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 { parseEmail } from '@/lib/server/email-parser';
import { LRUCache } from 'lru-cache';

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

export async function GET(
  request: Request,
  { params }: { params: { id: string } }
) {
  try {
    // 1. Get email ID from params (properly awaited)
    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. Get the current folder from the request URL
    const url = new URL(request.url);
    const folder = url.searchParams.get('folder') || 'INBOX';

    // 6. 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();
      
      // 7. Open the folder
      const mailbox = await client.mailboxOpen(folder);
      console.log(`Mailbox opened: ${folder}, total messages: ${mailbox.exists}`);
      
      // 8. Download the raw message data using a dynamic fetch approach
      console.log(`Attempting to fetch message with UID: ${id}`);
      
      // Create a loop to process all messages until we find the right one
      let foundMessage = null;
      const chunkSize = 10;
      
      for (let i = 1; i <= mailbox.exists; i += chunkSize) {
        const endIdx = Math.min(i + chunkSize - 1, mailbox.exists);
        const range = `${i}:${endIdx}`;
        
        console.log(`Scanning messages ${range}`);
        
        // Fetch messages in chunks with UID
        const messages = client.fetch(range, {
          uid: true,
          envelope: true,
          flags: true,
          bodyStructure: true,
          source: true
        });
        
        for await (const message of messages) {
          if (message.uid.toString() === id) {
            console.log(`Found matching message with UID ${id}`);
            foundMessage = message;
            break;
          }
        }
        
        if (foundMessage) {
          break;
        }
      }
      
      if (!foundMessage) {
        console.log(`No message found with UID ${id}`);
        return NextResponse.json(
          { error: `Email not found with UID ${id}` },
          { status: 404 }
        );
      }

      console.log(`Successfully fetched message, parsing content...`);
      
      // 9. Parse the email content
      const parsedEmail = await parseEmail(foundMessage.source.toString());
      
      // Debug the parsed email structure
      console.log('Parsed email data structure:', {
        hasHtml: !!parsedEmail.html,
        hasText: !!parsedEmail.text,
        htmlLength: parsedEmail.html ? parsedEmail.html.length : 0,
        textLength: parsedEmail.text ? parsedEmail.text.length : 0,
        attachmentsCount: parsedEmail.attachments ? parsedEmail.attachments.length : 0
      });
      
      // 10. Prepare the full email object with all needed data
      const fullEmail = {
        id,
        from: foundMessage.envelope.from?.[0]?.address || '',
        fromName: foundMessage.envelope.from?.[0]?.name || 
                 foundMessage.envelope.from?.[0]?.address?.split('@')[0] || '',
        to: foundMessage.envelope.to?.map((addr: any) => addr.address).join(', ') || '',
        subject: foundMessage.envelope.subject || '(No subject)',
        date: foundMessage.envelope.date?.toISOString() || new Date().toISOString(),
        content: typeof parsedEmail.html === 'string' ? parsedEmail.html : 
                 typeof parsedEmail.text === 'string' ? parsedEmail.text : '',
        textContent: typeof parsedEmail.text === 'string' ? parsedEmail.text : '',
        rawContent: typeof foundMessage.source === 'object' ? 
                   foundMessage.source.toString() : 
                   String(foundMessage.source || ''),
        read: foundMessage.flags.has('\\Seen'),
        starred: foundMessage.flags.has('\\Flagged'),
        folder: folder,
        hasAttachments: foundMessage.bodyStructure?.type === 'multipart',
        attachments: parsedEmail.attachments || [],
        flags: Array.from(foundMessage.flags),
        headers: parsedEmail.headers || {}
      };

      // Log the structure of the email being returned
      console.log('Returning email object with content structure:', {
        id: fullEmail.id,
        hasContent: !!fullEmail.content,
        contentLength: fullEmail.content ? fullEmail.content.length : 0,
        hasTextContent: !!fullEmail.textContent,
        textContentLength: fullEmail.textContent ? fullEmail.textContent.length : 0
      });

      // 11. Mark as read if not already
      if (!foundMessage.flags.has('\\Seen')) {
        try {
          // Use the same sequence range to mark message as read
          for (let i = 1; i <= mailbox.exists; i += chunkSize) {
            const endIdx = Math.min(i + chunkSize - 1, mailbox.exists);
            const range = `${i}:${endIdx}`;
            
            // Find message and mark as read
            const messages = client.fetch(range, { uid: true });
            for await (const message of messages) {
              if (message.uid.toString() === id) {
                await client.messageFlagsAdd(i.toString(), ['\\Seen']);
                break;
              }
            }
          }
        } catch (error) {
          console.error('Error marking message as read:', error);
        }
      }

      // 12. Cache the email content
      emailContentCache.set(cacheKey, fullEmail);

      // 13. Return the full email
      return NextResponse.json(fullEmail);
    } finally {
      // 14. 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' },
      { status: 500 }
    );
  }
}