import { useState, useEffect, useCallback, useRef } from 'react';
import { useToast } from './use-toast';

interface EmailFetchState {
  email: any | null;
  loading: boolean;
  error: string | null;
}

interface UseEmailFetchProps {
  onEmailLoaded?: (email: any) => void;
  onError?: (error: string) => void;
}

export function useEmailFetch({ onEmailLoaded, onError }: UseEmailFetchProps = {}) {
  const [state, setState] = useState<EmailFetchState>({
    email: null,
    loading: false,
    error: null
  });
  
  const abortControllerRef = useRef<AbortController | null>(null);
  const { toast } = useToast();

  // Validate email fetch parameters
  const validateFetchParams = (emailId: string, accountId: string, folder: string) => {
    if (!emailId || typeof emailId !== 'string') {
      throw new Error('Invalid email ID');
    }
    
    if (!accountId || typeof accountId !== 'string') {
      throw new Error('Invalid account ID');
    }
    
    if (!folder || typeof folder !== 'string') {
      throw new Error('Invalid folder');
    }
    
    // Validate UID format
    if (!/^\d+$/.test(emailId)) {
      throw new Error('Email ID must be a numeric UID');
    }
  };

  // Fetch email with proper error handling and cancellation
  const fetchEmail = useCallback(async (emailId: string, accountId: string, folder: string) => {
    if (!emailId || !accountId || !folder) {
      console.error('Missing required parameters for fetchEmail');
      return;
    }

    // CRITICAL FIX: Always abort any previous request when fetching a new email
    // This prevents race conditions when switching accounts or folders
    if (abortControllerRef.current) {
      console.log(`useEmailFetch: Aborting previous request to fetch email ${emailId} from account ${accountId}`);
      abortControllerRef.current.abort();
    }
    
    // Create a new abort controller for this request
    abortControllerRef.current = new AbortController();

    setState(prev => ({ ...prev, loading: true, error: null }));

    try {
      console.log('useEmailFetch: Fetching email with params:', { emailId, accountId, folder });
      const response = await fetch(
        `/api/courrier/${emailId}?accountId=${encodeURIComponent(accountId)}&folder=${encodeURIComponent(folder)}`,
        {
          signal: abortControllerRef.current?.signal
        }
      );
      
      if (!response.ok) {
        throw new Error(`Failed to fetch email: ${response.statusText}`);
      }

      const data = await response.json();
      console.log('useEmailFetch: Raw API response:', JSON.stringify(data, null, 2));
      
      // Transform the data if needed
      const transformedEmail = {
        ...data,
        content: data.content || {
          text: data.text || '',
          html: data.html || ''
        }
      };
      
      console.log('useEmailFetch: Transformed email:', JSON.stringify(transformedEmail, null, 2));
      
      setState({ email: transformedEmail, loading: false, error: null });
      onEmailLoaded?.(transformedEmail);
      
      // Mark as read if not already
      if (!transformedEmail.flags?.seen) {
        try {
          await fetch(`/api/courrier/${emailId}/mark-read`, {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({ action: 'mark-read' })
          });
        } catch (err) {
          console.error('Error marking email as read:', err);
        }
      }
    } catch (err) {
      // Don't set error if request was aborted
      if (err.name === 'AbortError') {
        return;
      }
      
      console.error('useEmailFetch: Error fetching email:', err);
      const errorMessage = err instanceof Error ? err.message : 'Failed to load email';
      setState(prev => ({ ...prev, loading: false, error: errorMessage }));
      onError?.(errorMessage);
      
      // Show toast for user feedback
      toast({
        title: 'Error',
        description: errorMessage,
        variant: 'destructive'
      });
    }
  }, [onEmailLoaded, onError, toast]);

  // Cleanup on unmount
  useEffect(() => {
    return () => {
      if (abortControllerRef.current) {
        abortControllerRef.current.abort();
      }
    };
  }, []);

  return {
    ...state,
    fetchEmail
  };
}