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

import 'package:file_picker/file_picker.dart';

/// Picks a photo from the device and returns it as a small PNG data URI,
/// ready to store as a profile `pic`. Null when nothing was picked or the
/// file was not an image.
class PhotoPicker {
  /// Long edge of the stored portrait. Big enough for the largest avatar on
  /// a 3x screen, small enough to keep in local storage.
  static const int _edge = 256;

  static Future<String?> pickPortrait() async {
    final FilePickerResult? result =
        await FilePicker.pickFiles(type: FileType.image, withData: true);
    final Uint8List? bytes = result == null || result.files.isEmpty
        ? null
        : result.files.first.bytes;
    if (bytes == null) {
      return null;
    }

    try {
      final ui.Codec codec = await ui.instantiateImageCodec(bytes,
          targetWidth: _edge, targetHeight: null);
      final ui.FrameInfo frame = await codec.getNextFrame();
      final ByteData? png =
          await frame.image.toByteData(format: ui.ImageByteFormat.png);
      if (png == null) {
        return null;
      }
      return "data:image/png;base64,${base64Encode(png.buffer.asUint8List())}";
    } catch (e) {
      return null;
    }
  }
}