import { Pool, PoolClient, QueryResult, QueryResultRow } from "pg";

// ─── Connection pool ──────────────────────────────────────────────────────────

let pool: Pool | null = null;

function getPool(): Pool {
  if (!pool) {
    const connectionString = process.env.DATABASE_URL;
    if (!connectionString) {
      throw new Error("DATABASE_URL environment variable is not set.");
    }
    pool = new Pool({
      connectionString,
      max: 10,
      idleTimeoutMillis: 30_000,
      connectionTimeoutMillis: 5_000,
    });

    pool.on("error", (err) => {
      console.error("[db] Unexpected pool error:", err);
    });
  }
  return pool;
}

// ─── Query helpers ────────────────────────────────────────────────────────────

export async function query<T extends QueryResultRow = Record<string, unknown>>(
  text: string,
  params?: unknown[]
): Promise<QueryResult<T>> {
  return getPool().query<T>(text, params);
}

/**
 * Runs a callback inside a transaction.
 * Commits on success, rolls back on any thrown error.
 */
export async function withTransaction<T>(
  fn: (client: PoolClient) => Promise<T>
): Promise<T> {
  const client = await getPool().connect();
  try {
    await client.query("BEGIN");
    const result = await fn(client);
    await client.query("COMMIT");
    return result;
  } catch (err) {
    await client.query("ROLLBACK");
    throw err;
  } finally {
    client.release();
  }
}

// ─── Song queries ─────────────────────────────────────────────────────────────

export interface SongRow {
  mbid: string;
  title: string;
  artist: string;
  duration_seconds: number | null;
  acousticbrainz_bpm: number | null;
  acousticbrainz_time_sig_num: number | null;
  source: string;
  created_at: Date;
  updated_at: Date;
}

export async function getSongByMbid(mbid: string): Promise<SongRow | null> {
  const { rows } = await query<SongRow>("SELECT * FROM songs WHERE mbid = $1", [mbid]);
  return rows[0] ?? null;
}

export async function searchSongs(q: string, limit = 20): Promise<SongRow[]> {
  const { rows } = await query<SongRow>(
    `SELECT * FROM songs
     WHERE to_tsvector('english', title || ' ' || artist) @@ plainto_tsquery('english', $1)
     ORDER BY ts_rank(to_tsvector('english', title || ' ' || artist), plainto_tsquery('english', $1)) DESC
     LIMIT $2`,
    [q, limit]
  );
  return rows;
}

export async function upsertSong(song: Omit<SongRow, "created_at" | "updated_at">): Promise<void> {
  await query(
    `INSERT INTO songs (mbid, title, artist, duration_seconds, acousticbrainz_bpm, acousticbrainz_time_sig_num, source)
     VALUES ($1, $2, $3, $4, $5, $6, $7)
     ON CONFLICT (mbid) DO UPDATE SET
       title = EXCLUDED.title,
       artist = EXCLUDED.artist,
       duration_seconds = EXCLUDED.duration_seconds,
       acousticbrainz_bpm = EXCLUDED.acousticbrainz_bpm,
       acousticbrainz_time_sig_num = EXCLUDED.acousticbrainz_time_sig_num,
       source = EXCLUDED.source`,
    [
      song.mbid,
      song.title,
      song.artist,
      song.duration_seconds,
      song.acousticbrainz_bpm,
      song.acousticbrainz_time_sig_num,
      song.source,
    ]
  );
}

// ─── Tempo map queries ────────────────────────────────────────────────────────

export interface TempoMapRow {
  id: string;
  song_mbid: string;
  ctp_data: Record<string, unknown>;
  contributed_by: string;
  verified: boolean;
  upvotes: number;
  created_at: Date;
  updated_at: Date;
}

export async function getTempoMapsForSong(mbid: string): Promise<TempoMapRow[]> {
  const { rows } = await query<TempoMapRow>(
    `SELECT * FROM tempo_maps WHERE song_mbid = $1
     ORDER BY verified DESC, upvotes DESC, created_at ASC`,
    [mbid]
  );
  return rows;
}

export async function insertTempoMap(
  map: Pick<TempoMapRow, "song_mbid" | "ctp_data" | "contributed_by">
): Promise<TempoMapRow> {
  const { rows } = await query<TempoMapRow>(
    `INSERT INTO tempo_maps (song_mbid, ctp_data, contributed_by)
     VALUES ($1, $2, $3)
     RETURNING *`,
    [map.song_mbid, JSON.stringify(map.ctp_data), map.contributed_by]
  );
  return rows[0];
}