'use client';

import React, { useState, useRef, useEffect, useCallback } from 'react';
import { Loader2, Mail, Search, X } from 'lucide-react';
import { Email } from '@/hooks/use-courrier';
import EmailListItem from '@/components/email/EmailListItem';
import EmailListHeader from '@/components/email/EmailListHeader';
import BulkActionsToolbar from '@/components/email/BulkActionsToolbar';
import { Input } from '@/components/ui/input';

interface EmailListProps {
  emails: Email[];
  selectedEmailIds: string[];
  selectedEmail: Email | null;
  currentFolder: string;
  isLoading: boolean;
  totalEmails: number;
  hasMoreEmails: boolean;
  onSelectEmail: (emailId: string) => void;
  onToggleSelect: (emailId: string) => void;
  onToggleSelectAll: () => void;
  onBulkAction: (action: 'delete' | 'mark-read' | 'mark-unread' | 'archive') => void;
  onToggleStarred: (emailId: string) => void;
  onLoadMore: () => void;
  onSearch?: (query: string) => void;
}

export default function EmailList({
  emails,
  selectedEmailIds,
  selectedEmail,
  currentFolder,
  isLoading,
  totalEmails,
  hasMoreEmails,
  onSelectEmail,
  onToggleSelect,
  onToggleSelectAll,
  onBulkAction,
  onToggleStarred,
  onLoadMore,
  onSearch
}: EmailListProps) {
  const [scrollPosition, setScrollPosition] = useState(0);
  const [searchQuery, setSearchQuery] = useState('');
  const [isLoadingMore, setIsLoadingMore] = useState(false);
  const scrollRef = useRef<HTMLDivElement>(null);
  const scrollTimeoutRef = useRef<NodeJS.Timeout | null>(null);
  const prevEmailsLengthRef = useRef(emails.length);

  // Debounced scroll handler for better performance
  const handleScroll = useCallback((event: React.UIEvent<HTMLDivElement>) => {
    const target = event.target as HTMLDivElement;
    const { scrollTop, scrollHeight, clientHeight } = target;
    
    // Save scroll position for restoration
    setScrollPosition(scrollTop);
    
    // Clear any existing timeout to prevent rapid firing
    if (scrollTimeoutRef.current) {
      clearTimeout(scrollTimeoutRef.current);
    }
    
    // If near bottom (within 200px) and more emails are available, load more
    // Added additional checks to prevent loading loop
    const isNearBottom = scrollHeight - scrollTop - clientHeight < 200;
    if (isNearBottom && hasMoreEmails && !isLoading && !isLoadingMore) {
      setIsLoadingMore(true);
      
      // Use timeout to debounce load requests
      scrollTimeoutRef.current = setTimeout(() => {
        // Clear the timeout reference before loading
        scrollTimeoutRef.current = null;
        onLoadMore();
        
        // Reset loading state after a delay
        setTimeout(() => {
          setIsLoadingMore(false);
        }, 1500); // Increased from 1000ms to 1500ms to prevent quick re-triggering
      }, 200); // Increased from 100ms to 200ms for better debouncing
    }
  }, [hasMoreEmails, isLoading, isLoadingMore, onLoadMore]);

  // Restore scroll position when emails are loaded
  useEffect(() => {
    // Only attempt to restore position if:
    // 1. We have more emails than before
    // 2. We have a scroll reference
    // 3. We have a saved scroll position
    // 4. We're not in the middle of a loading operation
    if (emails.length > prevEmailsLengthRef.current && 
        scrollRef.current && 
        scrollPosition > 0 && 
        !isLoading) {
      // Use requestAnimationFrame to ensure the DOM has updated
      requestAnimationFrame(() => {
        if (scrollRef.current) {
          scrollRef.current.scrollTop = scrollPosition;
          console.log(`Restored scroll position to ${scrollPosition}`);
        }
      });
    }
    
    // Always update the reference for next comparison
    prevEmailsLengthRef.current = emails.length;
  }, [emails.length, scrollPosition, isLoading]);

  // Add listener for custom reset scroll event
  useEffect(() => {
    const handleResetScroll = () => {
      if (scrollRef.current) {
        scrollRef.current.scrollTop = 0;
        setScrollPosition(0);
      }
    };
    
    window.addEventListener('reset-email-scroll', handleResetScroll);
    
    return () => {
      window.removeEventListener('reset-email-scroll', handleResetScroll);
    };
  }, []);

  const handleSearch = (e: React.FormEvent) => {
    e.preventDefault();
    onSearch?.(searchQuery);
    
    // Reset scroll to top when searching
    if (scrollRef.current) {
      scrollRef.current.scrollTop = 0;
    }
  };

  const clearSearch = () => {
    setSearchQuery('');
    onSearch?.('');
  };

  const scrollToTop = () => {
    if (scrollRef.current) {
      // Use smooth scrolling for better UX
      scrollRef.current.scrollTo({
        top: 0,
        behavior: 'smooth'
      });
    }
  };

  // Render loading state
  if (isLoading && emails.length === 0) {
    return (
      <div className="flex justify-center items-center h-full p-8 bg-white/95 backdrop-blur-sm">
        <Loader2 className="h-8 w-8 text-blue-500 animate-spin" />
      </div>
    );
  }

  // Render empty state
  if (emails.length === 0) {
    return (
      <div className="flex flex-col justify-center items-center h-64 p-8 text-center bg-white/95 backdrop-blur-sm">
        <Mail className="h-8 w-8 text-gray-400 mb-2" />
        <p className="text-gray-500 text-sm">
          {searchQuery 
            ? 'No emails match your search'
            : currentFolder === 'INBOX' 
              ? "Your inbox is empty. You're all caught up!" 
              : 'No emails in this folder'}
        </p>
      </div>
    );
  }

  // Are all emails selected
  const allSelected = selectedEmailIds.length === emails.length && emails.length > 0;
  
  // Are some (but not all) emails selected
  const someSelected = selectedEmailIds.length > 0 && selectedEmailIds.length < emails.length;

  return (
    <div className="w-[320px] bg-white/95 backdrop-blur-sm border-r border-gray-100 flex flex-col">
      {/* Search header */}
      <div className="border-b border-gray-100">
        <div className="px-4 py-2">
          <div className="relative">
            <Search className="absolute left-2 top-2.5 h-4 w-4 text-gray-400" />
            <form onSubmit={handleSearch}>
              <Input
                type="search"
                placeholder="Search in folder..."
                className="pl-8 h-9 bg-gray-50"
                value={searchQuery}
                onChange={(e) => setSearchQuery(e.target.value)}
              />
              {searchQuery && (
                <button
                  type="button"
                  onClick={clearSearch}
                  className="absolute right-2 top-1/2 transform -translate-y-1/2"
                >
                  <X className="h-4 w-4 text-gray-400" />
                </button>
              )}
            </form>
          </div>
        </div>
        <EmailListHeader 
          allSelected={allSelected}
          someSelected={someSelected}
          onToggleSelectAll={onToggleSelectAll}
          currentFolder={currentFolder}
          totalEmails={totalEmails}
        />
      </div>
      
      {selectedEmailIds.length > 0 && (
        <BulkActionsToolbar 
          selectedCount={selectedEmailIds.length}
          onBulkAction={onBulkAction}
        />
      )}
      
      <div 
        ref={scrollRef}
        className="flex-1 overflow-y-auto"
        onScroll={handleScroll}
      >
        <div className="divide-y divide-gray-100">
          {/* Back to top button */}
          {scrollPosition > 300 && (
            <button
              onClick={scrollToTop}
              className="sticky top-0 w-full py-1 text-xs text-blue-600 bg-blue-50 hover:bg-blue-100 z-10"
            >
              ↑ Back to newest emails
            </button>
          )}
          
          {/* Email list */}
          {emails.map((email) => (
            <EmailListItem
              key={email.id}
              email={email}
              isSelected={selectedEmailIds.includes(email.id)}
              isActive={selectedEmail?.id === email.id}
              onSelect={() => onSelectEmail(email.id)}
              onToggleSelect={(e: React.MouseEvent) => {
                e.stopPropagation();
                onToggleSelect(email.id);
              }}
              onToggleStarred={(e: React.MouseEvent) => {
                e.stopPropagation();
                onToggleStarred(email.id);
              }}
            />
          ))}
          
          {/* Loading indicator */}
          {(isLoading || isLoadingMore) && (
            <div className="flex items-center justify-center p-4">
              <Loader2 className="h-4 w-4 text-blue-500 animate-spin" />
            </div>
          )}
          
          {/* Load more button - only show when near bottom but not auto-loading */}
          {hasMoreEmails && !isLoading && !isLoadingMore && (
            <button 
              onClick={onLoadMore}
              className="w-full py-2 text-gray-500 hover:bg-gray-100 text-sm"
            >
              Load more emails
            </button>
          )}
        </div>
      </div>
    </div>
  );
}