unshackle/tests/tracks/test_subtitle_skip.py

"""Tests for ``download_tracks_in_passes`` - the two-pass track download used by
``dl.result()`` when ``--skip-subtitle-errors`` is set.

The behaviour under test is the cancel-event interaction: a failed track sets the
process-global ``DOWNLOAD_CANCELLED`` event, which makes other in-flight tracks
early-return without raising. Running the fatal video/audio tracks to completion
*before* the skippable subtitles removes that race, so a subtitle failure can no
longer truncate the video/audio that still gets muxed.
"""

from __future__ import annotations

import pytest

from unshackle.commands.dl import SkippedSubtitle, download_tracks_in_passes
from unshackle.core.constants import DOWNLOAD_CANCELLED
from unshackle.core.tracks import Audio, Subtitle, Video


def make_video(track_id: str = "v") -> Video:
    return Video(
        id_=track_id,
        url=f"https://example.test/{track_id}.m3u8",
        language="en",
        codec=Video.Codec.AVC,
        range_=Video.Range.SDR,
        width=1920,
        height=1080,
        bitrate=5_000_000,
    )


def make_audio(track_id: str = "a") -> Audio:
    return Audio(
        id_=track_id,
        url=f"https://example.test/{track_id}.m3u8",
        language="en",
        codec=Audio.Codec.AAC,
        bitrate=128_000,
    )


def make_subtitle(track_id: str, language: str) -> Subtitle:
    return Subtitle(
        id_=track_id,
        url=f"https://example.test/{track_id}.vtt",
        language=language,
        codec=Subtitle.Codec.WebVTT,
    )


class Harness:
    """Mimics how ``dl.result`` drives the helper, with a controllable downloader.

    ``run_one`` mirrors ``Track.download``: it early-returns (without recording a
    completion) when the cancel event is already set, and a track flagged to fail
    sets the event and raises - exactly what the real cancel sites do.
    """

    def __init__(self, fail_ids: set[str]):
        self.fail_ids = fail_ids
        self.completed: list[str] = []
        self.early_returned: list[str] = []
        self.skipped: list[Subtitle] = []

    def run_one(self, track, _index):
        if DOWNLOAD_CANCELLED.is_set():
            self.early_returned.append(track.id)
            return
        if track.id in self.fail_ids:
            DOWNLOAD_CANCELLED.set()
            raise RuntimeError(f"{track.id} failed")
        self.completed.append(track.id)

    def on_subtitle_skipped(self, track):
        self.skipped.append(track)


@pytest.fixture(autouse=True)
def _clear_event():
    DOWNLOAD_CANCELLED.clear()
    yield
    DOWNLOAD_CANCELLED.clear()


def test_failed_subtitle_does_not_truncate_video_or_audio():
    """A subtitle that fails *and sets the cancel event* must not stop the video/audio."""
    video, audio = make_video(), make_audio()
    sub = make_subtitle("s-he", "he")
    h = Harness(fail_ids={"s-he"})

    download_tracks_in_passes(
        [video, audio, sub], 4, h.run_one,
        skip_subtitle_errors=True, on_subtitle_skipped=h.on_subtitle_skipped,
    )

    assert set(h.completed) == {"v", "a"}  # both fatal tracks fully downloaded
    assert h.early_returned == []  # nothing early-returned because of the subtitle
    assert h.skipped == [sub]  # the subtitle was recorded as skipped


def test_good_subtitle_kept_bad_subtitle_skipped():
    video = make_video()
    good, bad = make_subtitle("s-en", "en"), make_subtitle("s-fr", "fr")
    h = Harness(fail_ids={"s-fr"})

    download_tracks_in_passes(
        [video, good, bad], 4, h.run_one,
        skip_subtitle_errors=True, on_subtitle_skipped=h.on_subtitle_skipped,
    )

    assert "s-en" in h.completed  # the available subtitle still downloaded
    assert h.skipped == [bad]  # only the failing one was skipped


def test_subtitle_failure_stays_fatal_without_flag():
    """Default behaviour (flag off) is unchanged: a subtitle failure aborts the title."""
    video = make_video()
    sub = make_subtitle("s-he", "he")
    h = Harness(fail_ids={"s-he"})

    with pytest.raises(RuntimeError):
        download_tracks_in_passes(
            [video, sub], 4, h.run_one,
            skip_subtitle_errors=False, on_subtitle_skipped=h.on_subtitle_skipped,
        )

    assert not DOWNLOAD_CANCELLED.is_set()  # the finally clears the event even on the fatal path


def test_cancel_event_is_reset_between_titles():
    """A cancel left set by a previous title must not skip this title's tracks."""
    DOWNLOAD_CANCELLED.set()
    video, audio = make_video(), make_audio()
    h = Harness(fail_ids=set())

    download_tracks_in_passes(
        [video, audio], 4, h.run_one,
        skip_subtitle_errors=True, on_subtitle_skipped=h.on_subtitle_skipped,
    )

    assert set(h.completed) == {"v", "a"}
    assert h.early_returned == []


def test_cancel_event_cleared_after_failed_final_subtitle():
    """A subtitle failing in the last pass leaves the event clear on exit, not set."""
    video = make_video()
    sub = make_subtitle("s-he", "he")
    h = Harness(fail_ids={"s-he"})

    download_tracks_in_passes(
        [video, sub], 4, h.run_one,
        skip_subtitle_errors=True, on_subtitle_skipped=h.on_subtitle_skipped,
    )

    assert not DOWNLOAD_CANCELLED.is_set()  # the helper clears it on exit for any later code


def test_all_subtitles_skipped_video_audio_kept():
    """Every subtitle failing must not stop the video/audio, and each is recorded."""
    video, audio = make_video(), make_audio()
    s1, s2 = make_subtitle("s-en", "en"), make_subtitle("s-he", "he")
    h = Harness(fail_ids={"s-en", "s-he"})

    download_tracks_in_passes(
        [video, audio, s1, s2], 4, h.run_one,
        skip_subtitle_errors=True, on_subtitle_skipped=h.on_subtitle_skipped,
    )

    assert set(h.completed) == {"v", "a"}  # both fatal tracks survived
    assert {t.id for t in h.skipped} == {"s-en", "s-he"}  # every failing subtitle recorded


def test_duplicate_language_subtitles_distinguished_by_id():
    """Forced + SDH share a language; a failure of each must be distinguishable by track id -
    the reason ``SkippedSubtitle`` carries ``id`` and not just ``language``."""
    forced, sdh = make_subtitle("en-forced", "en"), make_subtitle("en-sdh", "en")
    h = Harness(fail_ids={"en-forced", "en-sdh"})

    download_tracks_in_passes(
        [make_video(), forced, sdh], 4, h.run_one,
        skip_subtitle_errors=True, on_subtitle_skipped=h.on_subtitle_skipped,
    )

    assert [t.id for t in h.skipped] == ["en-forced", "en-sdh"]  # same language, distinct ids


def test_skipped_subtitle_contract():
    """Pin the public ``skipped_subtitles`` entry shape - #113 serializes it into the job, so a
    field rename/removal here is a breaking change and must fail a test."""
    assert set(SkippedSubtitle.__annotations__) == {"id", "language", "title"}
    assert SkippedSubtitle.__required_keys__ == frozenset({"id", "language", "title"})