import React, { useState, useRef, useEffect, useCallback } from 'react';
import { v4 as uuidv4 } from 'uuid';
import { Plus, Play, Pause, SkipForward, SkipBack, Volume2, Gauge, Settings, Moon, Sun, Type, Keyboard } from 'lucide-react';
import { Article, PlaybackStatus, PlayerState, VoiceName, AudioSegment, ReaderSettings } from './types';
import { MIN_SPEED, MAX_SPEED, SPEED_STEP } from './constants';
import { extractArticleContent, generateSpeechFromText } from './services/geminiService';
import { base64ToUint8Array, createWavBlob } from './services/audioUtils';
import { segmentText } from './services/textUtils';
import { QueueItem } from './components/QueueItem';
import { VoiceSelector } from './components/VoiceSelector';
import { ReaderView } from './components/ReaderView';

export default function App() {
  // -- State --
  const [inputUrl, setInputUrl] = useState('');
  const [queue, setQueue] = useState<Article[]>([]);
  const [viewId, setViewId] = useState<string | null>(null);
  const [showSettings, setShowSettings] = useState(false);
  
  const [playerState, setPlayerState] = useState<PlayerState>({
    isPlaying: false,
    playbackRate: 1.0,
    currentArticleId: null,
    selectedVoice: VoiceName.Puck,
  });

  const [settings, setSettings] = useState<ReaderSettings>({
    isDarkMode: false,
    fontSize: 'lg',
    lineHeight: 'relaxed',
    fontFamily: 'serif',
    autoScroll: true
  });

  // -- Refs --
  const audioRef = useRef<HTMLAudioElement>(new Audio());
  const processingRef = useRef<Set<string>>(new Set());

  // -- Helpers --
  const getCurrentArticle = () => queue.find(a => a.id === playerState.currentArticleId);
  
  const getViewingArticle = () => {
    if (viewId) return queue.find(a => a.id === viewId);
    if (playerState.currentArticleId) return queue.find(a => a.id === playerState.currentArticleId);
    if (queue.length > 0) return queue[0];
    return null;
  };

  // -- State Updaters --

  const updateArticle = (id: string, updates: Partial<Article>) => {
    setQueue(prev => prev.map(item => item.id === id ? { ...item, ...updates } : item));
  };

  const updateSegment = (articleId: string, segmentId: string, updates: Partial<AudioSegment>) => {
    setQueue(prev => prev.map(article => {
      if (article.id !== articleId) return article;
      const newSegments = article.segments.map(seg => 
        seg.id === segmentId ? { ...seg, ...updates } : seg
      );
      return { ...article, segments: newSegments };
    }));
  };

  // -- Audio Generation Pipeline --

  const processSegmentAudio = useCallback(async (articleId: string, segmentId: string, text: string, voice: VoiceName) => {
    const uniqueKey = `${articleId}-${segmentId}`;
    if (processingRef.current.has(uniqueKey)) return;
    
    processingRef.current.add(uniqueKey);
    updateSegment(articleId, segmentId, { isLoading: true });

    try {
      const base64Audio = await generateSpeechFromText(text, voice);
      const pcmData = base64ToUint8Array(base64Audio);
      const wavBlob = createWavBlob(pcmData);
      const audioUrl = URL.createObjectURL(wavBlob);
      updateSegment(articleId, segmentId, { audioUrl, isLoading: false });
    } catch (error) {
      console.error("Segment generation failed", error);
      updateSegment(articleId, segmentId, { isLoading: false, hasError: true });
    } finally {
      processingRef.current.delete(uniqueKey);
    }
  }, []);

  const manageBuffer = useCallback(async (article: Article) => {
    const currentIndex = article.currentSegmentIndex;
    const segmentsToBuffer = article.segments.slice(currentIndex, currentIndex + 5);

    for (const seg of segmentsToBuffer) {
      if (!seg.audioUrl && !seg.isLoading && !seg.hasError) {
        processSegmentAudio(article.id, seg.id, seg.text, playerState.selectedVoice);
      }
    }
  }, [playerState.selectedVoice, processSegmentAudio]);

  // -- Handlers --

  const handleAddUrl = async () => {
    if (!inputUrl.trim()) return;
    
    const id = uuidv4();
    const newArticle: Article = {
      id,
      url: inputUrl,
      title: 'Fetching info...',
      text: '',
      segments: [],
      currentSegmentIndex: 0,
      status: PlaybackStatus.LOADING_TEXT
    };
    
    setQueue(prev => [...prev, newArticle]);
    setInputUrl('');
    if (!playerState.isPlaying) setViewId(id);

    try {
      const { title, text } = await extractArticleContent(newArticle.url);
      const segments = segmentText(text);
      
      if (title) {
        const titleSegment = segmentText(title)[0];
        if (titleSegment) segments.unshift(titleSegment);
      }
      
      updateArticle(id, {
        title,
        text,
        segments,
        status: PlaybackStatus.LOADING_AUDIO
      });

      if (segments.length > 0) {
        const initialLoadCount = Math.min(segments.length, 5);
        for(let i = 0; i < initialLoadCount; i++) {
            processSegmentAudio(id, segments[i].id, segments[i].text, playerState.selectedVoice);
        }
        updateArticle(id, { status: PlaybackStatus.READY });
        
        setQueue(prev => {
            const current = prev.find(a => a.id === id);
            if (current && !playerState.isPlaying) {
                playArticle(id);
            }
            return prev;
        });
      } else {
         updateArticle(id, { status: PlaybackStatus.ERROR, errorMessage: "No readable text found." });
      }

    } catch (error: any) {
      updateArticle(id, { 
        status: PlaybackStatus.ERROR, 
        errorMessage: error.message || "Failed to load article" 
      });
    }
  };

  // -- Playback Control --

  const playArticle = useCallback(async (id: string) => {
    setPlayerState(prev => ({ ...prev, currentArticleId: id, isPlaying: true }));
    setViewId(id);
    updateArticle(id, { status: PlaybackStatus.PLAYING });
  }, []);

  const pausePlayback = useCallback(() => {
    audioRef.current.pause();
    setPlayerState(prev => ({ ...prev, isPlaying: false }));
    if (playerState.currentArticleId) {
      updateArticle(playerState.currentArticleId, { status: PlaybackStatus.PAUSED });
    }
  }, [playerState.currentArticleId]);

  const skipSegment = useCallback((direction: 'next' | 'prev') => {
    setQueue(prevQueue => {
      const currentId = playerState.currentArticleId;
      if (!currentId) return prevQueue;
      
      const article = prevQueue.find(a => a.id === currentId);
      if (!article) return prevQueue;

      let newIndex = direction === 'next' 
        ? article.currentSegmentIndex + 1 
        : article.currentSegmentIndex - 1;
      
      // Boundary checks
      if (newIndex < 0) newIndex = 0;
      if (newIndex >= article.segments.length) {
         // If skipping past end, just stop for now (or go to next article logic)
         newIndex = article.segments.length - 1; 
      }

      return prevQueue.map(a => a.id === currentId ? { ...a, currentSegmentIndex: newIndex } : a);
    });
  }, [playerState.currentArticleId]);

  const handleSegmentSelect = useCallback((articleId: string, index: number) => {
    setPlayerState(prev => ({
        ...prev,
        currentArticleId: articleId,
        isPlaying: true
    }));
    updateArticle(articleId, {
        currentSegmentIndex: index,
        status: PlaybackStatus.PLAYING
    });
  }, []);

  // -- Keyboard Shortcuts --
  useEffect(() => {
    const handleKeyDown = (e: KeyboardEvent) => {
      // Ignore shortcuts if typing in input
      if (document.activeElement instanceof HTMLInputElement || document.activeElement instanceof HTMLTextAreaElement) {
        return;
      }

      switch (e.code) {
        case 'Space':
          e.preventDefault();
          if (playerState.isPlaying) pausePlayback();
          else if (playerState.currentArticleId) playArticle(playerState.currentArticleId);
          else if (queue.length > 0) playArticle(queue[0].id);
          break;
        case 'ArrowRight':
          skipSegment('next');
          break;
        case 'ArrowLeft':
          skipSegment('prev');
          break;
      }
    };

    window.addEventListener('keydown', handleKeyDown);
    return () => window.removeEventListener('keydown', handleKeyDown);
  }, [playerState.isPlaying, playerState.currentArticleId, queue, playArticle, pausePlayback, skipSegment]);

  // -- Effects --

  useEffect(() => {
    const article = queue.find(a => a.id === playerState.currentArticleId);
    if (!article || !playerState.isPlaying) return;

    const currentSegment = article.segments[article.currentSegmentIndex];
    
    if (!currentSegment) {
      updateArticle(article.id, { status: PlaybackStatus.COMPLETED });
      setPlayerState(prev => ({ ...prev, isPlaying: false }));
      return;
    }

    if (currentSegment.audioUrl) {
        const audioEl = audioRef.current;
        const currentSrc = audioEl.getAttribute('data-current-src');
        
        if (currentSrc !== currentSegment.audioUrl) {
            audioEl.src = currentSegment.audioUrl;
            audioEl.setAttribute('data-current-src', currentSegment.audioUrl);
            audioEl.playbackRate = playerState.playbackRate;
            audioEl.play().catch(e => console.warn("Playback interrupted", e));
        } else if (audioEl.paused) {
            audioEl.play().catch(e => console.warn("Resume failed", e));
        }
    } else {
        if (!currentSegment.isLoading && !currentSegment.hasError) {
            processSegmentAudio(article.id, currentSegment.id, currentSegment.text, playerState.selectedVoice);
        }
    }
    manageBuffer(article);

  }, [queue, playerState.currentArticleId, playerState.isPlaying, playerState.playbackRate, playerState.selectedVoice, manageBuffer, processSegmentAudio]);

  useEffect(() => {
    const audio = audioRef.current;
    const handleEnded = () => {
      const currentId = playerState.currentArticleId;
      setQueue(prevQueue => {
        const article = prevQueue.find(a => a.id === currentId);
        if (!article) return prevQueue;

        const nextIndex = article.currentSegmentIndex + 1;
        
        if (nextIndex < article.segments.length) {
           return prevQueue.map(a => a.id === currentId ? { ...a, currentSegmentIndex: nextIndex } : a);
        } else {
           const artIndex = prevQueue.findIndex(a => a.id === currentId);
           if (artIndex !== -1 && artIndex < prevQueue.length - 1) {
             setTimeout(() => playArticle(prevQueue[artIndex + 1].id), 100); 
             return prevQueue.map(a => a.id === currentId ? { ...a, status: PlaybackStatus.COMPLETED } : a);
           } else {
             setPlayerState(ps => ({ ...ps, isPlaying: false }));
             return prevQueue.map(a => a.id === currentId ? { ...a, status: PlaybackStatus.COMPLETED } : a);
           }
        }
      });
    };
    audio.addEventListener('ended', handleEnded);
    return () => audio.removeEventListener('ended', handleEnded);
  }, [playerState.currentArticleId, playArticle]); 

  const handleSpeedChange = (newSpeed: number) => {
    const speed = Math.max(MIN_SPEED, Math.min(MAX_SPEED, newSpeed));
    setPlayerState(prev => ({ ...prev, playbackRate: speed }));
    if (audioRef.current) {
      audioRef.current.playbackRate = speed;
    }
  };

  // -- Render --
  
  const currentArticle = getCurrentArticle();
  const viewingArticle = getViewingArticle();

  return (
    <div className={`${settings.isDarkMode ? 'dark' : ''} transition-colors duration-300`}>
      <div className="min-h-screen flex flex-col bg-slate-50 dark:bg-slate-950 pb-32 transition-colors duration-300">
        
        {/* Header */}
        <header className="bg-white dark:bg-slate-900 border-b border-slate-200 dark:border-slate-800 px-6 py-4 sticky top-0 z-20 shadow-sm transition-colors duration-300">
          <div className="max-w-7xl mx-auto flex items-center justify-between">
            <div className="flex items-center gap-2">
              <div className="bg-blue-600 text-white p-2 rounded-lg shadow-md">
                <Volume2 className="w-6 h-6" />
              </div>
              <h1 className="text-xl font-bold text-slate-900 dark:text-white tracking-tight hidden sm:block">NewsCaster AI</h1>
            </div>
            
            <div className="flex items-center gap-4">
              <VoiceSelector 
                selectedVoice={playerState.selectedVoice}
                onVoiceChange={(v) => setPlayerState(prev => ({ ...prev, selectedVoice: v }))}
                disabled={playerState.isPlaying} 
              />
              <button 
                onClick={() => setShowSettings(!showSettings)}
                className="p-2 rounded-lg text-slate-500 hover:bg-slate-100 dark:text-slate-400 dark:hover:bg-slate-800 transition-colors"
              >
                <Settings className="w-5 h-5" />
              </button>
            </div>
          </div>

          {/* Settings Menu */}
          {showSettings && (
            <div className="absolute right-4 top-16 bg-white dark:bg-slate-900 rounded-xl shadow-xl border border-slate-200 dark:border-slate-800 p-6 w-80 z-50 animate-in fade-in slide-in-from-top-4">
              <h3 className="text-sm font-semibold text-slate-400 uppercase tracking-wider mb-4 flex items-center gap-2">
                <Settings className="w-4 h-4" /> Reader Preferences
              </h3>
              
              <div className="space-y-6">
                {/* Theme */}
                <div className="flex items-center justify-between">
                  <span className="text-slate-700 dark:text-slate-300 text-sm font-medium">Theme</span>
                  <div className="flex bg-slate-100 dark:bg-slate-800 rounded-lg p-1">
                    <button 
                      onClick={() => setSettings(s => ({...s, isDarkMode: false}))}
                      className={`p-2 rounded-md transition-all ${!settings.isDarkMode ? 'bg-white shadow text-blue-600' : 'text-slate-400'}`}
                    >
                      <Sun className="w-4 h-4" />
                    </button>
                    <button 
                      onClick={() => setSettings(s => ({...s, isDarkMode: true}))}
                      className={`p-2 rounded-md transition-all ${settings.isDarkMode ? 'bg-slate-700 shadow text-blue-400' : 'text-slate-400'}`}
                    >
                      <Moon className="w-4 h-4" />
                    </button>
                  </div>
                </div>

                {/* Font Size */}
                <div className="space-y-2">
                   <div className="flex justify-between text-sm">
                      <span className="text-slate-700 dark:text-slate-300 font-medium">Text Size</span>
                   </div>
                   <input 
                      type="range" min="0" max="4" step="1"
                      value={['sm','base','lg','xl','2xl'].indexOf(settings.fontSize)}
                      onChange={(e) => {
                        const sizes = ['sm','base','lg','xl','2xl'] as const;
                        setSettings(s => ({...s, fontSize: sizes[parseInt(e.target.value)]}));
                      }}
                      className="w-full h-2 bg-slate-200 dark:bg-slate-700 rounded-lg appearance-none cursor-pointer accent-blue-600"
                   />
                   <div className="flex justify-between text-xs text-slate-400">
                     <span>Aa</span>
                     <span>Aa</span>
                   </div>
                </div>

                {/* Font Family */}
                <div className="space-y-2">
                  <span className="text-slate-700 dark:text-slate-300 text-sm font-medium block">Font Family</span>
                  <div className="grid grid-cols-3 gap-2">
                    {['serif', 'sans', 'mono'].map((font) => (
                      <button
                        key={font}
                        onClick={() => setSettings(s => ({...s, fontFamily: font as any}))}
                        className={`px-3 py-2 text-sm border rounded-lg transition-all capitalize ${
                          settings.fontFamily === font 
                          ? 'border-blue-500 bg-blue-50 text-blue-700 dark:bg-blue-900/30 dark:text-blue-300' 
                          : 'border-slate-200 dark:border-slate-700 text-slate-600 dark:text-slate-400'
                        }`}
                      >
                        {font}
                      </button>
                    ))}
                  </div>
                </div>
                
                {/* Shortcuts Hint */}
                <div className="pt-4 border-t border-slate-100 dark:border-slate-800">
                   <p className="text-xs text-slate-400 flex items-center gap-2">
                     <Keyboard className="w-3 h-3" />
                     Shortcuts: Space (Play), Arrows (Skip)
                   </p>
                </div>
              </div>
            </div>
          )}
        </header>

        {/* Main Content */}
        <main className="flex-grow px-4 py-6 max-w-7xl mx-auto w-full grid grid-cols-1 lg:grid-cols-12 gap-8">
          
          {/* Left Column: Controls & Queue */}
          <div className="lg:col-span-5 space-y-6">
              {/* Input */}
              <div className="bg-white dark:bg-slate-900 p-1 rounded-2xl shadow-sm border border-slate-200 dark:border-slate-800 flex gap-2 items-center pl-4 transition-colors duration-300">
              <input 
                  type="url" 
                  placeholder="Paste article URL here..."
                  className="flex-grow py-3 outline-none text-slate-700 dark:text-slate-200 bg-transparent placeholder:text-slate-400 min-w-0"
                  value={inputUrl}
                  onChange={(e) => setInputUrl(e.target.value)}
                  onKeyDown={(e) => e.key === 'Enter' && handleAddUrl()}
              />
              <button 
                  onClick={handleAddUrl}
                  disabled={!inputUrl.trim()}
                  className="bg-slate-900 hover:bg-slate-800 dark:bg-blue-600 dark:hover:bg-blue-500 disabled:opacity-50 disabled:cursor-not-allowed text-white px-4 sm:px-6 py-3 rounded-xl font-medium transition-all flex items-center gap-2 flex-shrink-0 shadow-lg"
              >
                  <Plus className="w-4 h-4" />
                  <span className="hidden sm:inline">Queue</span>
              </button>
              </div>

              {/* Queue List */}
              <div className="space-y-4">
              <div className="flex items-center justify-between px-1">
                  <h2 className="text-sm font-semibold text-slate-500 dark:text-slate-400 uppercase tracking-wider">Up Next</h2>
                  <span className="text-xs bg-slate-100 dark:bg-slate-800 text-slate-600 dark:text-slate-400 px-2 py-1 rounded-full">{queue.length} articles</span>
              </div>
              
              <div className="space-y-3">
                  {queue.length === 0 ? (
                  <div className="text-center py-12 border-2 border-dashed border-slate-200 dark:border-slate-800 rounded-2xl text-slate-400 dark:text-slate-600 bg-white dark:bg-slate-900/50">
                      <p>No articles queued.</p>
                  </div>
                  ) : (
                  queue.map(article => (
                      <div key={article.id} onClick={() => setViewId(article.id)} className="cursor-pointer">
                          <QueueItem 
                              article={article}
                              isActive={article.id === playerState.currentArticleId}
                              isPlaying={playerState.isPlaying}
                              onPlay={() => playArticle(article.id)}
                              onPause={pausePlayback}
                              onRemove={() => {
                                  if (playerState.currentArticleId === article.id) {
                                      pausePlayback();
                                      setPlayerState(prev => ({ ...prev, currentArticleId: null }));
                                  }
                                  setQueue(prev => prev.filter(a => a.id !== article.id));
                                  if (viewId === article.id) setViewId(null);
                              }}
                          />
                      </div>
                  ))
                  )}
              </div>
              </div>
          </div>

          {/* Right Column: Reader View */}
          <div className="lg:col-span-7 h-full hidden lg:block">
              <ReaderView 
                article={viewingArticle} 
                settings={settings} 
                onToggleAutoScroll={() => setSettings(s => ({...s, autoScroll: !s.autoScroll}))}
                onSegmentSelect={(index) => viewingArticle && handleSegmentSelect(viewingArticle.id, index)}
              />
          </div>
          
          <div className="lg:hidden block">
               {viewingArticle && (
                   <div className="mt-8">
                       <h3 className="text-sm font-semibold text-slate-500 mb-2">Article Reader</h3>
                       <div className="h-[500px]">
                          <ReaderView 
                            article={viewingArticle} 
                            settings={settings}
                            onToggleAutoScroll={() => setSettings(s => ({...s, autoScroll: !s.autoScroll}))}
                            onSegmentSelect={(index) => viewingArticle && handleSegmentSelect(viewingArticle.id, index)}
                          />
                       </div>
                   </div>
               )}
          </div>
        </main>

        {/* Player Bar */}
        <div className="fixed bottom-0 left-0 right-0 bg-white/90 dark:bg-slate-900/90 backdrop-blur-lg border-t border-slate-200 dark:border-slate-800 p-4 pb-6 shadow-[0_-4px_20px_rgba(0,0,0,0.05)] z-30 transition-colors duration-300">
          <div className="max-w-7xl mx-auto flex flex-col sm:flex-row items-center gap-4 sm:gap-8">
            
            <div className="flex-grow w-full sm:w-auto min-w-0 text-center sm:text-left">
              {currentArticle ? (
                <div>
                  <h4 className="font-bold text-slate-900 dark:text-white truncate">{currentArticle.title}</h4>
                  {/* Progress Bar */}
                  <div className="w-full h-1 bg-slate-200 dark:bg-slate-700 rounded-full mt-2 overflow-hidden">
                      <div 
                          className="h-full bg-blue-500 transition-all duration-300"
                          style={{ width: `${((currentArticle.currentSegmentIndex + 1) / Math.max(1, currentArticle.segments.length)) * 100}%`}}
                      />
                  </div>
                  <p className="text-xs text-slate-500 dark:text-slate-400 truncate mt-1">
                      Playing segment {currentArticle.currentSegmentIndex + 1} of {currentArticle.segments.length}
                  </p>
                </div>
              ) : (
                <div className="text-slate-400 dark:text-slate-500 text-sm font-medium">Ready to play</div>
              )}
            </div>

            <div className="flex items-center gap-6">
              <div className="hidden sm:flex items-center gap-2 group relative">
                 <Gauge className="w-4 h-4 text-slate-400" />
                 <div className="flex items-center gap-2 bg-slate-100 dark:bg-slate-800 rounded-lg p-1">
                   <button 
                      className="w-6 h-6 flex items-center justify-center hover:bg-white dark:hover:bg-slate-700 rounded text-xs font-bold text-slate-600 dark:text-slate-300 transition-colors"
                      onClick={() => handleSpeedChange(playerState.playbackRate - SPEED_STEP)}
                   >-</button>
                   <span className="text-xs font-mono w-8 text-center font-bold text-blue-600 dark:text-blue-400">{playerState.playbackRate.toFixed(1)}x</span>
                   <button 
                      className="w-6 h-6 flex items-center justify-center hover:bg-white dark:hover:bg-slate-700 rounded text-xs font-bold text-slate-600 dark:text-slate-300 transition-colors"
                      onClick={() => handleSpeedChange(playerState.playbackRate + SPEED_STEP)}
                   >+</button>
                 </div>
              </div>

              <div className="flex items-center gap-4">
                <button 
                  className="p-2 text-slate-400 hover:text-slate-600 dark:hover:text-slate-200 transition-colors"
                  onClick={() => skipSegment('prev')}
                >
                  <SkipBack className="w-5 h-5" />
                </button>

                <button 
                  className="w-12 h-12 rounded-full bg-slate-900 hover:bg-slate-800 dark:bg-blue-600 dark:hover:bg-blue-500 text-white flex items-center justify-center shadow-lg hover:shadow-xl hover:scale-105 transition-all active:scale-95"
                  onClick={() => {
                    if (playerState.isPlaying) pausePlayback();
                    else if (playerState.currentArticleId) playArticle(playerState.currentArticleId);
                    else if (queue.length > 0) playArticle(queue[0].id);
                  }}
                  disabled={queue.length === 0}
                >
                  {playerState.isPlaying ? <Pause className="w-5 h-5 fill-current" /> : <Play className="w-5 h-5 fill-current ml-1" />}
                </button>

                <button 
                  className="p-2 text-slate-400 hover:text-slate-600 dark:hover:text-slate-200 transition-colors"
                  onClick={() => skipSegment('next')}
                >
                  <SkipForward className="w-5 h-5" />
                </button>
              </div>
            </div>
          </div>
        </div>
      </div>
    </div>
  );
}