import sqlite3

from app.settings import settings

# Columns actually used by the app today. beets' `items` table has many more;
# add columns here as new features need them rather than SELECT *.
_ITEM_COLUMNS = ["id", "path", "title", "artist", "albumartist", "genres", "grouping", "isrc", "added", "format"]


def db_exists() -> bool:
    return settings.beets_db_path.exists()


def _connect() -> sqlite3.Connection:
    # mode=ro: alembic never writes through this connection. Mutations (tag
    # edits, imports) go through the `beet` CLI or beets.library.Library
    # in-process -- see services/library_edit.py (manual-fix feature).
    conn = sqlite3.connect(f"file:{settings.beets_db_path}?mode=ro", uri=True)
    conn.row_factory = sqlite3.Row
    return conn


def _decode_path(value) -> str:
    """beets stores `path` as a BLOB (raw filesystem bytes), not TEXT."""
    if isinstance(value, bytes):
        return value.decode("utf-8", errors="replace")
    return value or ""


def _row_to_dict(row: sqlite3.Row) -> dict:
    d = dict(row)
    if "path" in d:
        d["path"] = _decode_path(d["path"])
    return d


def query_items(grouping: str | None = None) -> list[dict]:
    """All items, optionally filtered to one playlist's grouping tag."""
    if not db_exists():
        return []
    cols = ", ".join(_ITEM_COLUMNS)
    conn = _connect()
    try:
        if grouping is not None:
            cur = conn.execute(f"SELECT {cols} FROM items WHERE grouping = ?", (grouping,))
        else:
            cur = conn.execute(f"SELECT {cols} FROM items")
        return [_row_to_dict(row) for row in cur.fetchall()]
    finally:
        conn.close()


def get_item(item_id: int) -> dict | None:
    if not db_exists():
        return None
    conn = _connect()
    try:
        cur = conn.execute("SELECT * FROM items WHERE id = ?", (item_id,))
        row = cur.fetchone()
        return _row_to_dict(row) if row else None
    finally:
        conn.close()


def stats() -> dict:
    """Cheap summary for the dashboard and for migration-verification
    (compare against `beet stats` during Stage 0 cutover)."""
    if not db_exists():
        return {"db_exists": False, "total_tracks": 0, "groupings": []}
    conn = _connect()
    try:
        total = conn.execute("SELECT COUNT(*) FROM items").fetchone()[0]
        rows = conn.execute(
            "SELECT DISTINCT grouping FROM items WHERE grouping IS NOT NULL AND grouping != ''"
        ).fetchall()
        return {
            "db_exists": True,
            "total_tracks": total,
            "groupings": sorted(r[0] for r in rows),
        }
    finally:
        conn.close()