"""
Where downloads are written.

The module is mostly browser plumbing — a directory handle from a picker, kept
in IndexedDB — but two pieces decide behaviour and can be checked here: that
automatic is the default, and that writing into the same folder repeatedly does
not quietly replace what is already there. The second one is the whole risk of
the automatic mode: a Save As dialog warns you about a collision, and a folder
you never look at does not.
"""

import json
import shutil
import subprocess
from pathlib import Path

import pytest

STATIC = Path(__file__).resolve().parents[1] / "src" / "meshbay_hub" / "static"
DOWNLOADS = STATIC / "downloads.js"

pytestmark = pytest.mark.skipif(
    shutil.which("node") is None or not DOWNLOADS.exists(),
    reason="node or the SPA sources are not available")


def _run(body, tmp_path):
    module = tmp_path / "downloads.mjs"
    module.write_text(DOWNLOADS.read_text())
    script = tmp_path / "case.mjs"
    script.write_text(
        # A localStorage good enough for a preference, so the module can be
        # imported outside a browser at all.
        "const store = new Map();\n"
        "globalThis.localStorage = {\n"
        "  getItem: k => (store.has(k) ? store.get(k) : null),\n"
        "  setItem: (k, v) => store.set(k, String(v)),\n"
        "};\n"
        f"const M = await import('{module.as_posix()}');\n"
        "const out = [];\n"
        "const say = (...a) => out.push(...a);\n"
        f"{body}\n"
        "console.log(JSON.stringify(out));\n")
    proc = subprocess.run(["node", str(script)], capture_output=True, text=True)
    assert proc.returncode == 0, proc.stderr
    return json.loads(proc.stdout)


def test_saving_automatically_is_the_default(tmp_path):
    """
    Grouped downloads are the reason this setting exists: twelve files must not
    mean twelve dialogs unless someone asked for that.
    """
    assert _run("say(M.getMode());", tmp_path) == ["auto"]


def test_the_choice_is_remembered_and_nothing_else_is_accepted(tmp_path):
    result = _run("""
M.setMode('ask');   say(M.getMode());
M.setMode('auto');  say(M.getMode());
M.setMode('nonsense'); say(M.getMode());
""", tmp_path)
    assert result == ["ask", "auto", "auto"]


def test_a_second_copy_does_not_replace_the_first(tmp_path):
    result = _run("""
const taken = new Set(['clip.mp4', 'clip (2).mp4', 'notes']);
const exists = async n => taken.has(n);
say(await M.freeName('clip.mp4', exists));
say(await M.freeName('other.mp4', exists));
say(await M.freeName('notes', exists));
say(await M.freeName('archive.tar.gz', exists));
""", tmp_path)
    assert result == [
        "clip (3).mp4",      # (2) was taken as well
        "other.mp4",         # free: left alone
        "notes (2)",         # no extension to keep
        "archive.tar.gz",    # free, and the double extension is not mangled
    ]


def test_the_suffix_goes_before_the_extension(tmp_path):
    """
    "clip.mp4 (2)" would stop being a video as far as the operating system is
    concerned, which is how a download folder ends up full of files nothing opens.
    """
    result = _run("""
say(await M.freeName('clip.mp4', async () => false));
say(await M.freeName('clip.mp4', async n => n === 'clip.mp4'));
""", tmp_path)
    assert result == ["clip.mp4", "clip (2).mp4"]


def test_a_browser_without_the_api_reports_it(tmp_path):
    """`SUPPORTED` decides whether Settings offers a choice or an explanation."""
    assert _run("say(M.SUPPORTED);", tmp_path) == [False]


def test_the_open_action_reads_the_file_back(tmp_path):
    """
    "Open" is the browser being handed the bytes, not a desktop application
    being started — no web page can do the second, and none can show a file
    manager either. It is only offered for a file written into a granted folder,
    since that is the one a page can read back.
    """
    src = DOWNLOADS.read_text()
    target = src[src.index("export async function openTarget"):]
    assert "getFile()" in target and "window.open(" in target
    assert "revokeObjectURL" in target, "the blob URL must not be leaked"


# ── Streaming to disk without the File System Access API ────────────────────

SW = STATIC / "sw.js"


def test_the_worker_only_answers_its_own_urls():
    """
    It is registered at the root scope, so it sees every request the page makes.
    Anything that is not a download of ours has to fall through untouched — a
    service worker that answers more than it should is a cache bug waiting to
    happen.
    """
    src = SW.read_text()
    assert "startsWith(PREFIX)" in src
    assert "self.location.origin" in src, "cross-origin requests must fall through"
    # The API, not the word: the file explains in prose that it caches nothing.
    for api in ("caches.open", "caches.match", "cache.put"):
        assert api not in src, f"this worker must not cache anything ({api})"


def test_the_download_is_announced_as_an_attachment():
    src = SW.read_text()
    assert "Content-Disposition" in src and "attachment" in src
    assert "filename*=UTF-8''" in src, "a name with accents would be mangled"
    assert "Content-Length" in src


def test_a_length_is_only_promised_when_it_is_known(tmp_path):
    """
    An archive is assembled as it goes and is larger than the files in it.
    Announcing the sum of their sizes would truncate the download at that mark.
    """
    src = SW.read_text()
    assert "if (entry.size > 0)" in src

    # The zip-directory download started in files-app.js (group-page refactor)
    # and was lifted into file-utils.js's downloadDirectory
    # (docs/MESHBAY_DESIGN.md §9.9) so photos-app.js's own "zip this album"
    # button calls the same implementation rather than a second one.
    # Anchored on the call, not on how its result is bound: the assignment
    # became a bare `target = ...` inside a try when _openDownloadTarget gained
    # the ability to refuse an oversized download (test_memory_ceiling.py).
    # What this test is about -- the `0` -- did not move.
    app = (STATIC / "file-utils.js").read_text()
    # Anchored on the argument list, not on the function name: the call became
    # `_openTargetInTurn(suggested, …)` when target openings were serialised.
    # The `0` this test is about did not move.
    zip_call = app[app.index("(suggested, totalBytes"):]
    zip_call = zip_call[:zip_call.index(");") + 2]
    assert zip_call.rstrip().endswith(", 0);"), (
        "the zip download announces a Content-Length it will not match")


def test_backpressure_is_real(tmp_path):
    """
    The point of the service worker path is not holding the file. A stream that
    is transferred gives `writer.write()` something to wait on; posting chunks
    to a port would queue them in memory and look identical from here.
    """
    src = DOWNLOADS.read_text()
    fn = src[src.index("export async function openStreamedDownload"):]
    assert "new TransformStream()" in fn
    # The transfer list may carry more than the stream — a reply port rides
    # along now — so this asserts that `readable` is transferred, not the exact
    # shape of the list.
    #
    # And every `postMessage` in here, not the first: a ping is sent to wake the
    # worker before it is handed anything, and it carries only a port. Reading
    # the first one would have moved this check onto the ping the day it was
    # added, leaving the stream unguarded while still passing.
    posts = []
    rest = fn
    while "worker.postMessage(" in rest:
        rest = rest[rest.index("worker.postMessage("):]
        # Bounded by the call's own end: the keep-alive ping transfers nothing
        # at all, and reaching past it for a `[` would read the next call's.
        posts.append(rest[:rest.index(");") + 2])
        rest = rest[len("worker.postMessage("):]
    lists = [c[c.index("["):c.index("]") + 1] for c in posts if "[" in c]
    assert len(posts) >= 2, "the wake-up and the stream are both posted from here"
    assert any("readable" in t for t in lists), (
        "the readable half must be transferred, not copied")
    assert "writer.write(bytes)" in fn
    assert "return null" in fn, "a browser that cannot transfer streams must say so"


def test_the_streamed_path_gives_up_rather_than_blocking_for_ever():
    """Reported 2026-08-16: a download frozen at exactly one chunk.

    The writable half applies real backpressure, which is the whole point — and
    the trap. If nothing ever reads the readable half, `writer.write()` waits
    for room that never comes, and the transfer stops dead after the stream's
    internal queue fills. Two ways that happens on a phone: the page is not yet
    *controlled* by the worker, so the iframe's request is never handed to its
    fetch handler; or the browser refuses a download started from a hidden
    iframe. Both are silent.

    So the worker confirms that it actually answered, and this path reports
    failure instead of returning a sink nobody drains.
    """
    src = DOWNLOADS.read_text()
    fn = src[src.index("export async function openStreamedDownload"):]
    assert "mbdl-serving" in fn, "the worker has to confirm it served the request"
    assert "Promise.race" in fn, "the confirmation needs a deadline"
    assert "writable.abort" in fn, "give up cleanly so the caller can fall back"

    sw = (DOWNLOADS.parent / "sw.js").read_text()
    assert "mbdl-serving" in sw, "and the worker has to send that confirmation"


def test_an_uncontrolled_page_is_not_treated_as_ready():
    """`registration.active` says a worker exists, not that it will see our fetch."""
    # Anchored on the streaming section rather than on one function: waiting
    # for control moved into `_awaitControl`/`_claimController` when the budget
    # became a parameter, and `serviceWorker()` no longer contains the words.
    # The behaviour itself is executed in test_streamed_download_reliability.py;
    # this stays as the cheap guard on the module's shape.
    src = DOWNLOADS.read_text()
    section = src[src.index("// ── Streaming to disk"):]
    assert "navigator.serviceWorker.controller" in section
    assert "controllerchange" in section, (
        "control can arrive a tick after registration; waiting beats refusing")
    assert "mbdl-claim" in section, (
        "an active-but-uncontrolled page must ask for a claim, not give up")


def test_an_apostrophe_in_a_name_does_not_lose_the_name(tmp_path):
    """
    `encodeURIComponent` leaves `'` alone, and `'` is the delimiter in RFC
    5987's `filename*=<charset>'<lang>'<value>`. One apostrophe made the header
    unparseable, and a browser that cannot parse it names the file after the
    last segment of the URL — which for this worker is a made-up id. The file
    arrived complete and 449 MB of it was called "mtsshk9w-ohqty535".

    Found by downloading three files where exactly one had an apostrophe.
    Nothing in the suite could have: the header was built correctly for every
    name anybody had tested with.

    The real function is lifted out of sw.js and run — a second copy here would
    have the same blind spot as the first.
    """
    src = SW.read_text()
    fn = src[src.index("function contentDisposition"):]
    fn = fn[:fn.index("\n}") + 2]

    script = tmp_path / "case.mjs"
    script.write_text(fn + """
const out = {};
for (const name of ["S03E02. Queen's Landing.mp4", 'Caf\\u00e9 (2019).mkv',
                    'plain.mp4', 'quote".mp4', 'star*.mp4']) {
  out[name] = contentDisposition(name);
}
console.log(JSON.stringify(out));
""")
    proc = subprocess.run(["node", str(script)], capture_output=True, text=True)
    assert proc.returncode == 0, proc.stderr
    out = json.loads(proc.stdout)

    for name, header in out.items():
        starred = header.split("filename*=UTF-8''", 1)[1]
        assert "'" not in starred, (
            f"{name!r}: an apostrophe survived into the starred value, which "
            f"is where RFC 5987 puts its delimiter — the name is lost")
        for forbidden in "()*":
            assert forbidden not in starred, (
                f"{name!r}: {forbidden!r} is not an attr-char and must be "
                f"percent-encoded")
        # The starred value has to decode back to the real name, or the escaping
        # fixed the parse and broke the result.
        from urllib.parse import unquote
        assert unquote(starred) == name

    # The ASCII fallback must not end its own quoted string.
    for name, header in out.items():
        ascii_part = header.split('filename="', 1)[1].split('";', 1)[0]
        assert '"' not in ascii_part and "\\" not in ascii_part


def test_a_sink_that_stops_consuming_fails_instead_of_hanging(tmp_path):
    """
    `writable.write()` was the one await on the download path with no bound.

    Every other one reports itself: `_sendAndWait` logs a Response timeout,
    `_fetchChunkResilient` retries and throws. A sink that stops consuming — a
    service-worker stream the browser has stopped reading — leaves `write()`
    pending for ever. It never rejects, so there is no error, no log and no
    failed transfer: the progress bar stops, the console stays empty, and the
    node is healthy throughout.

    That combination is what made it unfindable: three separate measurements
    cleared the node, the transport and the worker, because none of them was
    wrong. Bounding it does not fix whatever stopped the sink — it turns an
    unexplainable freeze into a failed transfer that names itself.
    """
    src = (STATIC / "file-utils.js").read_text()
    fn = src[src.index("async function _writeOrStall"):]
    fn = fn[:fn.index("\n}\n") + 2]

    script = tmp_path / "case.mjs"
    script.write_text("""
const t = (key, vars) => key + ' ' + JSON.stringify(vars);
const WRITE_STALL_MS = 300;      // the real value is 60s; the shape is the test
""" + fn + """
const out = {};
// A sink that never resolves — the frozen download, exactly.
const dead = { write: () => new Promise(() => {}) };
const t0 = Date.now();
try {
  await _writeOrStall(dead, new Uint8Array(4), 41);
  out.threw = null;
} catch (e) { out.threw = e.message; }
out.ms = Date.now() - t0;

// And a working sink is not slowed down or wrapped in anything.
const live = { write: async () => {} };
await _writeOrStall(live, new Uint8Array(4), 0);
out.liveOk = true;
console.log(JSON.stringify(out));
""")
    proc = subprocess.run(["node", str(script)], capture_output=True, text=True)
    assert proc.returncode == 0, proc.stderr
    out = json.loads(proc.stdout)
    assert out["threw"], "a dead sink hung for ever instead of failing"
    assert "group.download_write_stalled" in out["threw"], (
        "the failure must name itself in the transfers panel")
    assert "41" in out["threw"], "and say which chunk it stopped at"
    assert out["ms"] < 3000
    assert out["liveOk"] is True


def test_the_worker_is_kept_alive_while_it_streams():
    """
    A service worker with no event for ~30 s is terminated — Firefox does it,
    and `respondWith(new Response(stream))` does not extend its life while the
    response is still being written. The reader vanishes mid-file, the page's
    next `write()` never resolves and never rejects: the progress bar stops,
    the console stays empty, and the node looks healthy throughout.

    Measured in real Firefox 154 on 2026-09-08, writing 1 MB every 2 s:
    without the ping it stalled at 17 MB after 59 s; with it, 40 MB in 80 s,
    complete. The first version of that probe wrote 450 MB in two seconds and
    passed — fast enough to hide the bug entirely, which is why the pacing
    matters and is written down here.

    Source-reading, because the behaviour needs a browser and a minute of wall
    clock. What it protects is that the ping exists at all, is cleared on both
    exits, and is answered by the worker.
    """
    dl = DOWNLOADS.read_text()
    sw = SW.read_text()

    assert "SW_KEEPALIVE_MS" in dl and "mbdl-ping" in dl, (
        "nothing keeps the worker alive; downloads longer than ~30 s will "
        "stall on Firefox with no error anywhere")
    fn = dl[dl.index("async function _attemptStreamedDownload"):]
    interval = fn[fn.index("setInterval"):]
    assert "mbdl-ping" in interval[:200]

    # Cleared on both ways out, or a finished download leaves a timer pinging a
    # worker for the life of the page.
    for exit_path in ("close:", "abort:"):
        block = fn[fn.index(exit_path):]
        assert "clearInterval(keepAlive)" in block[:220], (
            f"the keep-alive is not cleared in {exit_path} — it outlives the "
            f"download")

    # And the worker has to answer it: a message it ignores still counts as an
    # event, but the reply is what tells the page it is talking to the worker
    # that holds its stream.
    assert "mbdl-ping" in sw and "mbdl-pong" in sw


def _turn_harness(tmp_path, name, body, *, picker=True, budget_ms=90000):
    """Run the real `_openTargetInTurn` against a stubbed opener.

    Both it and `_waitBriefly` are lifted out of `file-utils.js` as text; only
    the budget is supplied here, so a case about the budget need not wait a
    minute and a half for it.
    """
    src = (STATIC / "file-utils.js").read_text()

    def lift(decl):
        cut = src[src.index(decl):]
        return cut[:cut.index("\n}\n") + 2]

    picker_js = ("window.showSaveFilePicker = async () => ({});"
                 if picker else "")
    script = tmp_path / f"{name}.mjs"
    script.write_text(f"""
const out = [];
let live = 0, peak = 0;
const asked = [];
// Stands in for _openDownloadTarget: records how many are open at once, and
// whether each was told it is not the first of its batch.
const _openDownloadTarget = async (name, size, opts, swSize, flags) => {{
  live += 1; peak = Math.max(peak, live);
  asked.push(!!(flags && flags.batched));
  if (name === 'stuck') return await new Promise(() => {{}});
  await new Promise(r => setTimeout(r, 20));
  live -= 1;
  if (name === 'boom') throw new Error('refused');
  return {{ name }};
}};
// Only a browser with a Save As dialog has anything to serialise.
globalThis.window = {{}};
{picker_js}
let _targetQueue = Promise.resolve();
let _targetsInFlight = 0;
const TARGET_QUEUE_BUDGET_MS = {budget_ms};
""" + lift("function _openTargetInTurn") + lift("function _waitBriefly") + f"""
{body}
console.log(JSON.stringify(out));
""")
    proc = subprocess.run(["node", str(script)], capture_output=True, text=True)
    assert proc.returncode == 0, proc.stderr
    return json.loads(proc.stdout)


def test_targets_are_opened_one_at_a_time(tmp_path):
    """
    A browser shows one file picker at a time and grants one per user gesture,
    so four downloads asking at once get one dialog and three failures.

    That used to be prevented by accident: `downloadEntry` awaited the target
    inline and files-app.js's `for (…) await downloadFile(e)` serialised them.
    Opening the target inside `prepare` — so the row appears at the click rather
    than tens of seconds later — removed the accident, and four pickers raced.
    Reported from Chrome: one file downloaded, a prompt for the second, the
    other two timed out.

    The queue is on the *targets*, never on the rows: every download still
    appears the moment it is asked for.

    Queueing alone was not enough: a second dialog with no gesture behind it
    still waits for a human, and the two behind it wait for the dialog. So
    everything that has to wait its turn is also marked `batched`, which the
    opener reads as "do not ask" — see the streamed-path branch in
    test_memory_ceiling.py.
    """
    peak, statuses, batched = _turn_harness(tmp_path, "one_at_a_time", """
const results = await Promise.allSettled(
  ['a', 'boom', 'c', 'd'].map(n => _openTargetInTurn(n)));
out.push(peak);
out.push(results.map(r => r.status).join(','));
out.push(asked);
""")
    assert peak == 1, f"{peak} targets were being opened at once"
    # And one refusal must not stop the rest: a chain that breaks on a rejection
    # leaves every later download unable to open anything at all.
    assert statuses == "fulfilled,rejected,fulfilled,fulfilled"
    assert batched == [False, True, True, True], (
        "only the first of a batch holds the user's gesture; the rest must be "
        "opened without asking")


def test_a_browser_with_no_dialog_does_not_queue_at_all(tmp_path):
    """Firefox and Safari have no `showSaveFilePicker`, so no two openings there
    can race a dialog and there is nothing for a queue to protect.

    Queueing them anyway was a regression: four downloads that had always opened
    their targets at the same time began waiting on the slowest, and all four
    sat at "preparing". A queue that buys nothing must not be paid for.
    """
    peak, = _turn_harness(tmp_path, "no_picker", """
await Promise.all(['a', 'b', 'c', 'd'].map(n => _openTargetInTurn(n)));
out.push(peak);
""", picker=False)
    assert peak == 4, (
        f"only {peak} target opening(s) ran at once; without a dialog to "
        "serialise, all four must proceed together as they did before")


def test_one_stuck_opening_does_not_hold_the_others_for_ever(tmp_path):
    """`_targetQueue` is never reset, so an opening that never settles would
    otherwise leave the page unable to start any download again — a panel that
    only a reload can fix.

    The budget is 60 ms here; in the page it is ninety seconds, long enough that
    a real dialog is never cut in front of.
    """
    statuses, batched = _turn_harness(tmp_path, "stuck", """
const first = _openTargetInTurn('stuck');
first.catch(() => {});
const rest = await Promise.allSettled(
  ['b', 'c'].map(n => _openTargetInTurn(n)));
out.push(rest.map(r => r.status).join(','));
out.push(asked);
""", budget_ms=60)
    assert statuses == "fulfilled,fulfilled", (
        "an opening that never settles must not strand the ones behind it")
    assert batched == [False, True, True], (
        "the stuck one is still the only holder of the gesture, so the released "
        "openings must not try for a dialog of their own")


def test_a_pause_falls_between_chunks_and_resumes_at_one(tmp_path):
    """What makes resuming exact rather than approximate.

    Everything written is a whole number of chunks, because the loop checks for
    a pause between two of them and never inside one. So `fromChunk` is a
    position, not an estimate, and a resumed download is never appended to at an
    offset nobody verified — the failure mode being avoided is a file that looks
    complete and is quietly corrupt.

    The real `pipelinedDownload` is lifted out and run against stubs, on the
    rule this repo follows for the video player: model the environment, never
    the code under test.
    """
    src = (STATIC / "file-utils.js").read_text()
    fn = src[src.index("async function pipelinedDownload"):]
    fn = fn[:fn.index("\n}\n") + 2]

    script = tmp_path / "pipeline.mjs"
    script.write_text("""
const CHUNK_SIZE = 8;
const PIPELINE_WINDOW = 4;
const written = [];
// `ct` has to be truthy: chunk 0 with a falsy body is refused as undecryptable,
// which is the guard working, not the harness.
const _fetchChunkResilient = async (transport, fileId, i) =>
  ({ ct: new Uint8Array([i & 0xff]), nonce: new Uint8Array(12) });
const _writeOrStall = async (w, bytes, index) => { written.push(index); };
globalThis.window = { MeshBayCrypto: {
  // The plaintext carries its own index, so what lands where can be checked.
  decryptChunkBin: async (k, id, index) => ({ byteLength: CHUNK_SIZE, index }),
} };
""" + fn + """
const out = {};
const signal = { aborted: false, paused: false };
// Stop it part way, the way the store does.
let seen = 0;
const onChunk = () => { if (++seen === 3) signal.paused = true; };
try {
  await pipelinedDownload({}, 'k', 'file', 10, onChunk, {}, signal, '', 0);
  out.threw = 'no';
} catch (err) {
  out.threw = err.name;
}
out.resumeFrom = signal.resumeFrom;
out.writtenBeforePause = written.slice();

// And again, from where it said.
signal.paused = false;
written.length = 0;
await pipelinedDownload({}, 'k', 'file', 10, () => {}, {}, signal, '',
                        out.resumeFrom);
out.writtenAfterResume = written.slice();
console.log(JSON.stringify(out));
""")
    proc = subprocess.run(["node", str(script)], capture_output=True, text=True)
    assert proc.returncode == 0, proc.stderr
    out = json.loads(proc.stdout)

    assert out["threw"] == "PausedError", out
    # Whole chunks only, in order, with nothing skipped.
    assert out["writtenBeforePause"] == list(range(len(out["writtenBeforePause"])))
    assert out["resumeFrom"] == len(out["writtenBeforePause"]), (
        f"stopped after {len(out['writtenBeforePause'])} chunks but asked to "
        f"resume at {out['resumeFrom']} — that gap is a hole in the file")
    # The resumed run covers exactly the rest, and repeats nothing.
    assert out["writtenAfterResume"] == list(range(out["resumeFrom"], 10)), out