Add support for countdown posts

lib/ui/tiles/post_tile.dart

@@ -15,6 +15,7 @@ import 'package:comunic/models/post.dart';
 import 'package:comunic/models/user.dart';
 import 'package:comunic/ui/tiles/comment_tile.dart';
 import 'package:comunic/ui/widgets/account_image_widget.dart';
+import 'package:comunic/ui/widgets/countdown_widget.dart';
 import 'package:comunic/ui/widgets/network_image_widget.dart';
 import 'package:comunic/ui/widgets/survey_widget.dart';
 import 'package:comunic/utils/date_utils.dart';
@@ -176,6 +177,10 @@ class _PostTileState extends State<PostTile> {
         postContent = _buildPostWebLink();
         break;
 
+      case PostKind.COUNTDOWN:
+        postContent = _buildCountDownTimer();
+        break;
+
       case PostKind.SURVEY:
         postContent = _buildPostSurvey();
         break;
@@ -320,6 +325,13 @@ class _PostTileState extends State<PostTile> {
     );
   }
 
+  Widget _buildCountDownTimer() {
+    return CountdownWidget(
+      startTime: widget.post.timeSent,
+      endTime: widget.post.timeEnd,
+    );
+  }
+
   /// Build post survey
   Widget _buildPostSurvey() {
     return SurveyWidget(

lib/ui/widgets/countdown_widget.dart

@@ -0,0 +1,84 @@
+import 'dart:async';
+
+import 'package:comunic/utils/date_utils.dart';
+import 'package:comunic/utils/intl_utils.dart';
+import 'package:flutter/material.dart';
+
+/// Countdown widget
+///
+/// @author Pierre HUBERT
+
+class CountdownWidget extends StatefulWidget {
+  final int startTime;
+  final int endTime;
+
+  const CountdownWidget({
+    Key key,
+    @required this.startTime,
+    @required this.endTime,
+  })  : assert(startTime != null),
+        assert(endTime != null),
+        super(key: key);
+
+  @override
+  _CountdownWidgetState createState() => _CountdownWidgetState();
+}
+
+class _CountdownWidgetState extends State<CountdownWidget> {
+  int get remainingTime => widget.endTime - time();
+
+  int get totalDuration => (widget.endTime - widget.startTime).abs();
+
+  String get remainingTimeStr {
+    final remaining = Duration(seconds: remainingTime);
+
+    return tr(
+      "%days% Days %hours% Hours %minutes% Minutes %seconds% Seconds",
+      args: {
+        "days": remaining.inDays.toString(),
+        "hours": (remaining.inHours % 24).toString(),
+        "minutes": (remaining.inMinutes % 60).toString(),
+        "seconds": (remaining.inSeconds % 60).toString(),
+      },
+    );
+  }
+
+  @override
+  void initState() {
+    super.initState();
+
+    Timer.periodic(Duration(seconds: 1), _timerCb);
+  }
+
+  void _timerCb(Timer timer) {
+    if (!mounted) timer.cancel();
+
+    setState(() {});
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+      width: 300,
+      child: Column(
+        children: <Widget>[
+          Padding(
+            padding: const EdgeInsets.all(8.0),
+            child: Text(remainingTimeStr),
+          ),
+          Padding(
+            padding: const EdgeInsets.all(8.0),
+            child: LinearProgressIndicator(
+              value: remainingTime <= 0
+                  ? 1.0
+                  : 1 - (remainingTime / totalDuration),
+              backgroundColor: Theme.of(context).accentColor,
+              valueColor: AlwaysStoppedAnimation<Color>(
+                  Theme.of(context).backgroundColor),
+            ),
+          )
+        ],
+      ),
+    );
+  }
+}