// web/src/components/ChatArea.tsx
import React, { useState, useRef, useEffect, useMemo } from 'react';
import { Button } from './ui/button';
import { Textarea } from './ui/textarea';
import { Send, ArrowDown, Trash2, Share2 } from 'lucide-react';
import { Message } from './Message';
import { FileUploadArea } from './FileUploadArea';
import { MemoryLine } from './MemoryLine';
import type { Message as MessageType, LearningMode, UploadedFile, FileType, SpaceType } from '../App';
import { toast } from 'sonner';
import { DropdownMenu, DropdownMenuContent, DropdownMenuItem, DropdownMenuTrigger } from './ui/dropdown-menu';

interface ChatAreaProps {
  messages: MessageType[];
  onSendMessage: (content: string) => void;

  uploadedFiles: UploadedFile[];
  onFileUpload: (files: File[]) => void;
  onRemoveFile: (index: number) => void;
  onFileTypeChange: (index: number, type: FileType) => void;

  // ✅ feedback 需要 userId
  userId?: string;

  // ✅ 由 App.tsx 传入 currentDocTypeForChat
  docType?: string;

  memoryProgress: number;
  isLoggedIn: boolean;
  learningMode: LearningMode;
  onClearConversation: () => void;
  onLearningModeChange: (mode: LearningMode) => void;
  spaceType: SpaceType;
}

export function ChatArea({
  messages,
  onSendMessage,
  uploadedFiles,
  onFileUpload,
  onRemoveFile,
  onFileTypeChange,
  userId,
  docType = 'Other',
  memoryProgress,
  isLoggedIn,
  learningMode,
  onClearConversation,
  onLearningModeChange,
  spaceType,
}: ChatAreaProps) {
  const [input, setInput] = useState('');
  const [isTyping, setIsTyping] = useState(false);
  const [showScrollButton, setShowScrollButton] = useState(false);
  const messagesEndRef = useRef<HTMLDivElement>(null);
  const scrollContainerRef = useRef<HTMLDivElement>(null);

  const lastUserMessageContent = useMemo(() => {
    for (let i = messages.length - 1; i >= 0; i--) {
      if (messages[i].role === 'user' && messages[i].content?.trim()) return messages[i].content;
    }
    return '';
  }, [messages]);

  const scrollToBottom = () => {
    messagesEndRef.current?.scrollIntoView({ behavior: 'smooth' });
  };

  useEffect(() => {
    scrollToBottom();
  }, [messages]);

  useEffect(() => {
    const handleScroll = () => {
      if (!scrollContainerRef.current) return;
      const { scrollTop, scrollHeight, clientHeight } = scrollContainerRef.current;
      setShowScrollButton(scrollHeight - scrollTop - clientHeight > 100);
    };

    const container = scrollContainerRef.current;
    container?.addEventListener('scroll', handleScroll);
    return () => container?.removeEventListener('scroll', handleScroll);
  }, []);

  const handleSubmit = (e: React.FormEvent) => {
    e.preventDefault();
    if (!input.trim() || !isLoggedIn) return;

    onSendMessage(input);
    setInput('');
    setIsTyping(true);
    setTimeout(() => setIsTyping(false), 1200);
  };

  const handleKeyDown = (e: React.KeyboardEvent) => {
    if (e.key === 'Enter' && !e.shiftKey) {
      e.preventDefault();
      handleSubmit(e);
    }
  };

  const modeLabels: Record<LearningMode, string> = {
    concept: 'Concept Explainer',
    socratic: 'Socratic Tutor',
    exam: 'Exam Prep',
    assignment: 'Assignment Helper',
    summary: 'Quick Summary',
  };

  const handleClearClick = () => {
    if (messages.length <= 1) {
      toast.info('No conversation to clear');
      return;
    }
    if (window.confirm('Are you sure you want to clear the conversation? This cannot be undone.')) {
      onClearConversation();
      toast.success('Conversation cleared');
    }
  };

  const handleShareClick = () => {
    if (messages.length <= 1) {
      toast.info('No conversation to share');
      return;
    }
    const conversationText = messages
      .map((msg) => `${msg.role === 'user' ? 'You' : 'Clare'}: ${msg.content}`)
      .join('\n\n');

    navigator.clipboard
      .writeText(conversationText)
      .then(() => toast.success('Conversation copied to clipboard!'))
      .catch(() => toast.error('Failed to copy conversation'));
  };

  return (
    <div className="flex flex-col h-full">
      <div className="flex-1 relative border-b-2 border-border">
        {messages.length > 1 && (
          <div className="absolute top-4 right-12 z-10 flex gap-2">
            <Button
              variant="ghost"
              size="sm"
              onClick={handleShareClick}
              disabled={!isLoggedIn}
              className="gap-2 bg-background/95 backdrop-blur-sm shadow-sm hover:shadow-md transition-all group"
            >
              <Share2 className="h-4 w-4" />
              <span className="hidden group-hover:inline">Share</span>
            </Button>
            <Button
              variant="ghost"
              size="sm"
              onClick={handleClearClick}
              disabled={!isLoggedIn}
              className="gap-2 bg-background/95 backdrop-blur-sm shadow-sm hover:shadow-md transition-all group"
            >
              <Trash2 className="h-4 w-4" />
              <span className="hidden group-hover:inline">Clear</span>
            </Button>
          </div>
        )}

        <div ref={scrollContainerRef} className="h-full max-h-[600px] overflow-y-auto px-4 py-6 pb-36">
          <div className="max-w-4xl mx-auto space-y-6">
            {messages.map((m) => (
              <Message
                key={m.id}
                message={m}
                showSenderInfo={spaceType === 'group'}
                userId={userId}
                isLoggedIn={isLoggedIn}
                learningMode={learningMode}
                docType={docType}
                lastUserText={lastUserMessageContent}
              />
            ))}

            {isTyping && (
              <div className="flex gap-3">
                <div className="w-8 h-8 rounded-full bg-gradient-to-br from-purple-500 to-blue-500 flex items-center justify-center flex-shrink-0">
                  <span className="text-white text-sm">C</span>
                </div>
                <div className="bg-muted rounded-2xl px-4 py-3">
                  <div className="flex gap-1">
                    <div className="w-2 h-2 rounded-full bg-muted-foreground/50 animate-bounce" style={{ animationDelay: '0ms' }} />
                    <div className="w-2 h-2 rounded-full bg-muted-foreground/50 animate-bounce" style={{ animationDelay: '150ms' }} />
                    <div className="w-2 h-2 rounded-full bg-muted-foreground/50 animate-bounce" style={{ animationDelay: '300ms' }} />
                  </div>
                </div>
              </div>
            )}

            <div ref={messagesEndRef} />
          </div>
        </div>

        {showScrollButton && (
          <div className="absolute bottom-24 left-1/2 -translate-x-1/2 z-20">
            <Button
              variant="secondary"
              size="icon"
              className="rounded-full shadow-lg hover:shadow-xl transition-shadow bg-background"
              onClick={scrollToBottom}
            >
              <ArrowDown className="h-4 w-4" />
            </Button>
          </div>
        )}

        <div className="absolute bottom-0 left-0 right-0 bg-background/95 backdrop-blur-sm z-10">
          <div className="max-w-4xl mx-auto px-4 py-4">
            <form onSubmit={handleSubmit}>
              <div className="relative">
                <DropdownMenu>
                  <DropdownMenuTrigger asChild>
                    <Button
                      variant="ghost"
                      size="sm"
                      className="absolute bottom-3 left-2 gap-1.5 h-8 px-2 text-xs z-10 hover:bg-muted/50"
                      disabled={!isLoggedIn}
                      type="button"
                    >
                      <span>{modeLabels[learningMode]}</span>
                      <svg className="h-3 w-3 opacity-50" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                        <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M19 9l-7 7-7-7" />
                      </svg>
                    </Button>
                  </DropdownMenuTrigger>
                  <DropdownMenuContent align="start" className="w-56">
                    {(['concept', 'socratic', 'exam', 'assignment', 'summary'] as LearningMode[]).map((mode) => (
                      <DropdownMenuItem
                        key={mode}
                        onClick={() => onLearningModeChange(mode)}
                        className={learningMode === mode ? 'bg-accent' : ''}
                      >
                        <span className="font-medium">{modeLabels[mode]}</span>
                      </DropdownMenuItem>
                    ))}
                  </DropdownMenuContent>
                </DropdownMenu>

                <Textarea
                  value={input}
                  onChange={(e) => setInput(e.target.value)}
                  onKeyDown={handleKeyDown}
                  placeholder={
                    isLoggedIn
                      ? spaceType === 'group'
                        ? 'Type a message... (mention @Clare to get AI assistance)'
                        : 'Ask Clare anything about the course...'
                      : 'Please log in on the right to start chatting...'
                  }
                  disabled={!isLoggedIn}
                  className="min-h-[80px] pl-4 pr-12 resize-none bg-background border-2 border-border"
                />
                <Button type="submit" size="icon" disabled={!input.trim() || !isLoggedIn} className="absolute bottom-2 right-2 rounded-full">
                  <Send className="h-4 w-4" />
                </Button>
              </div>
            </form>
          </div>
        </div>
      </div>

      <div className="bg-card">
        <div className="max-w-4xl mx-auto px-4 py-4">
          <div className="grid grid-cols-1 lg:grid-cols-2 gap-4">
            <FileUploadArea
              uploadedFiles={uploadedFiles}
              onFileUpload={onFileUpload}
              onRemoveFile={onRemoveFile}
              onFileTypeChange={onFileTypeChange}
              disabled={!isLoggedIn}
            />
            <MemoryLine progress={memoryProgress} />
          </div>
        </div>
      </div>
    </div>
  );
}