// RM Circle — wallet-verified member messaging.
// Identity = the wallet that owns a position (proved by a free personal_sign,
// verified server-side via vendored keccak256 + secp256k1 recovery — the two
// files in ./vendor are pinned; see the commit that added them).
// Permission = the matrix: you may message your own downline (direct or
// broadcast) and your own upline chain. Nothing else. Admin can review all
// messages (disclosed in the UI).
'use strict';
const fs = require('fs');
const path = require('path');
const crypto = require('crypto');
const secp = require('./vendor/secp256k1.js');
const sha3 = require('./vendor/sha3.js');
const keccak256 = sha3.keccak256;

secp.utils.hmacSha256Sync = (key, ...msgs) => {
  const h = crypto.createHmac('sha256', Buffer.from(key));
  msgs.forEach(m => h.update(Buffer.from(m)));
  return Uint8Array.from(h.digest());
};

const SESSION_TTL = 30 * 24 * 3600 * 1000;
const CHALLENGE_TTL = 10 * 60 * 1000;
const MAX_BODY = 1500;
const MAX_STORE = 5000;
const DAILY_DIRECT = 30, DAILY_BROADCAST = 3;

let DATA_DIR = null, chain = null, IS_PROD = false;
let sessions = new Map();           // token -> {address, id, expires}
const challenges = new Map();       // addressLower -> {message, exp}

const MSG_FILE = () => path.join(DATA_DIR, 'messages.json');
const SESS_FILE = () => path.join(DATA_DIR, 'msg-sessions.json');
function readJson(f, fb) { try { return JSON.parse(fs.readFileSync(f, 'utf8')); } catch (e) { return fb; } }
function writeJson(f, v) { fs.writeFileSync(f, JSON.stringify(v)); }
function loadSessions() { const o = readJson(SESS_FILE(), {}); sessions = new Map(Object.entries(o).filter(([, s]) => s.expires > Date.now())); }
function saveSessions() { writeJson(SESS_FILE(), Object.fromEntries(sessions)); }
function getMessages() { return readJson(MSG_FILE(), []); }
function saveMessages(m) { writeJson(MSG_FILE(), m.slice(-MAX_STORE)); }

function init(opts) { DATA_DIR = opts.dataDir; chain = opts.chain; IS_PROD = !!opts.isProd; loadSessions(); }

// ---- crypto ----
function personalDigest(msg) {
  const m = Buffer.from(msg, 'utf8');
  const pre = Buffer.from('\x19Ethereum Signed Message:\n' + m.length, 'utf8');
  return Buffer.from(keccak256(Buffer.concat([pre, m])), 'hex');
}
function recoverAddress(msg, signature) {
  const raw = Buffer.from(String(signature).replace(/^0x/, ''), 'hex');
  if (raw.length !== 65) throw new Error('Bad signature length');
  let v = raw[64]; if (v >= 27) v -= 27;
  if (v !== 0 && v !== 1) throw new Error('Bad signature recovery byte');
  const pub = secp.recoverPublicKey(personalDigest(msg), raw.slice(0, 64), v, false);
  return '0x' + keccak256(Buffer.from(pub.slice(1))).slice(-40);
}

// ---- auth ----
const ADDR_RE = /^0x[0-9a-fA-F]{40}$/;
// EIP-55 checksum (needed for the SIWE message format; wallets render
// EIP-4361-formatted requests with their friendly "Sign-in" UI instead of a
// raw-signature warning — matters for member trust in MetaMask)
function checksumAddress(address) {
  const a = address.toLowerCase().replace(/^0x/, '');
  const h = keccak256(a);
  let out = '0x';
  for (let i = 0; i < a.length; i++) out += parseInt(h[i], 16) >= 8 ? a[i].toUpperCase() : a[i];
  return out;
}
function makeChallenge(address) {
  const a = address.toLowerCase();
  const nonce = crypto.randomBytes(16).toString('hex');
  const message = `rmcircle.team wants you to sign in with your Ethereum account:\n${checksumAddress(a)}\n\nRM Circle member sign-in for on-site messaging. This signature is free and cannot move funds or approve anything.\n\nURI: https://rmcircle.team\nVersion: 1\nChain ID: 137\nNonce: ${nonce}\nIssued At: ${new Date().toISOString()}`;
  challenges.set(a, { message, exp: Date.now() + CHALLENGE_TTL });
  return message;
}
function verifyChallenge(address, signature) {
  const a = address.toLowerCase();
  const ch = challenges.get(a);
  if (!ch || ch.exp < Date.now()) return { error: 'Challenge expired - tap sign-in again.' };
  let rec;
  try { rec = recoverAddress(ch.message, signature); } catch (e) { return { error: 'Invalid signature: ' + e.message }; }
  if (rec !== a) return { error: 'Signature does not match this wallet.' };
  challenges.delete(a);
  const id = chain.memberIdByAccount(a);
  if (!id) return { error: 'No RM Circle position is registered to this wallet.' };
  const token = crypto.randomBytes(32).toString('hex');
  sessions.set(token, { address: a, id, expires: Date.now() + SESSION_TTL });
  saveSessions();
  return { token, id };
}
// Mini App sessions: identity was already proved once (wallet-verified
// Telegram link), and Telegram re-proves the chat via signed initData — so a
// session can be minted without a fresh wallet signature. No address attached.
function mintSession(id) {
  if (!Number.isInteger(id) || id < 1) return null;
  const token = crypto.randomBytes(32).toString('hex');
  sessions.set(token, { address: null, id, expires: Date.now() + SESSION_TTL, via: 'tg' });
  saveSessions();
  return token;
}
function authFromCookie(req) {
  const m = /(?:^|;\s*)ctb\.msid=([^;]+)/.exec(req.headers.cookie || '');
  if (!m) return null;
  const s = sessions.get(decodeURIComponent(m[1]));
  if (!s || s.expires < Date.now()) return null;
  return s;
}
function sessionCookie(token) {
  return `ctb.msid=${encodeURIComponent(token)}; Path=/; HttpOnly; SameSite=Lax; Max-Age=${SESSION_TTL / 1000}${IS_PROD ? '; Secure' : ''}`;
}

// ---- permissions ----
function canMessage(fromId, toId) {
  if (fromId === toId) return false;
  return chain.isInTeam(toId, fromId) || chain.isInTeam(fromId, toId);
}
function isRecipient(msg, myId) {
  if (msg.toId === myId) return true;
  if (msg.org && msg.fromId !== myId && chain.isInTeam(myId, msg.fromId)) return true;
  return false;
}

// ---- operations ----
function sanitizeBody(b) {
  return String(b || '').replace(/\r/g, '').replace(/[\u0000-\u0008\u000b-\u001f\u007f]/g, '').trim().slice(0, MAX_BODY);
}
function send(sess, body) {
  const text = sanitizeBody(body.body);
  if (!text) return { error: 'Write a message first.' };
  const org = !!body.org;
  const msgs = getMessages();
  const dayAgo = Date.now() - 24 * 3600 * 1000;
  const mine = msgs.filter(m => m.fromId === sess.id && m.ts > dayAgo);
  if (org && mine.filter(m => m.org).length >= DAILY_BROADCAST) return { error: `Broadcast limit reached (${DAILY_BROADCAST}/day).` };
  if (!org && mine.filter(m => !m.org).length >= DAILY_DIRECT) return { error: `Daily message limit reached (${DAILY_DIRECT}/day).` };
  let toId = 0;
  if (!org) {
    toId = Number(body.toId);
    if (!Number.isInteger(toId) || toId < 1) return { error: 'Enter the member ID to send to.' };
    if (!canMessage(sess.id, toId)) return { error: `#${toId} is not in your team or upline - messaging follows your matrix lines only.` };
  }
  const rec = { mid: crypto.randomBytes(8).toString('hex'), fromId: sess.id, toId, org, body: text, ts: Date.now(), read: {} };
  msgs.push(rec);
  saveMessages(msgs);
  return { ok: true, mid: rec.mid };
}
function inbox(sess) {
  const msgs = getMessages();
  const forMe = [], sent = [];
  for (const m of msgs) {
    if (m.fromId === sess.id) sent.push(m);
    else if (isRecipient(m, sess.id)) forMe.push(m);
  }
  const shape = (m, mine) => ({ mid: m.mid, fromId: m.fromId, toId: m.toId || null, org: !!m.org, body: m.body, ts: m.ts, read: mine ? undefined : !!(m.read && m.read[sess.id]), mine });
  return {
    id: sess.id,
    inbox: forMe.slice(-100).reverse().map(m => shape(m, false)),
    sent: sent.slice(-30).reverse().map(m => shape(m, true))
  };
}
function markRead(sess, mids) {
  const msgs = getMessages();
  let changed = false;
  for (const m of msgs) {
    if (mids.includes(m.mid) && isRecipient(m, sess.id) && !(m.read && m.read[sess.id])) {
      m.read = m.read || {}; m.read[sess.id] = Date.now(); changed = true;
    }
  }
  if (changed) saveMessages(msgs);
  return { ok: true };
}
function unreadCount(id) {
  if (!Number.isInteger(id) || id < 1) return 0;
  return getMessages().filter(m => isRecipient(m, id) && !(m.read && m.read[id])).length;
}
function adminList() {
  return getMessages().slice(-300).reverse().map(m => ({ mid: m.mid, fromId: m.fromId, toId: m.toId || null, org: !!m.org, body: m.body, ts: m.ts, readCount: Object.keys(m.read || {}).length }));
}

module.exports = { init, makeChallenge, verifyChallenge, mintSession, authFromCookie, sessionCookie, send, inbox, markRead, unreadCount, adminList, ADDR_RE };