import { NextResponse } from 'next/server';
import { ImapFlow } from 'imapflow';
import { getServerSession } from 'next-auth';
import { authOptions } from '@/app/api/auth/[...nextauth]/route';
import { prisma } from '@/lib/prisma';
import { LRUCache } from 'lru-cache';

// Define types
interface Email {
  id: string;
  from: string;
  fromName?: string;
  to: string;
  subject: string;
  date: string;
  read: boolean;
  starred: boolean;
  folder: string;
  hasAttachments: boolean;
  flags: string[];
  preview?: string | null;
}

interface CachedData {
  emails: Email[];
  folders: string[];
  total: number;
  hasMore: boolean;
  page: number;
  limit: number;
}

// Configure efficient caching with TTL - fix the type to allow any data
const emailCache = new LRUCache<string, any>({
  max: 500, // Store up to 500 emails
  ttl: 1000 * 60 * 5, // Cache for 5 minutes
});

// Simple in-memory cache for email content
const emailContentCache = new LRUCache<string, any>({
  max: 100, 
  ttl: 1000 * 60 * 15, // 15 minutes
});

// Keep IMAP connections per user with timeouts
const connectionPool = new Map<string, {
  client: ImapFlow;
  lastUsed: number;
}>();

// Clean up idle connections periodically
setInterval(() => {
  const now = Date.now();
  connectionPool.forEach((connection, userId) => {
    if (now - connection.lastUsed > 1000 * 60 * 2) { // 2 minutes idle
      connection.client.logout().catch(console.error);
      connectionPool.delete(userId);
    }
  });
}, 60000); // Check every minute

// Get or create IMAP client for user
async function getImapClient(userId: string, credentials: any): Promise<ImapFlow> {
  const existing = connectionPool.get(userId);
  
  if (existing) {
    existing.lastUsed = Date.now();
    return existing.client;
  }
  
  // Remove invalid options
  const client = new ImapFlow({
    host: credentials.host,
    port: credentials.port,
    secure: true,
    auth: {
      user: credentials.email,
      pass: credentials.password,
    },
    logger: false,
    emitLogs: false,
    tls: {
      rejectUnauthorized: false
    },
    disableAutoIdle: true
  });
  
  await client.connect();
  
  connectionPool.set(userId, {
    client,
    lastUsed: Date.now()
  });
  
  return client;
}

// Generate cache key
function getCacheKey(userId: string, folder: string, page: number, limit: number): string {
  return `${userId}:${folder}:${page}:${limit}`;
}

export async function GET(
  request: Request,
  { params }: { params: { id: string } }
) {
  try {
    // 1. Properly await params to avoid Next.js error
    const { id } = await Promise.resolve(params);
    
    // 2. Authentication check
    const session = await getServerSession(authOptions);
    if (!session?.user?.id) {
      return NextResponse.json(
        { error: 'Unauthorized' },
        { status: 401 }
      );
    }

    // 3. Check cache first
    const cacheKey = `email:${session.user.id}:${id}`;
    const cachedEmail = emailContentCache.get(cacheKey);
    if (cachedEmail) {
      return NextResponse.json(cachedEmail);
    }

    // 4. Get credentials from database
    const credentials = await prisma.mailCredentials.findUnique({
      where: {
        userId: session.user.id
      }
    });

    if (!credentials) {
      return NextResponse.json(
        { error: 'No mail credentials found. Please configure your email account.' },
        { status: 401 }
      );
    }

    // 5. Create IMAP client
    const client = new ImapFlow({
      host: credentials.host,
      port: credentials.port,
      secure: true,
      auth: {
        user: credentials.email,
        pass: credentials.password,
      },
      logger: false,
      emitLogs: false,
      tls: {
        rejectUnauthorized: false
      },
      disableAutoIdle: true
    });
    
    try {
      await client.connect();
      
      // 6. Open INBOX
      await client.mailboxOpen('INBOX');
      
      // 7. Fetch the email with UID search
      const options = {
        uid: true,  // This is crucial - we must specify uid:true to fetch by UID
        source: true,
        envelope: true,
        bodyStructure: true,
        flags: true
      };
      
      // 7. Fetch by UID
      const message = await client.fetchOne(id, options);
      
      if (!message) {
        return NextResponse.json(
          { error: 'Email not found' },
          { status: 404 }
        );
      }

      // 8. Parse the email content
      const emailContent = {
        id: message.uid,
        from: message.envelope.from?.[0]?.address || '',
        fromName: message.envelope.from?.[0]?.name || 
                 message.envelope.from?.[0]?.address?.split('@')[0] || '',
        to: message.envelope.to?.map((addr: any) => addr.address).join(', ') || '',
        subject: message.envelope.subject || '(No subject)',
        date: message.envelope.date?.toISOString() || new Date().toISOString(),
        content: message.source?.toString() || '',
        read: message.flags.has('\\Seen'),
        starred: message.flags.has('\\Flagged'),
        flags: Array.from(message.flags),
        hasAttachments: message.bodyStructure?.type === 'multipart'
      };

      // 9. Cache the email content
      emailContentCache.set(cacheKey, emailContent);

      // 10. Return the email content
      return NextResponse.json(emailContent);
    } finally {
      // 11. Close the connection
      try {
        await client.logout();
      } catch (e) {
        console.error('Error during IMAP logout:', e);
      }
    }
  } catch (error) {
    console.error('Error fetching email:', error);
    return NextResponse.json(
      { error: 'Failed to fetch email content' },
      { status: 500 }
    );
  }
}

// Helper method to release connection when app shutting down
export async function cleanup() {
  for (const [userId, connection] of connectionPool.entries()) {
    await connection.client.logout().catch(console.error);
    connectionPool.delete(userId);
  }
}