const prisma = require('../config/db');

// Escape user-controlled strings before inserting them into HTML
function escapeHtml(str) {
  return String(str || '')
    .replace(/&/g, '&')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;')
    .replace(/'/g, '&#x27;');
}

// Utilities shared with attendees emailing
function fmtDate(d) {
  try { return new Date(d).toLocaleString(); } catch { return String(d); }
}

function getFrontendBaseUrl() {
  const base = process.env.FRONTEND_URL || process.env.APP_BASE_URL || 'http://localhost:3001';
  return String(base).replace(/\/$/, '');
}

function buildEventContext(event) {
  if (!event) return { eventTitle: '', eventStart: '', eventLink: '', eventLinkHtml: '' };
  const eventTitle = event.title || '';
  const eventStart = event.startDate ? fmtDate(event.startDate) : '';
  const eventLink = `${getFrontendBaseUrl()}/events/${encodeURIComponent(event.id)}`;
  const eventLinkHtml = `<a href="${eventLink}">${eventLink}</a>`;
  return { eventTitle, eventStart, eventLink, eventLinkHtml };
}

const { replacePlaceholders } = require('../utils/placeholders');

function parseFreeformEmails(lines) {
  // Supports formats:
  //  - email@example.com
  //  - Name <email@example.com>
  //  - "Name" <email@example.com>
  const recipients = [];
  const input = Array.isArray(lines) ? lines : String(lines || '').split(/\r?\n/);
  for (const raw of input) {
    const s = String(raw || '').trim();
    if (!s) continue;
    let name = '';
    let email = '';
    const m = s.match(/^(.*?)<\s*([^>\s]+@[^>\s]+)\s*>\s*$/);
    if (m) {
      name = m[1].trim().replace(/^"|"$/g, '').trim();
      email = m[2].trim();
    } else {
      // If it just looks like an email, accept it
      const em = s.match(/^[^\s@]+@[^\s@]+\.[^\s@]+$/) ? s : '';
      if (em) email = em; else continue;
    }
    recipients.push({ email, name });
  }
  return recipients;
}

// @desc    Preview broadcast recipients and sample
// @route   POST /api/broadcasts/preview
// @access  Private/Supervisor or Admin
const previewBroadcast = async (req, res) => {
  try {
    const { userIds, emails, eventId } = req.body || {};

    // Resolve users
    const ids = Array.isArray(userIds) ? userIds.filter(x => typeof x === 'string' && x) : [];
    let users = [];
    if (ids.length) {
      users = await prisma.user.findMany({ where: { id: { in: ids } }, select: { id: true, name: true, email: true } });
    }

    // Parse freeform emails
    const extra = parseFreeformEmails(emails);

    // Merge and de-duplicate by email
    const map = new Map();
    for (const u of users) {
      const email = String(u.email || '').trim();
      if (!email) continue;
      if (!map.has(email)) map.set(email, { email, name: u.name || '' });
    }
    for (const r of extra) {
      const email = String(r.email || '').trim();
      if (!email) continue;
      if (!map.has(email)) map.set(email, { email, name: r.name || '' });
    }
    const recipients = Array.from(map.values());

    // Optionally resolve event info for link/title placeholder
    let event = null;
    if (eventId && typeof eventId === 'string') {
      event = await prisma.event.findUnique({ where: { id: eventId } });
    }
    const eventCtx = buildEventContext(event);

    return res.json({ matched: recipients.length, recipients: recipients.slice(0, 20), event: event ? { id: event.id, title: event.title } : null, placeholders: ['{{name}}','{{event.title}}','{{event.start}}','{{event.link}}'] });
  } catch (error) {
    return res.status(400).json({ message: error.message });
  }
};

// @desc    Send broadcast now
// @route   POST /api/broadcasts/send
// @access  Private/Supervisor or Admin
const sendBroadcast = async (req, res) => {
  try {
    const { subject, html, text, userIds, emails, eventId } = req.body || {};
    if (!subject || !(html || text)) {
      return res.status(400).json({ message: 'Subject and message (html or text) are required' });
    }

    // Resolve recipients similar to preview
    const ids = Array.isArray(userIds) ? userIds.filter(x => typeof x === 'string' && x) : [];
    let users = [];
    if (ids.length) {
      users = await prisma.user.findMany({ where: { id: { in: ids } }, select: { id: true, name: true, email: true } });
    }
    const extra = parseFreeformEmails(emails);

    const map = new Map();
    for (const u of users) {
      const email = String(u.email || '').trim();
      if (!email) continue;
      if (!map.has(email)) map.set(email, { email, name: u.name || '' });
    }
    for (const r of extra) {
      const email = String(r.email || '').trim();
      if (!email) continue;
      if (!map.has(email)) map.set(email, { email, name: r.name || '' });
    }
    const recipients = Array.from(map.values());
    if (recipients.length === 0) {
      return res.status(400).json({ message: 'No valid recipients' });
    }

    // Resolve event
    let event = null;
    if (eventId && typeof eventId === 'string') {
      event = await prisma.event.findUnique({ where: { id: eventId } });
    }
    const eventCtx = buildEventContext(event);

    const { sendMail } = require('../utils/email');

    // Send all emails in parallel instead of sequentially — critical for large recipient lists
    const results = await Promise.allSettled(recipients.map(async rcpt => {
      const ctxBase = {
        name: rcpt.name || '',
        eventTitle: eventCtx.eventTitle,
        eventStart: eventCtx.eventStart,
        eventLink: eventCtx.eventLink,
      };
      const ctxForHtml = html ? {
        name: escapeHtml(rcpt.name || ''),
        eventTitle: escapeHtml(eventCtx.eventTitle),
        eventStart: escapeHtml(eventCtx.eventStart),
        eventLink: escapeHtml(eventCtx.eventLink),
        eventLinkHtml: eventCtx.eventLinkHtml,
      } : ctxBase;
      const finalSubject = await replacePlaceholders(subject, ctxBase);
      const finalHtml = html ? await replacePlaceholders(html, ctxForHtml) : undefined;
      const finalText = (!html ? await replacePlaceholders(text || '', ctxBase) : undefined);
      await sendMail({ to: rcpt.email, subject: finalSubject, html: finalHtml, text: finalText });
    }));

    const sent = results.filter(r => r.status === 'fulfilled').length;
    results.forEach((r, i) => {
      if (r.status === 'rejected') {
        try { console.warn('[broadcast] failed to send to', recipients[i]?.email, r.reason?.message || r.reason); } catch {}
      }
    });

    return res.json({ matched: recipients.length, sent });
  } catch (error) {
    return res.status(400).json({ message: error.message });
  }
};

// @desc    Schedule a broadcast
// @route   POST /api/broadcasts/schedule
// @access  Private/Supervisor or Admin
const scheduleBroadcast = async (req, res) => {
  try {
    const { scheduledAt, subject, html, text, userIds, emails, eventId } = req.body || {};
    if (!scheduledAt) return res.status(400).json({ message: 'scheduledAt is required' });
    const when = new Date(scheduledAt);
    if (isNaN(when.getTime())) return res.status(400).json({ message: 'scheduledAt must be a valid ISO date-time' });
    if (!subject || !(html || text)) return res.status(400).json({ message: 'Subject and message (html or text) are required' });

    const payload = { subject, html, text, userIds, emails, eventId };

    const { addJob } = require('../utils/scheduledEmails');
    const created = addJob({
      broadcast: true,
      scheduledAt: when.toISOString(),
      createdById: req.user?.id || null,
      payload,
    });

    return res.status(201).json({ message: 'Broadcast scheduled', job: created });
  } catch (error) {
    return res.status(400).json({ message: error.message });
  }
};

module.exports = { previewBroadcast, sendBroadcast, scheduleBroadcast };