import 'dart:io';
import 'dart:math';
import 'dart:ui';
import 'package:flutter/services.dart';
import 'package:flutter/foundation.dart';
import 'package:image/image.dart' as img;
import 'package:image_picker/image_picker.dart';
import 'package:tflite_flutter/tflite_flutter.dart';
import 'package:camera/camera.dart';

/// A detection result parsed from the model's end-to-end output.
class DetectionResult {
  final String className;
  final int classIndex;
  final double confidence;
  /// Normalized bounding box (0.0 - 1.0)
  final Rect normalizedBox;

  const DetectionResult({
    required this.className,
    required this.classIndex,
    required this.confidence,
    required this.normalizedBox,
  });

  Color getStatusColor() {
    if (className == 'Empty_Bunch' || className == 'Abnormal') return const Color(0xFFF44336); // Colors.red
    if (className == 'Ripe' || className == 'Overripe') return const Color(0xFF4CAF50); // Colors.green
    return const Color(0xFFFF9800); // Colors.orange
  }
}

/// Custom TFLite inference service that correctly decodes the end-to-end
/// YOLO model output format [1, N, 6] = [batch, detections, (x1,y1,x2,y2,conf,class_id)].
class TfliteService {
  static const _modelAsset = 'best.tflite';
  static const _labelsAsset = 'labels.txt';
  static const int _inputSize = 640;
  static const double _confidenceThreshold = 0.25;

  Interpreter? _interpreter;
  List<String> _labels = [];
  final ImagePicker _picker = ImagePicker();
  bool _isInitialized = false;

  bool get isInitialized => _isInitialized;

  Future<void> initModel() async {
    try {
      // Load labels
      final labelData = await rootBundle.loadString('assets/$_labelsAsset');
      _labels = labelData.split('\n').where((l) => l.trim().isNotEmpty).map((l) => l.trim()).toList();

      // Load model
      final interpreterOptions = InterpreterOptions()..threads = 4;
      _interpreter = await Interpreter.fromAsset(
        'assets/$_modelAsset',
        options: interpreterOptions,
      );

      _isInitialized = true;
      print('TfliteService: Model loaded. Labels: $_labels');
      print('TfliteService: Input: ${_interpreter!.getInputTensors().map((t) => t.shape)}');
      print('TfliteService: Output: ${_interpreter!.getOutputTensors().map((t) => t.shape)}');
    } catch (e) {
      print('TfliteService init error: $e');
      rethrow;
    }
  }

  Future<XFile?> pickImage() async {
    return await _picker.pickImage(
      source: ImageSource.gallery,
      maxWidth: _inputSize.toDouble(),
      maxHeight: _inputSize.toDouble(),
    );
  }

  /// Run inference on the image at [imagePath].
  /// Returns a list of [DetectionResult] sorted by confidence descending.
  /// Offloaded to a background isolate to keep UI smooth.
  Future<List<DetectionResult>> runInference(String imagePath) async {
    if (!_isInitialized) await initModel();

    final imageBytes = await File(imagePath).readAsBytes();
    
    // We pass the raw bytes and asset paths to the isolate.
    // The isolate will handle decoding, resizing, and inference.
    return await _runInferenceInIsolate(imageBytes);
  }

  /// Run inference on a [CameraImage] from the stream.
  /// Throttled by the caller.
  Future<List<DetectionResult>> runInferenceOnStream(CameraImage image) async {
    if (!_isInitialized) await initModel();

    // We pass the CameraImage planes to the isolate for conversion and inference.
    return await compute(_inferenceStreamTaskWrapper, {
      'planes': image.planes.map((p) => {
        'bytes': p.bytes,
        'bytesPerRow': p.bytesPerRow,
        'bytesPerPixel': p.bytesPerPixel,
      }).toList(),
      'width': image.width,
      'height': image.height,
      'format': image.format.group,
      'modelBytes': (await rootBundle.load('assets/$_modelAsset')).buffer.asUint8List(),
      'labelData': await rootBundle.loadString('assets/$_labelsAsset'),
    });
  }

  static List<DetectionResult> _inferenceStreamTaskWrapper(Map<String, dynamic> args) {
    final modelBytes = args['modelBytes'] as Uint8List;
    final labelData = args['labelData'] as String;
    final planes = args['planes'] as List<dynamic>;
    final width = args['width'] as int;
    final height = args['height'] as int;
    
    final interpreter = Interpreter.fromBuffer(modelBytes);
    final labels = labelData.split('\n').where((l) => l.trim().isNotEmpty).map((l) => l.trim()).toList();

    try {
      final size = width < height ? width : height;
      final offsetX = (width - size) ~/ 2;
      final offsetY = (height - size) ~/ 2;

      img.Image? image;
      if (args['format'] == ImageFormatGroup.yuv420) {
        image = _convertYUV420ToImage(
          planes: planes,
          width: width,
          height: height,
          cropSize: size,
          offsetX: offsetX,
          offsetY: offsetY,
        );
      } else if (args['format'] == ImageFormatGroup.bgra8888) {
        final fullImage = img.Image.fromBytes(
          width: width,
          height: height,
          bytes: planes[0]['bytes'].buffer,
          format: img.Format.uint8,
          numChannels: 4,
          order: img.ChannelOrder.bgra,
        );
        image = img.copyCrop(fullImage, x: offsetX, y: offsetY, width: size, height: size);
      }

      if (image == null) return [];

      // Resize and Run
      final resized = img.copyResize(image, width: _inputSize, height: _inputSize);
      
      final inputTensor = List.generate(1, (_) =>
        List.generate(_inputSize, (y) =>
          List.generate(_inputSize, (x) {
            final pixel = resized.getPixel(x, y);
            return [pixel.r / 255.0, pixel.g / 255.0, pixel.b / 255.0];
          })
        )
      );

      final outputShape = interpreter.getOutputTensors()[0].shape;
      final outputTensor = List.generate(1, (_) =>
        List.generate(outputShape[1], (_) =>
          List<double>.filled(outputShape[2], 0.0)
        )
      );

      interpreter.run(inputTensor, outputTensor);
      
      // Map detections back to full frame
      return _decodeDetections(
        outputTensor[0], 
        labels, 
        cropSize: size, 
        offsetX: offsetX, 
        offsetY: offsetY, 
        fullWidth: width, 
        fullHeight: height
      );
    } finally {
      interpreter.close();
    }
  }

  static img.Image _convertYUV420ToImage({
    required List<dynamic> planes,
    required int width,
    required int height,
    required int cropSize,
    required int offsetX,
    required int offsetY,
  }) {
    final yPlane = planes[0];
    final uPlane = planes[1];
    final vPlane = planes[2];

    final yBytes = yPlane['bytes'] as Uint8List;
    final uBytes = uPlane['bytes'] as Uint8List;
    final vBytes = vPlane['bytes'] as Uint8List;

    final yRowStride = yPlane['bytesPerRow'] as int;
    final uvRowStride = uPlane['bytesPerRow'] as int;
    final uvPixelStride = uPlane['bytesPerPixel'] as int;

    final image = img.Image(width: cropSize, height: cropSize);

    for (int y = 0; y < cropSize; y++) {
      for (int x = 0; x < cropSize; x++) {
        final int actualX = x + offsetX;
        final int actualY = y + offsetY;

        final int uvIndex = (uvRowStride * (actualY / 2).floor()) + (uvPixelStride * (actualX / 2).floor());
        final int yIndex = (actualY * yRowStride) + actualX;

        // Ensure we don't go out of bounds
        if (yIndex >= yBytes.length || uvIndex >= uBytes.length || uvIndex >= vBytes.length) continue;

        final int yp = yBytes[yIndex];
        final int up = uBytes[uvIndex];
        final int vp = vBytes[uvIndex];

        // Standard YUV to RGB conversion
        int r = (yp + (1.370705 * (vp - 128))).toInt().clamp(0, 255);
        int g = (yp - (0.337633 * (up - 128)) - (0.698001 * (vp - 128))).toInt().clamp(0, 255);
        int b = (yp + (1.732446 * (up - 128))).toInt().clamp(0, 255);

        image.setPixelRgb(x, y, r, g, b);
      }
    }
    return image;
  }

  static List<DetectionResult> _decodeDetections(
    List<List<double>> rawDetections, 
    List<String> labels, {
    int? cropSize,
    int? offsetX,
    int? offsetY,
    int? fullWidth,
    int? fullHeight,
  }) {
    final detections = <DetectionResult>[];
    for (final det in rawDetections) {
      if (det.length < 6) continue;
      final conf = det[4];
      if (conf < _confidenceThreshold) continue;

      double x1 = det[0].clamp(0.0, 1.0);
      double y1 = det[1].clamp(0.0, 1.0);
      double x2 = det[2].clamp(0.0, 1.0);
      double y2 = det[3].clamp(0.0, 1.0);
      
      // If crop info is provided, map back to full frame
      if (cropSize != null && offsetX != null && offsetY != null && fullWidth != null && fullHeight != null) {
        x1 = (x1 * cropSize + offsetX) / fullWidth;
        x2 = (x2 * cropSize + offsetX) / fullWidth;
        y1 = (y1 * cropSize + offsetY) / fullHeight;
        y2 = (y2 * cropSize + offsetY) / fullHeight;
      }

      final classId = det[5].round();

      if (x2 <= x1 || y2 <= y1) continue;

      final label = (classId >= 0 && classId < labels.length) ? labels[classId] : 'Unknown';

      detections.add(DetectionResult(
        className: label,
        classIndex: classId,
        confidence: conf,
        normalizedBox: Rect.fromLTRB(x1, y1, x2, y2),
      ));
    }
    detections.sort((a, b) => b.confidence.compareTo(a.confidence));
    return detections;
  }

  Future<List<DetectionResult>> _runInferenceInIsolate(Uint8List imageBytes) async {
    // We need the model and labels passed as data
    final modelData = await rootBundle.load('assets/$_modelAsset');
    final labelData = await rootBundle.loadString('assets/$_labelsAsset');
    
    // Use compute to run in a real isolate
    return await compute(_inferenceTaskWrapper, {
      'imageBytes': imageBytes,
      'modelBytes': modelData.buffer.asUint8List(),
      'labelData': labelData,
    });
  }

  static List<DetectionResult> _inferenceTaskWrapper(Map<String, dynamic> args) {
    return _inferenceTask(
      args['imageBytes'] as Uint8List,
      args['modelBytes'] as Uint8List,
      args['labelData'] as String,
    );
  }

  /// The static task that runs in the background isolate
  static List<DetectionResult> _inferenceTask(Uint8List imageBytes, Uint8List modelBytes, String labelData) {
    // 1. Initialize Interpreter inside the isolate
    final interpreter = Interpreter.fromBuffer(modelBytes);
    final labels = labelData.split('\n').where((l) => l.trim().isNotEmpty).map((l) => l.trim()).toList();

    try {
      // 2. Preprocess image
      final decoded = img.decodeImage(imageBytes);
      if (decoded == null) throw Exception('Could not decode image');

      // Center-Square Crop
      final int width = decoded.width;
      final int height = decoded.height;
      final int size = width < height ? width : height;
      final int offsetX = (width - size) ~/ 2;
      final int offsetY = (height - size) ~/ 2;
      
      final cropped = img.copyCrop(decoded, x: offsetX, y: offsetY, width: size, height: size);
      final resized = img.copyResize(cropped, width: _inputSize, height: _inputSize, interpolation: img.Interpolation.linear);

      final inputTensor = List.generate(1, (_) =>
        List.generate(_inputSize, (y) =>
          List.generate(_inputSize, (x) {
            final pixel = resized.getPixel(x, y);
            return [pixel.r / 255.0, pixel.g / 255.0, pixel.b / 255.0];
          })
        )
      );

      // 3. Prepare output
      final outputShape = interpreter.getOutputTensors()[0].shape;
      final outputTensor = List.generate(1, (_) =>
        List.generate(outputShape[1], (_) =>
          List<double>.filled(outputShape[2], 0.0)
        )
      );

      // 4. Run
      interpreter.run(inputTensor, outputTensor);

      // Map detections back to full frame
      return _decodeDetections(
        outputTensor[0], 
        labels, 
        cropSize: size, 
        offsetX: offsetX, 
        offsetY: offsetY, 
        fullWidth: width, 
        fullHeight: height
      );
    } finally {
      interpreter.close();
    }
  }

  void dispose() {
    _interpreter?.close();
    _interpreter = null;
    _isInitialized = false;
  }
}