import { NextResponse } from 'next/server';
import Imap from 'imap';
import { simpleParser } from 'mailparser';

// Debug logging for environment variables
console.log('Environment Variables:', {
  IMAP_USER: process.env.IMAP_USER,
  IMAP_HOST: process.env.IMAP_HOST,
  IMAP_PORT: process.env.IMAP_PORT,
  IMAP_PASSWORD: process.env.IMAP_PASSWORD ? '***' : undefined,
  NODE_ENV: process.env.NODE_ENV
});

// Store for credentials (in memory, you might want to use a proper storage solution)
let storedCredentials: {
  user: string;
  password: string;
  host: string;
  port: string;
} | null = null;

// Helper function to get stored credentials
function getStoredCredentials() {
  // Server-side: use stored credentials
  if (typeof window === 'undefined') {
    return storedCredentials;
  }
  
  // Client-side: use localStorage
  const stored = localStorage.getItem('imapCredentials');
  return stored ? JSON.parse(stored) : null;
}

// IMAP configuration
const getImapConfig = () => {
  const credentials = getStoredCredentials();
  
  if (!credentials?.user || !credentials?.password) {
    throw new Error('Email credentials not found. Please log in first.');
  }

  return {
    user: credentials.user,
    password: credentials.password,
    host: credentials.host || 'mail.infomaniak.com',
    port: parseInt(credentials.port || '993', 10),
    tls: true,
    tlsOptions: { 
      rejectUnauthorized: false,
      servername: credentials.host || 'mail.infomaniak.com'
    },
    authTimeout: 10000,
    connTimeout: 10000,
    debug: console.log
  };
};

// Debug logging for IMAP configuration
console.log('IMAP Configuration:', {
  user: getImapConfig().user,
  host: getImapConfig().host,
  port: getImapConfig().port,
  tls: getImapConfig().tls,
  hasPassword: !!getImapConfig().password,
  authTimeout: getImapConfig().authTimeout,
  connTimeout: getImapConfig().connTimeout
});

interface ImapMessage {
  header: {
    from?: string[];
    to?: string[];
    subject?: string[];
    date?: string[];
    [key: string]: string[] | undefined;
  };
  body: string;
  attributes: {
    flags: string[];
  };
}

interface ImapError extends Error {
  type?: string;
  textCode?: string;
  source?: string;
}

interface Email {
  id: string;
  from: string;
  subject: string;
  date: string;
  body: string;
  read: boolean;
  starred: boolean;
}

interface EmailHeaders {
  from: string;
  subject: string;
  date: string;
}

function parseEmailHeaders(buffer: string): EmailHeaders {
  const headers: EmailHeaders = {
    from: '',
    subject: '',
    date: ''
  };

  const lines = buffer.split('\r\n');
  for (const line of lines) {
    if (line.toLowerCase().startsWith('from:')) {
      headers.from = line.substring(5).trim();
    } else if (line.toLowerCase().startsWith('subject:')) {
      headers.subject = line.substring(8).trim();
    } else if (line.toLowerCase().startsWith('date:')) {
      headers.date = line.substring(5).trim();
    }
  }

  return headers;
}

// Helper function to create a promise-based IMAP connection
function createImapConnection(config: any): Promise<Imap> {
  return new Promise((resolve, reject) => {
    const imap = new Imap({
      user: config.user,
      password: config.password,
      host: config.host,
      port: config.port,
      tls: true,
      tlsOptions: { 
        rejectUnauthorized: false,
        servername: config.host
      },
      authTimeout: 10000,
      connTimeout: 10000,
      debug: console.log,
      autotls: 'always',
      keepalive: true
    });

    imap.once('ready', () => {
      console.log('IMAP connection established successfully');
      resolve(imap);
    });
    
    imap.once('error', (err: ImapError) => {
      console.error('IMAP connection error:', err);
      console.error('Error details:', {
        type: err.type,
        textCode: err.textCode,
        source: err.source
      });
      reject(err);
    });

    imap.once('end', () => console.log('[connection] Ended'));
    imap.once('close', () => console.log('[connection] Closed'));

    try {
      console.log('Attempting to connect to IMAP server...');
      console.log('Using credentials:', {
        user: config.user,
        passwordLength: config.password.length,
        host: config.host,
        port: config.port
      });
      imap.connect();
    } catch (err) {
      console.error('Error during IMAP connection:', err);
      reject(err);
    }
  });
}

// Helper function to promisify the message fetching
function fetchMessages(imap: Imap, box: string): Promise<ImapMessage[]> {
  return new Promise((resolve, reject) => {
    imap.openBox(box, false, (err, mailbox) => {
      if (err) {
        reject(err);
        return;
      }

      // Search for all messages
      imap.search(['ALL'], (err, results) => {
        if (err) {
          reject(err);
          return;
        }

        // No messages found
        if (!results || !results.length) {
          resolve([]);
          return;
        }

        const fetch = imap.fetch(results, {
          bodies: ['HEADER.FIELDS (FROM TO SUBJECT DATE)', 'TEXT'],
          struct: true
        });

        const messages: ImapMessage[] = [];

        fetch.on('message', (msg) => {
          const message: Partial<ImapMessage> = {};

          msg.on('body', (stream, info) => {
            let buffer = '';
            stream.on('data', (chunk) => {
              buffer += chunk.toString('utf8');
            });
            stream.once('end', () => {
              if (info.which === 'TEXT') {
                message.body = buffer;
              } else {
                message.header = Imap.parseHeader(buffer);
              }
            });
          });

          msg.once('attributes', (attrs) => {
            message.attributes = attrs;
          });

          msg.once('end', () => {
            messages.push(message as ImapMessage);
          });
        });

        fetch.once('error', (err) => {
          reject(err);
        });

        fetch.once('end', () => {
          resolve(messages);
        });
      });
    });
  });
}

export async function GET() {
  try {
    // Get stored credentials
    const credentials = getStoredCredentials();
    if (!credentials) {
      return NextResponse.json(
        { error: 'No IMAP credentials found. Please configure your email account.' },
        { status: 401 }
      );
    }

    console.log('Starting email fetch process...');
    console.log('IMAP Configuration:', {
      user: credentials.user,
      host: credentials.host,
      port: credentials.port,
      tls: true,
      hasPassword: !!credentials.password
    });

    // Create IMAP connection
    const imap = await createImapConnection({
      user: credentials.user,
      password: credentials.password,
      host: credentials.host,
      port: parseInt(credentials.port),
      tls: true
    });

    return new Promise((resolve, reject) => {
      imap.once('ready', () => {
        console.log('IMAP connection ready');
        imap.openBox('INBOX', false, (err, box) => {
          if (err) {
            console.error('Error opening inbox:', err);
            imap.end();
            reject(new Error('Failed to open inbox'));
            return;
          }

          const fetch = imap.seq.fetch('1:10', {
            bodies: ['HEADER', 'TEXT'],
            struct: true
          });

          const messages: Email[] = [];

          fetch.on('message', (msg) => {
            const email: Email = {
              id: '',
              from: '',
              subject: '',
              date: '',
              body: '',
              read: false,
              starred: false
            };

            msg.on('body', (stream) => {
              let buffer = '';
              stream.on('data', (chunk) => {
                buffer += chunk.toString('utf8');
              });
              stream.on('end', () => {
                const headers = parseEmailHeaders(buffer);
                email.from = headers.from;
                email.subject = headers.subject;
                email.date = headers.date;
              });
            });

            msg.once('attributes', (attrs) => {
              email.id = attrs.uid.toString();
              email.read = !attrs.flags.includes('\\Unseen');
              email.starred = attrs.flags.includes('\\Flagged');
            });

            msg.once('end', () => {
              messages.push(email);
            });
          });

          fetch.once('error', (err) => {
            console.error('Fetch error:', err);
            imap.end();
            reject(new Error('Failed to fetch messages'));
          });

          fetch.once('end', () => {
            imap.end();
            resolve(NextResponse.json(messages));
          });
        });
      });

      imap.once('error', (err: ImapError) => {
        console.error('IMAP connection error:', err);
        console.error('Error details:', {
          type: err.type,
          textCode: err.textCode,
          source: err.source
        });
        imap.end();
        reject(new Error(err.message));
      });

      imap.connect();
    });
  } catch (error) {
    console.error('Error in GET handler:', error);
    if (error instanceof Error) {
      if (error.message.includes('Invalid login or password')) {
        return NextResponse.json(
          { error: 'Invalid login or password', details: error.message },
          { status: 401 }
        );
      }
      return NextResponse.json(
        { error: 'Failed to fetch emails', details: error.message },
        { status: 500 }
      );
    }
    return NextResponse.json(
      { error: 'Unknown error occurred' },
      { status: 500 }
    );
  }
}

export async function POST(request: Request) {
  try {
    const body = await request.json();
    const { email, password, host, port } = body;

    if (!email || !password || !host || !port) {
      return NextResponse.json(
        { error: 'Missing required fields' },
        { status: 400 }
      );
    }

    // Store credentials
    storedCredentials = {
      user: email,
      password,
      host,
      port
    };

    // Test the connection
    const imap = await createImapConnection(storedCredentials);
    imap.end();

    return NextResponse.json({ success: true });
  } catch (error) {
    console.error('Error in POST handler:', error);
    if (error instanceof Error) {
      if (error.message.includes('Invalid login or password')) {
        return NextResponse.json(
          { error: 'Invalid login or password', details: error.message },
          { status: 401 }
        );
      }
      return NextResponse.json(
        { error: 'Failed to connect to email server', details: error.message },
        { status: 500 }
      );
    }
    return NextResponse.json(
      { error: 'Unknown error occurred' },
      { status: 500 }
    );
  }
}