import React, { useState, useCallback, useRef } from 'react';
import { VlaData, TaskSegment, Interaction } from './types';
import { generateOverallGoal, generateTasksAndInteractions } from './services/backendService';
import { extractFramesFromVideo } from './utils/videoProcessor';
import { VideoUploader } from './components/VideoUploader';
import { VideoPlayer } from './components/VideoPlayer';
import { ResultsDisplay } from './components/ResultsDisplay';
import { WandSparkles } from './components/Icons';

// Type for the point to be highlighted on the video
type HighlightPoint = { x: number; y: number; isEditing: boolean } | null;
// Type for the coordinate picker callback function
type CoordinatePickerCallback = ((coords: { x: number; y: number }) => void) | null;


export default function App(): React.ReactNode {
  const [videoFile, setVideoFile] = useState<File | null>(null);
  const [videoSrc, setVideoSrc] = useState<string | null>(null);
  const [videoDuration, setVideoDuration] = useState<number>(0);
  const [vlaData, setVlaData] = useState<VlaData | null>(null);
  const [isLoading, setIsLoading] = useState<boolean>(false);
  const [loadingMessage, setLoadingMessage] = useState<string>('');
  const [error, setError] = useState<string | null>(null);
  const [totalFrames, setTotalFrames] = useState<number>(0);
  const [highlightPoint, setHighlightPoint] = useState<HighlightPoint>(null);
  const [coordinatePicker, setCoordinatePicker] = useState<CoordinatePickerCallback>(null);
  const [usedFallback, setUsedFallback] = useState<boolean>(false);

  const videoRef = useRef<HTMLVideoElement>(null);
  const isGeneratingRef = useRef(false);

  const handleVideoUpload = useCallback((file: File) => {
    if (file.type.startsWith('video/')) {
      setVideoFile(file);

      if (videoSrc) {
        URL.revokeObjectURL(videoSrc);
      }

      const url = URL.createObjectURL(file);
      setVideoSrc(url);
      setVlaData(null);
      setError(null);
      setUsedFallback(false);
      setVideoDuration(0);
      setTotalFrames(0);

      const videoElement = document.createElement('video');
      videoElement.preload = 'metadata';
      videoElement.src = url;
      videoElement.onloadedmetadata = () => {
        setVideoDuration(videoElement.duration);
      };
      videoElement.onerror = () => {
        setError("Could not read video metadata to get duration.");
      };
    } else {
      setError('Please upload a valid video file.');
    }
  }, [videoSrc]);

  const handleGenerate = useCallback(async () => {
    if (!videoFile || isGeneratingRef.current) {
      if (!videoFile) setError('No video file selected.');
      return;
    }

    isGeneratingRef.current = true;
    setIsLoading(true);
    setError(null);
    setVlaData(null);
    setUsedFallback(false); // Reset on each generation

    try {
      const FRAMES_PER_SECOND = 2; // Extract 2 frames per second
      const MAX_FRAMES_TOTAL = 360; // Cap at 360 frames (e.g., 3 minutes at 2fps) to manage memory/performance
      
      let calculatedFrames = Math.ceil(videoDuration * FRAMES_PER_SECOND);
      if (calculatedFrames > MAX_FRAMES_TOTAL) {
          calculatedFrames = MAX_FRAMES_TOTAL;
      }
      if (calculatedFrames === 0 && videoDuration > 0) {
        calculatedFrames = 1; // ensure at least one frame for very short videos
      }
      setTotalFrames(calculatedFrames);

      // Step 1: Extract frames
      setLoadingMessage(`Step 1/3: Extracting ${calculatedFrames} frames from video...`);
      const frames = await extractFramesFromVideo(videoFile, calculatedFrames);
      
      if (frames.length === 0) {
        throw new Error("Could not extract any frames from the video. The file might be corrupted or in an unsupported format.");
      }

      // Step 2: Generate Overall Goal
      setLoadingMessage('Step 2/3: Determining overall goal...');
      const keyframes = [frames[0], frames[Math.floor(frames.length / 2)], frames[frames.length - 1]];
      const overallGoal = await generateOverallGoal(keyframes, videoDuration);
      
      const initialVlaData: VlaData = { overallGoal, tasks: [] };
      setVlaData(initialVlaData);

      // Step 3: Generate Task Segments and Interactions in one go
      setLoadingMessage('Step 3/3: Analyzing tasks and interactions...');
      const vlaData = await generateTasksAndInteractions(
        frames, 
        overallGoal, 
        videoDuration, 
        totalFrames,
        (current, total) => {
          // Progress callback - you could update loading message here
          console.log(`Progress: ${current}/${total}`);
        }
      );
      
      setVlaData(vlaData);

    } catch (err) {
      console.error(err);
      const errorMessage = err instanceof Error ? err.message : 'An unknown error occurred.';
      setError(`Failed to process video. ${errorMessage}`);
      setVlaData(null); // Clear partial data on major failure
    } finally {
      setIsLoading(false);
      setLoadingMessage('');
      isGeneratingRef.current = false;
    }
  }, [videoFile, videoDuration]);

  const handleDownload = useCallback(() => {
    if (!vlaData || !videoFile) return;

    const dataStr = JSON.stringify(vlaData, null, 2);
    const dataBlob = new Blob([dataStr], { type: 'application/json' });
    const dataUrl = URL.createObjectURL(dataBlob);
    
    const link = document.createElement('a');
    link.href = dataUrl;
    const baseName = videoFile.name.substring(0, videoFile.name.lastIndexOf('.')) || videoFile.name;
    link.download = `${baseName}_vla_data.json`;

    document.body.appendChild(link);
    link.click();
    document.body.removeChild(link);
    URL.revokeObjectURL(dataUrl);
  }, [vlaData, videoFile]);
  
  const handleSeekToTime = useCallback((time: number) => {
    if (videoRef.current) {
      videoRef.current.currentTime = time;
    }
  }, []);
  
  const handleUpdateInteraction = useCallback((taskId: number, interactionIndex: number, updatedInteraction: Interaction) => {
    setVlaData(currentData => {
      if (!currentData) return null;

      const newTasks = currentData.tasks.map(task => {
        if (task.id === taskId) {
          const newInteractions = [...task.interactions];
          newInteractions[interactionIndex] = updatedInteraction;
          return { ...task, interactions: newInteractions };
        }
        return task;
      });

      return { ...currentData, tasks: newTasks };
    });
  }, []);

  const handleVideoClick = useCallback((coords: { x: number; y: number }) => {
    if (coordinatePicker) {
      coordinatePicker(coords);
    }
  }, [coordinatePicker]);

  const handleHighlightPoint = useCallback((point: HighlightPoint) => {
    // Prevent hover from overriding a sticky editing highlight
    if (highlightPoint?.isEditing && !point?.isEditing) {
      return;
    }
    setHighlightPoint(point);
  }, [highlightPoint?.isEditing]);
  
  const handleSetCoordinatePicker = useCallback((callback: CoordinatePickerCallback) => {
    setCoordinatePicker(() => callback);
  }, []);

  return (
    <div className="min-h-screen bg-slate-900 text-slate-200 font-sans">
      <main className="grid grid-cols-1 lg:grid-cols-2 gap-6 p-4 md:p-8 max-w-screen-2xl mx-auto">
        {/* Left Column: Video and Controls */}
        <div className="flex flex-col gap-6 lg:h-[calc(100vh-4rem)]">
          <header>
            <h1 className="text-3xl md:text-4xl font-bold text-white tracking-tight">VLA Data Generator</h1>
            <p className="text-slate-400 mt-2">Upload a screen recording to automatically generate structured data about user actions.</p>
          </header>

          <div 
            className={`bg-slate-800/50 rounded-2xl p-2 aspect-video flex-grow flex items-center justify-center ${coordinatePicker ? 'cursor-crosshair' : ''}`}
          >
            {videoSrc ? (
              <VideoPlayer 
                src={videoSrc} 
                ref={videoRef}
                highlightPoint={highlightPoint}
                onVideoClick={handleVideoClick}
              />
            ) : (
              <VideoUploader onVideoSelect={handleVideoUpload} />
            )}
          </div>

          {videoFile && (
            <button
              onClick={handleGenerate}
              disabled={isLoading || videoDuration === 0}
              className="w-full flex items-center justify-center gap-3 bg-indigo-600 hover:bg-indigo-500 disabled:bg-indigo-800 disabled:text-slate-400 disabled:cursor-not-allowed text-white font-bold py-3 px-4 rounded-xl transition-all duration-300 text-lg shadow-lg shadow-indigo-900/50"
            >
              <WandSparkles className="w-6 h-6" />
              {isLoading ? 'Generating...' : (videoDuration === 0 ? 'Reading Video...' : 'Generate Action Data')}
            </button>
          )}
        </div>

        {/* Right Column: Results */}
        <div className="bg-slate-800 rounded-2xl lg:h-[calc(100vh-4rem)] flex flex-col">
          <ResultsDisplay
            vlaData={vlaData}
            isLoading={isLoading}
            loadingMessage={loadingMessage}
            error={error}
            hasVideo={!!videoFile}
            videoDuration={videoDuration}
            totalFrames={totalFrames}
            usedFallback={usedFallback}
            onDownload={handleDownload}
            onSeekToTime={handleSeekToTime}
            onUpdateInteraction={handleUpdateInteraction}
            onHighlightPoint={handleHighlightPoint}
            onSetCoordinatePicker={handleSetCoordinatePicker}
          />
        </div>
      </main>
    </div>
  );
}