import { useState, useCallback, useEffect } from 'react';
import { useSession } from 'next-auth/react';
import { useToast } from './use-toast';
import { formatEmailForReplyOrForward } from '@/lib/utils/email-formatter';
import { getCachedEmailsWithTimeout, refreshEmailsInBackground } from '@/lib/services/prefetch-service';

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

export interface Email {
  id: string;
  from: EmailAddress[];
  to: EmailAddress[];
  cc?: EmailAddress[];
  bcc?: EmailAddress[];
  subject: string;
  content: string;
  preview?: string;
  date: string;
  read: boolean;
  starred: boolean;
  attachments?: { filename: string; contentType: string; size: number; content?: string }[];
  folder: string;
  hasAttachments: boolean;
  contentFetched?: boolean;
}

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

export interface EmailData {
  to: string;
  cc?: string;
  bcc?: string;
  subject: string;
  body: string;
  attachments?: Array<{
    name: string;
    content: string;
    type: string;
  }>;
}

export type MailFolder = string;

// Hook for managing email operations
export const useCourrier = () => {
  // State for email data
  const [emails, setEmails] = useState<Email[]>([]);
  const [selectedEmail, setSelectedEmail] = useState<Email | null>(null);
  const [selectedEmailIds, setSelectedEmailIds] = useState<string[]>([]);
  const [currentFolder, setCurrentFolder] = useState<MailFolder>('INBOX');
  const [mailboxes, setMailboxes] = useState<string[]>([]);
  
  // State for UI
  const [isLoading, setIsLoading] = useState(false);
  const [isSending, setIsSending] = useState(false);
  const [isDeleting, setIsDeleting] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const [searchQuery, setSearchQuery] = useState('');
  const [page, setPage] = useState(1);
  const [perPage, setPerPage] = useState(20);
  const [totalEmails, setTotalEmails] = useState(0);
  const [totalPages, setTotalPages] = useState(0);
  
  // Auth and notifications
  const { data: session } = useSession();
  const { toast } = useToast();

  // Load emails from the server
  const loadEmails = useCallback(async (isLoadMore = false, accountId?: string) => {
    if (!session?.user?.id) return;
    
    setIsLoading(true);
    setError(null);
    
    // Keep reference to the current page for this request
    const currentRequestPage = page;
    
    try {
      // Build query params
      const queryParams = new URLSearchParams({
        folder: currentFolder,
        page: currentRequestPage.toString(),
        perPage: perPage.toString()
      });
      
      if (searchQuery) {
        queryParams.set('search', searchQuery);
      }
      
      // Add accountId if provided
      if (accountId) {
        queryParams.set('accountId', accountId);
      }
      
      // First try Redis cache with low timeout
      const cachedEmails = await getCachedEmailsWithTimeout(session.user.id, currentFolder, currentRequestPage, perPage, 100);
      if (cachedEmails) {
        // Ensure cached data has emails array property
        if (Array.isArray(cachedEmails.emails)) {
          if (isLoadMore) {
            // When loading more, always append to the existing list
            setEmails(prevEmails => {
              // Create a Set of existing email IDs to avoid duplicates
              const existingIds = new Set(prevEmails.map(email => email.id));
              // Filter out any duplicates before appending
              const newEmails = cachedEmails.emails.filter((email: Email) => !existingIds.has(email.id));
              
              // Log pagination info
              console.log(`Added ${newEmails.length} cached emails from page ${currentRequestPage} to existing ${prevEmails.length} emails`);
              
              // Combine emails and sort them by date (newest first)
              const combinedEmails = [...prevEmails, ...newEmails];
              return combinedEmails.sort((a: Email, b: Email) => new Date(b.date).getTime() - new Date(a.date).getTime());
            });
          } else {
            // For initial load, replace emails
            console.log(`Setting ${cachedEmails.emails.length} cached emails for page ${currentRequestPage}`);
            // Ensure emails are sorted by date (newest first)
            setEmails(cachedEmails.emails.sort((a: Email, b: Email) => new Date(b.date).getTime() - new Date(a.date).getTime()));
          }
          
          // Set pagination info from cache if available
          if (cachedEmails.totalEmails) setTotalEmails(cachedEmails.totalEmails);
          if (cachedEmails.totalPages) setTotalPages(cachedEmails.totalPages);
          
          // Update available mailboxes if provided
          if (cachedEmails.mailboxes && cachedEmails.mailboxes.length > 0) {
            setMailboxes(cachedEmails.mailboxes);
          }
        } else if (Array.isArray(cachedEmails)) {
          // Direct array response
          if (isLoadMore) {
            setEmails(prevEmails => {
              // Create a Set of existing email IDs to avoid duplicates
              const existingIds = new Set(prevEmails.map(email => email.id));
              // Filter out any duplicates before appending
              const newEmails = cachedEmails.filter((email: Email) => !existingIds.has(email.id));
              
              // Log pagination info
              console.log(`Added ${newEmails.length} cached emails from page ${currentRequestPage} to existing ${prevEmails.length} emails`);
              
              // Combine emails and sort them by date (newest first)
              const combinedEmails = [...prevEmails, ...newEmails];
              return combinedEmails.sort((a: Email, b: Email) => new Date(b.date).getTime() - new Date(a.date).getTime());
            });
          } else {
            // For initial load, replace emails
            console.log(`Setting ${cachedEmails.length} cached emails for page ${currentRequestPage}`);
            // Ensure emails are sorted by date (newest first)
            setEmails(cachedEmails.sort((a: Email, b: Email) => new Date(b.date).getTime() - new Date(a.date).getTime()));
          }
        } else {
          console.warn('Invalid cache format:', cachedEmails);
        }
        
        setIsLoading(false);
        
        // Still refresh in background for fresh data
        refreshEmailsInBackground(session.user.id, currentFolder, currentRequestPage, perPage).catch(err => {
          console.error('Background refresh error:', err);
        });
        return;
      }
      
      // Fetch emails from API
      const response = await fetch(`/api/courrier?${queryParams.toString()}`);
      
      if (!response.ok) {
        const errorData = await response.json();
        throw new Error(errorData.error || 'Failed to fetch emails');
      }
      
      const data: EmailListResult = await response.json();
      
      // Update state with the fetched data
      if (isLoadMore) {
        setEmails(prev => {
          // Create a Set of existing email IDs to avoid duplicates
          const existingIds = new Set(prev.map(email => email.id));
          // Filter out any duplicates before appending
          const newEmails = data.emails.filter((email: Email) => !existingIds.has(email.id));
          
          // Log pagination info
          console.log(`Added ${newEmails.length} fetched emails from page ${currentRequestPage} to existing ${prev.length} emails`);
          
          // Combine emails and sort them by date (newest first)
          const combinedEmails = [...prev, ...newEmails];
          return combinedEmails.sort((a: Email, b: Email) => new Date(b.date).getTime() - new Date(a.date).getTime());
        });
      } else {
        // Ensure we always set an array even if API returns invalid data
        console.log(`Setting ${data.emails?.length || 0} fetched emails for page ${currentRequestPage}`);
        // Ensure emails are sorted by date (newest first)
        if (Array.isArray(data.emails)) {
          setEmails(data.emails.sort((a: Email, b: Email) => new Date(b.date).getTime() - new Date(a.date).getTime()));
        } else {
          setEmails([]);
        }
      }
      
      setTotalEmails(data.totalEmails);
      setTotalPages(data.totalPages);
      
      // Update available mailboxes if provided
      if (data.mailboxes && data.mailboxes.length > 0) {
        setMailboxes(data.mailboxes);
      }
      
      // Clear selection if not loading more
      if (!isLoadMore) {
        setSelectedEmail(null);
        setSelectedEmailIds([]);
      }
    } catch (err) {
      console.error(`Error loading emails for page ${currentRequestPage}:`, err);
      // Set emails to empty array on error to prevent runtime issues
      if (!isLoadMore) {
        setEmails([]);
      }
      setError(err instanceof Error ? err.message : 'Failed to load emails');
      toast({
        variant: "destructive",
        title: "Error",
        description: err instanceof Error ? err.message : 'Failed to load emails'
      });
    } finally {
      setIsLoading(false);
    }
  }, [currentFolder, page, perPage, searchQuery, session?.user?.id, toast]);

  // Load emails when folder or page changes
  useEffect(() => {
    if (session?.user?.id) {
      // If page is greater than 1, we're loading more emails
      const isLoadingMore = page > 1;
      loadEmails(isLoadingMore);
      
      // If we're loading the first page, publish an event to reset scroll position
      if (page === 1 && typeof window !== 'undefined') {
        // Use a custom event to communicate with the EmailList component
        const event = new CustomEvent('reset-email-scroll');
        window.dispatchEvent(event);
      }
    }
  }, [currentFolder, page, perPage, session?.user?.id, loadEmails]);

  // Fetch a single email's content
  const fetchEmailContent = useCallback(async (emailId: string) => {
    try {
      const response = await fetch(`/api/courrier/${emailId}?folder=${encodeURIComponent(currentFolder)}`);
      
      if (!response.ok) {
        throw new Error(`Failed to fetch email content: ${response.status}`);
      }
      
      const data = await response.json();
      return data;
    } catch (error) {
      console.error('Error fetching email content:', error);
      throw error;
    }
  }, [currentFolder]);

  // Select an email to view
  const handleEmailSelect = useCallback(async (emailId: string) => {
    setIsLoading(true);
    
    try {
      // Find the email in the current list
      const email = emails.find(e => e.id === emailId);
      
      if (!email) {
        throw new Error('Email not found');
      }
      
      // If content is not fetched, get the full content
      if (!email.contentFetched) {
        const fullEmail = await fetchEmailContent(emailId);
        
        // Merge the full content with the email
        const updatedEmail = {
          ...email,
          content: fullEmail.content,
          attachments: fullEmail.attachments,
          contentFetched: true
        };
        
        // Update the email in the list
        setEmails(emails.map(e => e.id === emailId ? updatedEmail : e));
        setSelectedEmail(updatedEmail);
      } else {
        setSelectedEmail(email);
      }
      
      // Mark the email as read if it's not already
      if (!email.read) {
        markEmailAsRead(emailId, true);
      }
    } catch (err) {
      console.error('Error selecting email:', err);
      toast({
        variant: "destructive",
        title: "Error",
        description: "Could not load email content"
      });
    } finally {
      setIsLoading(false);
    }
  }, [emails, fetchEmailContent, toast]);

  // Mark an email as read/unread
  const markEmailAsRead = useCallback(async (emailId: string, isRead: boolean) => {
    try {
      const response = await fetch(`/api/courrier/${emailId}/mark-read`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json'
        },
        body: JSON.stringify({
          isRead,
          folder: currentFolder
        })
      });
      
      if (!response.ok) {
        throw new Error('Failed to mark email as read');
      }
      
      // Update the email in the list
      setEmails(emails.map(email => 
        email.id === emailId ? { ...email, read: isRead } : email
      ));
      
      // If the selected email is the one being marked, update it too
      if (selectedEmail && selectedEmail.id === emailId) {
        setSelectedEmail({ ...selectedEmail, read: isRead });
      }
      
      return true;
    } catch (error) {
      console.error('Error marking email as read:', error);
      return false;
    }
  }, [emails, selectedEmail, currentFolder]);

  // Toggle starred status for an email
  const toggleStarred = useCallback(async (emailId: string) => {
    const email = emails.find(e => e.id === emailId);
    if (!email) return;
    
    const newStarredStatus = !email.starred;
    
    try {
      const response = await fetch(`/api/courrier/${emailId}/star`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json'
        },
        body: JSON.stringify({
          starred: newStarredStatus,
          folder: currentFolder
        })
      });
      
      if (!response.ok) {
        throw new Error('Failed to toggle star status');
      }
      
      // Update the email in the list
      setEmails(emails.map(email => 
        email.id === emailId ? { ...email, starred: newStarredStatus } : email
      ));
      
      // If the selected email is the one being starred, update it too
      if (selectedEmail && selectedEmail.id === emailId) {
        setSelectedEmail({ ...selectedEmail, starred: newStarredStatus });
      }
    } catch (error) {
      console.error('Error toggling star status:', error);
      toast({
        variant: "destructive",
        title: "Error",
        description: "Could not update star status"
      });
    }
  }, [emails, selectedEmail, currentFolder, toast]);

  // Send an email
  const sendEmail = useCallback(async (emailData: EmailData) => {
    if (!session?.user?.id) {
      toast({
        variant: "destructive",
        title: "Error",
        description: "You must be logged in to send emails"
      });
      return { success: false, error: "Not authenticated" };
    }
    
    setIsSending(true);
    
    try {
      const response = await fetch('/api/courrier/send', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json'
        },
        body: JSON.stringify(emailData)
      });
      
      const result = await response.json();
      
      if (!response.ok) {
        throw new Error(result.error || 'Failed to send email');
      }
      
      toast({
        title: "Success",
        description: "Email sent successfully"
      });
      
      return { success: true, messageId: result.messageId };
    } catch (error) {
      console.error('Error sending email:', error);
      
      toast({
        variant: "destructive",
        title: "Error",
        description: error instanceof Error ? error.message : 'Failed to send email'
      });
      
      return { 
        success: false, 
        error: error instanceof Error ? error.message : 'Failed to send email' 
      };
    } finally {
      setIsSending(false);
    }
  }, [session?.user?.id, toast]);

  // Delete selected emails
  const deleteEmails = useCallback(async (emailIds: string[]) => {
    if (emailIds.length === 0) return;
    
    setIsDeleting(true);
    
    try {
      const response = await fetch('/api/courrier/delete', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json'
        },
        body: JSON.stringify({
          emailIds,
          folder: currentFolder
        })
      });
      
      if (!response.ok) {
        throw new Error('Failed to delete emails');
      }
      
      // Remove the deleted emails from the list
      setEmails(emails.filter(email => !emailIds.includes(email.id)));
      
      // Clear selection if the selected email was deleted
      if (selectedEmail && emailIds.includes(selectedEmail.id)) {
        setSelectedEmail(null);
      }
      
      // Clear selected IDs
      setSelectedEmailIds([]);
      
      toast({
        title: "Success",
        description: `${emailIds.length} email(s) deleted`
      });
    } catch (error) {
      console.error('Error deleting emails:', error);
      
      toast({
        variant: "destructive",
        title: "Error",
        description: "Failed to delete emails"
      });
    } finally {
      setIsDeleting(false);
    }
  }, [emails, selectedEmail, currentFolder, toast]);

  // Toggle selection of an email
  const toggleEmailSelection = useCallback((emailId: string) => {
    setSelectedEmailIds(prev => {
      if (prev.includes(emailId)) {
        return prev.filter(id => id !== emailId);
      } else {
        return [...prev, emailId];
      }
    });
  }, []);
  
  // Select all emails
  const toggleSelectAll = useCallback(() => {
    if (selectedEmailIds.length === emails.length) {
      setSelectedEmailIds([]);
    } else {
      setSelectedEmailIds(emails.map(email => email.id));
    }
  }, [emails, selectedEmailIds]);

  // Change folder and load emails
  const changeFolder = useCallback((folder: string, accountId?: string) => {
    setCurrentFolder(folder);
    setPage(1); // Reset to first page when changing folders
    setSelectedEmail(null);
    setSelectedEmailIds([]);
    
    // Load the emails for this folder
    // The loadEmails function will be called by the useEffect above
    // due to the dependency on currentFolder
  }, []);

  // Search emails
  const searchEmails = useCallback((query: string) => {
    setSearchQuery(query);
    setPage(1);
    loadEmails();
  }, [loadEmails]);

  // Format an email for reply or forward
  const formatEmailForAction = useCallback((email: Email, type: 'reply' | 'reply-all' | 'forward') => {
    if (!email) return null;
    
    return formatEmailForReplyOrForward(email, type);
  }, []);

  // Return all the functionality and state values
  return {
    // Data
    emails,
    selectedEmail,
    selectedEmailIds,
    currentFolder,
    mailboxes,
    isLoading,
    isSending,
    isDeleting,
    error,
    searchQuery,
    page,
    perPage,
    totalEmails,
    totalPages,
    
    // Functions
    loadEmails,
    handleEmailSelect,
    markEmailAsRead,
    toggleStarred,
    sendEmail,
    deleteEmails,
    toggleEmailSelection,
    toggleSelectAll,
    changeFolder,
    searchEmails,
    formatEmailForAction,
    setPage,
    setPerPage,
    setSearchQuery,
  };
};