feat: add appstream service

lib/appstream.dart

@@ -0,0 +1,2 @@
+export 'src/appstream/appstream_service.dart';
+export 'src/appstream/appstream_utils.dart';

lib/src/appstream/appstream_service.dart

@@ -0,0 +1,227 @@
+import 'dart:collection';
+
+import 'package:appstream/appstream.dart';
+import 'package:flutter/foundation.dart';
+import 'package:snowball_stemmer/snowball_stemmer.dart';
+
+import '/l10n.dart';
+import 'appstream_utils.dart';
+
+extension _Tokenizer on String {
+  List<String> tokenize() => split(RegExp('\\W'));
+}
+
+class _CachedComponent {
+  final AppstreamComponent component;
+  final String id;
+  late String name;
+  late List<String> keywords;
+  late List<String> summary;
+  late List<String> description;
+  late String origin;
+  late String package;
+  late List<String> mediaTypes;
+
+  _CachedComponent(this.component) : id = component.id.toLowerCase() {
+    name = _getLocalizedComponentAttribute(component.name)?.toLowerCase() ?? '';
+    keywords = _getLocalizedComponentAttribute(component.keywords)
+            ?.map((e) => e.toLowerCase())
+            .toList() ??
+        [];
+    summary = _getLocalizedComponentAttribute(component.summary)
+            ?.toLowerCase()
+            .tokenize() ??
+        [];
+    description = _getLocalizedComponentAttribute(component.description)
+            ?.toLowerCase()
+            .tokenize() ??
+        [];
+    origin = ''; // XXX: https://github.com/canonical/appstream.dart/issues/25
+    package = component.package?.toLowerCase() ?? '';
+    mediaTypes = [];
+    for (final provider in component.provides) {
+      if (provider is AppstreamProvidesMediatype) {
+        mediaTypes.add(provider.mediaType.toLowerCase());
+      }
+    }
+  }
+
+  static T? _getLocalizedComponentAttribute<T>(Map<String, T> attribute) {
+    final languageKey = bestLanguageKey(attribute.keys);
+    if (languageKey == null) return null;
+    return attribute[languageKey];
+  }
+
+  int match(List<String> tokens) {
+    int score = _MatchScore.none.value;
+    for (final token in tokens) {
+      if (id.toLowerCase().contains(token)) {
+        score |= _MatchScore.id.value;
+      }
+      if (name.contains(token)) {
+        score |= _MatchScore.name.value;
+      }
+      if (keywords.contains(token)) {
+        score |= _MatchScore.keyword.value;
+      }
+      if (summary.contains(token)) {
+        score |= _MatchScore.summary.value;
+      }
+      if (description.contains(token)) {
+        score |= _MatchScore.description.value;
+      }
+      if (origin.contains(token)) {
+        score |= _MatchScore.origin.value;
+      }
+      if (package.contains(token)) {
+        score |= _MatchScore.pkgName.value;
+      }
+      if (mediaTypes.any((e) => e.contains(token))) {
+        score |= _MatchScore.mediaType.value;
+      }
+      if (score == _MatchScore.all.value) break;
+    }
+    return score;
+  }
+
+  @override
+  bool operator ==(Object other) =>
+      other is _CachedComponent && component.id == other.component.id;
+
+  @override
+  int get hashCode => component.id.hashCode;
+}
+
+enum _MatchScore {
+  none(0),
+  mediaType(1 << 0),
+  pkgName(1 << 1),
+  origin(1 << 2),
+  description(1 << 3),
+  summary(1 << 4),
+  keyword(1 << 5),
+  name(1 << 6),
+  id(1 << 7),
+  all(1 << 0 | 1 << 1 | 1 << 2 | 1 << 3 | 1 << 4 | 1 << 5 | 1 << 6 | 1 << 7);
+
+  final int value;
+  const _MatchScore(this.value);
+}
+
+class _ScoredComponent {
+  final int score;
+  final AppstreamComponent component;
+  const _ScoredComponent(this.score, this.component);
+}
+
+class AppstreamService {
+  final AppstreamPool _pool;
+  late final Future<void> _loader = _pool.load().then((_) => _populateCache());
+
+  // TODO: cache AppstreamPool
+  AppstreamService({@visibleForTesting AppstreamPool? pool})
+      : _pool = pool ?? AppstreamPool() {
+    PlatformDispatcher.instance.onLocaleChanged = () async {
+      await _loader;
+      _populateCache();
+    };
+  }
+
+  final HashSet<_CachedComponent> _cache = HashSet<_CachedComponent>();
+  @visibleForTesting
+  int get cacheSize => _cache.length;
+
+  void _populateCache() {
+    _cache.clear();
+    for (final component in _pool.components) {
+      _cache.add(_CachedComponent(component));
+    }
+  }
+
+  List<String> get _greylist =>
+      lookupAppLocalizations(PlatformDispatcher.instance.locale)
+          .appstreamSearchGreylist
+          .split(';');
+
+  Future<void> init() async => _loader;
+
+  static final stemmersMap = <String, Algorithm>{
+    'ar': Algorithm.arabic,
+    'hy': Algorithm.armenian,
+    'eu': Algorithm.basque,
+    'ca': Algorithm.catalan,
+    'da': Algorithm.danish,
+    'nl': Algorithm.dutch,
+    'en': Algorithm.english,
+    'fi': Algorithm.finnish,
+    'fr': Algorithm.french,
+    'de': Algorithm.german,
+    'el': Algorithm.greek,
+    'hi': Algorithm.hindi,
+    'hu': Algorithm.hungarian,
+    'id': Algorithm.indonesian,
+    'ga': Algorithm.irish,
+    'it': Algorithm.italian,
+    'lt': Algorithm.lithuanian,
+    'ne': Algorithm.nepali,
+    'nb': Algorithm.norwegian,
+    'pt': Algorithm.portuguese,
+    'ro': Algorithm.romanian,
+    'ru': Algorithm.russian,
+    'sr': Algorithm.serbian,
+    'es': Algorithm.spanish,
+    'sv': Algorithm.swedish,
+    'ta': Algorithm.tamil,
+    'tr': Algorithm.turkish,
+    'yi': Algorithm.yiddish,
+  };
+
+  // Re-implementation of as_pool_build_search_tokens()
+  // (https://www.freedesktop.org/software/appstream/docs/api/appstream-AsPool.html#as-pool-build-search-tokens)
+  List<String> _buildSearchTokens(String search) {
+    final words = search.toLowerCase().split(RegExp(r'\s'));
+    // Filter out too generic search terms
+    words.removeWhere((element) => _greylist.contains(element));
+    if (words.isEmpty) {
+      words.addAll(search.toLowerCase().split(RegExp(r'\s')));
+    }
+    // Filter out short tokens, and those containing markup
+    words.removeWhere(
+      (element) => element.length <= 1 || element.contains(RegExp(r'[<>()]')),
+    );
+    // Extract only the common stems from the tokens
+    final algorithm =
+        stemmersMap[PlatformDispatcher.instance.locale.languageCode];
+    if (algorithm != null) {
+      final stemmer = SnowballStemmer(algorithm);
+      return words.map((element) => stemmer.stem(element)).toSet().toList();
+    } else {
+      return words;
+    }
+  }
+
+  // Re-implementation of as_pool_search()
+  // (https://www.freedesktop.org/software/appstream/docs/api/appstream-AsPool.html#as-pool-search)
+  Future<List<AppstreamComponent>> search(String search) async {
+    final tokens = _buildSearchTokens(search);
+    await _loader;
+    if (tokens.isEmpty) {
+      if (search.length <= 1) {
+        // Search query too broad, matching everything
+        return _pool.components;
+      } else {
+        // No valid search tokens
+        return [];
+      }
+    }
+    final scored = <_ScoredComponent>[];
+    for (final entry in _cache) {
+      final score = entry.match(tokens);
+      if (score > 0) {
+        scored.add(_ScoredComponent(score, entry.component));
+      }
+    }
+    scored.sort((a, b) => b.score.compareTo(a.score));
+    return scored.map((e) => e.component).toList();
+  }
+}

lib/src/appstream/appstream_utils.dart

@@ -0,0 +1,66 @@
+import 'dart:io';
+import 'dart:ui';
+
+import 'package:appstream/appstream.dart';
+import 'package:collection/collection.dart';
+
+// TODO: uncomment once we re-add packagekit
+// import 'package:packagekit/packagekit.dart';
+// import 'package:ubuntu_service/ubuntu_service.dart';
+
+String? bestLanguageKey(Iterable<String> keys, {Locale? locale}) {
+  locale ??= PlatformDispatcher.instance.locale;
+  if (locale.toLanguageTag() != 'und') {
+    var key = '${locale.languageCode}_${locale.countryCode}';
+    if (keys.contains(key)) return key;
+    key = locale.languageCode;
+    if (keys.contains(key)) return key;
+  }
+  const fallback = 'C';
+  if (keys.contains(fallback)) return fallback;
+  return null;
+}
+
+extension LocalizedComponent on AppstreamComponent {
+  String localizedName({Locale? locale}) =>
+      name[bestLanguageKey(name.keys, locale: locale)] ?? '';
+  String localizedSummary({Locale? locale}) =>
+      summary[bestLanguageKey(summary.keys, locale: locale)] ?? '';
+  String localizedDescription({Locale? locale}) =>
+      description[bestLanguageKey(description.keys, locale: locale)] ?? '';
+}
+
+// TODO: uncomment once we re-add packagekit
+// extension PackageKitId on AppstreamComponent {
+//   Future<PackageKitPackageId> get packageKitId =>
+//       getService<PackageService>().resolve(package ?? id);
+// }
+
+int _sizeComparison(int? a, int? b) => a?.compareTo(b ?? 0) ?? 0;
+
+extension Icons on AppstreamComponent {
+  String? get icon {
+    final cached = icons.whereType<AppstreamCachedIcon>().toList();
+    cached.sort((a, b) => _sizeComparison(b.width, a.width));
+    //for (final icon in cached) {
+    //  XXX: we need the origin to determine if a cached icon exists on disk
+    //  (https://github.com/canonical/appstream.dart/issues/25)
+    //}
+
+    final local = icons.whereType<AppstreamLocalIcon>().toList();
+    local.sort((a, b) => _sizeComparison(b.width, a.width));
+    for (final icon in local) {
+      if (File(icon.filename).existsSync()) {
+        return icon.filename;
+      }
+    }
+
+    final stock = icons.whereType<AppstreamStockIcon>().firstOrNull;
+    if (stock != null) {
+      // TODO: check whether the stock icon exists on disk, and return it
+    }
+
+    final remote = icons.whereType<AppstreamRemoteIcon>().firstOrNull;
+    return remote?.url;
+  }
+}

lib/src/l10n/app_en.arb

@@ -1,4 +1,5 @@
 {
+    "appstreamSearchGreylist": "app;application;package;program;programme;suite;tool",
     "detailPageChannelLabel": "Channel",
     "detailPageConfinementLabel": "Confinement",
     "detailPageContactPublisherLabel": "Contact {publisher}",

pubspec.yaml

@@ -8,6 +8,7 @@ environment:
   flutter: '^3.10.6'
 
 dependencies:
+  appstream: ^0.2.8
   args: ^2.4.2
   cached_network_image: ^3.2.3
   collection: ^1.17.0
@@ -30,6 +31,7 @@ dependencies:
   shimmer: ^3.0.0
   snapcraft_launcher: ^0.1.0
   snapd: ^0.4.11
+  snowball_stemmer: ^0.1.0
   ubuntu_localizations: ^0.3.3
   ubuntu_service: ^0.2.2
   ubuntu_test: ^0.1.0-0