/*!
 * Statum - client-side state library (document module).
 *
 * The render walk: expands `stm-for` loops and `stm-if` chains, applies the
 * structural and DOM-level `stm-*` bindings (`stm-class.*`,
 * `stm-attribute.*`, `stm-disabled`, `stm-text`, `stm-html`), wires
 * `stm-action` elements, and recurses into child elements. The bindings
 * register through core's attribute seam and this module installs core's
 * render driver, so `renderAll` drives the walk defined here. The
 * structural attributes (`stm-for`, `stm-if`/`stm-else-if`/`stm-else` and
 * `stm-def-*`) stay hardcoded in the walk: they build the scope and the
 * element list every handler receives.
 *
 * Load order: SECOND - requires statum-core.js, which creates `window.statum`
 * and the `_bridge` this module registers through. Like core: an IIFE, no
 * dependencies, no build step, plain script tag.
 */
(function () {
  'use strict';

  if (!window.statum || !window.statum._bridge) {
    console.error('[statum] statum-document.js requires statum-core.js');
    return;
  }

  // Core machinery shared through the module seam (see statum-core.js).
  // Aliased so the moved code keeps its original call shapes.
  var bridge = window.statum._bridge;
  var evalExpr = bridge.evalExpr;
  var childScope = bridge.childScope;
  var stateScope = bridge.stateScope;
  var triggerConfirm = bridge.triggerConfirm;
  var performAction = bridge.performAction;
  var applyErrorClasses = bridge.applyErrorClasses;


  // ---------------------------------------------------------------------------
  // 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');
    });
  }


  // ---------------------------------------------------------------------------
  // stm-text / stm-html
  // ---------------------------------------------------------------------------
  // (stm-markdown and stm-h-demotion moved to statum-markdown.js and register
  // through the same seam, ordered after `stm-html`.)

  /**
   * Bind `stm-text`. Per the "leave original DOM content" policy, an
   * unresolved value (`undefined`) leaves the element untouched; otherwise
   * the value is stringified (`null` becomes empty).
   */
  function handleText(el, scope) {
    if (el.hasAttribute('stm-text')) {
      var text = evalExpr(el.getAttribute('stm-text'), scope);
      if (text !== undefined) el.textContent = text === null ? '' : String(text);
    }
  }

  /**
   * Bind `stm-html`, with the same policy as `stm-text`.
   */
  function handleHtml(el, scope) {
    if (el.hasAttribute('stm-html')) {
      var html = evalExpr(el.getAttribute('stm-html'), scope);
      if (html !== undefined) el.innerHTML = html === null ? '' : String(html);
    }
  }


  /**
   * 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.
   *
   * Handlers run in the seam's resolved order (see registerAttribute in
   * statum-core.js): once all modules have loaded it is stm-class.* ->
   * stm-attribute.* -> stm-disabled -> stm-text -> stm-html ->
   * stm-markdown -> stm-h-demotion, the order this walk used when it called
   * the handlers directly. A throwing handler aborts the render cycle via
   * renderAll's try/catch, as before.
   */
  function processInner(el, scope) {
    var s = applyDefs(el, scope); // local definitions: element + descendants
    el.__stmScope = s; // latest scope, used when an action fires
    var registered = bridge.attributeHandlers;
    for (var i = 0; i < registered.length; i++) {
      var h = registered[i];
      if (h.prefix ? hasAttrPrefix(el, h.name) : el.hasAttribute(h.name)) h.fn(el, s);
    }
    wireAction(el);
    render(el, s);
  }

  /** Whether `el` carries any attribute starting with `prefix`. */
  function hasAttrPrefix(el, prefix) {
    var attrs = el.attributes;
    for (var i = 0; i < attrs.length; i++) {
      if (attrs[i].name.indexOf(prefix) === 0) return true;
    }
    return false;
  }


  /**
   * 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);
    }
  }

  // ---------------------------------------------------------------------------
  // 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);
    });
  }

  /**
   * 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);
    }
  }

  // ---------------------------------------------------------------------------
  // Registration (module seam)
  // ---------------------------------------------------------------------------

  // Registration order mirrors the order these handlers had when processInner
  // called them directly; statum-markdown.js constrains its own handlers
  // relative to `stm-html`.
  bridge.registerAttribute('stm-class.', handleClass);
  bridge.registerAttribute('stm-attribute.', handleAttribute);
  bridge.registerAttribute('stm-disabled', handleDisabled);
  bridge.registerAttribute('stm-text', handleText);
  bridge.registerAttribute('stm-html', handleHtml);

  // Core's renderAll drives the walk defined in this module.
  bridge.installRenderDriver(function (scope) { render(document.body, scope); });
})();