import 'dart:async';

import 'package:build/build.dart';
import 'package:yaml/yaml.dart';

/// Builder that generates version.g.dart from pubspec.yaml.
Builder versionBuilder(BuilderOptions options) => VersionBuilder();

class VersionBuilder implements Builder {
  @override
  final buildExtensions = const {
    r'$package$': ['lib/version.g.dart'],
  };

  @override
  Future<void> build(BuildStep buildStep) async {
    final pubspecId = AssetId(buildStep.inputId.package, 'pubspec.yaml');
    final pubspecContent = await buildStep.readAsString(pubspecId);
    final pubspec = loadYaml(pubspecContent) as YamlMap;

    final name = pubspec['name'] as String;
    final description = pubspec['description'] as String? ?? '';
    final versionString = pubspec['version'] as String;

    // Parse version: "0.2.0+2" -> version="0.2.0", buildNumber=2
    final versionParts = versionString.split('+');
    final version = versionParts[0];
    final buildNumber = versionParts.length > 1 ? int.parse(versionParts[1]) : 0;

    final output = '''
// GENERATED FILE - DO NOT EDIT
// Generated by build_runner from pubspec.yaml

/// Application version information from pubspec.yaml
class AppVersion {
  AppVersion._();

  static const String name = '$name';
  static const String description = '$description';
  static const String version = '$version';
  static const int buildNumber = $buildNumber;
  static const String fullVersion = '$version+$buildNumber';
}
''';

    final outputId = AssetId(buildStep.inputId.package, 'lib/version.g.dart');
    await buildStep.writeAsString(outputId, output);
  }
}