feat: Text encoding for BYHOUR, BYMINUTE, BYSECOND

lib/src/codecs/text/encoder.dart

@@ -120,7 +120,9 @@ class RecurrenceRuleToTextEncoder extends Converter<RecurrenceRule, String> {
         combination: input.hasByWeekDays
             ? ListCombination.disjunctive
             : ListCombination.conjunctiveShort,
-      ));
+      ))
+      // [at 8:00 & 12:00]
+      ..add(_formatByTime(input));
   }
 
   void _convertWeekly(RecurrenceRule input, StringBuffer output) {
@@ -137,7 +139,9 @@ class RecurrenceRuleToTextEncoder extends Converter<RecurrenceRule, String> {
         variant: input.hasBySetPositions
             ? InOnVariant.instanceOf
             : InOnVariant.simple,
-      ));
+      ))
+      // [at 8:00 & 12:00]
+      ..add(_formatByTime(input));
   }
 
   void _convertMonthly(RecurrenceRule input, StringBuffer output) {
@@ -176,7 +180,9 @@ class RecurrenceRuleToTextEncoder extends Converter<RecurrenceRule, String> {
         combination: input.hasByWeekDays
             ? ListCombination.disjunctive
             : ListCombination.conjunctiveShort,
-      ));
+      ))
+      // [at 8:00 & 12:00]
+      ..add(_formatByTime(input));
   }
 
   void _convertYearly(RecurrenceRule input, StringBuffer output) {
@@ -283,6 +289,8 @@ class RecurrenceRuleToTextEncoder extends Converter<RecurrenceRule, String> {
     if (limits.isNotEmpty) {
       output.add(l10n.list(limits, ListCombination.conjunctiveLong));
     }
+
+    output.add(_formatByTime(input));
   }
 
   String? _formatBySetPositions(RecurrenceRule input) {
@@ -378,6 +386,22 @@ class RecurrenceRuleToTextEncoder extends Converter<RecurrenceRule, String> {
       variant: variant,
     );
   }
+
+  String? _formatByTime(RecurrenceRule input) {
+    final byHours = input.hasByHours ? input.byHours : {null};
+    final byMinutes = input.hasByMinutes ? input.byMinutes : {null};
+    final bySeconds = input.hasBySeconds ? input.bySeconds : {null};
+
+    final timesOfDay = [
+      for (var hour in byHours)
+        for (var minute in byMinutes)
+          for (var second in bySeconds)
+            if (!(hour == null && minute == null && second == null))
+              l10n.timeOfDay(hour, minute, second)
+    ];
+
+    return timesOfDay.isEmpty ? null : l10n.atTimesOfDay(timesOfDay);
+  }
 }
 
 extension on StringBuffer {

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

@@ -181,4 +181,23 @@ class RruleL10nEn extends RruleL10n {
 
     return number < 0 ? '$string-to-last' : string;
   }
+
+  @override
+  String timeOfDay(int? hour, int? minute, int? second) {
+    final minutesFormat = NumberFormat('00');
+    final secondsFormat = minutesFormat;
+
+    final parts = [
+      if (hour != null) hour.toString(),
+      if (minute != null) ':${minutesFormat.format(minute)}',
+      if (minute == null && second != null) ':',
+      if (second != null) ':${secondsFormat.format(second)}'
+    ];
+    return parts.join();
+  }
+
+  @override
+  String atTimesOfDay(List<String> timesOfDay) {
+    return 'at ${list(timesOfDay, ListCombination.conjunctiveShort)}';
+  }
 }

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

@@ -103,6 +103,10 @@ abstract class RruleL10n {
   }
 
   String ordinal(int number);
+
+  String timeOfDay(int? hour, int? minute, int? second);
+
+  String atTimesOfDay(List<String> timesOfDay);
 }
 
 enum InOnVariant { simple, also, instanceOf }

lib/src/recurrence_rule.dart

@@ -363,13 +363,10 @@ class RecurrenceRule {
 
   /// Whether this rule can be converted to a human-readable string.
   ///
-  /// - Unsupported attributes: [bySeconds], [byMinutes], [byHours]
   /// - Unsupported frequencies (if any by-parts are specified):
   ///   [Frequency.secondly], [Frequency.hourly], [Frequency.daily]
   bool get canFullyConvertToText {
-    if (hasBySeconds || hasByMinutes || hasByHours) {
-      return false;
-    } else if (frequency <= Frequency.daily) {
+    if (frequency <= Frequency.daily) {
       return true;
     } else if (hasBySetPositions ||
         hasBySeconds ||

test/codecs/text/daily_test.dart

@@ -107,4 +107,20 @@ void main() {
     string:
         'RRULE:FREQ=DAILY;BYSETPOS=1,-2;BYMONTH=1,12;BYMONTHDAY=1,-1;BYDAY=MO,TH',
   );
+
+  // Time of day.
+
+  testText(
+    'Daily at 8:30 & 12:30',
+    string: 'RRULE:FREQ=DAILY;BYHOUR=8,12;BYMINUTE=30',
+  );
+
+  test('canConvertToText is true when byHours is specified', () async {
+    final rrule = RecurrenceRule(frequency: Frequency.daily, byHours: {8});
+    expect(rrule.canFullyConvertToText, isTrue);
+    expect(
+      rrule.toText(l10n: await RruleL10nEn.create()),
+      equals('Daily at 8'),
+    );
+  });
 }