#!/usr/bin/env python3
"""Static + logic tests for the task event-log page's client JS.

The app binary cannot be built in every container (statum-mkpstm /
libstatum are build-time dependencies), so this suite verifies
src/pages/task_log.html two ways:

1. Statically - the <script> body must be ASCII-only (the page
   compiler HTML-escapes script bodies, so any non-ASCII literal is
   re-served as literal entity text like "&middot;" after the
   browser's one decode pass), must wire the SSE stream through
   `onmessage` (the server sends id:/data: frames with no `event:`
   name, so named listeners can never fire), must not listen for an
   'append' event name, and its delimiter structure must balance
   after strings and comments are stripped.

2. Behaviourally - the ingest / render-order / scroll-stick /
   load-more logic is ported verbatim below as pure python functions
   and unit-tested: oldest-first chronology, id dedupe, the 48px
   bottom-stick rule, prepend-mode scroll anchoring, and the
   newest-first-page reversal with the `more` -> exhausted flag.

Runnable standalone: python3 test/test_task_log_js.py
"""

import os
import re
import unittest

PAGE = os.path.join(os.path.dirname(os.path.abspath(__file__)),
                    os.pardir, "src", "pages", "task_log.html")


def script_body():
    with open(PAGE, encoding="utf-8") as handle:
        source = handle.read()
    head, rest = source.split("<script>", 1)
    body, _ = rest.split("</script>", 1)
    assert head, "no content before the script block"
    return body


# ---------------------------------------------------------------------------
# Static checks
# ---------------------------------------------------------------------------

class ScriptSourceTests(unittest.TestCase):
    """What the served bytes must look like after compilation."""

    def setUp(self):
        self.body = script_body()

    def test_script_is_ascii_only(self):
        """Non-ASCII in a script body comes back as literal entity
        text ("&middot;") because the compiler escapes script bodies
        and the browser decodes exactly once. ASCII (with \\uXXXX
        escapes for the characters we want) is immune."""
        offenders = [(index, hex(ord(char)))
                     for index, char in enumerate(self.body) if ord(char) > 127]
        self.assertEqual(offenders, [])

    def test_unicode_escapes_used_for_separators(self):
        """The separator characters must still render - as escapes,
        not as raw bytes and not as HTML entities."""
        for escape in ("\\u00b7", "\\u2026", "\\u2014"):
            self.assertIn(escape, self.body)
        self.assertNotIn("&middot;", self.body)
        self.assertNotIn("&mdash;", self.body)

    def test_stream_wired_through_onmessage(self):
        self.assertRegex(self.body, r"stream\.onmessage\s*=")
        self.assertNotIn("addEventListener('append'", self.body)
        self.assertNotIn('addEventListener("append"', self.body)

    def test_heartbeat_ping_is_skipped(self):
        self.assertRegex(self.body, r"message\.data\s*===\s*'ping'")

    def test_load_more_pages_before_oldest(self):
        self.assertRegex(self.body, r"/events\?before='\s*\+\s*\(state\.oldest")

    def test_page_is_reversed_before_ingest(self):
        self.assertIn("slice().reverse().forEach(ingest)", self.body)

    def test_exhausted_set_when_no_more(self):
        self.assertIn("state.exhausted = true", self.body)

    def test_more_button_sits_above_the_feed(self):
        # Search the page markup only - the script's comments also
        # mention [data-log-feed], before the elements do.
        with open(PAGE, encoding="utf-8") as handle:
            markup = handle.read().split("</script>", 1)[1]
        more = markup.index("data-log-more")
        feed = markup.index("data-log-feed")
        self.assertLess(more, feed,
                        "the load-older control must precede the feed markup")

    def test_delimiters_balance(self):
        """A cheap structural stand-in for a JS parser (none is
        installed here): after stripping comments and string literals
        every bracket must close."""
        body = self.body
        out = []
        i = 0
        mode = None  # None | 'line' | 'block' | "'" | '"'
        while i < len(body):
            char = body[i]
            nxt = body[i + 1] if i + 1 < len(body) else ""
            if mode is None:
                if char == "/" and nxt == "/":
                    mode = "line"
                    i += 2
                    continue
                if char == "/" and nxt == "*":
                    mode = "block"
                    i += 2
                    continue
                if char in "'\"":
                    mode = char
                    i += 1
                    continue
                out.append(char)
            elif mode == "line":
                if char == "\n":
                    mode = None
                    out.append("\n")
            elif mode == "block":
                if char == "*" and nxt == "/":
                    mode = None
                    i += 2
                    continue
            else:  # inside a string literal
                if char == "\\":
                    i += 2
                    continue
                if char == mode:
                    mode = None
            i += 1
        self.assertEqual(mode, None, "unterminated comment or string literal")
        pairs = {")": "(", "]": "[", "}": "{"}
        stack = []
        for char in out:
            if char in "([{":
                stack.append(char)
            elif char in pairs:
                self.assertTrue(stack and stack[-1] == pairs[char],
                                "unbalanced %r at depth %s" % (char, stack))
                stack.pop()
        self.assertEqual(stack, [], "unclosed delimiters %s" % stack)


# ---------------------------------------------------------------------------
# Port of the client logic (keep in step with task_log.html)
# ---------------------------------------------------------------------------

STICK_THRESHOLD = 48  # px that still counts as "reading the tail"
PAGE_SIZE = 30


class Feed(object):
    """Scroll-state stand-in for [data-log-feed]."""

    def __init__(self, scroll_height=0, client_height=600, scroll_top=0):
        self.scroll_height = scroll_height
        self.client_height = client_height
        self.scroll_top = scroll_top


def at_bottom(feed):
    """PORT: a feed shorter than its viewport counts as at-bottom."""
    return feed.scroll_height - feed.scroll_top - feed.client_height \
        <= STICK_THRESHOLD


class State(object):
    """PORT: the module-level `state` object."""

    def __init__(self):
        self.events = []
        self.oldest = 0
        self.exhausted = False
        self.loading = False
        self.seeded = False


def ingest(state, evt):
    """PORT: keep state.events oldest-first (ascending id); skip ids
    already held (SSE replay after a reconnect resends a frame)."""
    i = 0
    while i < len(state.events) and state.events[i]["id"] < evt["id"]:
        i += 1
    if i < len(state.events) and state.events[i]["id"] == evt["id"]:
        return
    state.events.insert(i, evt)
    if evt["id"] < state.oldest or state.oldest == 0:
        state.oldest = evt["id"]


def render(state, feed, mode=None, height_after=None):
    """PORT of render(mode): decide the post-render scroll position.
    height_after stands in for the DOM rebuild's new scrollHeight."""
    was_at_bottom = at_bottom(feed)
    height_before = feed.scroll_height
    scroll_top_before = feed.scroll_top
    if height_after is not None:
        feed.scroll_height = height_after
    if not state.seeded and len(state.events) > 0:
        state.seeded = True
        feed.scroll_top = feed.scroll_height  # scrollToBottom()
    elif mode == "prepend":
        if was_at_bottom:
            feed.scroll_top = feed.scroll_height
        else:
            feed.scroll_top = scroll_top_before + (feed.scroll_height
                                                   - height_before)
    elif was_at_bottom:
        feed.scroll_top = feed.scroll_height
    else:
        feed.scroll_top = scroll_top_before
    return feed.scroll_top


def server_page(newest, oldest, more):
    """The endpoint's wire shape: newest-first within the page."""
    return {"events": [{"id": i} for i in range(newest, oldest - 1, -1)],
            "more": more}


def load_more(state, feed, page, height_after):
    """PORT of loadMore's success path: reverse the newest-first page
    into chronological order, ingest it, set exhausted, render."""
    rows = page["events"]
    for evt in reversed(rows):
        ingest(state, evt)
    if not page["more"] or len(rows) == 0:
        state.exhausted = True
    return render(state, feed, mode="prepend", height_after=height_after)


def on_stream_message(state, feed, data, height_after):
    """PORT of onStreamMessage: skip heartbeats, ingest one row."""
    if data == "ping":
        return feed.scroll_top
    ingest(state, {"id": int(data)})
    return render(state, feed, mode="append", height_after=height_after)


# ---------------------------------------------------------------------------
# Behaviour tests
# ---------------------------------------------------------------------------

def ids(state):
    return [evt["id"] for evt in state.events]


class ChronologyTests(unittest.TestCase):

    def test_initial_window_renders_oldest_first(self):
        """The SSE replay / first JSON page arrives newest-first
        ([30..1]); the feed must render [1..30] - oldest at the top."""
        state = State()
        for evt in server_page(30, 1, True)["events"]:
            ingest(state, evt)
        self.assertEqual(ids(state), list(range(1, 31)))
        self.assertEqual(state.oldest, 1)

    def test_live_appends_land_in_order(self):
        state = State()
        for i in range(30, 0, -1):
            ingest(state, {"id": i})
        ingest(state, {"id": 31})
        ingest(state, {"id": 33})
        ingest(state, {"id": 32})  # out of order arrival
        self.assertEqual(ids(state)[-3:], [31, 32, 33])

    def test_duplicate_ids_are_dropped(self):
        state = State()
        ingest(state, {"id": 5})
        ingest(state, {"id": 5})  # EventSource reconnect replay
        self.assertEqual(ids(state), [5])


class ScrollStickTests(unittest.TestCase):

    def test_first_render_with_rows_seeds_at_the_bottom(self):
        state = State()
        feed = Feed(scroll_height=0, client_height=600)
        for evt in server_page(30, 1, True)["events"]:
            ingest(state, evt)
        render(state, feed, height_after=3000)
        self.assertTrue(state.seeded)
        self.assertEqual(feed.scroll_top, 3000)

    def test_append_sticks_when_reading_the_tail(self):
        state = State()
        feed = Feed(scroll_height=3000, client_height=600)
        state.seeded = True
        feed.scroll_top = 2400  # exactly at the bottom
        self.assertTrue(at_bottom(feed))
        ingest(state, {"id": 31})
        render(state, feed, mode="append", height_after=3100)
        self.assertEqual(feed.scroll_top, 3100)

    def test_append_within_threshold_still_sticks(self):
        feed = Feed(scroll_height=3000, client_height=600, scroll_top=2360)
        self.assertTrue(at_bottom(feed))  # 40px shy: close enough

    def test_just_past_threshold_is_not_the_tail(self):
        feed = Feed(scroll_height=3000, client_height=600, scroll_top=2351)
        self.assertFalse(at_bottom(feed))  # 49px shy: reading history

    def test_scrolled_up_reader_is_never_yanked(self):
        state = State()
        feed = Feed(scroll_height=3000, client_height=600, scroll_top=500)
        state.seeded = True
        self.assertFalse(at_bottom(feed))
        ingest(state, {"id": 31})
        render(state, feed, mode="append", height_after=3100)
        self.assertEqual(feed.scroll_top, 500)

    def test_short_feed_counts_as_at_bottom(self):
        """A feed shorter than its viewport cannot be scrolled away
        from the newest row."""
        feed = Feed(scroll_height=100, client_height=600, scroll_top=0)
        self.assertTrue(at_bottom(feed))

    def test_heartbeat_does_not_touch_anything(self):
        state = State()
        feed = Feed(scroll_height=3000, client_height=600, scroll_top=2400)
        state.seeded = True
        before = (list(ids(state)), feed.scroll_top)
        on_stream_message(state, feed, "ping", height_after=3100)
        self.assertEqual((list(ids(state)), feed.scroll_top), before)


class LoadMoreTests(unittest.TestCase):

    def test_older_page_is_reversed_and_prepended(self):
        """before=<oldest>=1 returns [60..31] newest-first on the
        wire; the display must gain [31..60] above [1..30]."""
        state = State()
        feed = Feed(scroll_height=3000, client_height=600, scroll_top=500)
        for evt in server_page(30, 1, True)["events"]:
            ingest(state, evt)
        state.seeded = True
        render(state, feed, height_after=3000)
        feed.scroll_top = 500  # the reader scrolled up into history
        load_more(state, feed, server_page(60, 31, True), height_after=6000)
        self.assertEqual(ids(state), list(range(1, 61)))
        self.assertEqual(state.oldest, 1)
        self.assertFalse(state.exhausted)

    def test_prepend_keeps_the_viewport_anchored(self):
        """Content added above must not move the rows under the
        reader's cursor: scrollTop grows by the added height."""
        state = State()
        feed = Feed(scroll_height=3000, client_height=600, scroll_top=500)
        state.seeded = True
        self.assertFalse(at_bottom(feed))
        delta = 3000
        load_more(state, feed, server_page(60, 31, True),
                  height_after=3000 + delta)
        self.assertEqual(feed.scroll_top, 500 + delta)

    def test_prepend_while_at_bottom_stays_at_bottom(self):
        state = State()
        feed = Feed(scroll_height=3000, client_height=600, scroll_top=2400)
        state.seeded = True
        self.assertTrue(at_bottom(feed))
        load_more(state, feed, server_page(60, 31, True), height_after=6000)
        self.assertEqual(feed.scroll_top, 6000)

    def test_exhausted_when_more_is_false(self):
        state = State()
        feed = Feed(scroll_height=3000, client_height=600, scroll_top=2400)
        state.seeded = True
        load_more(state, feed, server_page(60, 31, False), height_after=6000)
        self.assertTrue(state.exhausted)

    def test_empty_page_exhausts_too(self):
        """A defensive guard: a page with no rows means no older
        history, whatever the flag says."""
        state = State()
        feed = Feed(scroll_height=3000, client_height=600, scroll_top=2400)
        state.seeded = True
        ingest(state, {"id": 1})
        load_more(state, feed, {"events": [], "more": True}, height_after=3000)
        self.assertTrue(state.exhausted)


class EndToEndSequenceTests(unittest.TestCase):
    """The whole first-minute story: replay, live tail, history."""

    def test_replay_then_append_then_history(self):
        state = State()
        feed = Feed(scroll_height=0, client_height=600)
        # 1. SSE replay: most-recent-30 oldest-first on the wire.
        for evt in server_page(30, 1, True)["events"]:
            ingest(state, evt)
        render(state, feed, height_after=3000)
        self.assertEqual(ids(state), list(range(1, 31)))
        self.assertEqual(feed.scroll_top, 3000)  # seeded at the tail

        # 2. Two live rows arrive; the reader is at the bottom.
        on_stream_message(state, feed, "31", height_after=3100)
        on_stream_message(state, feed, "32", height_after=3200)
        self.assertEqual(ids(state)[-2:], [31, 32])
        self.assertEqual(feed.scroll_top, 3200)

        # 3. A heartbeat is ignored, then the reader scrolls up.
        on_stream_message(state, feed, "ping", height_after=3200)
        feed.scroll_top = 100
        on_stream_message(state, feed, "33", height_after=3300)
        self.assertEqual(feed.scroll_top, 100)  # never yanked

        # 4. Load older: before=1 -> [60..31] newest-first wire page.
        self.assertEqual(state.oldest, 1)
        load_more(state, feed, server_page(60, 31, False), height_after=6300)
        self.assertEqual(ids(state), list(range(1, 61)))
        self.assertTrue(state.exhausted)
        self.assertEqual(feed.scroll_top, 100 + 3000)  # anchored


if __name__ == "__main__":
    unittest.main(verbosity=2)