// Site-side member accounts for InstantAdPay.
// The chain is the source of truth for money, credits, and qualification;
// this module holds what the chain doesn't: free members (email + password,
// the way normal people join), sponsor attribution before first purchase
// (spec §4), and the wallet link once one is connected at purchase time.
// Wiping this file = the clean reset between rehearsal and mainnet.
const fs = require('fs');
const path = require('path');
const crypto = require('crypto');

let DATA_DIR = null;
const FILE = () => path.join(DATA_DIR, 'accounts.json');
let db = { v: 2, byEmail: {}, byAddress: {}, joins: 0 };

function load() {
  try { db = JSON.parse(fs.readFileSync(FILE(), 'utf8')); } catch (e) {}
  if (!db || !db.v) db = { v: 2, byEmail: {}, byAddress: {}, joins: 0 };
  if (db.v === 1) { db.v = 2; db.byEmail = db.byEmail || {}; } // early rehearsal file
}
function save() {
  try {
    const tmp = FILE() + '.tmp';
    fs.writeFileSync(tmp, JSON.stringify(db), { mode: 0o600 });
    fs.renameSync(tmp, FILE());
  } catch (e) { console.error('accounts save failed', e.message); }
}
function init(opts) { DATA_DIR = opts.dataDir; load(); }

// ---- password hashing (scrypt, no deps) ----
function hashPassword(password) {
  const salt = crypto.randomBytes(16);
  const hash = crypto.scryptSync(String(password), salt, 32);
  return salt.toString('hex') + ':' + hash.toString('hex');
}
function checkPassword(password, stored) {
  try {
    const [saltHex, hashHex] = String(stored).split(':');
    const hash = crypto.scryptSync(String(password), Buffer.from(saltHex, 'hex'), 32);
    return crypto.timingSafeEqual(hash, Buffer.from(hashHex, 'hex'));
  } catch (e) { return false; }
}

const EMAIL_RE = /^[^\s@]+@[^\s@]+\.[^\s@]{2,}$/;
const normEmail = e => String(e || '').trim().toLowerCase();
const normAddr = a => String(a || '').trim().toLowerCase();

// ---- email accounts (the normal join path) ----
function signup(email, password, sponsorId) {
  const e = normEmail(email);
  if (!EMAIL_RE.test(e)) return { error: 'That email address does not look right.' };
  if (String(password || '').length < 8) return { error: 'Password needs at least 8 characters.' };
  if (db.byEmail[e]) return { error: 'That email already has an account. Log in instead.' };
  db.byEmail[e] = {
    email: e,
    pass: hashPassword(password),
    sponsorId: Number(sponsorId) || 0, // first touch, written on-chain at first purchase
    address: null,
    created: Date.now()
  };
  db.joins += 1;
  save();
  return { ok: true, account: publicView(db.byEmail[e]) };
}
function login(email, password) {
  const e = normEmail(email);
  const acct = db.byEmail[e];
  if (!acct || !checkPassword(password, acct.pass)) return { error: 'Wrong email or password.' };
  acct.lastSeen = Date.now(); save();
  return { ok: true, account: publicView(acct) };
}
function byEmail(email) { const a = db.byEmail[normEmail(email)]; return a ? publicView(a) : null; }
function byAddress(address) {
  const e = db.byAddress[normAddr(address)];
  return e ? publicView(db.byEmail[e]) : null;
}

// ---- wallet link (happens at purchase / payout activation time) ----
// First link wins and is permanent for the account; one wallet, one account.
function linkWallet(email, address) {
  const e = normEmail(email);
  const a = normAddr(address);
  const acct = db.byEmail[e];
  if (!acct) return { error: 'No such account.' };
  if (!/^0x[0-9a-f]{40}$/.test(a)) return { error: 'Bad wallet address.' };
  if (acct.address && acct.address !== a) return { error: 'This account is already linked to wallet '
    + acct.address.slice(0, 6) + '…' + acct.address.slice(-4) + '. Earnings pay to that wallet. Connect it instead.' };
  if (db.byAddress[a] && db.byAddress[a] !== e) return { error: 'That wallet is already linked to a different account.' };
  acct.address = a;
  db.byAddress[a] = e;
  save();
  return { ok: true, account: publicView(acct) };
}

function publicView(a) {
  return { email: a.email, sponsorId: a.sponsorId || 0, address: a.address || null, created: a.created };
}
function count() { return Object.keys(db.byEmail).length; }

module.exports = { init, signup, login, byEmail, byAddress, linkWallet, count };