import 'dart:async';

import 'package:universal_html/html.dart' as html;


class PickedCsvFile {
  final String name;
  final String content;

  const PickedCsvFile({required this.name, required this.content});
}

abstract class CsvInputService {
  Future<PickedCsvFile?> pickCsv();
}

class WebCsvInputService implements CsvInputService {
  @override
  Future<PickedCsvFile?> pickCsv() async {
    final input = html.FileUploadInputElement()
      ..accept = '.csv,text/csv'
      ..multiple = false;

    final completer = Completer<html.File?>();
    input.onChange.listen((_) {
      completer.complete(
        input.files?.isNotEmpty == true ? input.files!.first : null,
      );
    });
    input.click();

    final file = await completer.future;
    if (file == null) return null;

    final reader = html.FileReader();
    final readCompleter = Completer<String>();
    reader.onError.listen((_) {
      readCompleter.completeError(StateError('Failed to read file'));
    });
    reader.onLoadEnd.listen((_) {
      final result = reader.result;
      if (result is String) {
        readCompleter.complete(result);
      } else {
        readCompleter.completeError(StateError('Unsupported file payload'));
      }
    });
    reader.readAsText(file);

    final content = await readCompleter.future;
    return PickedCsvFile(name: file.name, content: content);
  }
}