feat: Add German localization

lib/src/codecs/text/l10n/de.dart

@@ -0,0 +1,166 @@
+import 'package:intl/date_symbol_data_local.dart';
+import 'package:intl/intl.dart';
+import 'package:meta/meta.dart';
+
+import '../../../frequency.dart';
+import 'l10n.dart';
+
+@immutable
+class RruleL10nDe extends RruleL10n {
+  const RruleL10nDe._();
+
+  static Future<RruleL10nDe> create() async {
+    // TODO(JonasWanke): Move `initializeDateFormatting(…)` call to the
+    // library's user
+    await initializeDateFormatting('de');
+    return const RruleL10nDe._();
+  }
+
+  @override
+  String get locale => 'de_DE';
+
+  @override
+  String frequencyInterval(Frequency frequency, int interval) {
+    String plurals({required String one, required String singular, required String plural}) {
+      return switch (interval) {
+        1 => one,
+        2 => singular,
+        _ => 'Alle $interval ${plural}',
+      };
+    }
+
+    return {
+      Frequency.secondly: plurals(one: 'Sekündlich', singular: 'Jede andere Sekunde', plural: 'Sekunden'),
+      Frequency.minutely: plurals(one: 'Minütlich', singular: 'Jede andere Minute', plural: 'Minuten'),
+      Frequency.hourly: plurals(one: 'Stündlich', singular: 'Jede andere Stunde', plural: 'Stunden'),
+      Frequency.daily: plurals(one: 'Täglich', singular: 'Jeden anderen Tag', plural: 'Tage'),
+      Frequency.weekly: plurals(one: 'Wöchentlich', singular: 'Jede andere Woche', plural: 'Wochen'),
+      Frequency.monthly: plurals(one: 'Monatlich', singular: 'Jeden anderen Monat', plural: 'Monate'),
+      Frequency.yearly: plurals(one: 'Jährlich', singular: 'Jedes andere Jahr', plural: 'Jahre'),
+    }[frequency]!;
+  }
+
+  @override
+  String until(DateTime until, Frequency frequency) {
+    final untilString =
+        formatWithIntl(() => DateFormat.yMMMMEEEEd().add_jms().format(until));
+    return ', bis $untilString';
+  }
+
+  @override
+  String count(int count) {
+    return switch (count) {
+      1 => ', ein Mal',
+      2 => ', zwei Mal',
+      _ => ', $count Mal',
+    };
+  }
+
+  @override
+  String onInstances(String instances) => 'an der $instances Instanz';
+
+  @override
+  String inMonths(String months, {InOnVariant variant = InOnVariant.simple}) =>
+      '${_inVariant(variant)} $months';
+
+  @override
+  String inWeeks(String weeks, {InOnVariant variant = InOnVariant.simple}) =>
+      '${_inVariant(variant)} der $weeks Woche des Jahres';
+
+  String _inVariant(InOnVariant variant) {
+    return switch (variant) {
+      InOnVariant.simple => 'in',
+      InOnVariant.also => 'auch in',
+      InOnVariant.instanceOf => 'von',
+    };
+  }
+
+  @override
+  String onDaysOfWeek(
+    String days, {
+    bool indicateFrequency = false,
+    DaysOfWeekFrequency? frequency = DaysOfWeekFrequency.monthly,
+    InOnVariant variant = InOnVariant.simple,
+  }) {
+    assert(variant != InOnVariant.also);
+
+    final frequencyString =
+        frequency == DaysOfWeekFrequency.monthly ? 'Monat' : 'Jahr';
+    final suffix = indicateFrequency ? ' von dem $frequencyString' : '';
+    return '${_onVariant(variant)} $days$suffix';
+  }
+
+  @override
+  String? get weekdaysString => 'Wochentage';
+  @override
+  String get everyXDaysOfWeekPrefix => 'jedem ';
+  @override
+  String nthDaysOfWeek(Iterable<int> occurrences, String daysOfWeek) {
+    if (occurrences.isEmpty) return daysOfWeek;
+
+    final ordinals = list(
+      occurrences.map(ordinal).toList(),
+      ListCombination.conjunctiveShort,
+    );
+    return 'dem $ordinals $daysOfWeek';
+  }
+
+  @override
+  String onDaysOfMonth(
+    String days, {
+    DaysOfVariant daysOfVariant = DaysOfVariant.dayAndFrequency,
+    InOnVariant variant = InOnVariant.simple,
+  }) {
+    final suffix = {
+      DaysOfVariant.simple: '',
+      DaysOfVariant.day: ' Tag',
+      DaysOfVariant.dayAndFrequency: ' Tag des Monats',
+    }[daysOfVariant];
+    return '${_onVariant(variant)} dem $days$suffix';
+  }
+
+  @override
+  String onDaysOfYear(
+    String days, {
+    InOnVariant variant = InOnVariant.simple,
+  }) =>
+      '${_onVariant(variant)} dem $days Tag des Jahres';
+
+  String _onVariant(InOnVariant variant) {
+    return switch (variant) {
+      InOnVariant.simple => 'an',
+      InOnVariant.also => 'sowie auch',
+      InOnVariant.instanceOf => 'von',
+    };
+  }
+
+  @override
+  String list(List<String> items, ListCombination combination) {
+    final (two, end) = switch (combination) {
+      ListCombination.conjunctiveShort => (' & ', ' & '),
+      ListCombination.conjunctiveLong => (' und ', ', und '),
+      ListCombination.disjunctive => (' oder ', ', oder '),
+    };
+    return RruleL10n.defaultList(items, two: two, end: end);
+  }
+
+  @override
+  String ordinal(int number) {
+    assert(number != 0);
+    if (number == -1) return 'letzten';
+
+    final n = number.abs();
+    String string;
+    if (n == 1 ) {
+      string = 'ersten';
+    } else if (n == 2 ) {
+      string = 'zweiten';
+    } else if (n == 3 ) {
+      string = 'vierten';
+    } else {
+      string = '${n}.';
+    }
+
+    return number < 0 ? '$string vorherigen' : string;
+  }
+}

lib/src/codecs/text/l10n/l10n.dart

@@ -8,6 +8,7 @@ import 'en.dart';
 
 export 'en.dart';
 export 'nl.dart';
+export 'de.dart';
 
 /// Contains localized strings used by [RecurrenceRule.toText].
 ///
@@ -34,12 +35,12 @@ abstract class RruleL10n {
   String inWeeks(String weeks, {InOnVariant variant = InOnVariant.simple});
 
   Set<int> get weekdays => {
-        DateTime.monday,
-        DateTime.tuesday,
-        DateTime.wednesday,
-        DateTime.thursday,
-        DateTime.friday,
-      };
+    DateTime.monday,
+    DateTime.tuesday,
+    DateTime.wednesday,
+    DateTime.thursday,
+    DateTime.friday,
+  };
   String onDaysOfWeek(
     String days, {
     bool indicateFrequency = false,