import React, { useState, useRef, useEffect } from 'react';
import { Language, OCRAnalysis, ChatMessage, Role, MessageType, OCRRecord } from '../types';
import { geminiService, decodeAudioData } from '../services/geminiService';
import { translations } from '../utils/localization';
import { processAndDownloadAudio } from '../utils/audioUtils';
import { ScanText, Upload, Camera, Loader2, Send, Book, PenTool, RotateCcw, History, Trash2, X, PanelRightClose, PanelRightOpen, Volume2, Square, MessageCircle, HelpCircle, ChevronLeft, FileText, Download, Image as ImageIcon, Sparkles } from 'lucide-react';
import ChatBubble from '../components/ChatBubble';

interface OCRViewProps {
  language: Language;
  history: OCRRecord[];
  onSaveToHistory: (record: OCRRecord) => void;
  onClearHistory: () => void;
  onDeleteHistoryItem: (id: string) => void;
  addToast: (type: 'success' | 'error' | 'info', msg: string) => void;
}

const OCRView: React.FC<OCRViewProps> = ({ language, history, onSaveToHistory, onClearHistory, onDeleteHistoryItem, addToast }) => {
  const t = translations[language].ocr;
  const tCommon = translations[language].common;
  
  const [isProcessing, setIsProcessing] = useState(false);
  const [analysis, setAnalysis] = useState<OCRAnalysis | null>(null);
  const [imagePreview, setImagePreview] = useState<string | null>(null);
  const [chatMessages, setChatMessages] = useState<ChatMessage[]>([]);
  const [chatInput, setChatInput] = useState('');
  const [isChatLoading, setIsChatLoading] = useState(false);
  const [isHistoryOpen, setIsHistoryOpen] = useState(false);
  
  // Mobile Tab State: 'content' (Text/Vocab/Notes) vs 'tutor' (Chat)
  const [mobileTab, setMobileTab] = useState<'content' | 'tutor'>('content');

  // Audio State
  const [playingAudioId, setPlayingAudioId] = useState<string | null>(null); // 'main' or 'vocab-word'
  const [isDownloading, setIsDownloading] = useState(false);
  const audioContextRef = useRef<AudioContext | null>(null);
  const audioSourceRef = useRef<AudioBufferSourceNode | null>(null);

  const chatEndRef = useRef<HTMLDivElement>(null);
  const fileInputRef = useRef<HTMLInputElement>(null);
  const cameraInputRef = useRef<HTMLInputElement>(null);

  // Selection State
  const [selectedText, setSelectedText] = useState<string | null>(null);
  const textRef = useRef<HTMLDivElement>(null);

  // Scroll to bottom of chat
  useEffect(() => {
    chatEndRef.current?.scrollIntoView({ behavior: 'smooth' });
  }, [chatMessages, mobileTab]);

  // Cleanup audio
  useEffect(() => {
    return () => {
        stopAudio();
    };
  }, [analysis]);

  // Handle Selection
  useEffect(() => {
    const handleSelectionChange = () => {
        const selection = window.getSelection();
        if (selection && !selection.isCollapsed && textRef.current && textRef.current.contains(selection.anchorNode)) {
            const text = selection.toString().trim();
            if (text.length > 0) {
                setSelectedText(text);
                return;
            }
        }
        setSelectedText(null);
    };

    document.addEventListener('selectionchange', handleSelectionChange);
    return () => document.removeEventListener('selectionchange', handleSelectionChange);
  }, [analysis]);

  const handleImageInput = (e: React.ChangeEvent<HTMLInputElement>) => {
    const file = e.target.files?.[0];
    if (!file) return;
    const reader = new FileReader();
    reader.onloadend = async () => {
        const base64 = reader.result as string;
        setImagePreview(base64);
        processImage(base64);
    };
    reader.readAsDataURL(file);
  };

  const processImage = async (base64: string) => {
    setIsProcessing(true);
    try {
        const result = await geminiService.extractAndAnalyzeText(base64, language);
        if (result) {
            setAnalysis(result);
            setChatMessages([{
                id: 'init',
                role: Role.MODEL,
                type: MessageType.TEXT,
                content: t.analyzedIntro.replace('$lang', result.detectedLanguage || 'Unknown'),
                timestamp: Date.now()
            }]);

            // Save to History
            const record: OCRRecord = {
                id: Date.now().toString(),
                timestamp: Date.now(),
                imagePreview: base64,
                analysis: result
            };
            onSaveToHistory(record);
            setIsHistoryOpen(false); // Collapse sidebar on new scan
            setMobileTab('content'); // Reset to source view

        } else {
            addToast('error', t.error);
        }
    } catch (e) {
        console.error(e);
        addToast('error', t.analysisFailed);
    } finally {
        setIsProcessing(false);
    }
  };

  const loadFromHistory = (record: OCRRecord) => {
      setAnalysis(record.analysis);
      setImagePreview(record.imagePreview);
      setIsHistoryOpen(false); // Collapse sidebar on load
      setMobileTab('content');
      setChatMessages([{
        id: 'init',
        role: Role.MODEL,
        type: MessageType.TEXT,
        content: t.historyIntro.replace('$lang', record.analysis?.detectedLanguage || 'Unknown'),
        timestamp: Date.now()
    }]);
  };

  const stopAudio = () => {
    if (audioSourceRef.current) {
        audioSourceRef.current.stop();
        audioSourceRef.current = null;
    }
    setPlayingAudioId(null);
  };

  const playAudio = async (text: string, id: string) => {
    if (playingAudioId === id) {
        stopAudio();
        return;
    }

    if (playingAudioId) stopAudio();
    setPlayingAudioId(id);

    try {
        const audioBase64 = await geminiService.generateSpeech(text);
        if (audioBase64) {
            if (!audioContextRef.current) {
                audioContextRef.current = new (window.AudioContext || (window as any).webkitAudioContext)();
            }
            const ctx = audioContextRef.current;
            if (ctx.state === 'suspended') await ctx.resume();

            const buffer = await decodeAudioData(audioBase64, ctx);
            const source = ctx.createBufferSource();
            source.buffer = buffer;
            source.connect(ctx.destination);
            source.onended = () => setPlayingAudioId(null);
            source.start();
            audioSourceRef.current = source;
        } else {
            setPlayingAudioId(null);
        }
    } catch (e) {
        console.error(e);
        setPlayingAudioId(null);
    }
  };

  const handleDownload = async (text: string) => {
      if (!text.trim()) return;
      setIsDownloading(true);
      try {
          const audioBase64 = await geminiService.generateSpeech(text);
          if (audioBase64) {
              processAndDownloadAudio(audioBase64, `ocr_extract_${Date.now()}.wav`);
          }
      } catch (e) {
          console.error(e);
      } finally {
          setIsDownloading(false);
      }
  };

  const handleAskTutor = async (customQuestion?: string) => {
    const question = customQuestion || chatInput;
    if (!question.trim() || !analysis) return;
    
    setMobileTab('tutor');

    if (!customQuestion) {
        setChatInput('');
    } else {
         if (window.getSelection) {
            window.getSelection()?.removeAllRanges();
        }
        setSelectedText(null);
    }

    setIsChatLoading(true);
    const newHistory = [...chatMessages, { id: Date.now().toString(), role: Role.USER, type: MessageType.TEXT, content: question, timestamp: Date.now() }];
    setChatMessages(newHistory);
    const historyText = newHistory.slice(-4).map(m => `${m.role}: ${m.content}`).join('\n');
    
    try {
        const dummyLesson = { title: "OCR Scan", japaneseContent: analysis.extractedText || '', translation: analysis.summary || '', vocabulary: [] };
        const answer = await geminiService.generateReadingTutorResponse(question, dummyLesson, historyText, language);
        setChatMessages(prev => [...prev, { id: (Date.now() + 1).toString(), role: Role.MODEL, type: MessageType.TEXT, content: answer, timestamp: Date.now() }]);
    } catch (e) {
        console.error(e);
    } finally {
        setIsChatLoading(false);
    }
  };

  const reset = () => { setAnalysis(null); setImagePreview(null); setChatMessages([]); };

  // History Sidebar Component
  const HistoryContent = () => (
    <div className="flex flex-col h-full bg-white">
        <div className="p-4 border-b border-slate-100 bg-slate-50/50 flex items-center justify-between">
            <h3 className="font-bold text-slate-700 flex items-center gap-2">
                <History size={18} className="text-indigo-500" /> {t.history}
            </h3>
            <div className="flex items-center gap-3">
                {history.length > 0 && (
                    <button onClick={onClearHistory} className="text-xs text-red-400 hover:text-red-600 hover:underline">
                        {t.clear}
                    </button>
                )}
                <button onClick={() => setIsHistoryOpen(false)} className="lg:hidden text-slate-400 hover:text-slate-600">
                    <X size={20} />
                </button>
            </div>
        </div>
        <div className="p-4 space-y-3 overflow-y-auto h-full pb-20">
            {history.length === 0 && (
                <div className="text-center text-slate-400 text-sm mt-10">{t.emptyHistory}</div>
            )}
            {history.slice().reverse().map(rec => (
                <div 
                    key={rec.id} 
                    onClick={() => loadFromHistory(rec)}
                    className="group flex items-start gap-3 p-3 rounded-xl bg-slate-50 border border-slate-100 hover:bg-white hover:shadow-md cursor-pointer transition-all relative"
                >
                    {/* Image Thumbnail */}
                    {rec.imagePreview ? (
                        <img src={rec.imagePreview} className="w-12 h-12 object-cover rounded-lg border border-slate-200 flex-shrink-0 bg-white" alt="scan thumbnail" />
                    ) : (
                        <div className="w-12 h-12 rounded-lg border border-slate-200 flex-shrink-0 bg-slate-100 flex items-center justify-center text-slate-300">
                            <ImageIcon size={20} />
                        </div>
                    )}
                    
                    {/* Content */}
                    <div className="flex-1 min-w-0">
                        <div className="flex justify-between items-start">
                             <div className="text-xs font-bold text-slate-700 line-clamp-1 pr-6">{(rec.analysis?.extractedText || '').substring(0, 30) || 'Text'}...</div>
                        </div>
                         <div className="flex justify-between items-center mt-1">
                             <span className="text-[10px] text-slate-400">
                                {new Date(rec.timestamp).toLocaleDateString()} {new Date(rec.timestamp).toLocaleTimeString([], {hour: '2-digit', minute:'2-digit'})}
                             </span>
                        </div>
                        <div className="text-[10px] text-indigo-400 mt-1 truncate">
                            {t.analyzedIntro.replace('$lang', rec.analysis?.detectedLanguage || 'Auto')}
                        </div>
                    </div>

                     {/* Delete Button */}
                     <button 
                        onClick={(e) => { e.stopPropagation(); onDeleteHistoryItem(rec.id); }}
                        className="absolute bottom-2 right-2 p-1.5 text-slate-300 hover:text-red-500 opacity-0 group-hover:opacity-100 transition-opacity"
                    >
                        <Trash2 size={14} />
                    </button>
                </div>
            ))}
        </div>
    </div>
  );

  // LOADING
  if (isProcessing) {
       return (
          <div className="h-full flex flex-col items-center justify-center bg-slate-50 animate-fade-in">
              <div className="relative">
                  {imagePreview && <img src={imagePreview} className="w-32 h-32 object-cover rounded-2xl opacity-50 blur-sm" alt="processing" />}
                  <div className="absolute inset-0 flex items-center justify-center">
                      <Loader2 size={48} className="text-indigo-600 animate-spin" />
                  </div>
              </div>
              <p className="mt-4 font-bold text-slate-600 animate-pulse">{t.processing}</p>
          </div>
      );
  }

  return (
    <div className="h-full flex bg-slate-50 relative overflow-hidden">
        
        {/* Main Content Area */}
        <div className="flex-1 flex flex-col h-full min-w-0 relative">
             
             {/* SETUP SCREEN */}
             {!analysis ? (
                 <div className="flex flex-col h-full">
                    {/* Sticky Header */}
                    <div className="flex items-center justify-end px-4 py-3 bg-slate-50/90 backdrop-blur z-20 sticky top-0">
                        <button
                            onClick={() => setIsHistoryOpen(!isHistoryOpen)}
                            className={`p-2 rounded-lg border transition-colors flex items-center gap-2 text-sm font-medium ${
                                isHistoryOpen 
                                ? 'bg-indigo-50 text-indigo-600 border-indigo-200' 
                                : 'bg-white text-slate-600 border-slate-200 hover:bg-slate-50'
                            }`}
                        >
                            <History size={18} />
                            <span className="hidden sm:inline">{t.history}</span>
                            {isHistoryOpen ? <PanelRightClose size={16} className="opacity-50" /> : <PanelRightOpen size={16} className="opacity-50" />}
                        </button>
                    </div>

                    <div className="flex-1 flex flex-col items-center justify-center p-6 animate-fade-in overflow-y-auto">
                        <div className="max-w-lg w-full bg-white p-10 rounded-3xl shadow-sm border border-slate-100 text-center animate-scale-in relative">
                            <div className="w-20 h-20 bg-indigo-50 text-indigo-600 rounded-full flex items-center justify-center mx-auto mb-6 shadow-inner">
                                <ScanText size={40} />
                            </div>
                            <h2 className="text-3xl font-extrabold text-slate-800 mb-2">{t.title}</h2>
                            <p className="text-slate-500 mb-8">{t.subtitle}</p>
                            <div className="grid grid-cols-1 sm:grid-cols-2 gap-4">
                                <button onClick={() => cameraInputRef.current?.click()} className="p-4 border-2 border-indigo-100 bg-indigo-50 hover:bg-indigo-100 hover:border-indigo-300 rounded-2xl flex flex-col items-center gap-2 transition-all group">
                                    <Camera size={28} className="text-indigo-500 group-hover:scale-110 transition-transform" />
                                    <span className="font-bold text-indigo-900">{t.cameraBtn}</span>
                                    <input type="file" ref={cameraInputRef} className="hidden" accept="image/*" capture="environment" onChange={handleImageInput} />
                                </button>
                                <button onClick={() => fileInputRef.current?.click()} className="p-4 border-2 border-slate-100 bg-slate-50 hover:bg-slate-100 hover:border-slate-300 rounded-2xl flex flex-col items-center gap-2 transition-all group">
                                    <Upload size={28} className="text-slate-500 group-hover:scale-110 transition-transform" />
                                    <span className="font-bold text-slate-700">{t.uploadBtn}</span>
                                    <input type="file" ref={fileInputRef} className="hidden" accept="image/*" onChange={handleImageInput} />
                                </button>
                            </div>
                        </div>
                    </div>
                 </div>
             ) : (
                 // ANALYSIS SCREEN
                 <div className="h-full flex flex-col lg:flex-row overflow-hidden">
                    
                    {/* LEFT: Main Content (Image, Text, Notes, Vocab) */}
                    <div className={`flex-1 flex-col h-full overflow-y-auto bg-white relative z-10 ${mobileTab === 'content' ? 'flex' : 'hidden lg:flex'}`}>
                        
                        {/* Header */}
                        <div className="p-4 border-b border-slate-100 flex items-center justify-between bg-white/80 backdrop-blur sticky top-0 z-20">
                            <div className="flex items-center gap-2">
                                <h3 className="font-bold text-slate-700 flex items-center gap-2 truncate"><ScanText className="text-indigo-500" size={20} /> {t.title}</h3>
                            </div>

                             {/* Mobile Tab Switcher */}
                             <div className="lg:hidden flex bg-slate-100 rounded-lg p-1 mx-2">
                                <button 
                                    onClick={() => setMobileTab('content')}
                                    className={`px-3 py-1 rounded-md text-xs font-bold transition-all ${mobileTab === 'content' ? 'bg-white text-indigo-600 shadow-sm' : 'text-slate-500'}`}
                                >
                                    <FileText size={14} className="inline mr-1" /> {tCommon.content}
                                </button>
                                <button 
                                    onClick={() => setMobileTab('tutor')}
                                    className={`px-3 py-1 rounded-md text-xs font-bold transition-all ${mobileTab === 'tutor' ? 'bg-white text-indigo-600 shadow-sm' : 'text-slate-500'}`}
                                >
                                    <MessageCircle size={14} className="inline mr-1" /> {tCommon.tutor}
                                </button>
                            </div>

                            <div className="flex gap-2 items-center">
                                <button onClick={reset} className="flex items-center gap-1 text-sm font-bold text-slate-500 hover:text-indigo-600 px-3 py-1 rounded-full hover:bg-slate-100 transition-colors">
                                    <RotateCcw size={16} /> <span className="hidden sm:inline">{t.reScan}</span>
                                </button>
                                
                                <button
                                    onClick={() => setIsHistoryOpen(!isHistoryOpen)}
                                    className={`p-2 rounded-lg border transition-colors flex items-center gap-2 text-sm font-medium ${
                                        isHistoryOpen 
                                        ? 'bg-indigo-50 text-indigo-600 border-indigo-200' 
                                        : 'bg-white text-slate-600 border-slate-200 hover:bg-slate-50'
                                    }`}
                                >
                                    {isHistoryOpen ? <PanelRightClose size={18} /> : <PanelRightOpen size={18} />}
                                </button>
                            </div>
                        </div>

                        {/* Content Scroll Area */}
                        <div className="p-6 lg:p-10 space-y-8 max-w-4xl mx-auto pb-24" ref={textRef}>
                            
                            {/* 1. Image & Extracted Text */}
                            <div className="flex flex-col md:flex-row gap-6">
                                <div className="w-full md:w-1/3">
                                     <div className="rounded-2xl overflow-hidden border border-slate-200 shadow-sm bg-slate-900/5">
                                        {imagePreview ? (
                                            <img src={imagePreview} className="w-full h-auto object-contain" alt="scan result" />
                                        ) : (
                                            <div className="w-full h-48 flex items-center justify-center text-slate-400">
                                                <ImageIcon size={48} />
                                            </div>
                                        )}
                                    </div>
                                </div>
                                <div className="flex-1">
                                    <div className="flex items-center justify-between mb-2">
                                        <h4 className="text-xs font-bold text-slate-400 uppercase tracking-wider">{t.extractedTitle}</h4>
                                        <div className="flex items-center gap-2">
                                            <button 
                                                onClick={() => playAudio(analysis?.extractedText || '', 'main')}
                                                className={`p-1.5 rounded-full transition-colors ${playingAudioId === 'main' ? 'bg-pink-100 text-pink-500' : 'text-slate-400 hover:bg-indigo-50 hover:text-indigo-500'}`}
                                            >
                                                {playingAudioId === 'main' ? <Square size={16} fill="currentColor" /> : <Volume2 size={16} />}
                                            </button>
                                            <button 
                                                onClick={() => handleDownload(analysis?.extractedText || '')}
                                                className={`p-1.5 rounded-full transition-colors ${isDownloading ? 'bg-slate-100 text-slate-500' : 'text-slate-400 hover:bg-slate-100 hover:text-slate-600'}`}
                                                disabled={isDownloading}
                                            >
                                                {isDownloading ? <Loader2 size={16} className="animate-spin" /> : <Download size={16} />}
                                            </button>
                                        </div>
                                    </div>
                                    <div className="p-4 bg-white rounded-2xl border border-slate-200 text-lg leading-relaxed whitespace-pre-wrap font-serif text-slate-800 shadow-sm">
                                        {analysis?.extractedText || ''}
                                    </div>
                                </div>
                            </div>

                            {/* 2. Summary */}
                            <div className="animate-fade-in-up delay-100">
                                <h4 className="text-xs font-bold text-slate-400 uppercase tracking-wider mb-2">{t.summaryHeader}</h4>
                                <p className="text-slate-700 leading-relaxed bg-indigo-50/50 p-6 rounded-2xl border border-indigo-100">{analysis?.summary || ''}</p>
                            </div>

                            {/* 3. Vocabulary */}
                            <div className="bg-white rounded-2xl p-6 border border-slate-200 shadow-sm animate-fade-in-up delay-200">
                                <h4 className="text-sm font-bold text-indigo-800 mb-4 flex items-center gap-2"><Book size={18} /> {t.vocabHeader}</h4>
                                <div className="grid grid-cols-1 md:grid-cols-2 gap-4">
                                    {analysis?.vocabulary?.map((v, i) => (
                                        v ? (
                                        <div key={i} className="bg-slate-50 p-3 rounded-xl border border-slate-100 flex flex-col group transition-all duration-300 hover:-translate-y-1 hover:shadow-md hover:bg-white">
                                            <div className="flex justify-between items-baseline mb-1">
                                                <div className="flex items-baseline gap-2">
                                                    <span className="font-bold text-slate-800">{v.word || ''}</span>
                                                    <span className="text-xs text-slate-500 font-mono">({v.reading || ''})</span>
                                                </div>
                                                <button 
                                                    onClick={() => playAudio(v.word || '', `vocab-${i}`)}
                                                    className={`p-1.5 rounded-full transition-colors ${playingAudioId === `vocab-${i}` ? 'bg-pink-100 text-pink-500' : 'text-slate-300 hover:bg-indigo-50 hover:text-indigo-500'}`}
                                                >
                                                    {playingAudioId === `vocab-${i}` ? <Loader2 size={14} className="animate-spin" /> : <Volume2 size={14} />}
                                                </button>
                                            </div>
                                            <span className="text-sm text-indigo-600 font-medium">{v.meaning || ''}</span>
                                        </div>
                                        ) : null
                                    ))}
                                </div>
                            </div>

                            {/* 4. Grammar */}
                             {analysis?.grammarPoints && analysis.grammarPoints?.length > 0 && (
                                <div className="bg-white rounded-2xl p-6 border border-slate-200 shadow-sm animate-fade-in-up delay-300">
                                    <h4 className="text-sm font-bold text-emerald-800 mb-4 flex items-center gap-2"><PenTool size={18} /> {t.grammarHeader}</h4>
                                    <div className="space-y-4">
                                        {analysis.grammarPoints.map((g, i) => (
                                            g ? (
                                            <div key={i} className="bg-emerald-50/50 p-4 rounded-xl border border-emerald-100 transition-all duration-300 hover:-translate-y-1 hover:shadow-md hover:bg-emerald-100">
                                                <h5 className="font-bold text-emerald-900 mb-1">{g.point || ''}</h5>
                                                <p className="text-sm text-emerald-700 leading-relaxed">{g.explanation || ''}</p>
                                            </div>
                                            ) : null
                                        ))}
                                    </div>
                                </div>
                            )}

                             {/* Floating Ask Button */}
                             {selectedText && (
                                <div className="absolute bottom-6 left-0 right-0 flex justify-center z-50 animate-fade-in-up px-4 pointer-events-none">
                                    <button
                                        onClick={() => handleAskTutor(`Explain: "${selectedText}"`)}
                                        className="pointer-events-auto flex items-center gap-2 px-6 py-3 bg-slate-900 text-white rounded-full shadow-2xl hover:scale-105 active:scale-95 transition-all font-bold text-sm border border-white/20"
                                    >
                                        <Sparkles size={16} className="text-yellow-300 animate-pulse" />
                                        Explain: <span className="max-w-[150px] truncate">"{selectedText}"</span>
                                    </button>
                                </div>
                            )}
                        </div>
                    </div>
                    
                    {/* RIGHT: Tutor Chat (Tab: tutor) */}
                    <div className={`w-full lg:w-96 bg-slate-50 flex-col h-full shadow-inner border-l border-slate-200 z-20 ${mobileTab === 'tutor' ? 'flex' : 'hidden lg:flex'}`}>
                        {/* Header */}
                        <div className="p-3 lg:p-4 bg-white border-b border-slate-200 flex items-center gap-2 shadow-sm">
                            <button onClick={() => setMobileTab('content')} className="lg:hidden mr-2 text-slate-400"><ChevronLeft size={20} /></button>
                            <HelpCircle className="text-indigo-500 animate-pulse" size={20} />
                            <span className="font-bold text-slate-700">{t.tutorChat}</span>
                        </div>
                        
                        {/* Chat Area */}
                        <div className="flex-1 overflow-y-auto p-4 space-y-3 bg-slate-50/50">
                            {chatMessages.map(msg => <ChatBubble key={msg.id} message={msg} language={language} />)}
                            {isChatLoading && (
                                <div className="flex items-center gap-2 text-xs text-slate-400 px-2 animate-pulse">
                                    <Loader2 size={14} className="animate-spin" /> {t.thinking}
                                </div>
                            )}
                            <div ref={chatEndRef} />
                        </div>

                        {/* Input Area */}
                        <div className="p-3 bg-white border-t border-slate-200 pb-[env(safe-area-inset-bottom)]">
                            <div className="flex items-center gap-2 bg-slate-100 rounded-full px-2 py-1 border border-slate-200 focus-within:ring-2 focus-within:ring-indigo-500 focus-within:bg-white transition-all">
                                <input 
                                    className="flex-1 bg-transparent border-none focus:ring-0 text-sm px-3 py-2 outline-none text-slate-700 placeholder:text-slate-400" 
                                    placeholder={t.chatPlaceholder} 
                                    value={chatInput} 
                                    onChange={(e) => setChatInput(e.target.value)} 
                                    onKeyDown={(e) => e.key === 'Enter' && handleAskTutor()} 
                                />
                                <button 
                                    onClick={() => handleAskTutor()} 
                                    disabled={!chatInput.trim() || isChatLoading} 
                                    className="p-2 bg-indigo-600 text-white rounded-full hover:bg-indigo-700 disabled:opacity-50 transform active:scale-95 transition-transform"
                                >
                                    {isChatLoading ? <Loader2 size={16} className="animate-spin" /> : <Send size={16} />}
                                </button>
                            </div>
                        </div>
                    </div>
                 </div>
             )}
        </div>
        
        {/* Sidebar History (Desktop) */}
        <div className={`
            hidden lg:block h-full bg-white border-l border-slate-200 transition-all duration-300 ease-in-out overflow-hidden z-30
            ${isHistoryOpen ? 'w-80 opacity-100' : 'w-0 opacity-0 border-none'}
        `}>
             <HistoryContent />
        </div>

        {/* Mobile Drawer (Slide Over) */}
        {isHistoryOpen && (
            <div className="fixed inset-0 z-50 lg:hidden flex justify-end">
                <div className="absolute inset-0 bg-slate-900/30 backdrop-blur-sm transition-opacity" onClick={() => setIsHistoryOpen(false)} />
                <div className="relative w-[85%] max-w-sm bg-white h-full shadow-2xl animate-slide-in-right z-50 flex flex-col">
                    <HistoryContent />
                </div>
            </div>
        )}
    </div>
  );
};

export default OCRView;