Initial project import

2026-07-24 23:11:20 +08:00
commit 6396eabb87
372 changed files with 49682 additions and 0 deletions
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+class ShanghaiTime {
+  ShanghaiTime._();
+
+  static const offset = Duration(hours: 8);
+
+  /// A device-timezone-independent civil clock for Asia/Shanghai.
+  static DateTime get now => toCivil(DateTime.now());
+
+  static DateTime toCivil(DateTime instant) {
+    final shifted = instant.toUtc().add(offset);
+    return DateTime(
+      shifted.year,
+      shifted.month,
+      shifted.day,
+      shifted.hour,
+      shifted.minute,
+      shifted.second,
+      shifted.millisecond,
+      shifted.microsecond,
+    );
+  }
+
+  static DateTime civilToUtc(DateTime civil) => DateTime.utc(
+    civil.year,
+    civil.month,
+    civil.day,
+    civil.hour,
+    civil.minute,
+    civil.second,
+    civil.millisecond,
+    civil.microsecond,
+  ).subtract(offset);
+
+  /// Parses API/cache instants. Legacy values without a zone were stored as UTC.
+  static DateTime parseUtcInstant(String value) {
+    final parsed = DateTime.parse(value);
+    if (value.endsWith('Z') || RegExp(r'[+-]\d{2}:?\d{2}$').hasMatch(value)) {
+      return parsed.toUtc();
+    }
+    return DateTime.utc(
+      parsed.year,
+      parsed.month,
+      parsed.day,
+      parsed.hour,
+      parsed.minute,
+      parsed.second,
+      parsed.millisecond,
+      parsed.microsecond,
+    );
+  }
+
+  static DateTime parseCivil(String value) => toCivil(parseUtcInstant(value));
+
+  static DateTime startOfDayUtc(DateTime civil) =>
+      civilToUtc(DateTime(civil.year, civil.month, civil.day));
+
+  static ({DateTime start, DateTime end}) monthRangeUtc(int year, int month) =>
+      (
+        start: civilToUtc(DateTime(year, month, 1)),
+        end: civilToUtc(DateTime(year, month + 1, 1)),
+      );
+
+  static ({DateTime start, DateTime end}) yearRangeUtc(int year) => (
+    start: civilToUtc(DateTime(year, 1, 1)),
+    end: civilToUtc(DateTime(year + 1, 1, 1)),
+  );
+
+  static ({DateTime start, DateTime end}) weekRangeUtc(DateTime civil) {
+    final date = DateTime(civil.year, civil.month, civil.day);
+    final start = date.subtract(Duration(days: date.weekday - DateTime.monday));
+    return (
+      start: civilToUtc(start),
+      end: civilToUtc(start.add(const Duration(days: 7))),
+    );
+  }
+
+  static String formatCivil(DateTime value) =>
+      '${value.year.toString().padLeft(4, '0')}-'
+      '${value.month.toString().padLeft(2, '0')}-'
+      '${value.day.toString().padLeft(2, '0')} '
+      '${value.hour.toString().padLeft(2, '0')}:'
+      '${value.minute.toString().padLeft(2, '0')}';
+
+  static String formatDateTime(DateTime instant) {
+    final value = toCivil(instant);
+    return formatCivil(value);
+  }
+}