// server/src/services/notifications.ts
import { createTransport } from 'nodemailer';
import { readFileSync, writeFileSync, existsSync, mkdirSync } from 'fs';
import { resolve } from 'path';
import { randomUUID } from 'crypto';
import type { MonitorUser, Notification, UserRole } from '../types/index.js';

// ─── Persistent JSON storage (simple file-based) ───
const DATA_DIR = resolve(process.cwd(), 'data');
const USERS_FILE = resolve(DATA_DIR, 'users.json');
const NOTIFICATIONS_FILE = resolve(DATA_DIR, 'notifications.json');

function ensureDataDir() {
  try { mkdirSync(DATA_DIR, { recursive: true }); } catch {}
}

function loadUsers(): MonitorUser[] {
  ensureDataDir();
  if (!existsSync(USERS_FILE)) {
    // Seed with the existing config users
    const seed: MonitorUser[] = [
      { id: randomUUID(), email: 'nafih@bshtechnologies.in', name: 'Nafih', role: 'server-admin', notifyOnError: true, createdAt: new Date().toISOString() },
      { id: randomUUID(), email: 'vivek@bshtechnologies.in', name: 'Vivek', role: 'developer', notifyOnError: true, createdAt: new Date().toISOString() },
    ];
    writeFileSync(USERS_FILE, JSON.stringify(seed, null, 2));
    return seed;
  }
  return JSON.parse(readFileSync(USERS_FILE, 'utf-8'));
}

function saveUsers(users: MonitorUser[]) {
  ensureDataDir();
  writeFileSync(USERS_FILE, JSON.stringify(users, null, 2));
}

function loadNotifications(): Notification[] {
  ensureDataDir();
  if (!existsSync(NOTIFICATIONS_FILE)) {
    writeFileSync(NOTIFICATIONS_FILE, '[]');
    return [];
  }
  return JSON.parse(readFileSync(NOTIFICATIONS_FILE, 'utf-8'));
}

function saveNotifications(notifs: Notification[]) {
  ensureDataDir();
  // Keep only last 200 notifications
  const trimmed = notifs.slice(-200);
  writeFileSync(NOTIFICATIONS_FILE, JSON.stringify(trimmed, null, 2));
}

// ─── SMTP Transport ───
const smtpTransport = createTransport({
  host: process.env.SMTP_HOST ?? 'mail.bshtech.net',
  port: parseInt(process.env.SMTP_PORT ?? '587'),
  secure: false,
  auth: {
    user: process.env.SMTP_USER ?? 'noreply@bshtech.net',
    pass: process.env.SMTP_PASS ?? 'Ev3ntifyN0Reply2026',
  },
  tls: { rejectUnauthorized: false },
});

// ─── Public API ───

export function getUsers(): MonitorUser[] {
  return loadUsers();
}

export function addUser(email: string, name: string, role: UserRole, notifyOnError = true): MonitorUser {
  const users = loadUsers();
  if (users.find(u => u.email === email)) {
    throw new Error(`User with email ${email} already exists`);
  }
  const user: MonitorUser = {
    id: randomUUID(),
    email,
    name,
    role,
    notifyOnError,
    createdAt: new Date().toISOString(),
  };
  users.push(user);
  saveUsers(users);
  return user;
}

export function updateUser(id: string, updates: Partial<Pick<MonitorUser, 'name' | 'role' | 'notifyOnError'>>): MonitorUser {
  const users = loadUsers();
  const idx = users.findIndex(u => u.id === id);
  if (idx < 0) throw new Error('User not found');
  users[idx] = { ...users[idx], ...updates };
  saveUsers(users);
  return users[idx];
}

export function deleteUser(id: string): void {
  const users = loadUsers();
  const filtered = users.filter(u => u.id !== id);
  if (filtered.length === users.length) throw new Error('User not found');
  saveUsers(filtered);
}

export function getNotifications(limit = 50): Notification[] {
  return loadNotifications().reverse().slice(0, limit);
}

export function markNotificationRead(id: string): void {
  const notifs = loadNotifications();
  const n = notifs.find(n => n.id === id);
  if (n) {
    n.read = true;
    saveNotifications(notifs);
  }
}

export function markAllRead(): void {
  const notifs = loadNotifications();
  notifs.forEach(n => n.read = true);
  saveNotifications(notifs);
}

export function getUnreadCount(): number {
  return loadNotifications().filter(n => !n.read).length;
}

export async function createNotification(
  type: Notification['type'],
  title: string,
  message: string,
  source: string,
): Promise<Notification> {
  const notif: Notification = {
    id: randomUUID(),
    type,
    title,
    message,
    source,
    timestamp: new Date().toISOString(),
    read: false,
    emailSent: false,
  };

  // Save to file
  const notifs = loadNotifications();
  notifs.push(notif);
  saveNotifications(notifs);

  // Send email to subscribed users
  if (type === 'error' || type === 'warning') {
    const users = loadUsers().filter(u => u.notifyOnError);
    if (users.length > 0) {
      try {
        await smtpTransport.sendMail({
          from: '"Eventify Monitor" <noreply@bshtech.net>',
          to: users.map(u => u.email).join(', '),
          subject: `[${type.toUpperCase()}] ${title}`,
          html: `
            <div style="font-family: sans-serif; max-width: 600px; margin: 0 auto;">
              <div style="background: ${type === 'error' ? '#dc2626' : '#f59e0b'}; color: white; padding: 16px 24px; border-radius: 8px 8px 0 0;">
                <h2 style="margin: 0; font-size: 18px;">${type === 'error' ? 'Error Alert' : 'Warning'}: ${title}</h2>
              </div>
              <div style="background: #f9fafb; padding: 24px; border: 1px solid #e5e7eb; border-top: none; border-radius: 0 0 8px 8px;">
                <p style="margin: 0 0 12px; color: #374151;">${message}</p>
                <p style="margin: 0 0 8px; color: #6b7280; font-size: 13px;"><strong>Source:</strong> ${source}</p>
                <p style="margin: 0; color: #6b7280; font-size: 13px;"><strong>Time:</strong> ${new Date().toLocaleString()}</p>
                <hr style="border: none; border-top: 1px solid #e5e7eb; margin: 16px 0;">
                <p style="margin: 0; color: #9ca3af; font-size: 12px;">
                  <a href="https://status.eventifyplus.com" style="color: #2563eb;">View Dashboard</a> | Eventify Server Monitor
                </p>
              </div>
            </div>
          `,
        });
        notif.emailSent = true;
        // Update the saved notification
        const updated = loadNotifications();
        const idx = updated.findIndex(n => n.id === notif.id);
        if (idx >= 0) {
          updated[idx].emailSent = true;
          saveNotifications(updated);
        }
        console.log(`[Notifications] Email sent to ${users.length} users for: ${title}`);
      } catch (err) {
        console.error(`[Notifications] Failed to send email:`, err);
      }
    }
  }

  return notif;
}