Step 2 of the specs/dot_alfred.md plan. Pure-dict in/out
(serialize(sidecar) -> dict, deserialize(data) -> ShowSidecar);
YAML I/O lives in the repository layer (step 3) and is kept out
for trivial testability.
DTOs mirror the YAML schema field-for-field:
- ShowSidecar (root: imdb_id, tmdb_id, schema_version, seasons)
- SeasonSidecar (number, path, optional audio/subtitles, optional episodes)
- EpisodeSidecar (number, path, optional audio/subtitles)
- SubtitleEntry (language, source, type)
The sidecar acts as a scan cache: it stores only what is genuinely
costly to recompute — folder/file paths (skipping the FS walk) and
probed track metadata (skipping ffprobe). Release identifiers
(group, source, quality, codec) live in folder/file names and are
derived on demand by the parser; they are deliberately absent from
the schema and rejected as unknown keys on deserialize.
The serializer is strict on schema: unknown keys at any level raise
SidecarSchemaError, missing required fields raise clearly, and bool
cannot sneak in as a season/episode number. Optional fields
(tmdb_id, empty audio/subtitles/episodes) are omitted from the
output rather than emitted as null / [].
Tests cover round-trip equivalence (DTO → dict → DTO and DTO → YAML
text → DTO), the Foundation S01 PACK case (real-world fixture with
mixed sub types — superset captured at season scope), and a
Breaking Bad S05 EPISODIC case. An on-disk tmp_path fixture
recreates the Foundation folder structure with placeholder files,
ready to be reused by the upcoming repository walk tests in step 3.
francwa