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

import 'package:flutter/widgets.dart' show Size;
import 'package:image/image.dart' as img;

/// Görüntü dosyasının gerçek piksel boyutu — tam decode yapmadan.
///
/// PNG/GIF/BMP/WebP: boyut ilk 33 baytta → elle parse.
/// JPEG: SOF büyük APP/EXIF segmentlerinin ardından gelebilir → package:image startDecode.
Size? pixelSizeOfFile(String path) {
  try {
    final file = File(path);
    final stat = file.statSync();
    const maxHead = 512 * 1024;
    final raf = file.openSync();
    final header = raf.readSync(stat.size < maxHead ? stat.size : maxHead);
    raf.closeSync();
    return _headerPixelSize(header);
  } catch (_) {}
  return null;
}

Size? _headerPixelSize(Uint8List b) {
  try {
    if (b.length >= 24 && b[0] == 0x89 && b[1] == 0x50) {
      // PNG
      final w = (b[16] << 24) | (b[17] << 16) | (b[18] << 8) | b[19];
      final h = (b[20] << 24) | (b[21] << 16) | (b[22] << 8) | b[23];
      return Size(w.toDouble(), h.toDouble());
    }
    if (b.length >= 10 && b[0] == 0x47 && b[1] == 0x49 && b[2] == 0x46) {
      // GIF (WBMP da GIF tabanlı olabilir)
      final w = b[6] | (b[7] << 8);
      final h = b[8] | (b[9] << 8);
      return Size(w.toDouble(), h.toDouble());
    }
    if (b.length >= 26 && b[0] == 0x42 && b[1] == 0x4D) {
      // BMP
      final w = b[18] | (b[19] << 8) | (b[20] << 16) | (b[21] << 24);
      final h = b[22] | (b[23] << 8) | (b[24] << 16) | (b[25] << 24);
      return Size(w.toDouble(), h.abs().toDouble());
    }
    if (b.length >= 30 &&
        b[0] == 0x52 &&
        b[1] == 0x49 &&
        b[2] == 0x46 &&
        b[3] == 0x46 &&
        b[8] == 0x57 &&
        b[9] == 0x45 &&
        b[10] == 0x42 &&
        b[11] == 0x50) {
      // WebP
      if (b[12] == 0x56 && b[13] == 0x50 && b[15] == 0x58) {
        // VP8X
        final w = b[24] | (b[25] << 8) | (b[26] << 16);
        final h = b[27] | (b[28] << 8) | (b[29] << 16);
        return Size((w + 1).toDouble(), (h + 1).toDouble());
      }
      if (b.length >= 25 && b[12] == 0x56 && b[13] == 0x50 && b[15] == 0x4C && b[20] == 0x2F) {
        // VP8L
        final w = (b[21] & 0x3F) | ((b[22] & 0x0F) << 6);
        final h = (b[23] & 0x3F) | ((b[24] & 0x0F) << 6);
        return Size((w + 1).toDouble(), (h + 1).toDouble());
      }
      if (b[12] == 0x56 && b[13] == 0x50 && b[15] == 0x20) {
        // VP8 (lossy)
        final w = (b[26] | (b[27] << 8)) & 0x3FFF;
        final h = (b[28] | (b[29] << 8)) & 0x3FFF;
        return Size(w.toDouble(), h.toDouble());
      }
    }
  } catch (_) {}
  try {
    // JPEG
    final info = img.JpegDecoder().startDecode(b);
    if (info != null) return Size(info.width.toDouble(), info.height.toDouble());
  } catch (_) {}
  return null;
}