import fs from 'fs';
import path from 'path';
import initSqlJs, { Database, Statement } from 'sql.js';

// Simple SQLite via sql.js persisted to a single file
const DATA_DIR = path.join(process.cwd(), 'data');
const DB_FILE = path.join(DATA_DIR, 'metoyou.sqlite');

function ensureDataDir() {
  if (!fs.existsSync(DATA_DIR)) fs.mkdirSync(DATA_DIR, { recursive: true });
}

let SQL: any = null;
let db: Database | null = null;

export async function initDB(): Promise<void> {
  if (db) return;
  SQL = await initSqlJs({ locateFile: (file: string) => require.resolve('sql.js/dist/sql-wasm.wasm') });
  ensureDataDir();

  if (fs.existsSync(DB_FILE)) {
    const fileBuffer = fs.readFileSync(DB_FILE);
    db = new SQL.Database(new Uint8Array(fileBuffer));
  } else {
    db = new SQL.Database();
  }

  // Initialize schema
  db.run(`
    CREATE TABLE IF NOT EXISTS users (
      id TEXT PRIMARY KEY,
      username TEXT UNIQUE NOT NULL,
      passwordHash TEXT NOT NULL,
      displayName TEXT NOT NULL,
      createdAt INTEGER NOT NULL
    );
  `);

  persist();
}

function persist(): void {
  if (!db) return;
  const data = db.export();
  const buffer = Buffer.from(data);
  fs.writeFileSync(DB_FILE, buffer);
}

export interface AuthUser {
  id: string;
  username: string;
  passwordHash: string;
  displayName: string;
  createdAt: number;
}

export async function getUserByUsername(username: string): Promise<AuthUser | null> {
  if (!db) await initDB();
  const stmt: Statement = db!.prepare('SELECT id, username, passwordHash, displayName, createdAt FROM users WHERE username = ? LIMIT 1');
  stmt.bind([username]);
  let row: AuthUser | null = null;
  if (stmt.step()) {
    const r = stmt.getAsObject() as any;
    row = {
      id: String(r.id),
      username: String(r.username),
      passwordHash: String(r.passwordHash),
      displayName: String(r.displayName),
      createdAt: Number(r.createdAt),
    };
  }
  stmt.free();
  return row;
}

export async function getUserById(id: string): Promise<AuthUser | null> {
  if (!db) await initDB();
  const stmt: Statement = db!.prepare('SELECT id, username, passwordHash, displayName, createdAt FROM users WHERE id = ? LIMIT 1');
  stmt.bind([id]);
  let row: AuthUser | null = null;
  if (stmt.step()) {
    const r = stmt.getAsObject() as any;
    row = {
      id: String(r.id),
      username: String(r.username),
      passwordHash: String(r.passwordHash),
      displayName: String(r.displayName),
      createdAt: Number(r.createdAt),
    };
  }
  stmt.free();
  return row;
}

export async function createUser(user: AuthUser): Promise<void> {
  if (!db) await initDB();
  const stmt = db!.prepare('INSERT INTO users (id, username, passwordHash, displayName, createdAt) VALUES (?, ?, ?, ?, ?)');
  stmt.bind([user.id, user.username, user.passwordHash, user.displayName, user.createdAt]);
  stmt.step();
  stmt.free();
  persist();
}