Use "clock" for mocking dates and datetimes

This should make the tests a bit more robust, specially in CI since these
tended to fail depending on how long and when the tests run. Also, rework
a bit the way the start and end dates in sessions were being handled and
initialised

Author: rolandgeider

lib/helpers/json.dart

@@ -67,8 +67,8 @@ String dateToUtcIso8601(DateTime dateTime) {
  * Needed e.g. when the wger api only sends a time but no date information.
  */
 TimeOfDay stringToTime(String? time) {
-  final String out = time ?? '00:00';
-  return TimeOfDay.fromDateTime(DateTime.parse('2020-01-01 $out'));
+  time ??= '00:00';
+  return TimeOfDay.fromDateTime(DateTime.parse('2020-01-01 $time'));
 }
 
 TimeOfDay? stringToTimeNull(String? time) {

lib/providers/gym_state.dart

@@ -1,3 +1,4 @@
+import 'package:clock/clock.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:logging/logging.dart';
@@ -26,7 +27,7 @@ class GymState {
       DateTime? validUntil,
       TimeOfDay? startTime}) {
     this.validUntil = validUntil ?? DateTime.now().add(DEFAULT_DURATION);
-    this.startTime = startTime ?? TimeOfDay.now();
+    this.startTime = startTime ?? TimeOfDay.fromDateTime(clock.now());
   }
 
   GymState copyWith({

lib/widgets/routines/forms/session.dart

@@ -44,8 +44,8 @@ class SessionForm extends StatefulWidget {
               dayId: dayId,
               impression: DEFAULT_IMPRESSION,
               date: clock.now(),
-              timeEnd: TimeOfDay.now(),
-              timeStart: TimeOfDay.now(),
+              timeEnd: TimeOfDay.fromDateTime(clock.now()),
+              timeStart: null,
             );
 
   @override
@@ -68,8 +68,10 @@ class _SessionFormState extends State<SessionForm> {
   void initState() {
     super.initState();
 
-    timeStartController.text = timeToString(widget._session.timeStart) ?? '';
-    timeEndController.text = timeToString(widget._session.timeEnd) ?? '';
+    timeStartController.text =
+        widget._session.timeStart == null ? '' : timeToString(widget._session.timeStart)!;
+    timeEndController.text =
+        widget._session.timeEnd == null ? '' : timeToString(widget._session.timeEnd)!;
     notesController.text = widget._session.notes;
 
     selectedImpression[widget._session.impression - 1] = true;
@@ -129,6 +131,7 @@ class _SessionFormState extends State<SessionForm> {
             },
           ),
           Row(
+            spacing: 10,
             children: [
               Flexible(
                 child: TextFormField(
@@ -163,16 +166,19 @@ class _SessionFormState extends State<SessionForm> {
                     if (timeStartController.text.isEmpty && timeEndController.text.isEmpty) {
                       return null;
                     }
-                    final TimeOfDay startTime = stringToTime(timeStartController.text);
-                    final TimeOfDay endTime = stringToTime(timeEndController.text);
-                    if (startTime.isAfter(endTime)) {
-                      return AppLocalizations.of(context).timeStartAhead;
+
+                    if (timeStartController.text.isNotEmpty && timeEndController.text.isNotEmpty) {
+                      final TimeOfDay startTime = stringToTime(timeStartController.text);
+                      final TimeOfDay endTime = stringToTime(timeEndController.text);
+                      if (startTime.isAfter(endTime)) {
+                        return AppLocalizations.of(context).timeStartAhead;
+                      }
                     }
+
                     return null;
                   },
                 ),
               ),
-              const SizedBox(width: 10),
               Flexible(
                 child: TextFormField(
                   key: const ValueKey('time-end'),

lib/widgets/routines/gym_mode/session_page.dart

@@ -45,8 +45,8 @@ class SessionPage extends StatelessWidget {
                 routineId: _routine.id!,
                 impression: DEFAULT_IMPRESSION,
                 date: clock.now(),
-                timeEnd: TimeOfDay.now(),
                 timeStart: start,
+                timeEnd: TimeOfDay.fromDateTime(clock.now()),
               ),
             );