// Tiny JSON-file persistence layer. No external DB, no config.
const fs = require('fs');
const path = require('path');
const crypto = require('crypto');

const DB_PATH = path.join(__dirname, '..', 'data', 'db.json');

let db = null;
let saveTimer = null;

function uid(len = 12) {
  return crypto.randomBytes(len).toString('base64url').slice(0, len);
}

function load() {
  if (fs.existsSync(DB_PATH)) {
    try {
      db = JSON.parse(fs.readFileSync(DB_PATH, 'utf8'));
    } catch (e) {
      console.error('db corrupt, starting fresh:', e.message);
      db = null;
    }
  }
  if (!db) {
    db = { users: {}, games: {}, sessions: {}, catalog: [] };
  }
  return db;
}

function get() {
  if (!db) load();
  return db;
}

function save() {
  // Debounced write so rapid studio ops don't hammer the disk.
  if (saveTimer) return;
  saveTimer = setTimeout(() => {
    saveTimer = null;
    fs.writeFileSync(DB_PATH, JSON.stringify(db));
  }, 500);
}

function saveNow() {
  if (saveTimer) { clearTimeout(saveTimer); saveTimer = null; }
  fs.writeFileSync(DB_PATH, JSON.stringify(db));
}

function findUserByName(username) {
  const u = Object.values(get().users).find(
    (x) => x.username.toLowerCase() === String(username).toLowerCase()
  );
  return u || null;
}

function publicUser(u) {
  if (!u) return null;
  return {
    id: u.id,
    username: u.username,
    avatar: u.avatar,
    created: u.created,
    stats: u.stats,
    system: !!u.system,
  };
}

module.exports = { get, load, save, saveNow, uid, findUserByName, publicUser };