-- 0014_subtitles.sql — subtitle tracks per item.
--
-- Vellum had no subtitle support at all. This is the storage half: a row per
-- track, whether it came from a file next to the video, a stream muxed into it,
-- or a download.
--
-- Three sources, and they are genuinely different shapes:
--
--   * 'sidecar'    a file beside the video (".en.srt"). Has a path, no stream.
--   * 'embedded'   a stream inside the container. Has a stream index, no path
--                    of its own — it only exists inside the video file.
--   * 'downloaded' fetched from a provider, cached under the config dir. Has a
--                    path, like a sidecar, but is regenerable and can be
--                    deleted without losing anything.
--
-- `stream_index` is -1 for the two file-backed sources rather than NULL, so the
-- UNIQUE below can do its job: NULL is never equal to NULL in SQL, and a unique
-- index over a nullable column would happily accept the same sidecar twice.
--
-- `language` is BCP-47 where we can tell ("en", "pt-BR") and empty when we
-- cannot. It is a display and preference key, not a correctness one: a track
-- with no language still plays, it just cannot be auto-selected.
--
-- This table is a cache of what is on disk. Deleting every row and rescanning
-- must reproduce it exactly, which is why nothing here is authoritative about
-- the media itself.

CREATE TABLE subtitles (
    id           INTEGER PRIMARY KEY,
    item_id      INTEGER NOT NULL REFERENCES media_items(id) ON DELETE CASCADE,
    source       TEXT    NOT NULL,                -- 'sidecar' | 'embedded' | 'downloaded'
    path         TEXT    NOT NULL DEFAULT '',     -- relative to the library root; empty when embedded
    stream_index INTEGER NOT NULL DEFAULT -1,     -- ffmpeg stream index; -1 when file-backed
    format       TEXT    NOT NULL DEFAULT '',     -- 'srt' | 'ass' | 'ssa' | 'vtt' | 'sub'
    language     TEXT    NOT NULL DEFAULT '',     -- BCP-47 where known
    label        TEXT    NOT NULL DEFAULT '',     -- what the client shows; the filename or stream title
    bytes        INTEGER NOT NULL DEFAULT 0,
    added_at     TEXT    NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now')),

    UNIQUE (item_id, source, path, stream_index)
);

-- The read is always "every track for this item", and it happens on every
-- player open, so it is the one index worth having.
CREATE INDEX idx_subtitles_item ON subtitles(item_id, source, language);