import Redis from 'ioredis';
import CryptoJS from 'crypto-js';
import { PrismaClient } from '@prisma/client';

const prisma = new PrismaClient();

// Initialize Redis client
let redisClient: Redis | null = null;

/**
 * Get a Redis client instance (singleton pattern)
 */
export function getRedisClient(): Redis {
  if (!redisClient) {
    // Set Redis connection parameters from environment variables only
    const redisOptions = {
      host: process.env.REDIS_HOST,
      port: process.env.REDIS_PORT ? parseInt(process.env.REDIS_PORT) : undefined,
      password: process.env.REDIS_PASSWORD,
      retryStrategy: (times: number) => {
        const delay = Math.min(times * 100, 5000);
        return delay;
      },
      maxRetriesPerRequest: 5,
      enableOfflineQueue: true
    };
    
    console.log('Connecting to Redis using environment variables');
    redisClient = new Redis(redisOptions);
    
    redisClient.on('error', (err) => {
      console.error('Redis connection error:', err);
    });
    
    redisClient.on('connect', () => {
      console.log('Successfully connected to Redis');
    });
    
    redisClient.on('reconnecting', () => {
      console.log('Reconnecting to Redis...');
    });
  }
  
  return redisClient;
}

/**
 * Close Redis connection (useful for serverless environments)
 */
export async function closeRedisConnection(): Promise<void> {
  if (redisClient) {
    await redisClient.quit();
    redisClient = null;
  }
}

// Encryption key from environment variable or fallback
const getEncryptionKey = () => {
  return process.env.REDIS_ENCRYPTION_KEY || 'default-encryption-key-change-in-production';
};

/**
 * Encrypt sensitive data before storing in Redis
 */
export function encryptData(data: string): string {
  return CryptoJS.AES.encrypt(data, getEncryptionKey()).toString();
}

/**
 * Decrypt sensitive data retrieved from Redis
 */
export function decryptData(encryptedData: string): string {
  const bytes = CryptoJS.AES.decrypt(encryptedData, getEncryptionKey());
  return bytes.toString(CryptoJS.enc.Utf8);
}

// Cache key definitions
export const KEYS = {
  CREDENTIALS: (userId: string) => `email:credentials:${userId}`,
  SESSION: (userId: string) => `email:session:${userId}`,
  EMAIL_LIST: (userId: string, folder: string, page: number, perPage: number) => 
    `email:list:${userId}:${folder}:${page}:${perPage}`,
  EMAIL_CONTENT: (userId: string, emailId: string) => 
    `email:content:${userId}:${emailId}`
};

// TTL constants in seconds
export const TTL = {
  CREDENTIALS: 60 * 60 * 24, // 24 hours
  SESSION: 60 * 60 * 4,      // 4 hours (increased from 30 minutes)
  EMAIL_LIST: 60 * 5,        // 5 minutes
  EMAIL_CONTENT: 60 * 15     // 15 minutes
};

interface EmailCredentials {
  id: string;
  userId: string;
  email: string;
  password: string;
  host: string;
  port: number;
  secure: boolean;
  smtp_host: string | null;
  smtp_port: number | null;
  smtp_secure: boolean | null;
  display_name: string | null;
  color: string | null;
  createdAt: Date;
  updatedAt: Date;
}

interface ImapSessionData {
  connectionId?: string;
  lastActive: number;
  mailboxes?: string[];
  lastVisit?: number;
}

/**
 * Cache email credentials in Redis
 */
export async function cacheEmailCredentials(userId: string, credentials: EmailCredentials): Promise<void> {
  const client = await getRedisClient();
  const key = `email_credentials:${userId}`;
  await client.set(key, JSON.stringify(credentials), 'EX', 3600); // 1 hour expiry
}

/**
 * Get cached email credentials from Redis
 */
export async function getCachedEmailCredentials(userId: string): Promise<EmailCredentials | null> {
  const client = await getRedisClient();
  const key = `email_credentials:${userId}`;
  const data = await client.get(key);
  return data ? JSON.parse(data) : null;
}

/**
 * Get email credentials from Redis or database
 */
export async function getEmailCredentials(userId: string): Promise<EmailCredentials | null> {
  // Try to get from cache first
  const cached = await getCachedEmailCredentials(userId);
  if (cached) {
    return cached;
  }

  // If not in cache, get from database
  const credentials = await prisma.mailCredentials.findFirst({
    where: { userId },
    select: {
      id: true,
      userId: true,
      email: true,
      password: true,
      host: true,
      port: true,
      secure: true,
      smtp_host: true,
      smtp_port: true,
      smtp_secure: true,
      display_name: true,
      color: true,
      createdAt: true,
      updatedAt: true
    }
  });

  if (!credentials) {
    return null;
  }

  // Cache the credentials
  await cacheEmailCredentials(userId, credentials);

  return credentials;
}

/**
 * Cache IMAP session data for quick reconnection
 */
export async function cacheImapSession(
  userId: string,
  sessionData: ImapSessionData
): Promise<void> {
  const redis = getRedisClient();
  const key = KEYS.SESSION(userId);
  
  // Always update the lastActive timestamp
  sessionData.lastActive = Date.now();
  
  await redis.set(key, JSON.stringify(sessionData), 'EX', TTL.SESSION);
}

/**
 * Get cached IMAP session data
 */
export async function getCachedImapSession(
  userId: string
): Promise<ImapSessionData | null> {
  const redis = getRedisClient();
  const key = KEYS.SESSION(userId);
  
  const cachedData = await redis.get(key);
  if (!cachedData) return null;
  
  return JSON.parse(cachedData) as ImapSessionData;
}

/**
 * Cache email list in Redis
 */
export async function cacheEmailList(
  userId: string,
  folder: string,
  page: number,
  perPage: number,
  data: any
): Promise<void> {
  const redis = getRedisClient();
  const key = KEYS.EMAIL_LIST(userId, folder, page, perPage);
  
  await redis.set(key, JSON.stringify(data), 'EX', TTL.EMAIL_LIST);
}

/**
 * Get cached email list from Redis
 */
export async function getCachedEmailList(
  userId: string,
  folder: string,
  page: number,
  perPage: number
): Promise<any | null> {
  const redis = getRedisClient();
  const key = KEYS.EMAIL_LIST(userId, folder, page, perPage);
  
  const cachedData = await redis.get(key);
  if (!cachedData) return null;
  
  return JSON.parse(cachedData);
}

/**
 * Cache email content in Redis
 */
export async function cacheEmailContent(
  userId: string,
  emailId: string,
  data: any
): Promise<void> {
  const redis = getRedisClient();
  const key = KEYS.EMAIL_CONTENT(userId, emailId);
  
  await redis.set(key, JSON.stringify(data), 'EX', TTL.EMAIL_CONTENT);
}

/**
 * Get cached email content from Redis
 */
export async function getCachedEmailContent(
  userId: string,
  emailId: string
): Promise<any | null> {
  const redis = getRedisClient();
  const key = KEYS.EMAIL_CONTENT(userId, emailId);
  
  const cachedData = await redis.get(key);
  if (!cachedData) return null;
  
  return JSON.parse(cachedData);
}

/**
 * Invalidate all email caches for a folder
 */
export async function invalidateFolderCache(
  userId: string,
  folder: string
): Promise<void> {
  const redis = getRedisClient();
  const pattern = `email:list:${userId}:${folder}:*`;
  
  // Use SCAN to find and delete keys matching the pattern
  let cursor = '0';
  do {
    const [nextCursor, keys] = await redis.scan(cursor, 'MATCH', pattern, 'COUNT', 100);
    cursor = nextCursor;
    
    if (keys.length > 0) {
      await redis.del(...keys);
    }
  } while (cursor !== '0');
}

/**
 * Invalidate email content cache
 */
export async function invalidateEmailContentCache(
  userId: string,
  emailId: string
): Promise<void> {
  const redis = getRedisClient();
  const key = KEYS.EMAIL_CONTENT(userId, emailId);
  
  await redis.del(key);
}

/**
 * Warm up Redis connection to avoid cold starts
 */
export async function warmupRedisCache(): Promise<boolean> {
  try {
    // Ping Redis to establish connection early
    const redis = getRedisClient();
    await redis.ping();
    console.log('Redis connection warmed up');
    return true;
  } catch (error) {
    console.error('Error warming up Redis:', error);
    return false;
  }
}

/**
 * Get Redis connection status
 */
export async function getRedisStatus(): Promise<{
  status: 'connected' | 'error';
  ping?: string;
  error?: string;
}> {
  try {
    const redis = getRedisClient();
    const pong = await redis.ping();
    return {
      status: 'connected',
      ping: pong
    };
  } catch (error) {
    return {
      status: 'error',
      error: error instanceof Error ? error.message : String(error)
    };
  }
}

/**
 * Invalidate all user email caches (email lists and content)
 */
export async function invalidateUserEmailCache(
  userId: string
): Promise<void> {
  const redis = getRedisClient();
  
  // Patterns to delete
  const patterns = [
    `email:list:${userId}:*`,
    `email:content:${userId}:*`
  ];
  
  for (const pattern of patterns) {
    let cursor = '0';
    do {
      const [nextCursor, keys] = await redis.scan(cursor, 'MATCH', pattern, 'COUNT', 100);
      cursor = nextCursor;
      
      if (keys.length > 0) {
        await redis.del(...keys);
      }
    } while (cursor !== '0');
  }
}