"""plex_items.transcode_hw: the facet says whether the GPU ENCODES, under the measured codec sets

Measured on prod (2026-11-07): the iGPU has no VC-1 Advanced decode, so a VC-1 film never ran on the
GPU although the facet said it did; VC-1, XviD and DivX now take the CPU-decode → GPU-encode path; and an
HDR film runs on the GPU through the OpenCL tonemap although the facet said software. The rule is
`plex.sync.transcode_hw_capable`; the two codec sets below are pinned to `plex.sync` by
tests/test_plex_playback_class.py.

Rewritten from the stored codec and bit depth. HDR is not stored, so a 10-bit HW-decodable item is set to
software here and its probe watermark cleared: the bit-depth backfill (`plex.sync._probe_media_batch`,
a bounded batch per Plex sync) reads its HDR flag again and moves an HDR one back to the GPU.
"""

from typing import Sequence, Union

from alembic import op

revision: str = "0119_plex_transcode_gpu"
down_revision: Union[str, None] = "0118_videos_shuffle_key"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None

HW_DECODABLE_CODECS = ("h264", "hevc", "h265", "vp9", "mpeg2video")
CPU_DECODE_CODECS = ("vc1", "mpeg4", "msmpeg4v3")


def _in(codecs: tuple[str, ...]) -> str:
    return ", ".join(f"'{c}'" for c in codecs)


def upgrade() -> None:
    op.execute(
        f"""
        UPDATE plex_items
           SET transcode_hw = CASE
               WHEN lower(codec_video) IN ({_in(HW_DECODABLE_CODECS)})
               THEN coalesce(video_bit_depth, 8) <= 8
               WHEN lower(codec_video) IN ({_in(CPU_DECODE_CODECS)})
               THEN coalesce(video_bit_depth, 8) <= 8
               ELSE false
           END
         WHERE playable = 'transcode'
        """
    )
    op.execute(
        f"""
        UPDATE plex_items
           SET media_probed_at = NULL
         WHERE playable = 'transcode'
           AND lower(codec_video) IN ({_in(HW_DECODABLE_CODECS)})
           AND video_bit_depth > 8
        """
    )


def downgrade() -> None:
    # The old rule: a decodable codec (VC-1 counted) at 8 bits; HDR and every other codec software.
    op.execute(
        f"""
        UPDATE plex_items
           SET transcode_hw = lower(codec_video) IN ({_in(HW_DECODABLE_CODECS + ("vc1",))})
                              AND coalesce(video_bit_depth, 8) <= 8
         WHERE playable = 'transcode'
        """
    )