'use server';

import 'server-only';
import { ImapFlow } from 'imapflow';
import nodemailer from 'nodemailer';
import { prisma } from '@/lib/prisma';
import { simpleParser } from 'mailparser';
import { 
  cacheEmailCredentials, 
  getCachedEmailCredentials,
  cacheEmailList,
  getCachedEmailList,
  cacheEmailContent,
  getCachedEmailContent,
  cacheImapSession,
  getCachedImapSession,
  invalidateFolderCache,
  invalidateEmailContentCache
} from '@/lib/redis';
import { EmailCredentials, EmailMessage, EmailAddress, EmailAttachment } from '@/lib/types';

// Types specific to this service
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,
  accountId?: string
): Promise<ImapFlow> {
  console.log(`Getting IMAP connection for user ${userId}${accountId ? ` account ${accountId}` : ''}`);
  
  // First try to get credentials from Redis cache
  let credentials = accountId 
    ? await getCachedEmailCredentials(userId, accountId)
    : await getCachedEmailCredentials(userId, 'default');
  
  // If not in cache, get from database and cache them
  if (!credentials) {
    console.log(`Credentials not found in cache for ${userId}${accountId ? ` account ${accountId}` : ''}, attempting database lookup`);
    credentials = await getUserEmailCredentials(userId);
    if (!credentials) {
      throw new Error('No email credentials found');
    }
    
    // Cache credentials for future use
    await cacheEmailCredentials(userId, accountId || 'default', credentials);
  }
  
  // Validate credentials
  if (!credentials.password) {
    console.error(`Missing password in credentials for user ${userId}${accountId ? ` account ${accountId}` : ''}`);
    throw new Error('No password configured');
  }
  
  if (!credentials.email || !credentials.host) {
    console.error(`Incomplete credentials for user ${userId}${accountId ? ` account ${accountId}` : ''}`);
    throw new Error('Invalid email credentials configuration');
  }
  
  const connectionKey = `${userId}:${credentials.email}`;
  const existingConnection = connectionPool[connectionKey];
  
  // Try to get session data from Redis
  const sessionData = await getCachedImapSession(userId);
  
  // Return existing connection if available and connected
  if (existingConnection) {
    try {
      if (existingConnection.client.usable) {
        existingConnection.lastUsed = Date.now();
        console.log(`Reusing existing IMAP connection for ${connectionKey}`);
        
        // Update session data in Redis
        if (sessionData) {
          await cacheImapSession(userId, {
            ...sessionData,
            lastActive: 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
    }
  }
  
  console.log(`Creating new IMAP connection for ${connectionKey}`);
  
  // 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();
    console.log(`Successfully connected to IMAP server for ${connectionKey}`);
    
    // Store in connection pool
    connectionPool[connectionKey] = {
      client,
      lastUsed: Date.now()
    };
    
    return client;
  } catch (error: unknown) {
    const errorMessage = error instanceof Error ? error.message : 'Unknown error';
    console.error(`IMAP connection error for ${connectionKey}:`, errorMessage);
    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.findFirst({
    where: { userId },
    select: {
      email: true,
      password: true,
      host: true,
      port: true,
      secure: true,
      smtp_host: true,
      smtp_port: true,
      smtp_secure: true,
      display_name: true,
      color: true
    }
  });

  if (!credentials) return null;

  return {
    email: credentials.email,
    password: credentials.password,
    host: credentials.host,
    port: credentials.port,
    secure: credentials.secure,
    smtp_host: credentials.smtp_host,
    smtp_port: credentials.smtp_port,
    smtp_secure: credentials.smtp_secure,
    display_name: credentials.display_name,
    color: credentials.color
  };
}

/**
 * Save or update user's email credentials
 */
export async function saveUserEmailCredentials(
  userId: string,
  accountId: string,
  credentials: EmailCredentials
): Promise<void> {
  console.log('Saving credentials for user:', userId, 'account:', accountId);
  
  // Extract only the fields that exist in the database schema
  const dbCredentials = {
    email: credentials.email,
    password: credentials.password ?? '',
    host: credentials.host,
    port: credentials.port
  };
  
  // Save to database - only using fields that exist in the schema
  await prisma.mailCredentials.upsert({
    where: { 
      id: accountId,
      userId 
    },
    update: dbCredentials,
    create: {
      id: accountId,
      userId,
      ...dbCredentials
    }
  });
  
  // Cache the full credentials object in Redis (with all fields)
  await cacheEmailCredentials(userId, accountId, credentials);
}

// 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 = '',
  accountId?: string
): Promise<EmailListResult> {
  // Try to get from cache first
  if (!searchQuery) {
    const cacheKey = accountId ? `${userId}:${accountId}:${folder}` : `${userId}:${folder}`;
    const cachedResult = await getCachedEmailList(userId, folder, page, perPage);
    if (cachedResult) {
      console.log(`Using cached email list for ${cacheKey}:${page}:${perPage}`);
      return cachedResult;
    }
  }
  
  console.log(`Cache miss for emails ${userId}:${folder}:${page}:${perPage}${accountId ? ` for account ${accountId}` : ''}, fetching from IMAP`);
  
  // If accountId is provided, connect to that specific account
  let client: ImapFlow;
  
  if (accountId) {
    try {
      // Get account from database
      const account = await prisma.mailCredentials.findUnique({
        where: { 
          id: accountId,
          userId 
        }
      });
      
      if (!account) {
        throw new Error(`Account with ID ${accountId} not found`);
      }
      
      // Connect to IMAP server for this specific account
      client = new ImapFlow({
        host: account.host,
        port: account.port,
        secure: true, // Default to secure connection
        auth: {
          user: account.email,
          pass: account.password,
        },
        logger: false,
        tls: {
          rejectUnauthorized: false
        }
      });
      
      await client.connect();
    } catch (error) {
      console.error(`Error connecting to account ${accountId}:`, error);
      // Fallback to default connection
      client = await getImapConnection(userId);
    }
  } else {
    // Use the default connection logic
    client = await getImapConnection(userId);
  }
  
  let mailboxes: string[] = [];
  
  try {
    console.log(`[DEBUG] Fetching mailboxes for user ${userId}`);
    // Get list of mailboxes first
    try {
      mailboxes = await getMailboxes(client);
      console.log(`[DEBUG] Found ${mailboxes.length} mailboxes:`, mailboxes);
      
      // Save mailboxes in session data
      const cachedSession = await getCachedImapSession(userId);
      await cacheImapSession(userId, {
        ...(cachedSession || { lastActive: Date.now() }),
        mailboxes
      });
      console.log(`[DEBUG] Updated cached session with mailboxes for user ${userId}`);
    } catch (mailboxError) {
      console.error(`[ERROR] Failed to fetch mailboxes:`, mailboxError);
    }
    
    // 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 result = {
        emails: [],
        totalEmails: 0,
        page,
        perPage,
        totalPages: 0,
        folder,
        mailboxes
      };
      
      // Cache even empty results
      if (!searchQuery) {
        await cacheEmailList(userId, folder, page, perPage, result);
      }
      
      return result;
    }
    
    // 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 result = {
      emails,
      totalEmails: totalMessages,
      page,
      perPage,
      totalPages: Math.ceil(totalMessages / perPage),
      folder,
      mailboxes
    };
    
    // Always cache the result if it's not a search query, even for pagination
    if (!searchQuery) {
      console.log(`Caching email list for ${userId}:${folder}:${page}:${perPage}`);
      await cacheEmailList(userId, folder, page, perPage, result);
    }
    
    return result;
  } 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> {
  // Try to get from cache first
  const cachedEmail = await getCachedEmailContent(userId, emailId);
  if (cachedEmail) {
    console.log(`Using cached email content for ${userId}:${emailId}`);
    return cachedEmail;
  }
  
  console.log(`Cache miss for email content ${userId}:${emailId}, fetching from IMAP`);
  
  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 || '';
    
    const email = {
      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
    };
    
    // Cache the email content
    await cacheEmailContent(userId, emailId, email);
    
    return email;
  } 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']);
    }
    
    // Invalidate content cache since the flags changed
    await invalidateEmailContentCache(userId, emailId);
    
    // Also invalidate folder cache because unread counts may have changed
    await invalidateFolderCache(userId, folder);
    
    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 with user's SMTP settings if available
  const transporter = nodemailer.createTransport({
    host: credentials.smtp_host || 'smtp.infomaniak.com',
    port: credentials.smtp_port || 587,
    secure: credentials.smtp_secure || false,
    auth: {
      user: credentials.email,
      pass: credentials.password,
    },
    tls: {
      rejectUnauthorized: false
    }
  });

  try {
    const info = await transporter.sendMail({
      from: credentials.email,
      to: emailData.to,
      cc: emailData.cc,
      bcc: emailData.bcc,
      subject: emailData.subject,
      text: emailData.body,
      html: emailData.body,
      attachments: emailData.attachments?.map(att => ({
        filename: att.name,
        content: att.content,
        contentType: att.type
      })),
    });

    return {
      success: true,
      messageId: info.messageId
    };
  } catch (error) {
    return {
      success: false,
      error: error instanceof Error ? error.message : 'Unknown error'
    };
  }
}