import * as SQLite from 'expo-sqlite';

let db: Promise<SQLite.SQLiteDatabase> | null = null;

/**
 * Локальная база офлайн-режима (docs/mobile.md#офлайн). `owner` — хэш «сервер + пользователь»:
 * скачанное, неотправленные события и реакции одного аккаунта не видны другому.
 */
export function getDb(): Promise<SQLite.SQLiteDatabase> {
  db ??= (async () => {
    const d = await SQLite.openDatabaseAsync('pipu.db');
    await d.execAsync(`
      PRAGMA journal_mode = WAL;
      CREATE TABLE IF NOT EXISTS downloads (
        owner    TEXT NOT NULL,
        track_id TEXT NOT NULL,
        track    TEXT NOT NULL,
        status   TEXT NOT NULL,
        bytes    INTEGER NOT NULL DEFAULT 0,
        added_at INTEGER NOT NULL,
        PRIMARY KEY (owner, track_id)
      );
      CREATE TABLE IF NOT EXISTS pending_events (
        id    INTEGER PRIMARY KEY AUTOINCREMENT,
        owner TEXT NOT NULL,
        body  TEXT NOT NULL
      );
      CREATE TABLE IF NOT EXISTS pending_reactions (
        owner    TEXT NOT NULL,
        track_id TEXT NOT NULL,
        reaction TEXT,
        PRIMARY KEY (owner, track_id)
      );
    `);
    return d;
  })();
  return db;
}