hamed/add_sync_time_cubit (#222)

- add sync time cubit

Author: hamed-rezaee

lib/state/sync_time/sync_time_cubit.dart

@@ -0,0 +1,60 @@
+import 'dart:async';
+
+import 'package:bloc/bloc.dart';
+
+import 'package:flutter_deriv_api/api/response/time_response_result.dart';
+import 'package:flutter_deriv_api/state/server_time/server_time_cubit.dart';
+
+part 'sync_time_state.dart';
+
+/// Sync time cubit.
+class SyncTimeCubit extends Cubit<SyncTimeState> {
+  /// Initializes Sync time cubit.
+  SyncTimeCubit(ServerTimeCubit serverTimeCubit)
+      : super(SyncTimeInitialState()) {
+    _currentDateTime = now;
+
+    _stopwatch.start();
+
+    _updateDateTime(serverTimeCubit.state);
+    _setPeriodicTimer();
+
+    serverTimeCubit.stream.listen(_updateDateTime);
+  }
+
+  final Stopwatch _stopwatch = Stopwatch();
+  final Duration _periodicTimerDuration = const Duration(seconds: 1);
+
+  late DateTime _currentDateTime;
+
+  /// Gets current date time.
+  DateTime get now => state.dateTime;
+
+  /// Updates date time with server.
+  Future<void> _updateDateTime(ServerTimeState serverTimeState) async {
+    DateTime? serverTime;
+
+    if (serverTimeState is ServerTimeFetched) {
+      serverTime = serverTimeState.serverTime;
+    }
+
+    _currentDateTime =
+        (serverTime ?? (await TimeResponse.fetchTime()).time)!.toUtc();
+
+    _stopwatch.reset();
+  }
+
+  Timer _setPeriodicTimer() => Timer.periodic(
+        _periodicTimerDuration,
+        (_) {
+          emit(
+            SyncTimeUpdatedState(
+              _currentDateTime = _currentDateTime
+                  .add(Duration(milliseconds: _stopwatch.elapsedMilliseconds)),
+            ),
+          );
+
+          _stopwatch.reset();
+        },
+      );
+}

lib/state/sync_time/sync_time_state.dart

@@ -0,0 +1,22 @@
+part of 'sync_time_cubit.dart';
+
+/// Sync time base state.
+abstract class SyncTimeState {
+  /// Initializes sync time base state.
+  const SyncTimeState(this.dateTime);
+
+  /// Keeps synced Date Time in UTC.
+  final DateTime dateTime;
+}
+
+/// Sync time initial state.
+class SyncTimeInitialState extends SyncTimeState {
+  /// Initializes sync time initial state.
+  SyncTimeInitialState() : super(DateTime.now().toUtc());
+}
+
+/// Sync time updates state.
+class SyncTimeUpdatedState extends SyncTimeState {
+  /// Initializes sync time updated state.
+  SyncTimeUpdatedState(DateTime dateTime) : super(dateTime);
+}