import 'dart:io';
import 'dart:typed_data';

import 'package:image/image.dart' as img;
import 'package:injectable/injectable.dart';

import 'image_resizer.dart';

@singleton
class LvglImageConverter {
  final ImageResizer _imageResizer;

  LvglImageConverter(this._imageResizer);
  static const int _magic = 0x19;
  static const int _colorFormatRgb565 = 0x12;
  static const int _flags = 0x00;

  int _toRgb565(int r, int g, int b) {
    return ((r & 0xF8) << 8) | ((g & 0xFC) << 3) | (b >> 3);
  }

  Future<void> convertPngToBin(String imagePath, String binPath) async {
    final imageFile = File(imagePath);
    if (!await imageFile.exists()) {
      throw FileSystemException('Image file not found', imagePath);
    }

    final bytes = await imageFile.readAsBytes();
    var image = img.decodeImage(bytes);
    if (image == null) {
      throw FormatException('Failed to decode image: $imagePath');
    }

    image = _imageResizer.resizeToFit(image);

    final w = image.width;
    final h = image.height;
    final stride = (w * 16 + 7) ~/ 8;

    final header = ByteData(12);
    header.setUint8(0, _magic);
    header.setUint8(1, _colorFormatRgb565);
    header.setUint16(2, _flags, Endian.little);
    header.setUint16(4, w, Endian.little);
    header.setUint16(6, h, Endian.little);
    header.setUint16(8, stride, Endian.little);
    header.setUint16(10, 0, Endian.little); // reserved

    final body = ByteData(w * h * 2);
    var offset = 0;
    for (var y = 0; y < h; y++) {
      for (var x = 0; x < w; x++) {
        final pixel = image.getPixel(x, y);
        final rgb565 = _toRgb565(pixel.r.toInt(), pixel.g.toInt(), pixel.b.toInt());
        body.setUint16(offset, rgb565, Endian.little);
        offset += 2;
      }
    }

    final binFile = File(binPath);
    await binFile.parent.create(recursive: true);
    await binFile.writeAsBytes([
      ...header.buffer.asUint8List(),
      ...body.buffer.asUint8List(),
    ]);
  }
}