"""Tests for the data-driven subtitle conversion registry (``tracks/subtitle_convert.py``).

Covers three things the refactor must guarantee:
- the capability matrix resolves the right backend chain per (source, target) and env
  (SubtitleEdit present or not),
- ``conversion_method`` pins a backend but still falls back (pin-then-fallback),
- styled SubStation (ASS/SSA) is never auto-downconverted to SRT unless explicitly forced.

Backends pysubs2/subby/pycaption are hard deps so the conversion paths run in CI without
SubtitleEdit; SubtitleEdit availability is simulated by patching ``binaries.SubtitleEdit``.
"""

from __future__ import annotations

import pathlib
import re
import struct

import pycaption
import pytest

from unshackle.core import binaries
from unshackle.core.tracks import subtitle_convert as sc
from unshackle.core.tracks.subtitle import Subtitle
from unshackle.core.tracks.track import Track

Codec = Subtitle.Codec

VTT_SAMPLE = """WEBVTT

1
00:00:01.000 --> 00:00:02.000
Hello

2
00:00:03.000 --> 00:00:04.000
World
"""

ASS_SAMPLE = """[Script Info]
ScriptType: v4.00+

[V4+ Styles]
Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
Style: Default,Arial,20,&H00FFFFFF,&H000000FF,&H00000000,&H00000000,0,0,0,0,100,100,0,0,1,2,1,2,10,10,18,1

[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:01.00,0:00:02.00,Default,,0,0,0,,{\\i1}Hello{\\i0}
Dialogue: 0,0:00:03.00,0:00:04.00,Default,,0,0,0,,World
"""


LAYERED_ASS_SAMPLE = ASS_SAMPLE.replace(
    "Dialogue: 0,0:00:01.00", "Dialogue: 1,0:00:05.00,0:00:06.00,Default,,0,0,0,,Sign\nDialogue: 0,0:00:01.00"
)

# Read before the autouse fixture below hides it.
INSTALLED_SUBTITLEEDIT = binaries.SubtitleEdit


@pytest.fixture(autouse=True)
def no_subtitleedit(monkeypatch):
    """Default every test to a SubtitleEdit-less environment; tests opt in when needed."""
    monkeypatch.setattr(binaries, "SubtitleEdit", None)


def make_sub(tmp_path, name: str, text: str, codec: Codec) -> Subtitle:
    path = tmp_path / name
    path.write_text(text, encoding="utf8")
    sub = Subtitle(url="https://example.test/x", language="en", codec=codec)
    sub.path = path
    return sub


def cue_count(path) -> int:
    return len(re.findall(r"-->", path.read_text("utf8")))


def test_resolve_webvtt_to_srt_order():
    chain = [b.name for b in sc.resolve_backends(Codec.WebVTT, Codec.SubRip)]
    assert chain == ["subby", "pysubs2", "pycaption"]


def test_resolve_ass_to_srt_only_pysubs2_without_subtitleedit():
    # subby and pycaption cannot read ASS, so only pysubs2 remains.
    chain = [b.name for b in sc.resolve_backends(Codec.SubStationAlphav4, Codec.SubRip)]
    assert chain == ["pysubs2"]


def test_subtitleedit_ranks_first_when_available(monkeypatch):
    monkeypatch.setattr(binaries, "SubtitleEdit", "/usr/bin/seconv")
    chain = [b.name for b in sc.resolve_backends(Codec.WebVTT, Codec.SubRip)]
    assert chain[0] == "subtitleedit"


def test_styled_ass_to_ttml_vtt_prefers_pysubs2_over_subtitleedit(monkeypatch):
    # Measured: SE flattens ASS inline styling to TTML/VTT; pysubs2 keeps i/b/u.
    monkeypatch.setattr(binaries, "SubtitleEdit", "/usr/bin/seconv")
    for target in (Codec.TimedTextMarkupLang, Codec.WebVTT):
        chain = [b.name for b in sc.resolve_backends(Codec.SubStationAlphav4, target)]
        assert chain[0] == "pysubs2", f"expected pysubs2 first for ASS->{target.name}, got {chain}"
        assert "subtitleedit" in chain  # still a fallback
    # ASS->SRT keeps SE first (only backend that keeps colour there).
    chain = [b.name for b in sc.resolve_backends(Codec.SubStationAlphav4, Codec.SubRip)]
    assert chain[0] == "subtitleedit"


def test_pin_then_fallback_orders_pin_first():
    chain = [b.name for b in sc.resolve_backends(Codec.WebVTT, Codec.SubRip, pin="pysubs2")]
    assert chain[0] == "pysubs2"
    assert "subby" in chain  # fallbacks remain after the pin


def test_pin_unavailable_falls_back_to_ranked_chain():
    # subtitleedit pinned but not installed -> just the ranked available backends.
    chain = [b.name for b in sc.resolve_backends(Codec.WebVTT, Codec.SubRip, pin="subtitleedit")]
    assert chain == ["subby", "pysubs2", "pycaption"]


def test_fallback_runs_when_first_backend_fails(tmp_path, monkeypatch):
    monkeypatch.setattr("unshackle.core.config.config.subtitle", {}, raising=False)

    def boom(self, source, src, target, out):
        raise RuntimeError("backend exploded")

    # WebVTT->SRT chain is [subby, pysubs2, pycaption]; kill subby, expect pysubs2 to finish.
    monkeypatch.setattr(sc.SubbyBackend, "convert", boom)
    sub = make_sub(tmp_path, "x.vtt", VTT_SAMPLE, Codec.WebVTT)
    out = sub.convert(Codec.SubRip, forced=True)
    assert sub.codec == Codec.SubRip
    assert cue_count(out) == 2


def test_no_backend_for_unsupported_target_raises(tmp_path):
    sub = make_sub(tmp_path, "x.ass", ASS_SAMPLE, Codec.SubStationAlphav4)
    with pytest.raises(NotImplementedError):
        sub.convert(Codec.fVTT, forced=True)  # no backend writes segmented fVTT


def test_ass_to_srt_kept_as_is_when_not_forced(tmp_path, monkeypatch):
    monkeypatch.setattr("unshackle.core.config.config.subtitle", {}, raising=False)
    sub = make_sub(tmp_path, "x.ass", ASS_SAMPLE, Codec.SubStationAlphav4)
    out = sub.convert(Codec.SubRip, forced=False)
    assert sub.codec == Codec.SubStationAlphav4  # unchanged
    assert out == sub.path
    assert out.suffix == ".ass"


def test_ass_to_srt_converts_when_forced(tmp_path, monkeypatch):
    monkeypatch.setattr("unshackle.core.config.config.subtitle", {}, raising=False)
    sub = make_sub(tmp_path, "x.ass", ASS_SAMPLE, Codec.SubStationAlphav4)
    out = sub.convert(Codec.SubRip, forced=True)
    assert sub.codec == Codec.SubRip
    assert out.suffix == ".srt"
    assert cue_count(out) == 2
    assert "{\\" not in out.read_text("utf8")  # override tags stripped


@pytest.mark.parametrize("target", [Codec.SubRip, Codec.WebVTT])
@pytest.mark.parametrize("backend", ["pysubs2", "subtitleedit"])
def test_layered_ass_converts_in_start_time_order(tmp_path, monkeypatch, backend, target):
    if backend == "subtitleedit":
        if not INSTALLED_SUBTITLEEDIT:
            pytest.skip("SubtitleEdit is not installed")
        monkeypatch.setattr(binaries, "SubtitleEdit", INSTALLED_SUBTITLEEDIT)
    monkeypatch.setattr("unshackle.core.config.config.subtitle", {"conversion_method": backend}, raising=False)
    sub = make_sub(tmp_path, "x.ass", LAYERED_ASS_SAMPLE, Codec.SubStationAlphav4)
    out = sub.convert(target, forced=True)
    starts = re.findall(r"(\d+:\d\d:\d\d[.,]\d{3}) -->", out.read_text("utf-8-sig"))
    assert len(starts) == 3
    assert starts == sorted(starts)
    assert [p.name for p in tmp_path.iterdir()] == [out.name]  # sorted copy removed


def test_ass_to_ssa_keeps_file_order(tmp_path, monkeypatch):
    monkeypatch.setattr("unshackle.core.config.config.subtitle", {}, raising=False)
    sub = make_sub(tmp_path, "x.ass", LAYERED_ASS_SAMPLE, Codec.SubStationAlphav4)
    out = sub.convert(Codec.SubStationAlpha, forced=True)
    text = out.read_text("utf8")
    assert text.index("Sign") < text.index("Hello")


def test_webvtt_to_srt_conversion(tmp_path, monkeypatch):
    monkeypatch.setattr("unshackle.core.config.config.subtitle", {}, raising=False)
    sub = make_sub(tmp_path, "x.vtt", VTT_SAMPLE, Codec.WebVTT)
    out = sub.convert(Codec.SubRip, forced=True)
    assert sub.codec == Codec.SubRip
    assert cue_count(out) == 2


def test_same_codec_is_noop(tmp_path):
    sub = make_sub(tmp_path, "x.srt", "1\n00:00:01,000 --> 00:00:02,000\nHi\n", Codec.SubRip)
    assert sub.convert(Codec.SubRip) == sub.path
    assert sub.codec == Codec.SubRip


FONT_ASS = """[Script Info]
ScriptType: v4.00+

[V4+ Styles]
Format: Name, Fontname, Fontsize, PrimaryColour, Bold, Italic, Alignment, MarginV, Encoding
Style: Default,Trebuchet MS,24,&H00FFFFFF,0,0,2,18,1
Style: sign,@Arial Unicode MS,20,&H00FFFFFF,0,0,8,10,1

[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:01.00,0:00:02.00,Default,,0,0,0,,{\\fnTimes New Roman}A sign
Dialogue: 0,0:00:03.00,0:00:04.00,Default,,0,0,0,,{\\fntimes new roman}lower case
Dialogue: 0,0:00:05.00,0:00:06.00,Default,,0,0,0,,{\\fnGeorgia\\b1}bold note
"""


def test_extract_fonts_styles_and_inline_overrides():
    fonts = Subtitle.extract_fonts(FONT_ASS)
    # Style fontnames (column located via Format line, @-prefix stripped) + inline \fn overrides
    assert fonts == {"Trebuchet MS", "Arial Unicode MS", "Times New Roman", "Georgia"}
    # case-insensitive de-dup keeps the mixed-case spelling, not "times new roman"
    assert "times new roman" not in fonts


def test_extract_fonts_handles_non_default_column_order():
    ass = (
        "[V4+ Styles]\n"
        "Format: Name, Fontsize, Fontname, Bold\n"  # Fontname not in the usual position
        "Style: Main,28,Verdana,0\n"
    )
    assert Subtitle.extract_fonts(ass) == {"Verdana"}


CJK_RTL_VTT = """WEBVTT

1
00:00:01.000 --> 00:00:02.000
مرحبا بالعالم

2
00:00:03.000 --> 00:00:04.000
안녕하세요

3
00:00:05.000 --> 00:00:06.000
你好世界
"""


@pytest.mark.parametrize(
    "pattern",
    [r"[؀-ۿ]", r"[가-힣]", r"[一-鿿]"],  # Arabic, Hangul, CJK
)
def test_non_latin_scripts_survive_vtt_to_srt(tmp_path, monkeypatch, pattern):
    monkeypatch.setattr("unshackle.core.config.config.subtitle", {}, raising=False)
    sub = make_sub(tmp_path, "x.vtt", CJK_RTL_VTT, Codec.WebVTT)
    out = sub.convert(Codec.SubRip, forced=True)
    text = out.read_text("utf8")
    assert cue_count(out) == 3
    assert re.search(pattern, text)  # script survived the round-trip, no mojibake


SDH_SRT = """1
00:00:01,000 --> 00:00:02,000
[door creaks]

2
00:00:03,000 --> 00:00:04,000
Hello there.

3
00:00:05,000 --> 00:00:06,000
♪ upbeat music ♪
"""


def test_sdh_stripping_removes_effects_keeps_dialogue(tmp_path, monkeypatch):
    # subby's SDHStripper runs on SRT without SubtitleEdit installed.
    monkeypatch.setattr("unshackle.core.config.config.subtitle", {"sdh_method": "subby"}, raising=False)
    sub = make_sub(tmp_path, "x.srt", SDH_SRT, Codec.SubRip)
    sub.strip_hearing_impaired()
    out = sub.path.read_text("utf8")
    assert "Hello there." in out  # real dialogue kept
    assert "door creaks" not in out  # bracketed effect removed (subby SDHStripper)


SDH_ASS = """[Script Info]
ScriptType: v4.00+

[V4+ Styles]
Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding
Style: Default,Arial,20,&H00FFFFFF,&H000000FF,&H00000000,&H00000000,0,0,0,0,100,100,0,0,1,2,1,2,10,10,18,1

[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:01.00,0:00:02.00,Default,,0,0,0,,[door creaks]
Dialogue: 0,0:00:03.00,0:00:04.00,Default,,0,0,0,,Hello there.
"""


def test_sdh_stripping_ass_without_subtitleedit_content_matches_codec(tmp_path, monkeypatch):
    # Regression: SDH-strip fallback must actually convert ASS->SRT so the file content and the
    # relabeled codec stay in sync (previously it mislabeled codec=SubRip over unchanged ASS bytes).
    # sdh_method="auto" + SubtitleEdit absent -> convert_before_strip fallback.
    monkeypatch.setattr("unshackle.core.config.config.subtitle", {"sdh_method": "auto"}, raising=False)
    sub = make_sub(tmp_path, "x.ass", SDH_ASS, Codec.SubStationAlphav4)
    sub.strip_hearing_impaired()

    assert sub.codec == Codec.SubRip  # relabeled to SRT...
    assert sub.path.suffix == ".srt"
    text = sub.path.read_text("utf8")
    assert "[Script Info]" not in text and "Dialogue:" not in text  # ...and content is real SRT, not ASS
    assert "-->" in text  # SRT cue timing present
    assert "Hello there." in text  # real dialogue kept
    assert "door creaks" not in text  # bracketed effect removed


# Segmented fVTT (wvtt) / fTTML (stpp) ship from DASH/HLS as fragmented MP4. The
# downloader concatenates init + media segments into one file; parse() reads the MP4 boxes directly.

FIXTURES = pathlib.Path(__file__).parent / "fixtures"


def caption_total(caption_set) -> int:
    return sum(len(caption_set.get_captions(lang)) for lang in caption_set.get_languages())


def build_stpp_mp4(*ttml_fragments: str) -> bytes:
    """A minimal stpp-style MP4: ftyp + one mdat per TTML fragment (what fTTML.parse reads)."""

    def box(box_type: bytes, payload: bytes) -> bytes:
        return struct.pack(">I", 8 + len(payload)) + box_type + payload

    data = box(b"ftyp", b"isom" + struct.pack(">I", 0) + b"isomiso6")
    for frag in ttml_fragments:
        data += box(b"mdat", frag.encode("utf8"))
    return data


def test_segmented_fvtt_parses_and_converts(tmp_path, monkeypatch):
    monkeypatch.setattr("unshackle.core.config.config.subtitle", {}, raising=False)
    data = (FIXTURES / "segmented.wvtt.mp4").read_bytes()

    caption_set = Subtitle.parse(data, Codec.fVTT)
    assert caption_total(caption_set) == 2

    seg = tmp_path / "seg.wvtt"
    seg.write_bytes(data)
    sub = Subtitle(url="https://example.test/x", language="en", codec=Codec.fVTT)
    sub.path = seg
    # download() converts fVTT -> WebVTT (not "forced"); chain is subby then pycaption.
    out = sub.convert(Codec.WebVTT)
    assert sub.codec == Codec.WebVTT
    assert cue_count(out) == 2


def test_segmented_fttml_joins_a_cue_split_at_a_segment_boundary():
    data = build_stpp_mp4(
        ttml_fragment(("00:00:01.000", "00:00:02.000", "Carried")),
        ttml_fragment(("00:00:02.000", "00:00:03.500", "Carried"), ("00:00:03.500", "00:00:04.000", "Next")),
    )

    captions = Subtitle.parse(data, Codec.fTTML).get_captions("en")

    assert [(c.start / 1e6, c.end / 1e6, c.get_text()) for c in captions] == [
        (1.0, 3.5, "Carried"),
        (3.5, 4.0, "Next"),
    ]


def test_segmented_fttml_parses_and_converts(tmp_path, monkeypatch):
    monkeypatch.setattr("unshackle.core.config.config.subtitle", {}, raising=False)
    frag = (
        '<?xml version="1.0" encoding="utf-8"?>'
        '<tt xmlns="http://www.w3.org/ns/ttml" xml:lang="en"><body><div>'
        '<p begin="00:00:0{a}.000" end="00:00:0{b}.000">Line {a}</p>'
        "</div></body></tt>"
    )
    data = build_stpp_mp4(frag.format(a=1, b=2), frag.format(a=3, b=4))

    caption_set = Subtitle.parse(data, Codec.fTTML)
    assert caption_total(caption_set) == 2

    seg = tmp_path / "seg.stpp"
    seg.write_bytes(data)
    sub = Subtitle(url="https://example.test/x", language="en", codec=Codec.fTTML)
    sub.path = seg
    # download() converts fTTML -> TTML (only pycaption can read fTTML); then -> SRT.
    sub.convert(Codec.TimedTextMarkupLang)
    assert sub.codec == Codec.TimedTextMarkupLang
    out = sub.convert(Codec.SubRip, forced=True)
    assert cue_count(out) == 2


def downloaded_subtitle(tmp_path, monkeypatch, codec, data: bytes, descriptor: Track.Descriptor, track_data: dict):
    """A Subtitle whose base download is a no-op, so download() runs only the post-processing on data."""
    monkeypatch.setattr("unshackle.core.config.config.subtitle", {}, raising=False)
    monkeypatch.setattr(Track, "download", lambda *args, **kwargs: None)
    sub = Subtitle(url="https://example.test/x", language="en", codec=codec, descriptor=descriptor, data=track_data)
    sub.path = tmp_path / f"seg.{codec.extension}"
    sub.path.write_bytes(data)
    return sub


def dash_subtitle(tmp_path, monkeypatch, codec, data: bytes, template: str):
    from lxml import etree

    track_data = {
        "dash": {
            "adaptation_set": etree.fromstring(f"<AdaptationSet>{template}</AdaptationSet>"),
            "representation": etree.fromstring("<Representation/>"),
            "segment_durations": [],
        }
    }
    return downloaded_subtitle(tmp_path, monkeypatch, codec, data, Track.Descriptor.DASH, track_data)


STPP_CUE = (
    '<?xml version="1.0" encoding="utf-8"?>'
    '<tt xmlns="http://www.w3.org/ns/ttml" xmlns:ttp="http://www.w3.org/ns/ttml#parameter"'
    ' ttp:timeBase="media" xml:lang="en"><body><div>'
    '<p begin="00:06:02.000" end="00:06:02.839">Line</p>'
    "</div></body></tt>"
)


@pytest.mark.parametrize(
    "template, offset, times",
    [
        (
            '<SegmentTemplate timescale="90000" presentationTimeOffset="180000">'
            '<SegmentTimeline><S t="180000" d="540000" r="10"/></SegmentTimeline></SegmentTemplate>',
            (2000, 6000),
            (360_000_000, 360_839_000),
        ),
        # cues already on presentation time stay where they are
        (
            '<SegmentTemplate timescale="1000" presentationTimeOffset="3600000" duration="6000"/>',
            (3_600_000, 6000),
            (362_000_000, 362_839_000),
        ),
    ],
)
def test_dash_fttml_cues_lose_the_presentation_time_offset(tmp_path, monkeypatch, template, offset, times):
    sub = dash_subtitle(tmp_path, monkeypatch, Codec.fTTML, build_stpp_mp4(STPP_CUE), template)
    assert sub.dash_offset_ms() == offset

    sub.download(None, None)  # type: ignore[arg-type]

    assert sub.codec == Codec.TimedTextMarkupLang
    (caption,) = Subtitle.parse(sub.path.read_bytes(), Codec.TimedTextMarkupLang).get_captions("en")
    assert (caption.start, caption.end) == times


def test_dash_fvtt_cues_lose_the_presentation_time_offset(tmp_path, monkeypatch):
    template = '<SegmentTemplate timescale="1000" presentationTimeOffset="1000" duration="2000"/>'
    data = (FIXTURES / "segmented.wvtt.mp4").read_bytes()
    sub = dash_subtitle(tmp_path, monkeypatch, Codec.fVTT, data, template)

    sub.download(None, None)  # type: ignore[arg-type]

    assert sub.codec == Codec.WebVTT
    text = sub.path.read_text("utf8")
    assert "00:00:00.000 --> 00:00:01.000" in text
    assert "00:00:02.000 --> 00:00:03.000" in text


def ttml_fragment(*cues: tuple[str, ...]) -> str:
    body = "".join(f'<p begin="{cue[0]}" end="{cue[1]}">{cue[2] if len(cue) > 2 else "Line"}</p>' for cue in cues)
    return f'<tt xmlns="http://www.w3.org/ns/ttml" xml:lang="en"><body><div>{body}</div></body></tt>'


def test_dash_fttml_with_no_cues_converts(tmp_path, monkeypatch):
    template = '<SegmentTemplate timescale="1000" presentationTimeOffset="2000" duration="6000"/>'
    sub = dash_subtitle(tmp_path, monkeypatch, Codec.fTTML, build_stpp_mp4(ttml_fragment()), template)

    sub.download(None, None)  # type: ignore[arg-type]

    assert sub.codec == Codec.TimedTextMarkupLang


@pytest.mark.parametrize(
    "fragments, expected",
    [
        # timed from each fragment's start, as Smooth Streaming packagers write it
        (
            [
                ttml_fragment(),
                ttml_fragment(("00:00:06.000", "00:00:07.000")),
                ttml_fragment(("00:00:00.500", "00:00:01.000")),
            ],
            [(14.0, 15.0), (16.5, 17.0)],
        ),
        # already on the stream timeline
        (
            [
                ttml_fragment(),
                ttml_fragment(("00:00:14.000", "00:00:15.000")),
                ttml_fragment(("00:00:16.500", "00:00:17.000")),
            ],
            [(14.0, 15.0), (16.5, 17.0)],
        ),
        # one cue carried across a fragment boundary comes out whole
        (
            [
                ttml_fragment(),
                ttml_fragment(("00:00:07.000", "00:00:08.000")),
                ttml_fragment(("00:00:00.000", "00:00:01.000")),
            ],
            [(15.0, 17.0)],
        ),
    ],
)
def test_ism_fttml_cues_land_on_the_stream_timeline(tmp_path, monkeypatch, fragments, expected):
    times = [0, 80_000_000, 160_000_000]
    track_data = {"ism": {"segment_times": times, "fragment_times": times, "timescale": 10_000_000}}
    sub = downloaded_subtitle(
        tmp_path, monkeypatch, Codec.fTTML, build_stpp_mp4(*fragments), Track.Descriptor.ISM, track_data
    )

    sub.download(None, None)  # type: ignore[arg-type]

    assert sub.codec == Codec.TimedTextMarkupLang
    captions = Subtitle.parse(sub.path.read_bytes(), Codec.TimedTextMarkupLang).get_captions("en")
    assert [(c.start / 1e6, c.end / 1e6) for c in captions] == expected


def test_fttml_with_viewport_units_converts(tmp_path, monkeypatch):
    """TTML2 ``vw``/``vh`` and ``rw``/``rh`` sizes, which pycaption rejects, still parse and convert.

    Only the size attributes pycaption parses are rewritten: a negative one becomes 0, while an ``rh``
    font size and the same units in cue text stay as they are.
    """
    monkeypatch.setattr("unshackle.core.config.config.subtitle", {}, raising=False)
    frag = (
        '<?xml version="1.0" encoding="utf-8"?>'
        '<tt xmlns="http://www.w3.org/ns/ttml" xmlns:tts="http://www.w3.org/ns/ttml#styling"'
        ' xmlns:ttp="http://www.w3.org/ns/ttml#parameter" xml:lang="ja" ttp:version="2">'
        '<head><styling><style xml:id="s1" tts:fontSize="5.33rh"/></styling><layout>'
        '<region xml:id="bottom" tts:extent="80vw 15vh" tts:position="center bottom 10vh"/>'
        '<region xml:id="side" tts:extent="15rw 80rh" tts:position="right 10vw center" tts:writingMode="tbrl"/>'
        "<region xml:id='edge' tts:origin='-5vw 80vh' tts:extent='90vw 10vh' tts:padding='1vh 2vw'/>"
        "</layout></head>"
        '<body region="bottom"><div>'
        '<p begin="00:00:01.000" end="00:00:02.000" style="s1">Speed 10vw</p>'
        '<p begin="00:00:03.000" end="00:00:04.000" region="side">Line 2</p>'
        '<p begin="00:00:05.000" end="00:00:06.000" region="edge">Line 3</p>'
        "</div></body></tt>"
    )
    # The fTTML merge keeps no style sheet, so the font size is checked on a plain TTML read.
    styled = pycaption.DFXPWriter().write(Subtitle.parse(frag.encode(), Codec.TimedTextMarkupLang))
    assert 'tts:fontSize="5.33rh"' in styled

    seg = tmp_path / "seg.stpp"
    seg.write_bytes(build_stpp_mp4(frag))
    sub = Subtitle(url="https://example.test/x", language="ja", codec=Codec.fTTML)
    sub.path = seg

    sub.convert(Codec.TimedTextMarkupLang)
    out = sub.convert(Codec.SubRip, forced=True)
    assert cue_count(out) == 3
    assert "Speed 10vw" in out.read_text("utf8")