import 'dart:math' as math;
import 'dart:typed_data';
import 'dart:ui' as ui;

import 'package:file_selector/file_selector.dart';

class BauteilPhotoService {
  Future<Uint8List?> pickPhoto() async {
    const images = XTypeGroup(
      label: 'Fotos',
      extensions: ['jpg', 'jpeg', 'png', 'webp'],
      uniformTypeIdentifiers: [
        'public.jpeg',
        'public.png',
        'org.webmproject.webp',
      ],
      mimeTypes: ['image/jpeg', 'image/png', 'image/webp'],
    );
    final file = await openFile(acceptedTypeGroups: [images]);
    if (file == null) return null;
    if (await file.length() > 15 * 1024 * 1024) {
      throw const FormatException('Das Foto darf höchstens 15 MB groß sein.');
    }
    return preparePhoto(await file.readAsBytes());
  }

  /// Stores a small, self-contained PNG, independent of temporary file paths.
  Future<Uint8List> preparePhoto(Uint8List bytes) async {
    final buffer = await ui.ImmutableBuffer.fromUint8List(bytes);
    try {
      final descriptor = await ui.ImageDescriptor.encoded(buffer);
      try {
        final scale = math.min(
          1.0,
          960 / math.max(descriptor.width, descriptor.height),
        );
        final codec = await descriptor.instantiateCodec(
          targetWidth: math.max(1, (descriptor.width * scale).round()),
          targetHeight: math.max(1, (descriptor.height * scale).round()),
        );
        try {
          final frame = await codec.getNextFrame();
          try {
            final data = await frame.image.toByteData(
              format: ui.ImageByteFormat.png,
            );
            if (data == null) {
              throw const FormatException('Foto konnte nicht gelesen werden.');
            }
            return data.buffer.asUint8List(
              data.offsetInBytes,
              data.lengthInBytes,
            );
          } finally {
            frame.image.dispose();
          }
        } finally {
          codec.dispose();
        }
      } finally {
        descriptor.dispose();
      }
    } finally {
      buffer.dispose();
    }
  }
}