T5: 1:1 port of the artist_vectors SuggestionsEngine into qbz-reco (~880 lines;
structure matches the Tauri source function-for-function). generate_suggestions:
ensure each seed vector (builder.ensure_vector), gate on a non-empty combined
playlist vector, rank candidates by DIRECT summed relationship weight via
store.get_all_related_artists (NOT cosine/find_nearest, D3), then pull + dedup +
exclude tracks from Qobuz with the validate_qobuz_artist + has_incompatible_genre
gates and optional reason strings. Keeps Tauri's Arc<Mutex>/RwLock ownership
(Send-safe). DTO reconciliation: crate::api -> qbz_qobuz::QobuzClient +
qbz_models::Track (4 Qobuz calls mapped to real signatures, field-by-field).
Adds rand (0.10, workspace) + qbz-models deps. 23 qbz-reco tests green.
cc
T4: 1:1 port of the artist_vectors vector builder into qbz-reco. Keeps Tauri's
Arc<Mutex>/RwLock ownership of the store + MusicBrainz client/cache + Qobuz
client (NOT the plan's by-ref pattern): MusicBrainzCache holds a !Sync rusqlite
Connection, so a borrowed &cache held across the MB-API await would make the
spawned suggestions future !Send. The interleaved short-lived locking (drop the
guard before each await) is the faithful + Send-safe shape. Swaps only
crate::api::QobuzClient -> qbz_qobuz::QobuzClient (get_similar_artists ->
SearchResultsPage<Artist>); the MusicBrainz types already live in
qbz_integrations so extract_relationships ports verbatim. Drops the dead
resolve_qobuz_to_mbid (D3). 21 qbz-reco tests green.
cc
T3: 1:1 port of the artist_vectors vector store into qbz-reco. open_at(base)
opens <base>/cache/artist_vectors.db (WAL) with the 3-table schema kept
byte-identical (CREATE IF NOT EXISTS) for cross-frontend reuse. Ports the
in-memory artist index, get_or_create_idx, set_vector (delete-then-insert per
(artist,source) + metadata nnz), get_vector (SUM GROUP BY), has_fresh_vector,
get_artist_name, and the production ranking get_related_artists /
get_all_related_artists (SUM ORDER BY total_weight DESC). Drops the dead
find_nearest cosine path (D3) and the Tauri State/tokio wrapper (lifecycle in
the frontend/core per ADR-006). 4 store tests, 20 qbz-reco tests green.
cc
New frontend-agnostic crate qbz-reco (ADR-006) for the playlist Suggested Songs
engine (sub-plan 2). T1: 1:1 port of the Tauri artist_vectors SparseVector
(sorted parallel index/value arrays, set/get, dot merge-join, magnitude/
normalize, serde) with its full test suite (13/13 green). Drops the dead
top_k_similar helper (its only caller find_nearest is dropped per epic D3);
keeps cosine_similarity for parity + tests but not for ranking.
cc
vicrodh