import { ImapFlow } from 'imapflow';
import nodemailer from 'nodemailer';
import { prisma } from '@/lib/prisma';
import { simpleParser } from 'mailparser';

// Types for the email service
export interface EmailCredentials {
  email: string;
  password: string;
  host: string;
  port: number;
}

export interface EmailMessage {
  id: string;
  messageId?: string;
  subject: string;
  from: EmailAddress[];
  to: EmailAddress[];
  cc?: EmailAddress[];
  bcc?: EmailAddress[];
  date: Date;
  flags: {
    seen: boolean;
    flagged: boolean;
    answered: boolean;
    deleted: boolean;
    draft: boolean;
  };
  preview?: string;
  content?: string;
  html?: string;
  text?: string;
  hasAttachments: boolean;
  attachments?: EmailAttachment[];
  folder: string;
  size?: number;
  contentFetched: boolean;
}

export interface EmailAddress {
  name: string;
  address: string;
}

export interface EmailAttachment {
  contentId?: string;
  filename: string;
  contentType: string;
  size: number;
  path?: string;
  content?: string;
}

export interface EmailListResult {
  emails: EmailMessage[];
  totalEmails: number;
  page: number;
  perPage: number;
  totalPages: number;
  folder: string;
  mailboxes: string[];
}

// Connection pool to reuse IMAP clients
const connectionPool: Record<string, { client: ImapFlow; lastUsed: number }> = {};
const CONNECTION_TIMEOUT = 5 * 60 * 1000; // 5 minutes

// Clean up idle connections periodically
setInterval(() => {
  const now = Date.now();
  
  Object.entries(connectionPool).forEach(([key, { client, lastUsed }]) => {
    if (now - lastUsed > CONNECTION_TIMEOUT) {
      console.log(`Closing idle IMAP connection for ${key}`);
      client.logout().catch(err => {
        console.error(`Error closing connection for ${key}:`, err);
      });
      delete connectionPool[key];
    }
  });
}, 60 * 1000); // Check every minute

/**
 * Get IMAP connection for a user, reusing existing connections when possible
 */
export async function getImapConnection(userId: string): Promise<ImapFlow> {
  // Get credentials from database
  const credentials = await getUserEmailCredentials(userId);
  if (!credentials) {
    throw new Error('No email credentials found');
  }
  
  const connectionKey = `${userId}:${credentials.email}`;
  const existingConnection = connectionPool[connectionKey];
  
  // Return existing connection if available and connected
  if (existingConnection) {
    try {
      if (existingConnection.client.usable) {
        existingConnection.lastUsed = Date.now();
        return existingConnection.client;
      }
    } catch (error) {
      console.warn(`Existing connection for ${connectionKey} is not usable, creating new connection`);
      // Will create a new connection below
    }
  }
  
  // Create new connection
  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();
    
    // Store in connection pool
    connectionPool[connectionKey] = {
      client,
      lastUsed: Date.now()
    };
    
    return client;
  } catch (error: unknown) {
    const errorMessage = error instanceof Error ? error.message : 'Unknown error';
    throw new Error(`Failed to connect to IMAP server: ${errorMessage}`);
  }
}

/**
 * Get user's email credentials from database
 */
export async function getUserEmailCredentials(userId: string): Promise<EmailCredentials | null> {
  const credentials = await prisma.mailCredentials.findUnique({
    where: { userId }
  });
  
  if (!credentials) {
    return null;
  }
  
  return {
    email: credentials.email,
    password: credentials.password,
    host: credentials.host,
    port: credentials.port
  };
}

/**
 * Save or update user's email credentials
 */
export async function saveUserEmailCredentials(
  userId: string, 
  credentials: EmailCredentials
): Promise<void> {
  await prisma.mailCredentials.upsert({
    where: { userId },
    update: {
      email: credentials.email,
      password: credentials.password,
      host: credentials.host,
      port: credentials.port
    },
    create: {
      userId,
      email: credentials.email,
      password: credentials.password,
      host: credentials.host,
      port: credentials.port
    }
  });
}

// Helper type for IMAP fetch options
interface FetchOptions {
  envelope: boolean;
  flags: boolean;
  bodyStructure: boolean;
  internalDate: boolean;
  size: boolean;
  bodyParts: { part: string; query: any; limit?: number }[];
}

/**
 * Get list of emails for a user
 */
export async function getEmails(
  userId: string,
  folder: string = 'INBOX',
  page: number = 1,
  perPage: number = 20,
  searchQuery: string = ''
): Promise<EmailListResult> {
  const client = await getImapConnection(userId);
  
  try {
    // Open mailbox
    const mailboxData = await client.mailboxOpen(folder);
    const totalMessages = mailboxData.exists;
    
    // Calculate range based on total messages
    const endIdx = page * perPage;
    const startIdx = (page - 1) * perPage + 1;
    const from = Math.max(totalMessages - endIdx + 1, 1);
    const to = Math.max(totalMessages - startIdx + 1, 1);
    
    // Empty result if no messages
    if (totalMessages === 0 || from > to) {
      const mailboxes = await getMailboxes(client);
      return {
        emails: [],
        totalEmails: 0,
        page,
        perPage,
        totalPages: 0,
        folder,
        mailboxes
      };
    }
    
    // Search if needed
    let messageIds: any[] = [];
    if (searchQuery) {
      messageIds = await client.search({ body: searchQuery });
      messageIds = messageIds.filter(id => id >= from && id <= to);
    } else {
      messageIds = Array.from({ length: to - from + 1 }, (_, i) => from + i);
    }
    
    // Fetch messages
    const emails: EmailMessage[] = [];
    
    for (const id of messageIds) {
      try {
        // Define fetch options with proper typing
        const fetchOptions: any = {
          envelope: true,
          flags: true,
          bodyStructure: true,
          internalDate: true,
          size: true,
          bodyParts: [{
            part: '1',
            query: { type: "text" },
            limit: 5000
          }]
        };
        
        const message = await client.fetchOne(id, fetchOptions);
        
        if (!message) continue;
        
        const { envelope, flags, bodyStructure, internalDate, size, bodyParts } = message;
        
        // Extract preview content
        let preview = '';
        if (bodyParts && typeof bodyParts === 'object') {
          // Convert to array if it's a Map
          const partsArray = Array.isArray(bodyParts) 
            ? bodyParts 
            : Array.from(bodyParts.values());
          
          const textPart = partsArray.find((part: any) => part.type === 'text/plain');
          const htmlPart = partsArray.find((part: any) => part.type === 'text/html');
          const content = textPart?.content || htmlPart?.content || '';
          
          if (typeof content === 'string') {
            preview = content.substring(0, 150) + '...';
          } else if (Buffer.isBuffer(content)) {
            preview = content.toString('utf-8', 0, 150) + '...';
          }
        }
        
        // Process attachments
        const attachments: EmailAttachment[] = [];
        
        const processAttachments = (node: any, path: Array<string | number> = []) => {
          if (!node) return;
          
          if (node.type === 'attachment') {
            attachments.push({
              contentId: node.contentId,
              filename: node.filename || 'attachment',
              contentType: node.contentType,
              size: node.size,
              path: [...path, node.part].join('.')
            });
          }
          
          if (node.childNodes) {
            node.childNodes.forEach((child: any, index: number) => {
              processAttachments(child, [...path, node.part || index + 1]);
            });
          }
        };
        
        if (bodyStructure) {
          processAttachments(bodyStructure);
        }
        
        // Convert flags from Set to boolean checks
        const flagsArray = Array.from(flags as Set<string>);
        
        emails.push({
          id: id.toString(),
          messageId: envelope.messageId,
          subject: envelope.subject || "(No Subject)",
          from: envelope.from.map((f: any) => ({
            name: f.name || f.address,
            address: f.address,
          })),
          to: envelope.to.map((t: any) => ({
            name: t.name || t.address,
            address: t.address,
          })),
          cc: (envelope.cc || []).map((c: any) => ({
            name: c.name || c.address,
            address: c.address,
          })),
          bcc: (envelope.bcc || []).map((b: any) => ({
            name: b.name || b.address,
            address: b.address,
          })),
          date: internalDate || new Date(),
          flags: {
            seen: flagsArray.includes("\\Seen"),
            flagged: flagsArray.includes("\\Flagged"),
            answered: flagsArray.includes("\\Answered"),
            deleted: flagsArray.includes("\\Deleted"),
            draft: flagsArray.includes("\\Draft"),
          },
          hasAttachments: attachments.length > 0,
          attachments,
          size,
          preview,
          folder,
          contentFetched: false
        });
      } catch (error) {
        console.error(`Error fetching message ${id}:`, error);
      }
    }
    
    // Sort by date, newest first
    emails.sort((a, b) => new Date(b.date).getTime() - new Date(a.date).getTime());
    
    const mailboxes = await getMailboxes(client);
    
    return {
      emails,
      totalEmails: totalMessages,
      page,
      perPage,
      totalPages: Math.ceil(totalMessages / perPage),
      folder,
      mailboxes
    };
  } finally {
    // Don't logout, keep connection in pool
    if (folder !== 'INBOX') {
      try {
        await client.mailboxClose();
      } catch (error) {
        console.error('Error closing mailbox:', error);
      }
    }
  }
}

/**
 * Get a single email with full content
 */
export async function getEmailContent(
  userId: string,
  emailId: string,
  folder: string = 'INBOX'
): Promise<EmailMessage> {
  const client = await getImapConnection(userId);
  
  try {
    await client.mailboxOpen(folder);
    
    const message = await client.fetchOne(emailId, {
      source: true,
      envelope: true,
      flags: true
    });
    
    if (!message) {
      throw new Error('Email not found');
    }
    
    const { source, envelope, flags } = message;
    
    // Parse the email content, ensuring all styles and structure are preserved
    const parsedEmail = await simpleParser(source.toString(), {
      skipHtmlToText: true, // Don't convert HTML to plain text
      keepCidLinks: true    // Keep Content-ID references for inline images
    });
    
    // Convert flags from Set to boolean checks
    const flagsArray = Array.from(flags as Set<string>);
    
    // Preserve the raw HTML exactly as it was in the original email
    const rawHtml = parsedEmail.html || '';
    
    return {
      id: emailId,
      messageId: envelope.messageId,
      subject: envelope.subject || "(No Subject)",
      from: envelope.from.map((f: any) => ({
        name: f.name || f.address,
        address: f.address,
      })),
      to: envelope.to.map((t: any) => ({
        name: t.name || t.address,
        address: t.address,
      })),
      cc: (envelope.cc || []).map((c: any) => ({
        name: c.name || c.address,
        address: c.address,
      })),
      bcc: (envelope.bcc || []).map((b: any) => ({
        name: b.name || b.address,
        address: b.address,
      })),
      date: envelope.date || new Date(),
      flags: {
        seen: flagsArray.includes("\\Seen"),
        flagged: flagsArray.includes("\\Flagged"),
        answered: flagsArray.includes("\\Answered"),
        deleted: flagsArray.includes("\\Deleted"),
        draft: flagsArray.includes("\\Draft"),
      },
      hasAttachments: parsedEmail.attachments?.length > 0,
      attachments: parsedEmail.attachments?.map(att => ({
        filename: att.filename || 'attachment',
        contentType: att.contentType,
        size: att.size || 0
      })),
      // Preserve the exact raw HTML to maintain all styling
      html: rawHtml,
      text: parsedEmail.text || undefined,
      // For content field, prioritize using the raw HTML to preserve all styling
      content: rawHtml || parsedEmail.text || '',
      folder,
      contentFetched: true
    };
  } finally {
    try {
      await client.mailboxClose();
    } catch (error) {
      console.error('Error closing mailbox:', error);
    }
  }
}

/**
 * Mark an email as read or unread
 */
export async function markEmailReadStatus(
  userId: string,
  emailId: string,
  isRead: boolean,
  folder: string = 'INBOX'
): Promise<boolean> {
  const client = await getImapConnection(userId);
  
  try {
    await client.mailboxOpen(folder);
    
    if (isRead) {
      await client.messageFlagsAdd(emailId, ['\\Seen']);
    } else {
      await client.messageFlagsRemove(emailId, ['\\Seen']);
    }
    
    return true;
  } catch (error) {
    console.error(`Error marking email ${emailId} as ${isRead ? 'read' : 'unread'}:`, error);
    return false;
  } finally {
    try {
      await client.mailboxClose();
    } catch (error) {
      console.error('Error closing mailbox:', error);
    }
  }
}

/**
 * Send an email
 */
export async function sendEmail(
  userId: string,
  emailData: {
    to: string;
    cc?: string;
    bcc?: string;
    subject: string;
    body: string;
    attachments?: Array<{
      name: string;
      content: string;
      type: string;
    }>;
  }
): Promise<{ success: boolean; messageId?: string; error?: string }> {
  const credentials = await getUserEmailCredentials(userId);
  
  if (!credentials) {
    return { 
      success: false, 
      error: 'No email credentials found' 
    };
  }
  
  // Create SMTP transporter
  const transporter = nodemailer.createTransport({
    host: 'smtp.infomaniak.com', // Using Infomaniak SMTP server
    port: 587,
    secure: false,
    auth: {
      user: credentials.email,
      pass: credentials.password,
    },
    tls: {
      rejectUnauthorized: false
    }
  });
  
  try {
    // Verify connection
    await transporter.verify();
    
    // Prepare email options
    const mailOptions = {
      from: credentials.email,
      to: emailData.to,
      cc: emailData.cc || undefined,
      bcc: emailData.bcc || undefined,
      subject: emailData.subject || '(No subject)',
      html: emailData.body,
      attachments: emailData.attachments?.map(file => ({
        filename: file.name,
        content: file.content,
        contentType: file.type
      })) || []
    };
    
    // Send email
    const info = await transporter.sendMail(mailOptions);
    
    return {
      success: true,
      messageId: info.messageId
    };
  } catch (error) {
    console.error('Error sending email:', error);
    
    return {
      success: false,
      error: error instanceof Error ? error.message : 'Unknown error'
    };
  }
}

/**
 * Get list of mailboxes (folders)
 */
export async function getMailboxes(client: ImapFlow): Promise<string[]> {
  try {
    const list = await client.list();
    return list.map(mailbox => mailbox.path);
  } catch (error) {
    console.error('Error listing mailboxes:', error);
    return [];
  }
}

/**
 * Test email connection with given credentials
 */
export async function testEmailConnection(credentials: EmailCredentials): Promise<boolean> {
  const client = new ImapFlow({
    host: credentials.host,
    port: credentials.port,
    secure: true,
    auth: {
      user: credentials.email,
      pass: credentials.password,
    },
    logger: false,
    tls: {
      rejectUnauthorized: false
    }
  });
  
  try {
    await client.connect();
    await client.mailboxOpen('INBOX');
    return true;
  } catch (error) {
    console.error('Connection test failed:', error);
    return false;
  } finally {
    try {
      await client.logout();
    } catch (e) {
      // Ignore logout errors
    }
  }
}

/**
 * Format email for reply/forward
 */
export function formatEmailForReplyOrForward(
  email: EmailMessage, 
  type: 'reply' | 'reply-all' | 'forward'
): {
  to: string;
  cc?: string;
  subject: string;
  body: string;
} {
  // Format the subject with Re: or Fwd: prefix
  const subject = formatSubject(email.subject, type);
  
  // Create the email quote with proper formatting
  const quoteHeader = createQuoteHeader(email);
  const quotedContent = email.html || email.text || '';
  
  // Format recipients
  let to = '';
  let cc = '';
  
  if (type === 'reply') {
    // Reply to sender only
    to = email.from.map(addr => `${addr.name} <${addr.address}>`).join(', ');
  } else if (type === 'reply-all') {
    // Reply to sender and all recipients
    to = email.from.map(addr => `${addr.name} <${addr.address}>`).join(', ');
    
    // Add all original recipients to CC, except ourselves
    const allRecipients = [
      ...(email.to || []),
      ...(email.cc || [])
    ];
    
    cc = allRecipients
      .map(addr => `${addr.name} <${addr.address}>`)
      .join(', ');
  } else if (type === 'forward') {
    formattedContent = `
      <div class="forwarded-message">
        <p>---------- Forwarded message ---------</p>
        <p>From: ${decoded.from || ''}</p>
        <p>Date: ${formatDate(decoded.date ? new Date(decoded.date) : null)}</p>
        <p>Subject: ${decoded.subject || ''}</p>
        <p>To: ${decoded.to || ''}</p>
        <br>
        ${decoded.html || `<pre>${decoded.text || ''}</pre>`}
      </div>
    `;
  }
  
  // Format the email body with quote
  const body = `
<div>
  <br/>
  <br/>
  <div>${quoteHeader}</div>
  <blockquote style="border-left: 2px solid #ccc; padding-left: 10px; margin-left: 10px; color: #777;">
    ${quotedContent}
  </blockquote>
</div>`;

  return {
    to,
    cc: cc || undefined,
    subject,
    body
  };
}

/**
 * Format subject with appropriate prefix (Re:, Fwd:)
 */
function formatSubject(subject: string, type: 'reply' | 'reply-all' | 'forward'): string {
  // Clean up any existing prefixes
  let cleanSubject = subject
    .replace(/^(Re|Fwd|FW|Forward):\s*/i, '')
    .trim();
    
  // Add appropriate prefix
  if (type === 'reply' || type === 'reply-all') {
    if (!subject.match(/^Re:/i)) {
      return `Re: ${cleanSubject}`;
    }
  } else if (type === 'forward') {
    if (!subject.match(/^(Fwd|FW|Forward):/i)) {
      return `Fwd: ${cleanSubject}`;
    }
  }
  
  return subject;
}

/**
 * Create a quote header for reply/forward
 */
function createQuoteHeader(email: EmailMessage): string {
  // Format the date
  const date = new Date(email.date);
  const formattedDate = date.toLocaleString('en-US', {
    weekday: 'short',
    year: 'numeric',
    month: 'short',
    day: 'numeric',
    hour: '2-digit', 
    minute: '2-digit'
  });
  
  // Format the sender
  const sender = email.from[0];
  const fromText = sender?.name 
    ? `${sender.name} <${sender.address}>`
    : sender?.address || 'Unknown sender';
  
  return `<div>On ${formattedDate}, ${fromText} wrote:</div>`;
}