573\n"
    + "boxhU 9576\nboxhd 9516\nboxhu 9524\nboxminus 8863\nboxplus 8862\nboxtimes 8864\n"
    + "boxuL 9563\nboxuR 9560\nboxul 9496\nboxur 9492\nboxv 9474\nboxvH 9578\nboxvL 9569\n"
    + "boxvR 9566\nboxvh 9532\nboxvl 9508\nboxvr 9500\nbprime 8245\nbreve 728\nbrvbar 166\n"
    + "bscr 119991\nbsemi 8271\nbsim 8765\nbsime 8909\nbsol 92\nbsolb 10693\nbsolhsub 10184\n"
    + "bull 8226\nbullet 8226\nbump 8782\nbumpE 10926\nbumpe 8783\nbumpeq 8783\ncacute 263\n"
    + "cap 8745\ncapand 10820\ncapbrcup 10825\ncapcap 10827\ncapcup 10823\ncapdot 10816\n"
    + "caps 8745,65024\ncaret 8257\ncaron 711\nccaps 10829\nccaron 269\nccedil 231\nccirc 265\n"
    + "ccups 10828\nccupssm 10832\ncdot 267\ncedil 184\ncemptyv 10674\ncent 162\ncenterdot 183\n"
    + "cfr 120096\nchcy 1095\ncheck 10003\ncheckmark 10003\nchi 967\ncir 9675\ncirE 10691\n"
    + "circ 710\ncirceq 8791\ncirclearrowleft 8634\ncirclearrowright 8635\ncircledR 174\n"
    + "circledS 9416\ncircledast 8859\ncircledcirc 8858\ncircleddash 8861\ncire 8791\n"
    + "cirfnint 10768\ncirmid 10991\ncirscir 10690\nclubs 9827\nclubsuit 9827\ncolon 58\n"
    + "colone 8788\ncoloneq 8788\ncomma 44\ncommat 64\ncomp 8705\ncompfn 8728\ncomplement 8705\n"
    + "complexes 8450\ncong 8773\ncongdot 10861\nconint 8750\ncopf 120148\ncoprod 8720\n"
    + "copy 169\ncopysr 8471\ncrarr 8629\ncross 10007\ncscr 119992\ncsub 10959\ncsube 10961\n"
    + "csup 10960\ncsupe 10962\nctdot 8943\ncudarrl 10552\ncudarrr 10549\ncuepr 8926\n"
    + "cuesc 8927\ncularr 8630\ncularrp 10557\ncup 8746\ncupbrcap 10824\ncupcap 10822\n"
    + "cupcup 10826\ncupdot 8845\ncupor 10821\ncups 8746,65024\ncurarr 8631\ncurarrm 10556\n"
    + "curlyeqprec 8926\ncurlyeqsucc 8927\ncurlyvee 8910\ncurlywedge 8911\ncurren 164\n"
    + "curvearrowleft 8630\ncurvearrowright 8631\ncuvee 8910\ncuwed 8911\ncwconint 8754\n"
    + "cwint 8753\ncylcty 9005\ndArr 8659\ndHar 10597\ndagger 8224\ndaleth 8504\ndarr 8595\n"
    + "dash 8208\ndashv 8867\ndbkarow 10511\ndblac 733\ndcaron 271\ndcy 1076\ndd 8518\n"
    + "ddagger 8225\nddarr 8650\nddotseq 10871\ndeg 176\ndelta 948\ndemptyv 10673\ndfisht 10623\n"
    + "dfr 120097\ndharl 8643\ndharr 8642\ndiam 8900\ndiamond 8900\ndiamondsuit 9830\n"
    + "diams 9830\ndie 168\ndigamma 989\ndisin 8946\ndiv 247\ndivide 247\ndivideontimes 8903\n"
    + "divonx 8903\ndjcy 1106\ndlcorn 8990\ndlcrop 8973\ndollar 36\ndopf 120149\ndot 729\n"
    + "doteq 8784\ndoteqdot 8785\ndotminus 8760\ndotplus 8724\ndotsquare 8865\n"
    + "doublebarwedge 8966\ndownarrow 8595\ndowndownarrows 8650\ndownharpoonleft 8643\n"
    + "downharpoonright 8642\ndrbkarow 10512\ndrcorn 8991\ndrcrop 8972\ndscr 119993\ndscy 1109\n"
    + "dsol 10742\ndstrok 273\ndtdot 8945\ndtri 9663\ndtrif 9662\nduarr 8693\nduhar 10607\n"
    + "dwangle 10662\ndzcy 1119\ndzigrarr 10239\neDDot 10871\neDot 8785\neacute 233\n"
    + "easter 10862\necaron 283\necir 8790\necirc 234\necolon 8789\necy 1101\nedot 279\nee 8519\n"
    + "efDot 8786\nefr 120098\neg 10906\negrave 232\negs 10902\negsdot 10904\nel 10905\n"
    + "elinters 9191\nell 8467\nels 10901\nelsdot 10903\nemacr 275\nempty 8709\nemptyset 8709\n"
    + "emptyv 8709\nemsp 8195\nemsp13 8196\nemsp14 8197\neng 331\nensp 8194\neogon 281\n"
    + "eopf 120150\nepar 8917\neparsl 10723\neplus 10865\nepsi 949\nepsilon 949\nepsiv 1013\n"
    + "eqcirc 8790\neqcolon 8789\neqsim 8770\neqslantgtr 10902\neqslantless 10901\nequals 61\n"
    + "equest 8799\nequiv 8801\nequivDD 10872\neqvparsl 10725\nerDot 8787\nerarr 10609\n"
    + "escr 8495\nesdot 8784\nesim 8770\neta 951\neth 240\neuml 235\neuro 8364\nexcl 33\n"
    + "exist 8707\nexpectation 8496\nexponentiale 8519\nfallingdotseq 8786\nfcy 1092\n"
    + "female 9792\nffilig 64259\nfflig 64256\nffllig 64260\nffr 120099\nfilig 64257\n"
    + "fjlig 102,106\nflat 9837\nfllig 64258\nfltns 9649\nfnof 402\nfopf 120151\nforall 8704\n"
    + "fork 8916\nforkv 10969\nfpartint 10765\nfrac12 189\nfrac13 8531\nfrac14 188\nfrac15 8533\n"
    + "frac16 8537\nfrac18 8539\nfrac23 8532\nfrac25 8534\nfrac34 190\nfrac35 8535\nfrac38 8540\n"
    + "frac45 8536\nfrac56 8538\nfrac58 8541\nfrac78 8542\nfrasl 8260\nfrown 8994\nfscr 119995\n"
    + "gE 8807\ngEl 10892\ngacute 501\ngamma 947\ngammad 989\ngap 10886\ngbreve 287\ngcirc 285\n"
    + "gcy 1075\ngdot 289\nge 8805\ngel 8923\ngeq 8805\ngeqq 8807\ngeqslant 10878\nges 10878\n"
    + "gescc 10921\ngesdot 10880\ngesdoto 10882\ngesdotol 10884\ngesl 8923,65024\ngesles 10900\n"
    + "gfr 120100\ngg 8811\nggg 8921\ngimel 8503\ngjcy 1107\ngl 8823\nglE 10898\ngla 10917\n"
    + "glj 10916\ngnE 8809\ngnap 10890\ngnapprox 10890\ngne 10888\ngneq 10888\ngneqq 8809\n"
    + "gnsim 8935\ngopf 120152\ngrave 96\ngscr 8458\ngsim 8819\ngsime 10894\ngsiml 10896\ngt 62\n"
    + "gtcc 10919\ngtcir 10874\ngtdot 8919\ngtlPar 10645\ngtquest 10876\ngtrapprox 10886\n"
    + "gtrarr 10616\ngtrdot 8919\ngtreqless 8923\ngtreqqless 10892\ngtrless 8823\ngtrsim 8819\n"
    + "gvertneqq 8809,65024\ngvnE 8809,65024\nhArr 8660\nhairsp 8202\nhalf 189\nhamilt 8459\n"
    + "hardcy 1098\nharr 8596\nharrcir 10568\nharrw 8621\nhbar 8463\nhcirc 293\nhearts 9829\n"
    + "heartsuit 9829\nhellip 8230\nhercon 8889\nhfr 120101\nhksearow 10533\nhkswarow 10534\n"
    + "hoarr 8703\nhomtht 8763\nhookleftarrow 8617\nhookrightarrow 8618\nhopf 120153\n"
    + "horbar 8213\nhscr 119997\nhslash 8463\nhstrok 295\nhybull 8259\nhyphen 8208\niacute 237\n"
    + "ic 8291\nicirc 238\nicy 1080\niecy 1077\niexcl 161\niff 8660\nifr 120102\nigrave 236\n"
    + "ii 8520\niiiint 10764\niiint 8749\niinfin 10716\niiota 8489\nijlig 307\nimacr 299\n"
    + "image 8465\nimagline 8464\nimagpart 8465\nimath 305\nimof 8887\nimped 437\nin 8712\n"
    + "incare 8453\ninfin 8734\ninfintie 10717\ninodot 305\nint 8747\nintcal 8890\n"
    + "integers 8484\nintercal 8890\nintlarhk 10775\nintprod 10812\niocy 1105\niogon 303\n"
    + "iopf 120154\niota 953\niprod 10812\niquest 191\niscr 119998\nisin 8712\nisinE 8953\n"
    + "isindot 8949\nisins 8948\nisinsv 8947\nisinv 8712\nit 8290\nitilde 297\niukcy 1110\n"
    + "iuml 239\njcirc 309\njcy 1081\njfr 120103\njmath 567\njopf 120155\njscr 119999\n"
    + "jsercy 1112\njukcy 1108\nkappa 954\nkappav 1008\nkcedil 311\nkcy 1082\nkfr 120104\n"
    + "kgreen 312\nkhcy 1093\nkjcy 1116\nkopf 120156\nkscr 120000\nlAarr 8666\nlArr 8656\n"
    + "lAtail 10523\nlBarr 10510\nlE 8806\nlEg 10891\nlHar 10594\nlacute 314\nlaemptyv 10676\n"
    + "lagran 8466\nlambda 955\nlang 10216\nlangd 10641\nlangle 10216\nlap 10885\nlaquo 171\n"
    + "larr 8592\nlarrb 8676\nlarrbfs 10527\nlarrfs 10525\nlarrhk 8617\nlarrlp 8619\n"
    + "larrpl 10553\nlarrsim 10611\nlarrtl 8610\nlat 10923\nlatail 10521\nlate 10925\n"
    + "lates 10925,65024\nlbarr 10508\nlbbrk 10098\nlbrace 123\nlbrack 91\nlbrke 10635\n"
    + "lbrksld 10639\nlbrkslu 10637\nlcaron 318\nlcedil 316\nlceil 8968\nlcub 123\nlcy 1083\n"
    + "ldca 10550\nldquo 8220\nldquor 8222\nldrdhar 10599\nldrushar 10571\nldsh 8626\nle 8804\n"
    + "leftarrow 8592\nleftarrowtail 8610\nleftharpoondown 8637\nleftharpoonup 8636\n"
    + "leftleftarrows 8647\nleftrightarrow 8596\nleftrightarrows 8646\nleftrightharpoons 8651\n"
    + "leftrightsquigarrow 8621\nleftthreetimes 8907\nleg 8922\nleq 8804\nleqq 8806\n"
    + "leqslant 10877\nles 10877\nlescc 10920\nlesdot 10879\nlesdoto 10881\nlesdotor 10883\n"
    + "lesg 8922,65024\nlesges 10899\nlessapprox 10885\nlessdot 8918\nlesseqgtr 8922\n"
    + "lesseqqgtr 10891\nlessgtr 8822\nlesssim 8818\nlfisht 10620\nlfloor 8970\nlfr 120105\n"
    + "lg 8822\nlgE 10897\nlhard 8637\nlharu 8636\nlharul 10602\nlhblk 9604\nljcy 1113\nll 8810\n"
    + "llarr 8647\nllcorner 8990\nllhard 10603\nlltri 9722\nlmidot 320\nlmoust 9136\n"
    + "lmoustache 9136\nlnE 8808\nlnap 10889\nlnapprox 10889\nlne 10887\nlneq 10887\nlneqq 8808\n"
    + "lnsim 8934\nloang 10220\nloarr 8701\nlobrk 10214\nlongleftarrow 10229\n"
    + "longleftrightarrow 10231\nlongmapsto 10236\nlongrightarrow 10230\nlooparrowleft 8619\n"
    + "looparrowright 8620\nlopar 10629\nlopf 120157\nloplus 10797\nlotimes 10804\nlowast 8727\n"
    + "lowbar 95\nloz 9674\nlozenge 9674\nlozf 10731\nlpar 40\nlparlt 10643\nlrarr 8646\n"
    + "lrcorner 8991\nlrhar 8651\nlrhard 10605\nlrm 8206\nlrtri 8895\nlsaquo 8249\nlscr 120001\n"
    + "lsh 8624\nlsim 8818\nlsime 10893\nlsimg 10895\nlsqb 91\nlsquo 8216\nlsquor 8218\n"
    + "lstrok 322\nlt 60\nltcc 10918\nltcir 10873\nltdot 8918\nlthree 8907\nltimes 8905\n"
    + "ltlarr 10614\nltquest 10875\nltrPar 10646\nltri 9667\nltrie 8884\nltrif 9666\n"
    + "lurdshar 10570\nluruhar 10598\nlvertneqq 8808,65024\nlvnE 8808,65024\nmDDot 8762\n"
    + "macr 175\nmale 9794\nmalt 10016\nmaltese 10016\nmap 8614\nmapsto 8614\nmapstodown 8615\n"
    + "mapstoleft 8612\nmapstoup 8613\nmarker 9646\nmcomma 10793\nmcy 1084\nmdash 8212\n"
    + "measuredangle 8737\nmfr 120106\nmho 8487\nmicro 181\nmid 8739\nmidast 42\nmidcir 10992\n"
    + "middot 183\nminus 8722\nminusb 8863\nminusd 8760\nminusdu 10794\nmlcp 10971\nmldr 8230\n"
    + "mnplus 8723\nmodels 8871\nmopf 120158\nmp 8723\nmscr 120002\nmstpos 8766\nmu 956\n"
    + "multimap 8888\nmumap 8888\nnGg 8921,824\nnGt 8811,8402\nnGtv 8811,824\nnLeftarrow 8653\n"
    + "nLeftrightarrow 8654\nnLl 8920,824\nnLt 8810,8402\nnLtv 8810,824\nnRightarrow 8655\n"
    + "nVDash 8879\nnVdash 8878\nnabla 8711\nnacute 324\nnang 8736,8402\nnap 8777\n"
    + "napE 10864,824\nnapid 8779,824\nnapos 329\nnapprox 8777\nnatur 9838\nnatural 9838\n"
    + "naturals 8469\nnbsp 160\nnbump 8782,824\nnbumpe 8783,824\nncap 10819\nncaron 328\n"
    + "ncedil 326\nncong 8775\nncongdot 10861,824\nncup 10818\nncy 1085\nndash 8211\nne 8800\n"
    + "neArr 8663\nnearhk 10532\nnearr 8599\nnearrow 8599\nnedot 8784,824\nnequiv 8802\n"
    + "nesear 10536\nnesim 8770,824\nnexist 8708\nnexists 8708\nnfr 120107\nngE 8807,824\n"
    + "nge 8817\nngeq 8817\nngeqq 8807,824\nngeqslant 10878,824\nnges 10878,824\nngsim 8821\n"
    + "ngt 8815\nngtr 8815\nnhArr 8654\nnharr 8622\nnhpar 10994\nni 8715\nnis 8956\nnisd 8954\n"
    + "niv 8715\nnjcy 1114\nnlArr 8653\nnlE 8806,824\nnlarr 8602\nnldr 8229\nnle 8816\n"
    + "nleftarrow 8602\nnleftrightarrow 8622\nnleq 8816\nnleqq 8806,824\nnleqslant 10877,824\n"
    + "nles 10877,824\nnless 8814\nnlsim 8820\nnlt 8814\nnltri 8938\nnltrie 8940\nnmid 8740\n"
    + "nopf 120159\nnot 172\nnotin 8713\nnotinE 8953,824\nnotindot 8949,824\nnotinva 8713\n"
    + "notinvb 8951\nnotinvc 8950\nnotni 8716\nnotniva 8716\nnotnivb 8958\nnotnivc 8957\n"
    + "npar 8742\nnparallel 8742\nnparsl 11005,8421\nnpart 8706,824\nnpolint 10772\nnpr 8832\n"
    + "nprcue 8928\nnpre 10927,824\nnprec 8832\nnpreceq 10927,824\nnrArr 8655\nnrarr 8603\n"
    + "nrarrc 10547,824\nnrarrw 8605,824\nnrightarrow 8603\nnrtri 8939\nnrtrie 8941\nnsc 8833\n"
    + "nsccue 8929\nnsce 10928,824\nnscr 120003\nnshortmid 8740\nnshortparallel 8742\nnsim 8769\n"
    + "nsime 8772\nnsimeq 8772\nnsmid 8740\nnspar 8742\nnsqsube 8930\nnsqsupe 8931\nnsub 8836\n"
    + "nsubE 10949,824\nnsube 8840\nnsubset 8834,8402\nnsubseteq 8840\nnsubseteqq 10949,824\n"
    + "nsucc 8833\nnsucceq 10928,824\nnsup 8837\nnsupE 10950,824\nnsupe 8841\nnsupset 8835,8402\n"
    + "nsupseteq 8841\nnsupseteqq 10950,824\nntgl 8825\nntilde 241\nntlg 8824\n"
    + "ntriangleleft 8938\nntrianglelefteq 8940\nntriangleright 8939\nntrianglerighteq 8941\n"
    + "nu 957\nnum 35\nnumero 8470\nnumsp 8199\nnvDash 8877\nnvHarr 10500\nnvap 8781,8402\n"
    + "nvdash 8876\nnvge 8805,8402\nnvgt 62,8402\nnvinfin 10718\nnvlArr 10498\nnvle 8804,8402\n"
    + "nvlt 60,8402\nnvltrie 8884,8402\nnvrArr 10499\nnvrtrie 8885,8402\nnvsim 8764,8402\n"
    + "nwArr 8662\nnwarhk 10531\nnwarr 8598\nnwarrow 8598\nnwnear 10535\noS 9416\noacute 243\n"
    + "oast 8859\nocir 8858\nocirc 244\nocy 1086\nodash 8861\nodblac 337\nodiv 10808\nodot 8857\n"
    + "odsold 10684\noelig 339\nofcir 10687\nofr 120108\nogon 731\nograve 242\nogt 10689\n"
    + "ohbar 10677\nohm 937\noint 8750\nolarr 8634\nolcir 10686\nolcross 10683\noline 8254\n"
    + "olt 10688\nomacr 333\nomega 969\nomicron 959\nomid 10678\nominus 8854\noopf 120160\n"
    + "opar 10679\noperp 10681\noplus 8853\nor 8744\norarr 8635\nord 10845\norder 8500\n"
    + "orderof 8500\nordf 170\nordm 186\norigof 8886\noror 10838\norslope 10839\norv 10843\n"
    + "oscr 8500\noslash 248\nosol 8856\notilde 245\notimes 8855\notimesas 10806\nouml 246\n"
    + "ovbar 9021\npar 8741\npara 182\nparallel 8741\nparsim 10995\nparsl 11005\npart 8706\n"
    + "pcy 1087\npercnt 37\nperiod 46\npermil 8240\nperp 8869\npertenk 8241\npfr 120109\n"
    + "phi 966\nphiv 981\nphmmat 8499\nphone 9742\npi 960\npitchfork 8916\npiv 982\nplanck 8463\n"
    + "planckh 8462\nplankv 8463\nplus 43\nplusacir 10787\nplusb 8862\npluscir 10786\n"
    + "plusdo 8724\nplusdu 10789\npluse 10866\nplusmn 177\nplussim 10790\nplustwo 10791\npm 177\n"
    + "pointint 10773\npopf 120161\npound 163\npr 8826\nprE 10931\nprap 10935\nprcue 8828\n"
    + "pre 10927\nprec 8826\nprecapprox 10935\npreccurlyeq 8828\npreceq 10927\n"
    + "precnapprox 10937\nprecneqq 10933\nprecnsim 8936\nprecsim 8830\nprime 8242\nprimes 8473\n"
    + "prnE 10933\nprnap 10937\nprnsim 8936\nprod 8719\nprofalar 9006\nprofline 8978\n"
    + "profsurf 8979\nprop 8733\npropto 8733\nprsim 8830\nprurel 8880\npscr 120005\npsi 968\n"
    + "puncsp 8200\nqfr 120110\nqint 10764\nqopf 120162\nqprime 8279\nqscr 120006\n"
    + "quaternions 8461\nquatint 10774\nquest 63\nquesteq 8799\nquot 34\nrAarr 8667\nrArr 8658\n"
    + "rAtail 10524\nrBarr 10511\nrHar 10596\nrace 8765,817\nracute 341\nradic 8730\n"
    + "raemptyv 10675\nrang 10217\nrangd 10642\nrange 10661\nrangle 10217\nraquo 187\nrarr 8594\n"
    + "rarrap 10613\nrarrb 8677\nrarrbfs 10528\nrarrc 10547\nrarrfs 10526\nrarrhk 8618\n"
    + "rarrlp 8620\nrarrpl 10565\nrarrsim 10612\nrarrtl 8611\nrarrw 8605\nratail 10522\n"
    + "ratio 8758\nrationals 8474\nrbarr 10509\nrbbrk 10099\nrbrace 125\nrbrack 93\nrbrke 10636\n"
    + "rbrksld 10638\nrbrkslu 10640\nrcaron 345\nrcedil 343\nrceil 8969\nrcub 125\nrcy 1088\n"
    + "rdca 10551\nrdldhar 10601\nrdquo 8221\nrdquor 8221\nrdsh 8627\nreal 8476\nrealine 8475\n"
    + "realpart 8476\nreals 8477\nrect 9645\nreg 174\nrfisht 10621\nrfloor 8971\nrfr 120111\n"
    + "rhard 8641\nrharu 8640\nrharul 10604\nrho 961\nrhov 1009\nrightarrow 8594\n"
    + "rightarrowtail 8611\nrightharpoondown 8641\nrightharpoonup 8640\nrightleftarrows 8644\n"
    + "rightleftharpoons 8652\nrightrightarrows 8649\nrightsquigarrow 8605\n"
    + "rightthreetimes 8908\nring 730\nrisingdotseq 8787\nrlarr 8644\nrlhar 8652\nrlm 8207\n"
    + "rmoust 9137\nrmoustache 9137\nrnmid 10990\nroang 10221\nroarr 8702\nrobrk 10215\n"
    + "ropar 10630\nropf 120163\nroplus 10798\nrotimes 10805\nrpar 41\nrpargt 10644\n"
    + "rppolint 10770\nrrarr 8649\nrsaquo 8250\nrscr 120007\nrsh 8625\nrsqb 93\nrsquo 8217\n"
    + "rsquor 8217\nrthree 8908\nrtimes 8906\nrtri 9657\nrtrie 8885\nrtrif 9656\nrtriltri 10702\n"
    + "ruluhar 10600\nrx 8478\nsacute 347\nsbquo 8218\nsc 8827\nscE 10932\nscap 10936\n"
    + "scaron 353\nsccue 8829\nsce 10928\nscedil 351\nscirc 349\nscnE 10934\nscnap 10938\n"
    + "scnsim 8937\nscpolint 10771\nscsim 8831\nscy 1089\nsdot 8901\nsdotb 8865\nsdote 10854\n"
    + "seArr 8664\nsearhk 10533\nsearr 8600\nsearrow 8600\nsect 167\nsemi 59\nseswar 10537\n"
    + "setminus 8726\nsetmn 8726\nsext 10038\nsfr 120112\nsfrown 8994\nsharp 9839\nshchcy 1097\n"
    + "shcy 1096\nshortmid 8739\nshortparallel 8741\nshy 173\nsigma 963\nsigmaf 962\nsigmav 962\n"
    + "sim 8764\nsimdot 10858\nsime 8771\nsimeq 8771\nsimg 10910\nsimgE 10912\nsiml 10909\n"
    + "simlE 10911\nsimne 8774\nsimplus 10788\nsimrarr 10610\nslarr 8592\nsmallsetminus 8726\n"
    + "smashp 10803\nsmeparsl 10724\nsmid 8739\nsmile 8995\nsmt 10922\nsmte 10924\n"
    + "smtes 10924,65024\nsoftcy 1100\nsol 47\nsolb 10692\nsolbar 9023\nsopf 120164\n"
    + "spades 9824\nspadesuit 9824\nspar 8741\nsqcap 8851\nsqcaps 8851,65024\nsqcup 8852\n"
    + "sqcups 8852,65024\nsqsub 8847\nsqsube 8849\nsqsubset 8847\nsqsubseteq 8849\nsqsup 8848\n"
    + "sqsupe 8850\nsqsupset 8848\nsqsupseteq 8850\nsqu 9633\nsquare 9633\nsquarf 9642\n"
    + "squf 9642\nsrarr 8594\nsscr 120008\nssetmn 8726\nssmile 8995\nsstarf 8902\nstar 9734\n"
    + "starf 9733\nstraightepsilon 1013\nstraightphi 981\nstrns 175\nsub 8834\nsubE 10949\n"
    + "subdot 10941\nsube 8838\nsubedot 10947\nsubmult 10945\nsubnE 10955\nsubne 8842\n"
    + "subplus 10943\nsubrarr 10617\nsubset 8834\nsubseteq 8838\nsubseteqq 10949\n"
    + "subsetneq 8842\nsubsetneqq 10955\nsubsim 10951\nsubsub 10965\nsubsup 10963\nsucc 8827\n"
    + "succapprox 10936\nsucccurlyeq 8829\nsucceq 10928\nsuccnapprox 10938\nsuccneqq 10934\n"
    + "succnsim 8937\nsuccsim 8831\nsum 8721\nsung 9834\nsup 8835\nsup1 185\nsup2 178\nsup3 179\n"
    + "supE 10950\nsupdot 10942\nsupdsub 10968\nsupe 8839\nsupedot 10948\nsuphsol 10185\n"
    + "suphsub 10967\nsuplarr 10619\nsupmult 10946\nsupnE 10956\nsupne 8843\nsupplus 10944\n"
    + "supset 8835\nsupseteq 8839\nsupseteqq 10950\nsupsetneq 8843\nsupsetneqq 10956\n"
    + "supsim 10952\nsupsub 10964\nsupsup 10966\nswArr 8665\nswarhk 10534\nswarr 8601\n"
    + "swarrow 8601\nswnwar 10538\nszlig 223\ntarget 8982\ntau 964\ntbrk 9140\ntcaron 357\n"
    + "tcedil 355\ntcy 1090\ntdot 8411\ntelrec 8981\ntfr 120113\nthere4 8756\ntherefore 8756\n"
    + "theta 952\nthetasym 977\nthetav 977\nthickapprox 8776\nthicksim 8764\nthinsp 8201\n"
    + "thkap 8776\nthksim 8764\nthorn 254\ntilde 732\ntimes 215\ntimesb 8864\ntimesbar 10801\n"
    + "timesd 10800\ntint 8749\ntoea 10536\ntop 8868\ntopbot 9014\ntopcir 10993\ntopf 120165\n"
    + "topfork 10970\ntosa 10537\ntprime 8244\ntrade 8482\ntriangle 9653\ntriangledown 9663\n"
    + "triangleleft 9667\ntrianglelefteq 8884\ntriangleq 8796\ntriangleright 9657\n"
    + "trianglerighteq 8885\ntridot 9708\ntrie 8796\ntriminus 10810\ntriplus 10809\ntrisb 10701\n"
    + "tritime 10811\ntrpezium 9186\ntscr 120009\ntscy 1094\ntshcy 1115\ntstrok 359\ntwixt 8812\n"
    + "twoheadleftarrow 8606\ntwoheadrightarrow 8608\nuArr 8657\nuHar 10595\nuacute 250\n"
    + "uarr 8593\nubrcy 1118\nubreve 365\nucirc 251\nucy 1091\nudarr 8645\nudblac 369\n"
    + "udhar 10606\nufisht 10622\nufr 120114\nugrave 249\nuharl 8639\nuharr 8638\nuhblk 9600\n"
    + "ulcorn 8988\nulcorner 8988\nulcrop 8975\nultri 9720\numacr 363\numl 168\nuogon 371\n"
    + "uopf 120166\nuparrow 8593\nupdownarrow 8597\nupharpoonleft 8639\nupharpoonright 8638\n"
    + "uplus 8846\nupsi 965\nupsih 978\nupsilon 965\nupuparrows 8648\nurcorn 8989\n"
    + "urcorner 8989\nurcrop 8974\nuring 367\nurtri 9721\nuscr 120010\nutdot 8944\nutilde 361\n"
    + "utri 9653\nutrif 9652\nuuarr 8648\nuuml 252\nuwangle 10663\nvArr 8661\nvBar 10984\n"
    + "vBarv 10985\nvDash 8872\nvangrt 10652\nvarepsilon 1013\nvarkappa 1008\nvarnothing 8709\n"
    + "varphi 981\nvarpi 982\nvarpropto 8733\nvarr 8597\nvarrho 1009\nvarsigma 962\n"
    + "varsubsetneq 8842,65024\nvarsubsetneqq 10955,65024\nvarsupsetneq 8843,65024\n"
    + "varsupsetneqq 10956,65024\nvartheta 977\nvartriangleleft 8882\nvartriangleright 8883\n"
    + "vcy 1074\nvdash 8866\nvee 8744\nveebar 8891\nveeeq 8794\nvellip 8942\nverbar 124\n"
    + "vert 124\nvfr 120115\nvltri 8882\nvnsub 8834,8402\nvnsup 8835,8402\nvopf 120167\n"
    + "vprop 8733\nvrtri 8883\nvscr 120011\nvsubnE 10955,65024\nvsubne 8842,65024\n"
    + "vsupnE 10956,65024\nvsupne 8843,65024\nvzigzag 10650\nwcirc 373\nwedbar 10847\n"
    + "wedge 8743\nwedgeq 8793\nweierp 8472\nwfr 120116\nwopf 120168\nwp 8472\nwr 8768\n"
    + "wreath 8768\nwscr 120012\nxcap 8898\nxcirc 9711\nxcup 8899\nxdtri 9661\nxfr 120117\n"
    + "xhArr 10234\nxharr 10231\nxi 958\nxlArr 10232\nxlarr 10229\nxmap 10236\nxnis 8955\n"
    + "xodot 10752\nxopf 120169\nxoplus 10753\nxotime 10754\nxrArr 10233\nxrarr 10230\n"
    + "xscr 120013\nxsqcup 10758\nxuplus 10756\nxutri 9651\nxvee 8897\nxwedge 8896\nyacute 253\n"
    + "yacy 1103\nycirc 375\nycy 1099\nyen 165\nyfr 120118\nyicy 1111\nyopf 120170\nyscr 120014\n"
    + "yucy 1102\nyuml 255\nzacute 378\nzcaron 382\nzcy 1079\nzdot 380\nzeetrf 8488\nzeta 950\n"
    + "zfr 120119\nzhcy 1078\nzigrarr 8669\nzopf 120171\nzscr 120015\nzwj 8205\nzwnj 8204\n"
  ;

  // ---------------------------------------------------------------------------
  // Markdown block structure (CommonMark 0.31.2, section 3)
  // ---------------------------------------------------------------------------
  //
  // A cmark-style line scanner: each line is matched against the stack of
  // open "container" blocks (document > blockquote > list > item > ...),
  // consuming their prefixes, then new blocks are attempted in order
  // (blockquote, ATX heading, fenced code, setext underline, thematic break,
  // list item, indented code). Whatever remains is appended to the deepest
  // open leaf, or becomes a lazy paragraph continuation.
  //
  // We do not implement HTML blocks as containers: raw HTML is a security
  // hazard for `innerHTML`, so HTML-block-looking paragraphs stay paragraphs
  // and get escaped by the inline pass like any other text. That also means
  // `<script>` cannot interrupt a paragraph the way the spec allows.

  /** Number of columns that count as an indented code block. */
  var MD_CODE_INDENT = 4;

  /** Characters that can begin a non-paragraph block (fast bail-out). */
  var MD_MAYBE_SPECIAL_RE = /^[#`~*+_=<>0-9\-]/;

  var MD_THEMATIC_RE = /^(?:\*[ \t]*){3,}$|^(?:_[ \t]*){3,}$|^(?:-[ \t]*){3,}$/;
  var MD_BULLET_RE = /^[*+\-]/;
  var MD_ORDERED_RE = /^(\d{1,9})([.)])/;
  var MD_ATX_RE = /^#{1,6}(?:[ \t]+|$)/;
  var MD_FENCE_RE = /^`{3,}(?!.*`)|^~{3,}/;
  var MD_CLOSE_FENCE_RE = /^(?:`{3,}|~{3,})(?=[ \t]*$)/;
  var MD_SETEXT_RE = /^(?:=+|-+)[ \t]*$/;
  var MD_NON_SPACE_RE = /[^ \t\f\v\r\n]/;

  /**
   * Create a block node of the given type.
   * @param {string} type document|blockquote|list|item|paragraph|heading|code|thematic
   */
  function mdNode(type) {
    return {
      type: type, parent: null, children: [], strings: [],
      open: true, info: '', literal: '',
      fenced: false, fenceChar: '', fenceLength: 0, fenceOffset: 0,
      level: 1, listData: null, tight: true, headingSetext: false,
      sourceLine: 0
    };
  }

  function mdParser() {
    var doc = mdNode('document');
    return {
      doc: doc, tip: doc, oldtip: doc,
      offset: 0, column: 0, nextNonspace: 0, nextNonspaceColumn: 0,
      indent: 0, indented: false, blank: false, partiallyConsumedTab: false,
      allClosed: true, lastMatchedContainer: doc,
      currentLine: '', lineNumber: 0, lastLineLength: 0,
      refmap: {}, lineOffsets: []
    };
  }

  /** Normalise endings and split into lines (trailing blank from final \n dropped). */
  function mdSplitInput(raw) {
    var text = String(raw).replace(/\r\n|\r(?!\n)/g, '\n').replace(/\r/g, '\n');
    var out = text.split('\n');
    if (out.length && out[out.length - 1] === '') out.pop();
    return out;
  }

  // --- parser cursor helpers ------------------------------------------------

  /** Find the next non-space/tab char; sets blank/indent/indented on p. */
  function mdFindNextNonspace(p) {
    var ln = p.currentLine, i = p.offset, cols = p.column, c;
    while ((c = ln.charAt(i)) !== '') {
      if (c === ' ') { i++; cols++; }
      else if (c === '\t') { i++; cols += 4 - (cols % 4); }
      else break;
    }
    p.blank = c === '' ;
    p.nextNonspace = i;
    p.nextNonspaceColumn = cols;
    p.indent = p.nextNonspaceColumn - p.column;
    p.indented = p.indent >= MD_CODE_INDENT;
  }

  /**
   * Advance the cursor by `count` columns (or characters when `columns` is
   * false). Handles partially consumed tabs, which stay in the line as the
   * equivalent spaces.
   */
  function mdAdvanceOffset(p, count, columns) {
    var ln = p.currentLine, charsToTab, advance, c;
    while (count > 0 && (c = ln.charAt(p.offset)) !== '') {
      if (c === '\t') {
        charsToTab = 4 - (p.column % 4);
        if (columns) {
          p.partiallyConsumedTab = charsToTab > count;
          advance = charsToTab > count ? count : charsToTab;
          p.column += advance;
          if (!p.partiallyConsumedTab) p.offset += 1;
          count -= advance;
        } else {
          p.partiallyConsumedTab = false;
          p.column += charsToTab;
          p.offset += 1;
          count -= 1;
        }
      } else {
        p.partiallyConsumedTab = false;
        p.offset += 1;
        p.column += 1;
        count -= 1;
      }
    }
  }

  function mdAdvanceNextNonspace(p) {
    p.offset = p.nextNonspace;
    p.column = p.nextNonspaceColumn;
    p.partiallyConsumedTab = false;
  }

  /**
   * Append the rest of the current line (from p.offset) to the tip. When a
   * tab was only partially consumed, the surviving columns are re-emitted as
   * spaces, exactly like cmark.
   */
  function mdAddLine(p) {
    var s = '';
    if (p.partiallyConsumedTab) {
      p.offset += 1; // skip the tab character itself
      var charsToTab = 4 - (p.column % 4);
      while (s.length < charsToTab) s += ' ';
    }
    p.tip.strings.push(s + p.currentLine.slice(p.offset));
  }

  function mdCanContain(type, child) {
    if (type === 'item' || type === 'blockquote' ||
        type === 'document' || type === 'list') {
      if (type === 'list') return child === 'item';
      return child !== 'item';
    }
    return false;
  }

  function mdAcceptsLines(type) {
    return type === 'paragraph' || type === 'code';
  }

  /** Close every block from tip down to (excluding) `lastMatched`. */
  function mdCloseUnmatched(p) {
    if (p.allClosed) return;
    while (p.oldtip !== p.lastMatchedContainer) {
      mdFinalize(p, p.oldtip, p.lineNumber - 1);
      p.oldtip = p.oldtip.parent;
    }
    p.allClosed = true;
  }

  /**
   * Add a child block of `tag` under the tip, finalising any tip that cannot
   * contain it first.
   */
  function mdAddChild(p, tag) {
    while (!mdCanContain(p.tip.type, tag)) mdFinalize(p, p.tip, p.lineNumber - 1);
    var node = mdNode(tag);
    node.parent = p.tip;
    node.sourceLine = p.lineNumber;
    p.tip.children.push(node);
    p.tip = node;
    return node;
  }

  // --- container continue checks -------------------------------------------
  // 0 = matched, 1 = not matched, 2 = line fully handled (fence close)

  function mdContinueBlock(p, container) {
    var ln = p.currentLine, t = container.type;

    if (t === 'document' || t === 'list') return 0;

    if (t === 'blockquote') {
      if (!p.indented && ln.charAt(p.nextNonspace) === '>') {
        mdAdvanceNextNonspace(p);
        mdAdvanceOffset(p, 1, false);
        if (ln.charAt(p.offset) === ' ' || ln.charAt(p.offset) === '\t') {
          mdAdvanceOffset(p, 1, true);
        }
        return 0;
      }
      return 1;
    }

    if (t === 'item') {
      if (p.blank) {
        if (!container.children.length) return 1; // blank after empty item
        mdAdvanceNextNonspace(p);
        return 0;
      }
      var need = container.listData.markerOffset + container.listData.padding;
      if (p.indent >= need) {
        mdAdvanceOffset(p, need, true);
        return 0;
      }
      return 1;
    }

    if (t === 'code') {
      if (container.fenced) {
        var rest = ln.slice(p.nextNonspace);
        if (p.indent <= 3 && ln.charAt(p.nextNonspace) === container.fenceChar &&
            MD_CLOSE_FENCE_RE.test(rest) && rest.match(MD_CLOSE_FENCE_RE)[0].length >= container.fenceLength) {
          mdFinalize(p, container, p.lineNumber);
          return 2;
        }
        // skip up to fenceOffset leading spaces
        var i = container.fenceOffset;
        while (i > 0 && (ln.charAt(p.offset) === ' ' || ln.charAt(p.offset) === '\t')) {
          mdAdvanceOffset(p, 1, true);
          i--;
        }
        return 0;
      }
      if (p.indent >= MD_CODE_INDENT) { mdAdvanceOffset(p, MD_CODE_INDENT, true); return 0; }
      if (p.blank) { mdAdvanceNextNonspace(p); return 0; }
      return 1;
    }

    if (t === 'heading' || t === 'thematic') return 1;
    if (t === 'paragraph') return p.blank ? 1 : 0;
    return 1;
  }

  /**
   * True when a blank line separates `node` from its following sibling (used
   * for the tight/loose list decision).
   */
  function mdEndsWithBlank(node) {
    if (!node.parent) return false;
    var idx = node.parent.children.indexOf(node);
    var next = node.parent.children[idx + 1];
    if (!next) return false;
    return mdNodeEndLine(node) !== next.sourceLine - 1;
  }

  /** Last source line number consumed by a node (tracked during the scan). */
  function mdNodeEndLine(node) {
    return node.endLine == null ? node.sourceLine : node.endLine;
  }

  // --- block starts ----------------------------------------------------------

  /**
   * Parse a list marker at the cursor. Returns the marker data or null.
   * Mirrors cmark: the marker itself, then 1-4 spaces (5+ or a blank rest
   * means "content starts one space after the marker").
   */
  function mdParseListMarker(p, container) {
    var rest = p.currentLine.slice(p.nextNonspace);
    var data = { type: null, tight: true, bulletChar: null, start: null,
                delimiter: null, padding: null, markerOffset: p.indent };
    var m, nextc;
    if (p.indent >= 4) return null;
    if ((m = rest.match(MD_BULLET_RE))) {
      data.type = 'bullet';
      data.bulletChar = m[0].charAt(0);
    } else if ((m = rest.match(MD_ORDERED_RE)) &&
              (container.type !== 'paragraph' || Number(m[1]) === 1)) {
      data.type = 'ordered';
      data.start = parseInt(m[1], 10);
      data.delimiter = m[2];
    } else {
      return null;
    }
    nextc = p.currentLine.charAt(p.nextNonspace + m[0].length);
    if (!(nextc === '' || nextc === ' ' || nextc === '\t')) return null;
    if (container.type === 'paragraph' &&
        !MD_NON_SPACE_RE.test(p.currentLine.slice(p.nextNonspace + m[0].length))) {
      return null;
    }
    mdAdvanceNextNonspace(p);
    mdAdvanceOffset(p, m[0].length, true);
    var spacesStartCol = p.column, spacesStartOffset = p.offset;
    do {
      mdAdvanceOffset(p, 1, true);
      nextc = p.currentLine.charAt(p.offset);
    } while (p.column - spacesStartCol < 5 && (nextc === ' ' || nextc === '\t'));
    var blankItem = p.currentLine.charAt(p.offset) === '' && p.offset >= p.currentLine.length;
    var spacesAfterMarker = p.column - spacesStartCol;
    if (spacesAfterMarker >= 5 || spacesAfterMarker < 1 || blankItem) {
      data.padding = m[0].length + 1;
      p.column = spacesStartCol;
      p.offset = spacesStartOffset;
      var c2 = p.currentLine.charAt(p.offset);
      if (c2 === ' ' || c2 === '\t') mdAdvanceOffset(p, 1, true);
    } else {
      data.padding = m[0].length + spacesAfterMarker;
    }
    return data;
  }

  function mdListsMatch(a, b) {
    return a.type === b.type && a.delimiter === b.delimiter &&
          a.bulletChar === b.bulletChar;
  }

  /**
   * Try to start a new block at the cursor. Returns 0 (no match), 1 (opened a
   * container, keep trying), or 2 (opened a leaf; the line is spent).
   */
  function mdTryBlockStart(p, container) {
    var ln = p.currentLine, m, node;

    // block quote
    if (!p.indented && ln.charAt(p.nextNonspace) === '>') {
      mdAdvanceNextNonspace(p);
      mdAdvanceOffset(p, 1, false);
      if (ln.charAt(p.offset) === ' ' || ln.charAt(p.offset) === '\t') {
        mdAdvanceOffset(p, 1, true);
      }
      mdCloseUnmatched(p);
      mdAddChild(p, 'blockquote');
      return 1;
    }

    // ATX heading
    if (!p.indented && (m = ln.slice(p.nextNonspace).match(MD_ATX_RE))) {
      mdAdvanceNextNonspace(p);
      mdAdvanceOffset(p, m[0].length, false);
      mdCloseUnmatched(p);
      node = mdAddChild(p, 'heading');
      node.level = m[0].replace(/[ \t]/g, '').length;
      node.strings.push(
        ln.slice(p.offset)
          .replace(/^[ \t]*#+[ \t]*$/, '')
          .replace(/[ \t]+#+[ \t]*$/, ''));
      mdAdvanceOffset(p, ln.length - p.offset, false);
      return 2;
    }

    // fenced code block
    if (!p.indented && (m = ln.slice(p.nextNonspace).match(MD_FENCE_RE))) {
      mdCloseUnmatched(p);
      node = mdAddChild(p, 'code');
      node.fenced = true;
      node.fenceLength = m[0].length;
      node.fenceChar = m[0].charAt(0);
      node.fenceOffset = p.indent;
      mdAdvanceNextNonspace(p);
      mdAdvanceOffset(p, m[0].length, false);
      return 2;
    }

    // setext heading underline
    if (!p.indented && container.type === 'paragraph' &&
        (m = ln.slice(p.nextNonspace).match(MD_SETEXT_RE))) {
      mdCloseUnmatched(p);
      var pos;
      var joined = container.strings.join('\n');
      while (joined.charAt(0) === '[' && (pos = mdParseReference(joined, p.refmap)) > 0) {
        joined = joined.slice(pos);
      }
      container.strings = joined.length ? [joined] : [];
      var content = container.strings.join('\n');
      if (content.length > 0) {
        node = mdNode('heading');
        node.level = m[0].charAt(0) === '=' ? 1 : 2;
        node.headingSetext = true;
        node.strings = container.strings.slice();
        node.sourceLine = container.sourceLine;
        node.endLine = p.lineNumber;
        node.parent = container.parent;
        var ci = container.parent.children.indexOf(container);
        container.parent.children[ci] = node;
        p.tip = node;
        mdAdvanceOffset(p, ln.length - p.offset, false);
        return 2;
      }
      return 0;
    }

    // thematic break
    if (!p.indented && MD_THEMATIC_RE.test(ln.slice(p.nextNonspace))) {
      mdCloseUnmatched(p);
      mdAddChild(p, 'thematic');
      mdAdvanceOffset(p, ln.length - p.offset, false);
      return 2;
    }

    // list item
    var data;
    if ((!p.indented || container.type === 'list') && (data = mdParseListMarker(p, container))) {
      mdCloseUnmatched(p);
      if (p.tip.type !== 'list' || !mdListsMatch(container.listData, data)) {
        var list = mdAddChild(p, 'list');
        list.listData = data;
        container = list;
      }
      var item = mdAddChild(p, 'item');
      item.listData = data;
      return 1;
    }

    // indented code block
    if (p.indented && p.tip.type !== 'paragraph' && !p.blank) {
      mdAdvanceOffset(p, MD_CODE_INDENT, true);
      mdCloseUnmatched(p);
      mdAddChild(p, 'code');
      return 2;
    }

    return 0;
  }


  // --- line incorporation and finalisation -----------------------------------

  /**
   * Process one source line into the open block tree: match container
   * prefixes, try to open new blocks, then hand the remainder to a leaf.
   */
  function mdIncorporateLine(p, ln) {
    var container = p.doc, lastChild, allMatched = true, res;

    p.oldtip = p.tip;
    p.offset = 0;
    p.column = 0;
    p.blank = false;
    p.partiallyConsumedTab = false;
    p.lineNumber += 1;
    p.currentLine = ln.indexOf('\u0000') >= 0 ? ln.replace(/\u0000/g, '\uFFFD') : ln;

    // 1. Match the open containers' prefixes, deepest first.
    while (container.children.length) {
      lastChild = container.children[container.children.length - 1];
      if (!lastChild.open) break;
      container = lastChild;
      mdFindNextNonspace(p);
      res = mdContinueBlock(p, container);
      if (res === 2) { p.lastLineLength = ln.length; return; }
      if (res === 1) { allMatched = false; container = container.parent; break; }
    }

    p.allClosed = container === p.oldtip;
    p.lastMatchedContainer = container;

    // 2. Unless we already sit in a leaf that accepts lines, try block starts.
    var matchedLeaf = container.type !== 'paragraph' && mdAcceptsLines(container.type);
    while (!matchedLeaf) {
      mdFindNextNonspace(p);
      if (!p.indented && !MD_MAYBE_SPECIAL_RE.test(p.currentLine.slice(p.nextNonspace))) {
        mdAdvanceNextNonspace(p);
        break;
      }
      res = mdTryBlockStart(p, container);
      if (res === 1) { container = p.tip; continue; }
      if (res === 2) { container = p.tip; matchedLeaf = true; break; }
      mdAdvanceNextNonspace(p);
      break;
    }

    // 3. The remainder is line content for the tip.
    if (!p.allClosed && !p.blank && p.tip.type === 'paragraph') {
      mdAddLine(p); // lazy paragraph continuation
    } else {
      mdCloseUnmatched(p);
      if (mdAcceptsLines(container.type)) {
        mdAddLine(p);
      } else if (p.offset < p.currentLine.length && !p.blank) {
        mdAddChild(p, 'paragraph');
        mdAdvanceNextNonspace(p);
        mdAddLine(p);
      }
    }
    p.lastLineLength = ln.length;
  }

  /**
   * Close a block: extract fenced info strings / indented-code literals, work
   * out list tightness, peel link reference definitions off paragraphs and
   * record which source line the block ended on.
   */
  function mdFinalize(p, block, endLine) {
    var above = block.parent;
    block.open = false;
    block.endLine = endLine == null ? p.lineNumber : endLine;

    if (block.type === 'code') {
      if (block.fenced) {
        var content = block.strings.join('\n');
        var nl = content.indexOf('\n');
        var firstLine = nl >= 0 ? content.slice(0, nl) : content;
        var rest = nl >= 0 ? content.slice(nl + 1) : '';
        block.info = mdUnescapeString(firstLine.replace(/^[ \t]+/, '').replace(/[ \t]+$/, ''));
        // cmark keeps the final newline of the block's content
        block.literal = rest.length ? rest + '\n' : (block.strings.length > 1 ? '\n' : '');
      } else {
        var lines = block.strings.slice();
        while (lines.length && !MD_NON_SPACE_RE.test(lines[lines.length - 1])) lines.pop();
        block.literal = lines.join('\n') + '\n';
      }
      block.strings = [];
    }

    if (block.type === 'paragraph') {
      // Reference definitions live at the start of paragraphs only; each
      // consumed definition must advance or we stop.
      var txt = block.strings.join('\n');
      var pos;
      while (txt.charAt(0) === '[' && (pos = mdParseReference(txt, p.refmap)) > 0) {
        txt = txt.slice(pos);
      }
      block.strings = txt.length ? [txt] : [];
      if (!txt.length) mdRemoveFromParent(block);
    }

    if ((block.type === 'item' || block.type === 'list') && block.children.length) {
      // items and lists end where their last child ends (a trailing blank
      // line is not part of them) — this drives the tight/loose rule.
      // Blockquotes deliberately keep the line their `>` marker last
      // appeared on: `  >` is not a blank line for these purposes.
      block.endLine = block.children[block.children.length - 1].endLine;
    }

    if (block.type === 'list') {
      block.tight = true;
      for (var i = 0; i < block.children.length; i++) {
        var item = block.children[i];
        if (i < block.children.length - 1 && mdEndsWithBlank(item)) { block.tight = false; break; }
        for (var j = 0; j < item.children.length; j++) {
          if (j < item.children.length - 1 && mdEndsWithBlank(item.children[j])) { block.tight = false; break; }
        }
        if (!block.tight) break;
      }
    }

    p.tip = above;
  }

  /** Detach a node (used when a paragraph turns out to be all references). */
  function mdRemoveFromParent(node) {
    if (!node.parent) return;
    var i = node.parent.children.indexOf(node);
    if (i >= 0) node.parent.children.splice(i, 1);
  }

  /** Parse the whole input into a block tree. */
  function mdParseDocument(raw) {
    var p = mdParser();
    var lines = mdSplitInput(raw);
    for (var i = 0; i < lines.length; i++) mdIncorporateLine(p, lines[i]);
    while (p.tip && p.tip.type !== 'document') mdFinalize(p, p.tip, lines.length);
    return p;
  }


  // --- shared inline regexes / URI handling -----------------------------------

  var MD_LINK_TITLE_RE = /(?:")([^"]*)(?:")|(?:')([^']*)(?:')/;

  /**
   * Scan a link title at `subject[pos]` without regex backtracking: a quoted
   * run (with `\"`-style escapes) or a parenthesised run. Returns
   * `{ text, len }` or null.
   * @param {string} subject
   * @param {number} pos
   * @returns {?{text: string, len: number}}
   */
  function mdScanLinkTitle(subject, pos) {
    var start = pos, q = subject.charAt(pos);
    if (q !== '"' && q !== "'" && q !== '(') return null;
    var close = q === '(' ? ')' : q;
    var i = pos + 1;
    while (i < subject.length) {
      var ch = subject.charAt(i);
      if (ch === '\\' && subject.charAt(i + 1) !== '' &&
          MD_ESCAPABLE.indexOf(subject.charAt(i + 1)) >= 0) { i += 2; continue; }
      if (ch === close) {
        return { text: subject.slice(start + 1, i), len: i + 1 - start };
      }
      if (ch === '\n' && subject.charAt(i + 1) === '\n') return null; // blank line ends it
      i++;
    }
    return null;
  }
  var MD_LINK_DEST_BRACES_RE = /^<(?:[^<>\n\\\x00]|\\.)*>/;
  /**
   * Match a raw HTML open/close tag at subject[pos] using a linear scan
   * (the equivalent regex backtracks catastrophically on malformed input).
   * Returns the matched text or null. SECURITY: callers render this escaped.
   * @param {string} subject
   * @param {number} pos
   * @returns {?string}
   */
  function mdScanHtmlTag(subject, pos) {
    var i = pos;
    if (subject.charAt(i) !== '<') return null;
    i++;
    var closing = subject.charAt(i) === '/';
    if (closing) i++;
    if (!/[A-Za-z]/.test(subject.charAt(i))) return null;
    var start = i;
    while (i < subject.length && /[A-Za-z0-9-]/.test(subject.charAt(i))) i++;
    if (i === start) return null;
    if (closing) {
      while (i < subject.length && /[ \t\n]/.test(subject.charAt(i))) i++;
      if (subject.charAt(i) === '>') return subject.slice(pos, i + 1);
      return null;
    }
    // attributes
    while (i < subject.length) {
      var wsStart = i;
      while (i < subject.length && /[ \t\n]/.test(subject.charAt(i))) i++;
      if (subject.charAt(i) === '>') return subject.slice(pos, i + 1);
      if (subject.charAt(i) === '/' && subject.charAt(i + 1) === '>') return subject.slice(pos, i + 2);
      if (i === wsStart) return null; // attribute must be preceded by space
      var an = i;
      while (i < subject.length && !/[\s/=><]/.test(subject.charAt(i))) i++;
      if (i === an) return null;
      var eq = i;
      while (i < subject.length && /[ \t\n]/.test(subject.charAt(i))) i++;
      if (subject.charAt(i) !== '=') { i = eq; continue; }
      i++;
      while (i < subject.length && /[ \t\n]/.test(subject.charAt(i))) i++;
      var q = subject.charAt(i);
      if (q === '"' || q === "'") {
        i++;
        var endq = subject.indexOf(q, i);
        if (endq < 0) return null;
        i = endq + 1;
      } else {
        var v = i;
        while (i < subject.length && !/[\s>]/.test(subject.charAt(i))) i++;
        if (i === v) return null;
      }
    }
    return null;
  }

  /**
   * CommonMark's URL normalisation: percent-encode every character that is
   * not in the RFC 3986 "unreserved + reserved + '#' escape" set. Non-ASCII
   * characters become UTF-8 percent-escapes (like encodeURIComponent).
   * @param {string} uri
   * @returns {string}
   */
  function mdNormalizeUri(uri) {
    if (!uri) return '';
    var out = '', ch, i;
    for (i = 0; i < uri.length; i++) {
      ch = uri.charAt(i);
      if (MD_URI_SAFE_RE.test(ch)) { out += ch; continue; }
      // encode one code point (surrogate pairs together)
      var cp = uri.charCodeAt(i);
      var str = ch;
      if (cp >= 0xD800 && cp <= 0xDBFF && i + 1 < uri.length) {
        str += uri.charAt(i + 1);
        i++;
      }
      out += encodeURIComponent(str);
    }
    return out;
  }

  /** URI characters kept literally (unreserved, reserved and '%'). */
  var MD_URI_SAFE_RE = /^[A-Za-z0-9;,\/?:@&=+\$\-_\.!~\*'\(\)%#]$/;

  /**
   * Normalise a link label for reference lookup: strip brackets, trim,
   * collapse internal whitespace, case-fold.
   * @param {string} label raw `[...]` including brackets
   * @returns {string}
   */
  function mdNormalizeReference(label) {
    return label.slice(1, label.length - 1).trim()
      .replace(/[ \t\r\n]+/g, ' ')
      .toLowerCase().toUpperCase();
  }

  /**
   * Parse one link reference definition from the start of `s`. Returns the
   * number of characters consumed, or 0.
   * @param {string} s
   * @param {Object} refmap
   * @returns {number}
   */
  function mdParseReference(s, refmap) {
    var subject = s, pos = 0, rawlabel, dest, title = null, startpos = 0;

    function peek2() { return pos < subject.length ? subject.charAt(pos) : ''; }
    function match2(re) {
      var m = re.exec(subject.slice(pos));
      if (m) pos += m[0].length;
      return m;
    }
    function spnl2() { match2(/^ *(?:\n *)?/); }

    // label: one bracketed run, no nested brackets, no blank line
    var depth = 0, i = 0, ch;
    while (i < subject.length) {
      ch = subject.charAt(i);
      if (ch === '\\') { i += 2; continue; }
      if (ch === '[') { depth++; if (depth > 1) return 0; }
      else if (ch === ']') break;
      i++;
    }
    if (depth !== 1 || subject.charAt(i) !== ']') return 0;
    rawlabel = subject.slice(0, i + 1);
    if (rawlabel.length > 1001) return 0;
    pos = i + 1;
    if (peek2() !== ':') return 0;
    pos++;
    spnl2();
    // destination
    var m2 = match2(MD_LINK_DEST_BRACES_RE);
    if (m2) {
      dest = mdNormalizeUri(mdUnescapeString(m2[0].slice(1, -1)));
    } else {
      var save = pos, openparens = 0, c;
      while ((c = peek2()) !== '') {
        if (c === '\\' && subject.charAt(pos + 1) !== '' &&
            MD_ESCAPABLE.indexOf(subject.charAt(pos + 1)) >= 0) {
          pos += 1;
          if (peek2() !== '') pos += 1;
        } else if (c === '(') { pos++; openparens++; }
        else if (c === ')') { if (openparens < 1) break; pos++; openparens--; }
        else if (MD_WS_CHAR_RE.test(c)) break;
        else pos++;
      }
      if (pos === save && c !== ')') return 0;
      if (openparens !== 0) return 0;
      dest = mdNormalizeUri(mdUnescapeString(subject.slice(save, pos)));
    }
    var beforetitle = pos;
    spnl2();
    if (pos !== beforetitle) {
      var t = mdScanLinkTitle(subject, pos);
      if (t) { title = mdUnescapeString(t.text); pos += t.len; }
    }
    if (title === null) pos = beforetitle;
    // must be at end of line
    var atLineEnd = match2(/^ *(?:\n|$)/) !== null;
    if (!atLineEnd) {
      if (title !== null) {
        title = null;
        pos = beforetitle;
        atLineEnd = match2(/^ *(?:\n|$)/) !== null;
      }
      if (!atLineEnd) return 0;
    }
    var normlabel = mdNormalizeReference(rawlabel);
    if (normlabel === '') return 0;
    if (!refmap[normlabel]) {
      refmap[normlabel] = { destination: dest, title: title == null ? '' : title };
    }
    return pos;
  }

  // ---------------------------------------------------------------------------
  // Markdown inline parsing (CommonMark 0.31.2, section 6)
  // ---------------------------------------------------------------------------
  //
  // A hand-rolled scanner over paragraph/heading content: plain text runs are
  // copied until a special character (\n ` [ ] \ ! < & * _), then that
  // character's handler runs. Emphasis is resolved afterwards with the
  // delimiter-run algorithm from the spec: openers are searched bottom-up
  // with the "rule of 3" and openers_bottom optimisation; leftover delimiter
  // text stays literal. Links and images share a bracket stack; links may
  // not contain links.
  //
  // Inline nodes form a doubly-linked list (firstChild/lastChild/next/prev on
  // the parent) exactly like the block tree: process_emphasis has to splice
  // nodes out of the middle, which is painful with arrays.

  var MD_ESCAPABLE = '!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~';
  var MD_ASCII_PUNCT_TEST_RE = /^[!-/:-@[-`{-~]$/;
  var MD_ENTITY_HERE_RE = /^&(?:#x[a-f0-9]{1,6}|#[0-9]{1,7}|[a-z][a-z0-9]{1,31});/i;
  var MD_TICKS_HERE_RE = /^`+/;
  var MD_WS_CHAR_RE = /[ \t\n\x0b\x0c\x0d]/;
  var MD_FINAL_SPACE_RE = / *$/;

  /**
   * Unicode punctuation/symbol code points (categories P* and S*) above the
   * ASCII range, as "lo-hi" hex ranges (binary-searched). Needed for the
   * left/right-flanking rules on non-ASCII text; ES5 has no \p{P}.
   */
  var MD_UNICODE_PUNCT_RANGES = [
    'A1-A9','AB-AC','AE-B1','B4','B6-B8','BB','BF','D7','F7','2C2-2C5','2D2-2DF','2E5-2EB',
    '2ED','2EF-2FF','375','37E','384-385','387','3F6','482','55A-55F','589-58A','58D-58F','5BE',
    '5C0','5C3','5C6','5F3-5F4','606-60F','61B','61D-61F','66A-66D','6D4','6DE','6E9','6FD-6FE',
    '700-70D','7F6-7F9','7FE-7FF','830-83E','85E','888','964-965','970','9F2-9F3','9FA-9FB',
    '9FD','A76','AF0-AF1','B70','BF3-BFA','C77','C7F','C84','D4F','D79','DF4','E3F','E4F',
    'E5A-E5B','F01-F17','F1A-F1F','F34','F36','F38','F3A-F3D','F85','FBE-FC5','FC7-FCC',
    'FCE-FDA','104A-104F','109E-109F','10FB','1360-1368','1390-1399','1400','166D-166E',
    '169B-169C','16EB-16ED','1735-1736','17D4-17D6','17D8-17DB','1800-180A','1940','1944-1945',
    '19DE-19FF','1A1E-1A1F','1AA0-1AA6','1AA8-1AAD','1B4E-1B4F','1B5A-1B6A','1B74-1B7F',
    '1BFC-1BFF','1C3B-1C3F','1C7E-1C7F','1CC0-1CC7','1CD3','1FBD','1FBF-1FC1','1FCD-1FCF',
    '1FDD-1FDF','1FED-1FEF','1FFD-1FFE','2010-2027','2030-205E','207A-207E','208A-208E',
    '20A0-20C0','2100-2101','2103-2106','2108-2109','2114','2116-2118','211E-2123','2125',
    '2127','2129','212E','213A-213B','2140-2144','214A-214D','214F','218A-218B','2190-2429',
    '2440-244A','249C-24E9','2500-2775','2794-2B73','2B76-2B95','2B97-2BFF','2CE5-2CEA',
    '2CF9-2CFC','2CFE-2CFF','2D70','2E00-2E2E','2E30-2E5D','2E80-2E99','2E9B-2EF3','2F00-2FD5',
    '2FF0-2FFF','3001-3004','3008-3020','3030','3036-3037','303D-303F','309B-309C','30A0',
    '30FB','3190-3191','3196-319F','31C0-31E5','31EF','3200-321E','322A-3247','3250',
    '3260-327F','328A-32B0','32C0-33FF','4DC0-4DFF','A490-A4C6','A4FE-A4FF','A60D-A60F','A673',
    'A67E','A6F2-A6F7','A700-A716','A720-A721','A789-A78A','A828-A82B','A836-A839','A874-A877',
    'A8CE-A8CF','A8F8-A8FA','A8FC','A92E-A92F','A95F','A9C1-A9CD','A9DE-A9DF','AA5C-AA5F',
    'AA77-AA79','AADE-AADF','AAF0-AAF1','AB5B','AB6A-AB6B','ABEB','FB29','FBB2-FBC2',
    'FD3E-FD4F','FDCF','FDFC-FDFF','FE10-FE19','FE30-FE52','FE54-FE66','FE68-FE6B','FF01-FF0F',
    'FF1A-FF20','FF3B-FF40','FF5B-FF65','FFE0-FFE6','FFE8-FFEE','FFFC-FFFD','10100-10102',
    '10137-1013F','10179-10189','1018C-1018E','10190-1019C','101A0','101D0-101FC','1039F',
    '103D0','1056F','10857','10877-10878','1091F','1093F','10A50-10A58','10A7F','10AC8',
    '10AF0-10AF6','10B39-10B3F','10B99-10B9C','10D6E','10D8E-10D8F','10EAD','10F55-10F59',
    '10F86-10F89','11047-1104D','110BB-110BC','110BE-110C1','11140-11143','11174-11175',
    '111C5-111C8','111CD','111DB','111DD-111DF','11238-1123D','112A9','113D4-113D5',
    '113D7-113D8','1144B-1144F','1145A-1145B','1145D','114C6','115C1-115D7','11641-11643',
    '11660-1166C','116B9','1173C-1173F','1183B','11944-11946','119E2','11A3F-11A46',
    '11A9A-11A9C','11A9E-11AA2','11B00-11B09','11BE1','11C41-11C45','11C70-11C71','11EF7-11EF8',
    '11F43-11F4F','11FD5-11FF1','11FFF','12470-12474','12FF1-12FF2','16A6E-16A6F','16AF5',
    '16B37-16B3F','16B44-16B45','16D6D-16D6F','16E97-16E9A','16FE2','1BC9C','1BC9F',
    '1CC00-1CCEF','1CD00-1CEB3','1CF50-1CFC3','1D000-1D0F5','1D100-1D126','1D129-1D164',
    '1D16A-1D16C','1D183-1D184','1D18C-1D1A9','1D1AE-1D1EA','1D200-1D241','1D245','1D300-1D356',
    '1D6C1','1D6DB','1D6FB','1D715','1D735','1D74F','1D76F','1D789','1D7A9','1D7C3',
    '1D800-1D9FF','1DA37-1DA3A','1DA6D-1DA74','1DA76-1DA83','1DA85-1DA8B','1E14F','1E2FF',
    '1E5FF','1E95E-1E95F','1ECAC','1ECB0','1ED2E','1EEF0-1EEF1','1F000-1F02B','1F030-1F093',
    '1F0A0-1F0AE','1F0B1-1F0BF','1F0C1-1F0CF','1F0D1-1F0F5','1F10D-1F1AD','1F1E6-1F202',
    '1F210-1F23B','1F240-1F248','1F250-1F251','1F260-1F265','1F300-1F6D7','1F6DC-1F6EC',
    '1F6F0-1F6FC','1F700-1F776','1F77B-1F7D9','1F7E0-1F7EB','1F7F0','1F800-1F80B','1F810-1F847',
    '1F850-1F859','1F860-1F887','1F890-1F8AD','1F8B0-1F8BB','1F8C0-1F8C1','1F900-1FA53',
    '1FA60-1FA6D','1FA70-1FA7C','1FA80-1FA89','1FA8F-1FAC6','1FACE-1FADC','1FADF-1FAE9',
    '1FAF0-1FAF8','1FB00-1FB92','1FB94-1FBEF',
  ];

  function mdIsUnicodePunct(cp) {
    var lo = 0, hi = MD_UNICODE_PUNCT_RANGES.length - 1;
    while (lo <= hi) {
      var mid = (lo + hi) >> 1;
      var dash = MD_UNICODE_PUNCT_RANGES[mid].indexOf('-');
      var a, b;
      if (dash < 0) { a = b = parseInt(MD_UNICODE_PUNCT_RANGES[mid], 16); }
      else {
        a = parseInt(MD_UNICODE_PUNCT_RANGES[mid].slice(0, dash), 16);
        b = parseInt(MD_UNICODE_PUNCT_RANGES[mid].slice(dash + 1), 16);
      }
      if (cp < a) hi = mid - 1;
      else if (cp > b) lo = mid + 1;
      else return true;
    }
    return false;
  }

  function mdIsPunct(ch) {
    if (ch === '' || ch == null) return false;
    if (MD_ASCII_PUNCT_TEST_RE.test(ch)) return true;
    var cp = ch.charCodeAt(0);
    if (cp < 0xA1) return false;
    // combine a surrogate pair into one code point
    if (cp >= 0xD800 && cp <= 0xDBFF && ch.length > 1) {
      var lo = ch.charCodeAt(1);
      if (lo >= 0xDC00 && lo <= 0xDFFF) cp = 0x10000 + ((cp - 0xD800) << 10) + (lo - 0xDC00);
    }
    return mdIsUnicodePunct(cp);
  }

  /**
   * String.fromCharCode with surrogate-pair support.
   * @param {number} cp
   * @returns {string}
   */
  function mdFromCodePoint(cp) {
    if (cp == null || cp < 0 || cp > 0x10FFFF || (cp >= 0xD800 && cp <= 0xDFFF)) return '\uFFFD';
    if (cp <= 0xFFFF) return String.fromCharCode(cp);
    var c = cp - 0x10000;
    return String.fromCharCode(0xD800 + (c >> 10), 0xDC00 + (c & 0x3FF));
  }

  var mdEntityMap = null;

  /** Parse MD_ENTITIES_PACKED into a name -> string map (once). */
  function mdGetEntityMap() {
    if (mdEntityMap) return mdEntityMap;
    var map = {}, recs = MD_ENTITIES_PACKED.split('\n');
    for (var i = 0; i < recs.length; i++) {
      var sp = recs[i].indexOf(' ');
      if (sp < 0) continue;
      var cps = recs[i].slice(sp + 1).split(',');
      var s = '';
      for (var j = 0; j < cps.length; j++) s += mdFromCodePoint(parseInt(cps[j], 10));
      map[recs[i].slice(0, sp)] = s;
    }
    mdEntityMap = map;
    return map;
  }

  /**
   * Resolve an entity reference at the start of `s`; null when invalid.
   * @param {string} s
   * @returns {?string}
   */
  function mdReplaceEntity(s) {
    var m = s.match(MD_ENTITY_HERE_RE);
    if (!m) return null;
    var body = m[0].slice(1, -1);
    if (body.charAt(0) === '#') {
      var num = body.charAt(1) === 'x' || body.charAt(1) === 'X'
        ? parseInt(body.slice(2), 16)
        : parseInt(body.slice(1), 10);
      if (isNaN(num) || num === 0 || num > 0x10FFFF) return '\uFFFD';
      return mdFromCodePoint(num);
    }
    var map = mdGetEntityMap();
    return Object.prototype.hasOwnProperty.call(map, body) ? map[body] : null;
  }

  /**
   * Replace backslash escapes and entity references (spec 2.2/2.3). Used on
   * link destinations, titles, labels and code info strings.
   * @param {string} s
   * @returns {string}
   */
  function mdUnescapeString(s) {
    if (s.indexOf('\\') < 0 && s.indexOf('&') < 0) return s;
    var out = '', i = 0, ch, rep, m;
    while (i < s.length) {
      ch = s.charAt(i);
      if (ch === '\\' && MD_ESCAPABLE.indexOf(s.charAt(i + 1)) >= 0) {
        out += s.charAt(i + 1);
        i += 2;
        continue;
      }
      if (ch === '&') {
        rep = mdReplaceEntity(s.slice(i));
        if (rep !== null) {
          m = s.slice(i).match(MD_ENTITY_HERE_RE);
          out += rep;
          i += m[0].length;
          continue;
        }
      }
      out += ch;
      i++;
    }
    return out;
  }

  // --- inline nodes -----------------------------------------------------------

  /**
   * Create an inline node. Types: text, softbreak, code, emph, strong,
   * link, image, html (escaped text).
   */
  function mdInlineNode(type, literal) {
    return { type: type, literal: literal == null ? '' : literal,
            parent: null, next: null, prev: null,
            firstChild: null, lastChild: null,
            destination: null, title: null, hardBreak: false };
  }

  function mdAppendChild(parent, node) {
    node.parent = parent;
    node.prev = parent.lastChild;
    if (parent.lastChild) parent.lastChild.next = node;
    else parent.firstChild = node;
    parent.lastChild = node;
    return node;
  }

  function mdUnlink(node) {
    if (node.prev) node.prev.next = node.next;
    else if (node.parent) node.parent.firstChild = node.next;
    if (node.next) node.next.prev = node.prev;
    else if (node.parent) node.parent.lastChild = node.prev;
    node.parent = null;
    node.next = null;
    node.prev = null;
  }

  function mdInsertAfter(node, sibling) {
    sibling.parent = node.parent;
    sibling.next = node.next;
    sibling.prev = node;
    if (node.next) node.next.prev = sibling;
    else if (node.parent) node.parent.lastChild = sibling;
    node.next = sibling;
  }

  /** Collect a node's children into an array (for rendering). */
  function mdChildren(node) {
    var out = [], c = node.firstChild;
    while (c) { out.push(c); c = c.next; }
    return out;
  }

  // --- the subject scanner ----------------------------------------------------

  /**
   * Parse the inline content of one leaf block.
   * @param {string} subject already-trimmed paragraph/heading text
   * @param {Object} refmap normalised-label -> { destination, title }
   * @returns {Object} a synthetic parent whose children are the inlines
   */
  function mdParseInlines(subject, refmap) {
    var block = { parent: null, next: null, prev: null,
                  firstChild: null, lastChild: null, type: 'root' };
    var pos = 0;
    var delimiters = null;  // linked list, newest first
    var brackets = null;    // linked list, newest first

    function text(s) { return mdAppendChild(block, mdInlineNode('text', s)); }
    function peek() { return pos < subject.length ? subject.charAt(pos) : ''; }
    function match(re) {
      var m = re.exec(subject.slice(pos));
      if (m) pos += m[0].length;
      return m;
    }
    function spnl() {
      match(/^ *(?:\n *)?/);
      return true;
    }

    // -- emphasis delimiter bookkeeping --

    function scanDelims(cc) {
      var numdelims = 0, startpos = pos;
      while (peek() === cc) { numdelims++; pos++; }
      // adjacent characters, taking surrogate pairs as one character
      var charBefore = startpos === 0 ? '\n'
        : (mdIsHighSurrogate(subject.charAt(startpos - 1))
            ? subject.slice(startpos - 2, startpos)
            : subject.charAt(startpos - 1));
      var nextCh = peek();
      var charAfter = nextCh === '' ? '\n'
        : (mdIsHighSurrogate(nextCh) ? subject.substr(pos, 2) : nextCh);
      var afterWs = /^\s/.test(charAfter);
      var beforeWs = /^\s/.test(charBefore);
      var afterPunct = mdIsPunct(charAfter);
      var beforePunct = mdIsPunct(charBefore);
      var leftFlanking = !afterWs && (!afterPunct || beforeWs || beforePunct);
      var rightFlanking = !beforeWs && (!beforePunct || afterWs || afterPunct);
      var canOpen, canClose;
      if (cc === '_') {
        canOpen = leftFlanking && (!rightFlanking || beforePunct);
        canClose = rightFlanking && (!leftFlanking || afterPunct);
      } else {
        canOpen = leftFlanking;
        canClose = rightFlanking;
      }
      pos = startpos;
      return { numdelims: numdelims, canOpen: canOpen, canClose: canClose };
    }

    function handleDelim(cc) {
      var res = scanDelims(cc);
      if (!res || res.numdelims === 0) return false;
      var node = text(subject.slice(pos, pos + res.numdelims));
      pos += res.numdelims;
      if (res.canOpen || res.canClose) {
        var d = { cc: cc, numdelims: res.numdelims, origdelims: res.numdelims,
                  node: node, previous: delimiters, next: null,
                  canOpen: res.canOpen, canClose: res.canClose };
        if (delimiters) delimiters.next = d;
        delimiters = d;
      }
      return true;
    }

    function removeDelimiter(d) {
      if (d.previous) d.previous.next = d.next;
      if (d.next === null) delimiters = d.previous;
      else d.next.previous = d.previous;
    }

    function removeDelimitersBetween(bottom, top) {
      if (bottom.next !== top) { bottom.next = top; top.previous = bottom; }
    }

    /** True for the high half of a UTF-16 surrogate pair. */
    function mdIsHighSurrogate(ch) {
      var c = ch.charCodeAt(0);
      return c >= 0xD800 && c <= 0xDBFF;
    }

    /** Emphasis resolution over the delimiter stack (spec 6.2). */
    function processEmphasis(stackBottom) {
      var openersBottom = new Array(8);
      for (var i = 0; i < 8; i++) openersBottom[i] = stackBottom;
      var closer = delimiters;
      while (closer !== null && closer.previous !== stackBottom) closer = closer.previous;
      var opener, openerInl, closerInl, useDelims, tmp, next, openerFound, oddMatch;
      while (closer !== null) {
        if (!closer.canClose) { closer = closer.next; continue; }
        opener = closer.previous;
        openerFound = false;
        // openers_bottom index: 0..3 for '_', 4..7 for '*' — see rule of 3
        var idx = (closer.cc === '_' ? 0 : 4) + (closer.canOpen ? 2 : 0) + (closer.origdelims % 3 === 0 ? 0 : 1);
        while (opener !== null && opener !== stackBottom && opener !== openersBottom[idx]) {
          oddMatch = (closer.canOpen || opener.canClose) &&
                    closer.origdelims % 3 !== 0 &&
                    (opener.origdelims + closer.origdelims) % 3 === 0;
          if (opener.cc === closer.cc && opener.canOpen && !oddMatch) { openerFound = true; break; }
          opener = opener.previous;
        }
        var oldCloser = closer;
        if (!openerFound) {
          openersBottom[idx] = oldCloser.previous;
          if (!oldCloser.canOpen) removeDelimiter(oldCloser);
          closer = closer.next;
          continue;
        }
        useDelims = closer.numdelims >= 2 && opener.numdelims >= 2 ? 2 : 1;
        openerInl = opener.node;
        closerInl = closer.node;
        opener.numdelims -= useDelims;
        closer.numdelims -= useDelims;
        openerInl.literal = openerInl.literal.slice(0, openerInl.literal.length - useDelims);
        closerInl.literal = closerInl.literal.slice(0, closerInl.literal.length - useDelims);
        var emph = mdInlineNode(useDelims === 1 ? 'emph' : 'strong');
        tmp = openerInl.next;
        while (tmp && tmp !== closerInl) {
          next = tmp.next;
          mdUnlink(tmp);
          mdAppendChild(emph, tmp);
          tmp = next;
        }
        mdInsertAfter(openerInl, emph);
        removeDelimitersBetween(opener, closer);
        if (opener.numdelims === 0) { mdUnlink(openerInl); removeDelimiter(opener); }
        if (closer.numdelims === 0) {
          mdUnlink(closerInl);
          var after = closer.next;
          removeDelimiter(closer);
          closer = after;
        }
        // when the closer still has delimiters left, stay on it: the next
        // iteration searches for another opener further left
      }
      while (delimiters !== null && delimiters !== stackBottom) removeDelimiter(delimiters);
    }

    // -- link / image machinery --

    /**
     * Parse a link title at pos; returns the unescaped title or null.
     * Uses the linear scanner (no regex backtracking).
     */
    function parseLinkTitle() {
      var res = mdScanLinkTitle(subject, pos);
      if (!res) return null;
      pos += res.len;
      return mdUnescapeString(res.text);
    }

    /** Parse `<dest>` or a bare destination; returns normalised URI or null. */
    function parseLinkDestination() {
      var m = match(MD_LINK_DEST_BRACES_RE);
      if (m) return mdNormalizeUri(mdUnescapeString(m[0].slice(1, -1)));
      if (peek() === '<') return null;
      var savepos = pos, openparens = 0, c;
      while ((c = peek()) !== '') {
        if (c === '\\' && subject.charAt(pos + 1) !== '' &&
            MD_ESCAPABLE.indexOf(subject.charAt(pos + 1)) >= 0) {
          pos += 1;
          if (peek() !== '') pos += 1;
        } else if (c === '(') { pos++; openparens++; }
        else if (c === ')') { if (openparens < 1) break; pos++; openparens--; }
        else if (MD_WS_CHAR_RE.test(c)) break;
        else pos++;
      }
      if (pos === savepos && c !== ')') return null;
      if (openparens !== 0) { pos = savepos; return null; }
      return mdNormalizeUri(mdUnescapeString(subject.slice(savepos, pos)));
    }


    /**
     * Parse `[...]` at pos; returns the consumed length (including both
     * brackets), or 0 when there is no well-formed label. A label may not
     * contain a blank line and is capped at 1000 characters.
     */
    function parseLinkLabel() {
      if (subject.charAt(pos) !== '[') return 0;
      var i = pos + 1, ch;
      while (i < subject.length) {
        ch = subject.charAt(i);
        if (ch === '\\') { i += 2; continue; }
        if (ch === '[') return 0;               // nested brackets are not labels
        if (ch === ']') break;
        i++;
      }
      if (subject.charAt(i) !== ']') return 0;
      var len = i + 1 - pos;
      var label = subject.slice(pos, i + 1);
      if (len > 1001) return 0;
      if (/\n[ \t]*\n/.test(label)) return 0;   // no blank lines inside
      return len;
    }

    function addBracket(node, index, image) {
      if (brackets) brackets.bracketAfter = true;
      brackets = { node: node, previous: brackets, previousDelimiter: delimiters,
                  index: index, image: image, active: true, bracketAfter: false };
    }

    function removeBracket() { brackets = brackets.previous; }

    function parseCloseBracket() {
      var startpos = pos, isImage, dest, title, matched = false, reflabel;
      pos += 1;
      var opener = brackets;
      if (opener === null) { text(']'); return true; }
      if (!opener.active) { text(']'); removeBracket(); return true; }
      isImage = opener.image;
      var savepos = pos;
      if (peek() === '(') {
        pos++;
        if (spnl() && (dest = parseLinkDestination()) !== null) {
          var beforeTitle = pos;
          spnl();
          // A title is only allowed when whitespace separated it from the
          // destination (spec: "optional... preceded by a space").
          if (pos !== beforeTitle) {
            var tryTitle = parseLinkTitle();
            if (tryTitle !== null) {
              title = tryTitle;
              spnl();
            } else {
              pos = beforeTitle;
            }
          }
          if (peek() === ')') {
            pos += 1;
            matched = true;
          } else {
            pos = savepos;
          }
        } else {
          pos = savepos;
        }
      }
      if (!matched) {
        var beforelabel = pos;
        var n = parseLinkLabel();
        if (n > 2) {
          // full reference: [text][label]
          reflabel = subject.slice(beforelabel, beforelabel + n);
          pos = beforelabel + n;
        } else if (n === 2 && !opener.bracketAfter) {
          // collapsed reference: [text][] — consume the empty label
          reflabel = '[' + subject.slice(opener.index, startpos) + ']';
          pos = beforelabel + n;
        } else if (!opener.bracketAfter) {
          // shortcut reference: [text]
          reflabel = '[' + subject.slice(opener.index, startpos) + ']';
        }
        if (n === 0) pos = savepos;
        if (reflabel) {
          var link = refmap[mdNormalizeReference(reflabel)];
          if (link) { dest = link.destination; title = link.title; matched = true; }
        }
      }
      if (matched) {
        var node = mdInlineNode(isImage ? 'image' : 'link');
        node.destination = dest == null ? '' : dest;
        node.title = title == null ? '' : title;
        var tmp = opener.node.next, next;
        while (tmp) {
          next = tmp.next;
          mdUnlink(tmp);
          mdAppendChild(node, tmp);
          tmp = next;
        }
        // the link takes the opener's position in the parent's child list
        mdInsertAfter(opener.node, node);
        processEmphasis(opener.previousDelimiter);
        removeBracket();
        mdUnlink(opener.node);
        if (!isImage) {
          var b = brackets;
          while (b !== null) { if (!b.image) b.active = false; b = b.previous; }
        }
        return true;
      }
      removeBracket();
      // NB: `startpos` was captured before consuming ']', so pos now sits
      // just after it — do not rewind onto the bracket again.
      pos = startpos + 1;
      text(']');
      return true;
    }

    // -- autolinks and raw HTML (neutralised) --

    var MD_EMAIL_AUTOLINK_RE = /^<([a-zA-Z0-9.!#$%&'*+\/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*)>/;
    var MD_AUTOLINK_RE = /^<[A-Za-z][A-Za-z0-9.+-]{1,31}:[^<>\x00-\x20]*>/i;

    /**
     * Try an autolink at pos. Returns the node or null.
     */
    function parseAutolink() {
      var rest = subject.slice(pos);
      var m = rest.match(MD_AUTOLINK_RE);
      var node;
      if (m) {
        node = mdInlineNode('link');
        node.destination = mdNormalizeUri(m[0].slice(1, -1));
        node.autolinkText = m[0].slice(1, -1);
        mdAppendChild(block, node);
        mdAppendChild(node, mdInlineNode('text', m[0].slice(1, -1)));
        pos += m[0].length;
        return node;
      }
      m = rest.match(MD_EMAIL_AUTOLINK_RE);
      if (m) {
        node = mdInlineNode('link');
        node.destination = 'mailto:' + m[1];
        node.autolinkText = m[1];
        mdAppendChild(block, node);
        mdAppendChild(node, mdInlineNode('text', m[1]));
        pos += m[0].length;
        return node;
      }
      return null;
    }

    /**
     * Match a raw HTML tag at pos. SECURITY: the matched text is returned so
     * the caller can render it escaped — it is never emitted as markup.
     */
    function parseHtmlTag() {
      var raw = mdScanHtmlTag(subject, pos);
      if (!raw) return null;
      var node = mdAppendChild(block, mdInlineNode('html'));
      node.literal = raw;
      pos += raw.length;
      return node;
    }

    // -- the main dispatch loop --

    while (pos < subject.length) {
      var c = peek();
      var res = false;
      switch (c) {
        case '\n':
          pos++;
          {
            var lastc = block.lastChild;
            if (lastc && lastc.type === 'text' && / $/.test(lastc.literal)) {
              var hard = / {2}$/.test(lastc.literal);
              lastc.literal = lastc.literal.replace(MD_FINAL_SPACE_RE, '');
              var sb = mdAppendChild(block, mdInlineNode('softbreak'));
              sb.hardBreak = hard;
            } else {
              mdAppendChild(block, mdInlineNode('softbreak'));
            }
            match(/^ */);
          }
          break;
        case '\\':
          if (subject.charAt(pos + 1) === '\n') {
            pos += 2;
            var hb = mdAppendChild(block, mdInlineNode('softbreak'));
            hb.hardBreak = true;
            match(/^ */);
          } else if (subject.charAt(pos + 1) !== '' &&
                    MD_ESCAPABLE.indexOf(subject.charAt(pos + 1)) >= 0) {
            text(subject.charAt(pos + 1));
            pos += 2;
          } else {
            text('\\');
            pos++;
          }
          break;
        case '`':
          {
            // opening run, then the next run of backticks of the SAME length
            var ticks = subject.slice(pos).match(MD_TICKS_HERE_RE)[0];
            var afterOpen = pos + ticks.length;
            var searchPos = afterOpen, run;
            var codeNode = null;
            while ((run = subject.slice(searchPos).match(/^[\s\S]*?(`+)/)) && run[1]) {
              var runStart = searchPos + run[0].length - run[1].length;
              if (run[1].length === ticks.length) {
                // newline -> space; spaces *before* a newline are dropped
                // (spec: "line endings are replaced by spaces... preceded
                // by a space are removed")
                var content = subject.slice(afterOpen, runStart)
                  .replace(/ *\n/g, '\n').replace(/\n/g, ' ');
                if (/^ /.test(content) && / $/.test(content) && content.replace(/ /g, '') !== '') {
                  content = content.slice(1, content.length - 1);
                }
                codeNode = mdAppendChild(block, mdInlineNode('code', content));
                pos = runStart + run[1].length;
                break;
              }
              searchPos = runStart + run[1].length;
            }
            if (!codeNode) {
              text(ticks);
              pos = afterOpen;
            }
          }
          break;
        case '*':
        case '_':
          handleDelim(c);
          break;
        case '[':
          {
            var node = text('[');
            addBracket(node, pos + 1, false);
            pos++;
          }
          break;
        case '!':
          if (subject.charAt(pos + 1) === '[') {
            var n2 = text('![');
            addBracket(n2, pos + 2, true);
            pos += 2;
          } else {
            text('!');
            pos++;
          }
          break;
        case ']':
          parseCloseBracket();
          break;
        case '<':
          if (parseAutolink()) break;
          if (parseHtmlTag()) break;
          text('<');
          pos++;
          break;
        case '&':
          {
            var rep = mdReplaceEntity(subject.slice(pos));
            if (rep !== null) {
              text(rep);
              pos += subject.slice(pos).match(MD_ENTITY_HERE_RE)[0].length;
            } else {
              text('&');
              pos++;
            }
          }
          break;
        default:
          {
            var m = subject.slice(pos).match(/^[^\n`\\[\]!<&*_]+/);
            if (!m) { text(c); pos++; }
            else { text(m[0]); pos += m[0].length; }
          }
      }
    }

    processEmphasis(null);
    return block;
  }


  // ---------------------------------------------------------------------------
  // Markdown HTML rendering
  // ---------------------------------------------------------------------------

  /**
   * Escape the five HTML-significant characters. `"` becomes `&quot;` (also
   * safe inside double-quoted attributes), matching cmark.
   * @param {string} s
   * @returns {string}
   */
  function mdEscape(s) {
    return s.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;')
            .replace(/"/g, '&quot;');
  }

  /**
   * Parse (once) and render a leaf block's inline content. The parsed inline
   * tree is cached on the block so image alt text can reuse it.
   */
  function mdLeafInlines(node, refmap) {
    if (!node._inlines) {
      node._inlines = mdParseInlines(node.strings.join('\n').trim(), refmap);
    }
    return node._inlines;
  }

  /** Render inline nodes to HTML (children of a paragraph/heading). */
  function mdRenderInlines(node) {
    var out = '', c = node.firstChild;
    while (c) {
      switch (c.type) {
        case 'text':
          out += mdEscape(c.literal);
          break;
        case 'softbreak':
          out += c.hardBreak ? '<br />\n' : '\n';
          break;
        case 'code':
          out += '<code>' + mdEscape(c.literal) + '</code>';
          break;
        case 'emph':
          out += '<em>' + mdRenderInlines(c) + '</em>';
          break;
        case 'strong':
          out += '<strong>' + mdRenderInlines(c) + '</strong>';
          break;
        case 'link':
          out += '<a href="' + safeMarkdownUrl(mdEscapeAttr(c.destination)) + '"' +
                (c.title ? ' title="' + mdEscapeAttr(c.title) + '"' : '') + '>' +
                mdRenderInlines(c) + '</a>';
          break;
        case 'image':
          out += '<img src="' + safeMarkdownUrl(mdEscapeAttr(c.destination)) + '"' +
                ' alt="' + mdImageAlt(c) + '"' +
                (c.title ? ' title="' + mdEscapeAttr(c.title) + '"' : '') + ' />';
          break;
        case 'html':
          out += mdEscape(c.literal);
          break;
        default:
          out += mdEscape(c.literal || '');
      }
      c = c.next;
    }
    return out;
  }

  /** Plain-text rendering of image alt text (markdown stripped). */
  function mdImageAlt(node) {
    var out = '', c = node.firstChild;
    while (c) {
      if (c.type === 'text' || c.type === 'code' || c.type === 'html') out += c.literal;
      else if (c.type === 'softbreak') out += c.hardBreak ? '\n' : '\n';
      else if (c.firstChild) out += mdImageAlt(c);
      c = c.next;
    }
    return mdEscapeAttr(out);
  }

  /** Escape for a double-quoted attribute value. */
  function mdEscapeAttr(s) {
    return String(s).replace(/&/g, '&amp;').replace(/"/g, '&quot;')
                    .replace(/</g, '&lt;').replace(/>/g, '>');
  }

  /**
   * Output buffer that suppresses repeated newlines (cmark's `cr`).
   */
  function mdOut() {
    // `last` starts as a newline so the very first cr() is a no-op
    return { s: '', last: '\n' };
  }

  /** Append a literal string. */
  function mdLit(out, s) {
    if (!s) return;
    out.s += s;
    out.last = s.charAt(s.length - 1);
  }

  /** Append a newline unless the output already ends with one. */
  function mdCr(out) {
    if (out.last !== '\n') mdLit(out, '\n');
  }

  /**
   * Render one block node (and its children) to HTML. `tight` is the
   * enclosing list's tightness: tight lists suppress `<p>` wrappers.
   */
  function mdRenderBlocks(node, tight, out, refmap) {
    var i, child;
    switch (node.type) {
      case 'document':
        for (i = 0; i < node.children.length; i++) mdRenderBlocks(node.children[i], tight, out, refmap);
        break;
      case 'paragraph':
        // in a tight list the paragraph renders bare
        if (tight) { mdLit(out, mdRenderInlines(mdLeafInlines(node, refmap))); }
        else {
          mdCr(out);
          mdLit(out, '<p>');
          mdLit(out, mdRenderInlines(mdLeafInlines(node, refmap)));
          mdLit(out, '</p>');
          mdCr(out);
        }
        break;
      case 'heading':
        mdCr(out);
        mdLit(out, '<h' + node.level + '>');
        mdLit(out, mdRenderInlines(mdLeafInlines(node, refmap)));
        mdLit(out, '</h' + node.level + '>');
        mdCr(out);
        break;
      case 'thematic':
        mdCr(out);
        mdLit(out, '<hr />');
        mdCr(out);
        break;
      case 'code':
        mdCr(out);
        var info = node.info ? node.info.split(/\s+/)[0] : '';
        var attrs = '';
        if (info) attrs = ' class="language-' + mdEscapeAttr(info) + '"';
        mdLit(out, '<pre><code' + attrs + '>' + mdEscape(node.literal) + '</code></pre>');
        mdCr(out);
        break;
      case 'blockquote':
        mdCr(out);
        mdLit(out, '<blockquote>');
        mdCr(out);
        // cmark unwraps paragraphs only when their grandparent is a tight
        // list; inside a blockquote they always keep their <p>.
        for (i = 0; i < node.children.length; i++) mdRenderBlocks(node.children[i], false, out, refmap);
        mdCr(out);
        mdLit(out, '</blockquote>');
        mdCr(out);
        break;
      case 'list':
        mdCr(out);
        var tag = node.listData.type === 'ordered' ? 'ol' : 'ul';
        var start = '';
        if (tag === 'ol' && node.listData.start != null && node.listData.start !== 1) {
          start = ' start="' + node.listData.start + '"';
        }
        mdLit(out, '<' + tag + start + '>');
        mdCr(out);
        for (i = 0; i < node.children.length; i++) mdRenderBlocks(node.children[i], node.tight, out, refmap);
        mdCr(out);
        mdLit(out, '</' + tag + '>');
        mdCr(out);
        break;
      case 'item':
        mdLit(out, '<li>');
        for (i = 0; i < node.children.length; i++) {
          // tightness applies to the item's own paragraphs and lists;
          // blockquote contents are always loose.
          mdRenderBlocks(node.children[i], node.children[i].type === 'blockquote' ? false : tight, out, refmap);
        }
        mdLit(out, '</li>');
        mdCr(out);
        break;
      default:
        break;
    }
  }

  /**
   * Render markdown to safe HTML.
   *
   * CommonMark 0.31.2 minus raw HTML (escaped instead, see the note at the
   * top of the markdown section) and minus HTML-block constructs that only
   * exist to feed raw HTML through.
   * @param {string} raw markdown source
   * @returns {string} HTML safe for `innerHTML`
   */
  function renderMarkdown(raw) {
    var parser = mdParseDocument(raw);
    var out = mdOut();
    mdRenderBlocks(parser.doc, false, out, parser.refmap);
    return out.s;
  }

  /**
   * Demote child header tags by N levels (h1 → h2, etc.), capping at h6.
   */
  function handleHDemotion(el) {
    var attr = el.getAttribute('stm-h-demotion');
    if (!attr) return;
    var n = parseInt(attr, 10);
    if (isNaN(n) || n <= 0) return;
    el.querySelectorAll('h1,h2,h3,h4,h5,h6').forEach(function (h) {
      var level = parseInt(h.tagName.charAt(1), 10);
      var newLevel = Math.min(level + n, 6);
      if (newLevel === level) return;
      var replacement = document.createElement('h' + newLevel);
      for (var i = 0; i < h.attributes.length; i++)
        replacement.setAttribute(h.attributes[i].name, h.attributes[i].value);
      while (h.firstChild) replacement.appendChild(h.firstChild);
      h.replaceWith(replacement);
    });
  }

  /**
   * Bind `stm-text` / `stm-html` / `stm-markdown`. Per the "leave original DOM
   * content" policy, an unresolved value (`undefined`) leaves the element
   * untouched; otherwise the value is stringified (`null` becomes empty).
   */
  function handleTextHtml(el, scope) {
    if (el.hasAttribute('stm-text')) {
      var text = evalExpr(el.getAttribute('stm-text'), scope);
      if (text !== undefined) el.textContent = text === null ? '' : String(text);
    }
    if (el.hasAttribute('stm-html')) {
      var html = evalExpr(el.getAttribute('stm-html'), scope);
      if (html !== undefined) el.innerHTML = html === null ? '' : String(html);
    }
    if (el.hasAttribute('stm-markdown')) {
      var md = evalExpr(el.getAttribute('stm-markdown'), scope);
      if (md !== undefined) el.innerHTML = renderMarkdown(md === null ? '' : String(md));
    }
    // stm-h-demotion runs after stm-html / stm-markdown so the rendered
    // headers are present in the DOM.
    if (el.hasAttribute('stm-h-demotion')) handleHDemotion(el);
  }

  /**
   * Expand a loop holder: reconcile its instances against the current array.
   * Keyed loops (`stm-key`) reuse DOM nodes for unchanged keys to preserve
   * focus/selection/input state; unkeyed loops rebuild wholesale.
   */
  function handleLoop(el, scope) {
    var info = getStmFor(el);
    if (!info) return;

    var template = templates.get(el);
    if (!template) {
      template = el.cloneNode(true);
      stripLoopAttrs(template);
      templates.set(el, template);
    }

    var raw = evalExpr(info.expr, scope);
    if (raw === undefined) {
      // No value for the source path yet: clear instances and restore the
      // server-rendered holder content (progressive enhancement).
      var prev = instancesByHolder.get(el) || [];
      prev.forEach(function (n) { n.remove(); });
      instancesByHolder.set(el, []);
      if (el.getAttribute('data-stm-active') === '1') {
        el.removeAttribute('data-stm-active');
        el.removeAttribute('hidden');
      }
      return;
    }
    var arr = Array.isArray(raw) ? raw : [];

    // Activate: hide the holder so only rendered instances are visible.
    if (el.getAttribute('data-stm-active') !== '1') {
      el.setAttribute('data-stm-active', '1');
      el.setAttribute('hidden', '');
    }

    var keyExpr = el.getAttribute('stm-key');
    var next = [];

    if (keyExpr) {
      var oldByKey = new Map();
      (instancesByHolder.get(el) || []).forEach(function (n) {
        if (n.__stmKey !== undefined) oldByKey.set(n.__stmKey, n);
      });
      var used = new Set();
      arr.forEach(function (item) {
        var child = childScope(scope, info.varName, item);
        var key = evalExpr(keyExpr, child);
        var node = (key !== undefined && !used.has(key)) ? oldByKey.get(key) : undefined;
        if (node) {
          used.add(key);
          processElement(node, child);
        } else {
          node = template.cloneNode(true);
          node.__stmKey = key;
          instanceNodes.add(node);
          processElement(node, child);
        }
        next.push(node);
      });
      oldByKey.forEach(function (n, key) { if (!used.has(key)) n.remove(); });
    } else {
      (instancesByHolder.get(el) || []).forEach(function (n) { n.remove(); });
      arr.forEach(function (item) {
        var child = childScope(scope, info.varName, item);
        var node = template.cloneNode(true);
        instanceNodes.add(node);
        processElement(node, child);
        next.push(node);
      });
    }

    // Place instances in order, immediately after the holder.
    var ref = el;
    next.forEach(function (node) {
      if (node !== ref.nextSibling) ref.parentNode.insertBefore(node, ref.nextSibling);
      ref = node;
    });
    instancesByHolder.set(el, next);
  }

  /**
   * Process one element's bindings (and recurse). Loop holders are handled by
   * {@link handleLoop}; `stm-else-if` / `stm-else` are owned by their `stm-if`.
   */
  function processElement(el, scope) {
    if (getStmFor(el)) { handleLoop(el, scope); return; }
    if (el.hasAttribute('stm-else-if') || el.hasAttribute('stm-else')) return;
    if (el.hasAttribute('stm-if')) {
      var active = handleIfChain(el, scope);
      if (active) processInner(active, scope);
      return;
    }
    processInner(el, scope);
  }

  /**
   * Collect `stm-def-{name}-as` attributes on an element into a child scope.
   * Each expression is evaluated against the incoming scope (so the new
   * variables cannot reference each other within the same element), and the
   * results are added to a child scope visible to the element and its
   * descendants. Multiple defs on one element are supported. If there are no
   * defs, the original scope is returned unchanged.
   * @param {Element} el
   * @param {object} scope
   * @returns {object}
   */
  function applyDefs(el, scope) {
    var attrs = el.attributes;
    var child = null;
    for (var i = 0; i < attrs.length; i++) {
      var name = attrs[i].name;
      if (name.indexOf('stm-def-') === 0 && name.slice(-3) === '-as') {
        var varName = name.slice(8, -3);
        if (!varName) continue;
        if (!child) child = Object.create(scope || null);
        child[varName] = evalExpr(attrs[i].value, scope);
      }
    }
    return child || scope;
  }

  /** Bind the non-control-flow attributes and recurse into children. */
  function processInner(el, scope) {
    var s = applyDefs(el, scope); // local definitions: element + descendants
    el.__stmScope = s; // latest scope, used when an action fires
    handleClass(el, s);
    handleAttribute(el, s);
    handleDisabled(el, s);
    handleTextHtml(el, s);
    wireAction(el);
    render(el, s);
  }

  /**
   * Walk an element's children, processing each. Loop instance nodes are
   * skipped here (they are owned and processed by their holder).
   */
  function render(root, scope) {
    if (!root || !root.children) return;
    // Snapshot the children: processing mutates the DOM (detaching branches,
    // inserting loop instances) and a live HTMLCollection would shift indices.
    var children = Array.prototype.slice.call(root.children);
    for (var i = 0; i < children.length; i++) {
      var el = children[i];
      if (instanceNodes.has(el)) continue;
      processElement(el, scope);
    }
  }

  /** Re-render the whole document against the current state. */
  /**
   * Evaluate every `<link rel="stm-guard">` in the document head. A guard whose
   * `require` predicate is false redirects the page to its `href`.
   *
   * Guards marked `pre-entrypoint` are evaluated on every cycle (including the
   * initial, pre-entrypoint render, which uses only hydrated state); guards
   * without it are evaluated only once the entrypoint has loaded. On every later
   * evaluate cycle (set/clear) all guards are re-checked, so logging out, for
   * example, can bounce the user off a guarded page.
   */
  function evaluateGuards() {
    if (guardRedirected) return;
    var scope = stateScope();
    var guards = document.querySelectorAll('link[rel~="stm-guard"]');
    for (var i = 0; i < guards.length; i++) {
      var g = guards[i];
      var preEntrypoint = g.hasAttribute('pre-entrypoint');
      if (!preEntrypoint && !entrypointLoaded) continue;
      var require = g.getAttribute('require');
      if (!require) continue;
      if (!evalExpr(require, scope)) {
        guardRedirected = true;
        var href = g.getAttribute('href') || '/';
        console.warn('[statum] guard failed (' + require + '); redirecting to ' + href);
        window.location.href = href;
        return;
      }
    }
  }

  // ---------------------------------------------------------------------------
  // Evaluation hooks (no-arg callbacks before/after each render cycle)
  // ---------------------------------------------------------------------------

  var beforeHooks = [];
  var afterHooks = [];

  function renderAll() {
    if (guardRedirected) return;
    beforeHooks.forEach(function (fn) { try { fn(); } catch (e) { console.error('[statum] beforeEvaluate hook error', e); } });
    try { render(document.body, stateScope()); }
    catch (e) { console.error('[statum] render error', e); }
    afterHooks.forEach(function (fn) { try { fn(); } catch (e) { console.error('[statum] afterEvaluate hook error', e); } });
    evaluateGuards();
  }

  // ---------------------------------------------------------------------------
  // HTML API: actions
  // ---------------------------------------------------------------------------

  /**
   * Collect data for an action trigger: `stm-data-{key}` attributes plus, for a
   * form, its named inputs.
   * @param {HTMLElement} el
   * @returns {object}
   */
  function collectData(el) {
    var data = {};
    var attrs = el.attributes;
    for (var i = 0; i < attrs.length; i++) {
      var name = attrs[i].name;
      if (name.indexOf('stm-data-') === 0) data[name.slice('stm-data-'.length)] = attrs[i].value;
    }
    if (el.tagName === 'FORM') {
      var fd = new FormData(el);
      fd.forEach(function (value, key) {
        data[key] = value instanceof File ? value.name : String(value);
      });
    }
    return data;
  }

  /**
   * Toggle the busy state of an action element: disables the element and its
   * descendant form controls and applies `stm-busy-class` classes while busy.
   *
   * On un-busy the disabled state is not "restored" to a captured snapshot
   * (that would clobber a `stm-disabled` value that `renderAll` applied during
   * the response); instead the nodes are re-enabled and `stm-disabled` is
   * re-evaluated, which re-disables any that should remain disabled.
   */
  function setBusyState(el, busy) {
    var nodes = [el].concat(Array.prototype.slice.call(
      el.querySelectorAll('button,input,select,textarea,fieldset')));
    var busyClasses = (el.getAttribute('stm-busy-class') || '').split(/\s+/).filter(Boolean);
    if (busy) {
      nodes.forEach(function (n) { n.setAttribute('disabled', ''); });
      busyClasses.forEach(function (c) { el.classList.add(c); });
    } else {
      nodes.forEach(function (n) { n.removeAttribute('disabled'); });
      busyClasses.forEach(function (c) { el.classList.remove(c); });
      reapplyDisabled(el);
    }
  }

  /** Re-apply `stm-disabled` to an element and any descendants that carry it. */
  function reapplyDisabled(el) {
    var scope = el.__stmScope || stateScope();
    if (el.hasAttribute('stm-disabled')) handleDisabled(el, scope);
    var scoped = el.querySelectorAll('[stm-disabled]');
    Array.prototype.forEach.call(scoped, function (n) {
      handleDisabled(n, n.__stmScope || scope);
    });
  }

  /** Apply or remove `stm-on-error` classes on an action element. */
  function applyErrorClasses(el, on) {
    if (!el || !el.hasAttribute || !el.hasAttribute('stm-on-error')) return;
    var classes = (el.getAttribute('stm-on-error') || '').split(/\s+/).filter(Boolean);
    classes.forEach(function (c) { on ? el.classList.add(c) : el.classList.remove(c); });
  }

  /**
   * Wire an element's primary action once. The listener resolves the action
   * object against the element's latest render scope, so loop instances bind to
   * their own item.
   */
  function wireAction(el) {
    if (!el.hasAttribute('stm-action') || wired.has(el)) return;
    wired.add(el);
    var eventName = el.tagName === 'FORM' ? 'submit' : 'click';
    el.addEventListener(eventName, function (event) {
      event.preventDefault();
      runElementAction(el);
    });
  }

  /**
   * Resolve and perform the action attached to an element, managing busy and
   * error-state classes around the request.
   * @param {HTMLElement} el
   */
  async function runElementAction(el) {
    var scope = el.__stmScope || stateScope();
    var action = evalExpr(el.getAttribute('stm-action'), scope);
    if (!action || typeof action.uri !== 'string') return;

    // stm-confirm: gate the action behind the confirm handler (async-capable,
    // so custom modals are supported).
    if (el.hasAttribute('stm-confirm')) {
      var confirmed = await triggerConfirm(el.getAttribute('stm-confirm'), el);
      if (!confirmed) return;
    }

    applyErrorClasses(el, false); // clear error state on a new attempt
    var data = collectData(el);
    setBusyState(el, true);
    try {
      await performAction(action, data, el);
    } catch (err) {
      // Already handled: stm-on-error classes and the onErrorHandler run inside
      // performAction/reportFailure. Swallow so an HTML-triggered action does
      // not surface as an unhandled rejection.
    } finally {
      setBusyState(el, false);
    }
  }

  // ---------------------------------------------------------------------------
  // Boot visibility (stm-preloader / stm-content)
  // ---------------------------------------------------------------------------

  /**
   * Toggle pre/post-entrypoint visibility with the `hidden` attribute. While
   * loading, `stm-preloader` elements are shown and `stm-content` elements
   * hidden; once ready, the reverse.
   *
   * To avoid a flash of un-bound template before the script runs, authors may
   * pre-set `hidden` directly on `stm-content` in the HTML (e.g.
   * `<div stm-content hidden>`); the library removes it once ready. The library
   * also sets `hidden` itself during loading as a fallback for authors who do
   * not pre-set it.
   * @param {boolean} ready
   */
  function setBootState(ready) {
    var preloaders = document.querySelectorAll('[stm-preloader]');
    var contents = document.querySelectorAll('[stm-content]');
    for (var i = 0; i < preloaders.length; i++) {
      ready ? preloaders[i].setAttribute('hidden', '') : preloaders[i].removeAttribute('hidden');
    }
    for (var j = 0; j < contents.length; j++) {
      ready ? contents[j].removeAttribute('hidden') : contents[j].setAttribute('hidden', '');
    }
  }

  // ---------------------------------------------------------------------------
  // Public state accessors
  // ---------------------------------------------------------------------------

  /** Build the scope used for expression evaluation: `{ typeName: public }`. */
  function stateScope() {
    var scope = {};
    store.forEach(function (entry, type) { scope[type] = entry.snapshot.public; });
    return scope;
  }

  /** Read a type's `public` data (what the attributes bind to). */
  function read(type) {
    var entry = store.get(type);
    return entry ? entry.snapshot.public : undefined;
  }

  /** Read a type's full snapshot object. */
  function getSnapshot(type) {
    var entry = store.get(type);
    return entry ? entry.snapshot : undefined;
  }

  /** Read the frame wrapping a type's snapshot. */
  function getFrame(type) {
    var entry = store.get(type);
    return entry ? entry.frame : undefined;
  }

  /** Build an object of `{ typeName: public }` for every held type. */
  function state() {
    var result = {};
    store.forEach(function (entry, type) { result[type] = entry.snapshot.public; });
    return result;
  }

  /**
   * Clear state. With a type argument, clears that type only; without, clears
   * all held state.
   * @param {string} [type]
   */
  function clear(type) {
    if (type === undefined) {
      Array.from(store.keys()).forEach(function (t) { clearType(t, { broadcast: true }); });
    } else {
      clearType(type, { broadcast: true });
    }
    renderAll();
  }

  /**
   * Perform an action. `action` may be an action object or a string path that
   * resolves to an action object within the current state.
   * @param {object|string} action
   * @param {object} [data]
   * @returns {Promise<void>}
   */
  function act(action, data) {
    var resolved = action;
    if (typeof action === 'string') resolved = evalExpr(action, stateScope());
    if (!resolved || typeof resolved.uri !== 'string') {
      return Promise.reject(new StatumError('Invalid action'));
    }
    return performAction(resolved, data, null);
  }

  /** Attach a state listener for a type. */
  function addStateListener(type, callback) {
    if (typeof callback !== 'function') return;
    if (!listeners.has(type)) listeners.set(type, new Set());
    listeners.get(type).add(callback);
  }

  /** Remove a previously-attached state listener. */
  function removeStateListener(type, callback) {
    var set = listeners.get(type);
    if (!set) return;
    set.delete(callback);
    if (set.size === 0) listeners.delete(type);
  }

  // ---------------------------------------------------------------------------
  // Initialization
  // ---------------------------------------------------------------------------

  /**
   * Inject the stylesheet that makes the `hidden` attribute authoritative.
   * Statum toggles `stm-if`/`stm-else` branches and loop holders via
   * `hidden`, whose user-agent rule loses specificity battles to ordinary
   * author CSS (a rule like `li { display: flex }` let hidden loop holders
   * leak as phantom rows). Idempotent: skipped when the stylesheet is
   * already present.
   */
  function injectHiddenStyle() {
    var id = 'statum-hidden-style';
    if (document.getElementById(id)) return;
    var head = document.head;
    if (!head) return;
    var style = document.createElement('style');
    style.id = id;
    style.textContent = '[hidden]{display:none !important}';
    head.appendChild(style);
  }

  /**
   * Scan the document for `pstm-*` attributes and `<pstm-*>` elements, which
   * are intended for server-side pre-rendering and should never reach the
   * browser. Emits a single `console.warn` summarizing them.
   */
  function warnServerSideMarkup() {
    var found = [];
    var els = document.querySelectorAll('*');
    for (var i = 0; i < els.length; i++) {
      var el = els[i];
      var tag = el.tagName.toLowerCase();
      if (tag.indexOf('pstm-') === 0) found.push('<' + tag + '>');
      var attrs = el.attributes;
      for (var j = 0; j < attrs.length; j++) {
        var name = attrs[j].name;
        if (name.indexOf('pstm-') === 0) found.push('<' + tag + '> ' + name);
      }
    }
    if (found.length) {
      console.warn('[statum] ' + found.length + ' server-side pstm-* attribute/element(s) ' +
        'found in the DOM; they should have been resolved during pre-rendering: ' +
        found.slice(0, 10).join(', ') + (found.length > 10 ? ' …' : ''));
    }
  }

  /**
   * Initialize Statum: read URL overrides, run the session-cookie check,
   * hydrate persisted state, open the cross-tab channel, fetch the entrypoint,
   * and render. Safe to call multiple times.
   * @returns {Promise<void>}
   */
  async function init() {
    if (initialized) return;
    initialized = true;

    // Before the first render and the boot visibility toggling, so `hidden`
    // wins over author CSS from the very first paint.
    injectHiddenStyle();

    var body = document.body;
    if (body) {
      if (body.hasAttribute('stm-entrypoint')) config.entrypointUrl = body.getAttribute('stm-entrypoint');
      if (body.hasAttribute('stm-slots')) config.slotsUrl = body.getAttribute('stm-slots');
      if (body.hasAttribute('stm-channel')) config.channelUrl = body.getAttribute('stm-channel');
      if (body.hasAttribute('stm-worker')) config.workerUrl = body.getAttribute('stm-worker');
    }

    try { warnServerSideMarkup(); } catch (e) {}

    try { initSession(); } catch (e) {}
    try { hydrate(); } catch (e) {}
    setupChannel();

    setBootState(false);
    renderAll(); // bind against any persisted/hydrated state immediately

    try {
      await loadEntrypoint();
    } catch (err) {
      console.error('[statum] entrypoint load failed', err);
    } finally {
      setBootState(true);
    }
  }

  function autoInit() {
    if (document.readyState === 'loading') {
      document.addEventListener('DOMContentLoaded', init);
    } else {
      init();
    }
  }

  // ---------------------------------------------------------------------------
  // Public API
  // ---------------------------------------------------------------------------

  /** @namespace statum */
  window.statum = {
    /** Library version. */
    version: '0.1.0',
    /** Mutable endpoint configuration. */
    config: config,
    /** (Re)initialize the library. Usually runs automatically on load. */
    init: init,
    /** Read a type's `public` data. */
    read: read,
    /** Read a type's full snapshot object. */
    getSnapshot: getSnapshot,
    /** Read the frame wrapping a type's snapshot. */
    getFrame: getFrame,
    /** Build `{ typeName: public }` for every held type. */
    state: state,
    /** Clear one type (`clear("x")`) or all state (`clear()`). */
    clear: clear,
    /** Perform an action object or named action. */
    act: act,
    /** Attach a state-changed listener for a type. */
    addStateListener: addStateListener,
    /** Remove a previously-attached listener. */
    removeStateListener: removeStateListener,
    /** Register a callback that runs before each render cycle (no arguments). */
    beforeEvaluate: function (fn) { if (typeof fn === 'function') beforeHooks.push(fn); },
    /** Register a callback that runs after each render cycle (no arguments). */
    afterEvaluate: function (fn) { if (typeof fn === 'function') afterHooks.push(fn); },
    /** The Statum error type (thrown by `act` and surfaced to handlers). */
    Error: StatumError,
    get onConfirmHandler() { return handlers.onConfirm; },
    set onConfirmHandler(v) { handlers.onConfirm = typeof v === 'function' ? v : null; },
    get onNotifyHandler() { return handlers.onNotify; },
    set onNotifyHandler(v) { handlers.onNotify = typeof v === 'function' ? v : null; },
    get onErrorHandler() { return handlers.onError; },
    set onErrorHandler(v) { handlers.onError = typeof v === 'function' ? v : null; }
  };

  autoInit();

  // Test-only escape hatch: tests/markdown loads this file under QuickJS with
  // `window.__STATUM_TEST__` set beforehand and reaches the markdown engine
  // through statum._testMarkdown. Shipped pages never set the flag, so this
  // adds no surface to the public API.
  if (window.__STATUM_TEST__) window.statum._testMarkdown = renderMarkdown;
})();