const axios = require('axios');
const path  = require('path');
const fs    = require('fs');
const { v4: uuidv4 } = require('uuid');

const BASE = 'https://api.wawp.net/v2';

// ─── Config cache (DB-backed, env fallback) ───────────────────────────────────

let _configCache   = null;
let _configCacheAt = 0;
const CONFIG_TTL_MS = 30_000; // 30 s

/**
 * Load WAWP credentials from DB (AppSetting table), falling back to .env.
 * Result is cached for 30 seconds so repeated calls don't hit the DB.
 */
async function getConfig() {
  const now = Date.now();
  if (_configCache && (now - _configCacheAt) < CONFIG_TTL_MS) return _configCache;

  try {
    const prisma = require('../config/db');
    const rows = await prisma.appSetting.findMany({
      where: { key: { in: ['WAWP_ACCESS_TOKEN', 'WAWP_INSTANCE_ID'] } },
    });
    const map = Object.fromEntries(rows.map(r => [r.key, r.value]));
    _configCache = {
      token:      map.WAWP_ACCESS_TOKEN || process.env.WAWP_ACCESS_TOKEN || '',
      instanceId: map.WAWP_INSTANCE_ID  || process.env.WAWP_INSTANCE_ID  || '',
    };
  } catch {
    // DB unavailable — fall back to env vars
    _configCache = {
      token:      process.env.WAWP_ACCESS_TOKEN || '',
      instanceId: process.env.WAWP_INSTANCE_ID  || '',
    };
  }
  _configCacheAt = now;
  return _configCache;
}

/** Save WAWP credentials to DB and invalidate the cache. */
async function setConfig(token, instanceId) {
  const prisma = require('../config/db');
  await prisma.$transaction([
    prisma.appSetting.upsert({
      where:  { key: 'WAWP_ACCESS_TOKEN' },
      update: { value: token },
      create: { key: 'WAWP_ACCESS_TOKEN', value: token },
    }),
    prisma.appSetting.upsert({
      where:  { key: 'WAWP_INSTANCE_ID' },
      update: { value: instanceId },
      create: { key: 'WAWP_INSTANCE_ID', value: instanceId },
    }),
  ]);
  _configCache = null; // force reload on next getConfig()
}

async function isConfigured() {
  const { token, instanceId } = await getConfig();
  return !!(token && instanceId);
}

// ─── SA phone normalisation ───────────────────────────────────────────────────

/**
 * Normalises any common South African phone format to 27xxxxxxxxx (11 digits).
 * Handles: 0821234567  /  082 123 4567  /  +27821234567  /  +27 82 123 4567
 * Returns null when the number cannot be resolved to a valid SA mobile.
 */
function normalizeZAPhone(raw) {
  if (!raw) return null;
  let digits = String(raw).replace(/\D/g, '');

  // Local format: leading 0 + 9 digits (total 10)
  if (digits.startsWith('0') && digits.length === 10) {
    digits = '27' + digits.slice(1);
  }

  // Must now be exactly 11 digits starting with 27
  if (/^27\d{9}$/.test(digits)) return digits;
  return null;
}

/** Returns true when raw is a valid SA mobile number. */
function isValidZAPhone(raw) {
  return normalizeZAPhone(raw) !== null;
}

/** Converts a phone number to the WAWP chatId format (e.g. 27821234567@c.us). */
function toChatId(raw) {
  const n = normalizeZAPhone(raw);
  return n ? `${n}@c.us` : null;
}

// ─── "Session not found" auto-recovery ───────────────────────────────────────

/**
 * Returns true when the WAWP error message indicates the session doesn't exist.
 */
function isSessionNotFound(e) {
  const msg = (e?.response?.data?.message || e?.message || '').toLowerCase();
  return msg.includes('session not found') || msg.includes('instance not found');
}

/** Extracts the WAWP API's own error reason when present, instead of axios's generic
 *  "Request failed with status code NNN" (which carries no information about what went wrong). */
function wawpErrorMessage(e) {
  return e?.response?.data?.message || e?.message || 'Unknown WhatsApp API error';
}

/**
 * If the WAWP API reports "Session not found", clear the stale instance ID
 * from the DB so the admin UI drops back to the Session Instance setup step.
 *
 * @param {Error} e - The error thrown by a WAWP API call
 */
async function handleSessionNotFound(e) {
  if (!isSessionNotFound(e)) throw e; // not our problem — re-throw

  console.warn('[whatsapp] Session not found — clearing instance ID from DB...');
  const { token, instanceId } = await getConfig();

  // Try to delete the stale session on WAWP (may fail — that's okay)
  try {
    await axios.post(`${BASE}/session/delete`, { access_token: token, instance_id: instanceId });
  } catch (delErr) {
    console.warn('[whatsapp] Delete stale session failed (ignored):', delErr?.response?.data?.message || delErr.message);
  }

  // Clear the instance ID from DB so the frontend goes back to Step 2
  await setConfig(token, '');
  console.info('[whatsapp] Instance ID cleared — admin must set up a new session instance.');

  throw new Error('SESSION_NOT_FOUND');
}

// ─── Session management ───────────────────────────────────────────────────────

async function getStatus() {
  const { token, instanceId } = await getConfig();
  try {
    const res = await axios.post(`${BASE}/session/info`, { access_token: token, instance_id: instanceId });
    return res.data;
  } catch (e) {
    await handleSessionNotFound(e);
  }
}

async function startSession() {
  const { token, instanceId } = await getConfig();
  try {
    const res = await axios.post(`${BASE}/session/start`, { access_token: token, instance_id: instanceId });
    return res.data;
  } catch (e) {
    await handleSessionNotFound(e);
  }
}

async function restartSession() {
  const { token, instanceId } = await getConfig();
  try {
    const res = await axios.post(`${BASE}/session/restart`, { access_token: token, instance_id: instanceId });
    return res.data;
  } catch (e) {
    await handleSessionNotFound(e);
  }
}

async function logoutSession() {
  const { token, instanceId } = await getConfig();
  const res = await axios.post(`${BASE}/session/logout`, { access_token: token, instance_id: instanceId });
  return res.data;
}

async function createInstance(name) {
  const { token } = await getConfig();
  const label = name || `hope-events-${Date.now()}`;
  const res = await axios.post(`${BASE}/session/create`, { access_token: token, name: label });
  const newInstanceId = res.data?.instance_id || res.data?.id;
  if (!newInstanceId) throw new Error('Create instance returned no instance_id');
  await setConfig(token, newInstanceId);
  return { ...res.data, instance_id: newInstanceId };
}

async function deleteInstance() {
  const { token, instanceId } = await getConfig();
  if (!instanceId) throw new Error('No instance configured');
  const res = await axios.post(`${BASE}/session/delete`, { access_token: token, instance_id: instanceId });
  // Clear instance_id from DB after deletion
  await setConfig(token, '');
  return res.data;
}

async function getQr() {
  const { token, instanceId } = await getConfig();
  try {
    const res = await axios.post(`${BASE}/auth/qr-image`, { access_token: token, instance_id: instanceId });
    return res.data; // { qr: 'data:image/png;base64,...' }
  } catch (e) {
    await handleSessionNotFound(e);
  }
}

async function requestPairingCode(phoneNumber) {
  const { token, instanceId } = await getConfig();
  const normalized = normalizeZAPhone(phoneNumber);
  if (!normalized) throw new Error('Invalid South African phone number');
  try {
    const res = await axios.post(`${BASE}/auth/request-code`, {
      access_token: token,
      instance_id:  instanceId,
      phone_number: normalized,
    });
    return res.data; // { code: 'ABCD-1234' }
  } catch (e) {
    await handleSessionNotFound(e);
  }
}

// ─── Messaging ────────────────────────────────────────────────────────────────

async function sendText(toPhone, message) {
  if (!(await isConfigured())) return;
  const chatId = toChatId(toPhone);
  if (!chatId) { console.warn('[whatsapp] Invalid phone, skipping text:', toPhone); return; }
  const { token, instanceId } = await getConfig();
  try {
    await axios.post(`${BASE}/send/text`, {
      access_token: token,
      instance_id:  instanceId,
      chatId,
      message,
    });
  } catch (e) {
    if (isSessionNotFound(e)) {
      try { await handleSessionNotFound(e); } catch {}
      throw new Error('Your WhatsApp session has disconnected. Reconnect it in Admin → WhatsApp Settings, then try again.');
    }
    throw new Error(`WhatsApp text send failed: ${wawpErrorMessage(e)}`);
  }
}

/**
 * Copies a local PDF to a temporary public URL, sends it via WAWP,
 * then schedules the temp file for deletion after 5 minutes.
 */
async function sendPdf(toPhone, localPdfPath, filename, caption) {
  if (!(await isConfigured())) return;
  const chatId = toChatId(toPhone);
  if (!chatId) { console.warn('[whatsapp] Invalid phone, skipping PDF:', toPhone); return; }

  const tempDir = path.join(__dirname, '../../public/uploads/tickets-temp');
  if (!fs.existsSync(tempDir)) fs.mkdirSync(tempDir, { recursive: true });

  const tempName = `${uuidv4()}.pdf`;
  const tempPath = path.join(tempDir, tempName);
  fs.copyFileSync(localPdfPath, tempPath);

  const backendUrl = (process.env.BACKEND_URL || '').replace(/\/$/, '');
  const isLocalhost = !backendUrl || /^https?:\/\/(localhost|127\.0\.0\.1)(:\d+)?$/.test(backendUrl);
  if (isLocalhost) {
    try { fs.unlinkSync(tempPath); } catch {}
    throw new Error(
      `WhatsApp PDF delivery requires a publicly accessible backend URL. ` +
      `BACKEND_URL is currently "${backendUrl || '(not set)'}". ` +
      `Set BACKEND_URL to your public backend URL (e.g. https://api.yourdomain.com) in your .env file.`
    );
  }
  const pdfUrl = `${backendUrl}/uploads/tickets-temp/${tempName}`;

  const { token, instanceId } = await getConfig();
  try {
    await axios.post(`${BASE}/send/pdf`, {
      access_token: token,
      instance_id:  instanceId,
      chatId,
      file: {
        url:      pdfUrl,
        filename: filename || 'tickets.pdf',
        mimetype: 'application/pdf',
      },
      caption: caption || '',
    });
  } catch (e) {
    try { fs.unlinkSync(tempPath); } catch {}
    if (isSessionNotFound(e)) {
      try { await handleSessionNotFound(e); } catch {}
      throw new Error('Your WhatsApp session has disconnected. Reconnect it in Admin → WhatsApp Settings, then try again.');
    }
    throw new Error(`WhatsApp PDF send failed: ${wawpErrorMessage(e)}`);
  }

  // Clean up after 5 minutes — WAWP will have fetched the file by then
  setTimeout(() => { try { fs.unlinkSync(tempPath); } catch {} }, 5 * 60 * 1000);
}

module.exports = {
  getConfig,
  setConfig,
  normalizeZAPhone,
  isValidZAPhone,
  toChatId,
  isConfigured,
  getStatus,
  startSession,
  restartSession,
  logoutSession,
  createInstance,
  deleteInstance,
  getQr,
  requestPairingCode,
  sendText,
  sendPdf,
};