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

import 'package:file_selector/file_selector.dart';

import 'package:image/image.dart' as metadata;

import '../models/identity.dart';
import 'contracts.dart';

class FilePhotoService implements PhotoService {
  const FilePhotoService();
  static const maxBytes = 10 * 1024 * 1024;
  @override
  Future<Photo?> pick() async {
    try {
      final file = await openFile(
        acceptedTypeGroups: const [
          XTypeGroup(
            label: 'JPEG / PNG',
            extensions: ['jpg', 'jpeg', 'png'],
            mimeTypes: ['image/jpeg', 'image/png'],
            uniformTypeIdentifiers: ['public.jpeg', 'public.png'],
          ),
        ],
      );
      if (file == null) return null;
      if (await file.length() > maxBytes)
        throw const KycException(KycError.tooLarge);
      final bytes = await file.readAsBytes();
      return await validate(bytes);
    } on KycException {
      rethrow;
    } catch (_) {
      throw const KycException(KycError.permission);
    }
  }

  static Future<Photo> validate(Uint8List bytes) async {
    try {
      if (bytes.length > maxBytes) throw const KycException(KycError.tooLarge);
      final png =
          bytes.length > 8 &&
          bytes[0] == 137 &&
          bytes[1] == 80 &&
          bytes[2] == 78 &&
          bytes[3] == 71;
      final jpg =
          bytes.length > 3 &&
          bytes[0] == 255 &&
          bytes[1] == 216 &&
          bytes[2] == 255;
      if (!png && !jpg) throw const KycException(KycError.format);
      final metadata.Decoder decoder = png
          ? metadata.PngDecoder()
          : metadata.JpegDecoder();
      final info = decoder.startDecode(bytes);
      if (info == null) throw const KycException(KycError.unreadable);
      if (info.width < 600 || info.height < 600)
        throw const KycException(KycError.tooSmall);
      if (info.width * info.height > 40000000)
        throw const KycException(KycError.tooLarge);
      final codec = await ui.instantiateImageCodec(
        bytes,
        targetWidth: 1000,
        allowUpscaling: false,
      );
      try {
        final frame = await codec.getNextFrame();
        frame.image.dispose();
      } finally {
        codec.dispose();
      }
      return Photo(bytes);
    } on KycException {
      rethrow;
    } catch (_) {
      throw const KycException(KycError.unreadable);
    }
  }
}