musicseerr/backend/infrastructure/persistence/genre_index.py

"""Domain 2 - Genre indexing persistence."""

import sqlite3
from typing import Any

from infrastructure.persistence._database import (
    PersistenceBase,
    _decode_json,
    _decode_rows,
    _encode_json,
    _normalize,
)

LIBRARY_ARTISTS_TABLE = "library_artists"
LIBRARY_ALBUMS_TABLE = "library_albums"


def _normalize_genre(value: str | None) -> str:
    return value.strip().lower() if isinstance(value, str) else ""


def _clean_genres(values: list[Any]) -> list[str]:
    cleaned: list[str] = []
    seen: set[str] = set()
    for value in values:
        if not isinstance(value, str):
            continue
        genre = value.strip()
        if not genre:
            continue
        normalized = _normalize_genre(genre)
        if normalized in seen:
            continue
        seen.add(normalized)
        cleaned.append(genre)
    return cleaned


class GenreIndex(PersistenceBase):
    """Owns tables: ``artist_genres``, ``artist_genre_lookup``.

    Genre queries JOIN against ``library_artists`` / ``library_albums``
    which live in the same SQLite database (owned by :class:`LibraryDB`).
    """

    def _ensure_tables(self) -> None:
        conn = self._connect()
        try:
            conn.execute(
                """
                CREATE TABLE IF NOT EXISTS artist_genres (
                    artist_mbid_lower TEXT PRIMARY KEY,
                    artist_mbid TEXT NOT NULL,
                    genres_json TEXT NOT NULL
                )
                """
            )
            conn.execute(
                """
                CREATE TABLE IF NOT EXISTS artist_genre_lookup (
                    artist_mbid_lower TEXT NOT NULL,
                    genre_lower TEXT NOT NULL,
                    PRIMARY KEY (artist_mbid_lower, genre_lower)
                )
                """
            )
            conn.execute(
                "CREATE INDEX IF NOT EXISTS idx_artist_genre_lookup_genre ON artist_genre_lookup(genre_lower, artist_mbid_lower)"
            )
            self._backfill_artist_genre_lookup(conn)
            conn.commit()
        finally:
            conn.close()

    def _replace_artist_genre_lookup(
        self,
        conn: sqlite3.Connection,
        artist_mbid: str,
        genres: list[str],
    ) -> None:
        artist_mbid_lower = _normalize(artist_mbid)
        conn.execute(
            "DELETE FROM artist_genre_lookup WHERE artist_mbid_lower = ?",
            (artist_mbid_lower,),
        )
        for genre in genres:
            conn.execute(
                "INSERT OR REPLACE INTO artist_genre_lookup (artist_mbid_lower, genre_lower) VALUES (?, ?)",
                (artist_mbid_lower, _normalize_genre(genre)),
            )

    def _backfill_artist_genre_lookup(self, conn: sqlite3.Connection) -> None:
        lookup_count_row = conn.execute(
            "SELECT COUNT(*) AS count FROM artist_genre_lookup"
        ).fetchone()
        if lookup_count_row is not None and int(lookup_count_row["count"] or 0) > 0:
            return

        rows = conn.execute(
            "SELECT artist_mbid, genres_json FROM artist_genres"
        ).fetchall()
        for row in rows:
            try:
                genres = _decode_json(row["genres_json"])
            except Exception:  # noqa: BLE001
                continue
            if not isinstance(genres, list):
                continue
            self._replace_artist_genre_lookup(conn, str(row["artist_mbid"]), _clean_genres(genres))

    async def save_artist_genres(self, artist_genres: dict[str, list[str]]) -> None:
        normalized = {
            mbid: _clean_genres(genres)
            for mbid, genres in artist_genres.items()
            if isinstance(mbid, str) and mbid
        }

        def operation(conn: sqlite3.Connection) -> None:
            for artist_mbid, genres in normalized.items():
                conn.execute(
                    """
                    INSERT INTO artist_genres (artist_mbid_lower, artist_mbid, genres_json)
                    VALUES (?, ?, ?)
                    ON CONFLICT(artist_mbid_lower) DO UPDATE SET
                        artist_mbid = excluded.artist_mbid,
                        genres_json = excluded.genres_json
                    """,
                    (_normalize(artist_mbid), artist_mbid, _encode_json(genres)),
                )
                self._replace_artist_genre_lookup(conn, artist_mbid, genres)

        await self._write(operation)

    async def get_artists_by_genre(self, genre: str, limit: int = 50) -> list[dict[str, Any]]:
        needle = _normalize_genre(genre)
        if not needle:
            return []

        def operation(conn: sqlite3.Connection) -> list[dict[str, Any]]:
            rows = conn.execute(
                """
                SELECT a.raw_json
                FROM library_artists a
                JOIN artist_genre_lookup g ON a.mbid_lower = g.artist_mbid_lower
                WHERE g.genre_lower = ?
                ORDER BY COALESCE(a.date_added, 0) DESC, a.name COLLATE NOCASE ASC
                LIMIT ?
                """,
                (needle, max(limit, 1)),
            ).fetchall()
            return _decode_rows(rows)

        return await self._read(operation)

    async def get_albums_by_genre(self, genre: str, limit: int = 50) -> list[dict[str, Any]]:
        needle = _normalize_genre(genre)
        if not needle:
            return []

        def operation(conn: sqlite3.Connection) -> list[dict[str, Any]]:
            rows = conn.execute(
                """
                SELECT a.raw_json
                FROM library_albums a
                JOIN artist_genre_lookup g ON a.artist_mbid_lower = g.artist_mbid_lower
                WHERE g.genre_lower = ?
                ORDER BY COALESCE(a.date_added, 0) DESC, a.title COLLATE NOCASE ASC
                LIMIT ?
                """,
                (needle, max(limit, 1)),
            ).fetchall()
            return _decode_rows(rows)

        return await self._read(operation)