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';

// Define the Email type
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;
}

// Add caching for better performance
const cache = new Map();

const getCachedEmail = (id: string) => cache.get(id);
const setCachedEmail = (id: string, email: Email) => cache.set(id, email);

// Add debouncing for folder changes
const debouncedLoadEmails = debounce((folder: string) => {
  loadEmails(folder);
}, 300);

// Add infinite scroll
const handleScroll = (e: React.UIEvent<HTMLDivElement>) => {
  const { scrollTop, scrollHeight, clientHeight } = e.currentTarget;
  if (scrollHeight - scrollTop === clientHeight) {
    // Load more emails
  }
};

export async function GET(request: Request) {
  try {
    const session = await getServerSession(authOptions);
    if (!session?.user?.id) {
      return NextResponse.json(
        { error: 'Unauthorized' },
        { status: 401 }
      );
    }

    const credentials = await prisma.mailCredentials.findUnique({
      where: { userId: session.user.id }
    });

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

    const url = new URL(request.url);
    const folder = url.searchParams.get('folder') || 'INBOX';
    const page = parseInt(url.searchParams.get('page') || '1');
    const limit = parseInt(url.searchParams.get('limit') || '20');
    const preview = url.searchParams.get('preview') === 'true';

    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 }
    });

    try {
      await client.connect();
      
      const mailboxes = await client.list();
      const availableFolders = mailboxes.map(box => box.path);
      
      const mailbox = await client.mailboxOpen(folder);
      
      const start = (page - 1) * limit + 1;
      const end = start + limit - 1;
      
      const result: Email[] = [];
      
      if (mailbox.exists > 0) {
        const adjustedStart = Math.min(start, mailbox.exists);
        const adjustedEnd = Math.min(end, mailbox.exists);
        
        const messages = await client.fetch(`${adjustedStart}:${adjustedEnd}`, { 
          envelope: true,
          flags: true,
          bodyStructure: true,
          ...(preview ? {
            bodyParts: ['TEXT'],
            bodyPartsOptions: {
              TEXT: {
                maxLength: 1000
              }
            }
          } : {})
        });
        
        for await (const message of messages) {
          const email: Email = {
            id: message.uid.toString(),
            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 => addr.address).join(', ') || '',
            subject: message.envelope.subject || '(No subject)',
            date: message.envelope.date?.toISOString() || new Date().toISOString(),
            read: message.flags.has('\\Seen'),
            starred: message.flags.has('\\Flagged'),
            folder: mailbox.path,
            hasAttachments: message.bodyStructure?.type === 'multipart',
            flags: Array.from(message.flags),
            preview: preview ? message.bodyParts?.get('TEXT')?.toString() : undefined
          };
          result.push(email);
        }
      }

      return NextResponse.json({
        emails: result,
        folders: availableFolders,
        total: mailbox.exists,
        hasMore: end < mailbox.exists
      });
    } finally {
      await client.logout();
    }
  } catch (error) {
    console.error('Error in courrier route:', error);
    return NextResponse.json(
      { error: 'An unexpected error occurred' },
      { status: 500 }
    );
  }
}