Add teachers to substitution plan (#1647)

## Demo


https://github.com/SharezoneApp/sharezone-app/assets/24459435/f9b89af0-f914-4ad5-abca-ff6e1d927745

## Summary

A user can add substitution teachers. Free users can see the teachers
now. Substitutions are a list on the client now.

## Description

This PR adds the option to add substitution teachers.

I changed that now free users can also see the teachers. Reason for
this: It doesn't really makes sense if a user can see the substitution
teacher, but not the normal teacher.

Before this PR, a lesson had only one substitution at the time. Now, a
lesson can have multiple substitutions (like room substitution and
teacher substitution). This **not** a breaking change thanks to a robust
database design.

## Related Tickets

Closes #1628

app/lib/dashboard/bloc/build_lesson_views.dart

@@ -35,15 +35,13 @@ LessonView _buildLessonView(
   required Date date,
 }) {
   final timeline = _getTimeStatus(lesson.startTime, lesson.endTime);
-  final substitution = lesson.getSubstitutionFor(date);
-  final newLocation = substitution is LocationChangedSubstitution
-      ? substitution.newLocation
-      : null;
+  final locationSubstitution =
+      lesson.getSubstitutionFor(date).getLocationChangedSubstitution();
   return LessonView(
     start: lesson.startTime.toString(),
     end: lesson.endTime.toString(),
     lesson: lesson,
-    room: newLocation ?? lesson.place,
+    room: locationSubstitution?.newLocation ?? lesson.place,
     design: groupInfo?.design ?? Design.standard(),
     abbreviation: groupInfo?.abbreviation ?? "",
     timeStatus: timeline,

app/lib/timetable/src/models/lesson.dart

@@ -7,7 +7,6 @@
 // SPDX-License-Identifier: EUPL-1.2
 
 import 'package:cloud_firestore_helper/cloud_firestore_helper.dart';
-import 'package:collection/collection.dart';
 import 'package:date/date.dart';
 import 'package:date/weekday.dart';
 import 'package:date/weektype.dart';
@@ -132,14 +131,14 @@ class Lesson {
     );
   }
 
-  /// Returns the substitution for the given [date].
+  /// Returns the substitutions for the given [date].
   ///
-  /// If there is no substitution for the given [date], `null` will be returned.
-  Substitution? getSubstitutionFor(Date date) {
-    return substitutions.values.firstWhereOrNull(
-      (substitution) =>
-          substitution.date == date && substitution.isDeleted == false,
-    );
+  /// If there is no substitution for the given [date], the list will be empty.
+  List<Substitution?> getSubstitutionFor(Date date) {
+    return substitutions.values
+        .where((substitution) =>
+            substitution.date == date && substitution.isDeleted == false)
+        .toList();
   }
 
   @override

app/lib/timetable/src/models/substitution.dart

@@ -7,6 +7,7 @@
 // SPDX-License-Identifier: EUPL-1.2
 
 import 'package:cloud_firestore/cloud_firestore.dart';
+import 'package:collection/collection.dart';
 import 'package:common_domain_models/common_domain_models.dart';
 import 'package:date/date.dart';
 import 'package:sharezone/timetable/src/models/substitution_id.dart';
@@ -18,13 +19,17 @@ enum SubstitutionType {
   /// The lesson is moved to another room.
   locationChanged,
 
+  /// The teacher changed for the lesson.
+  teacherChanged,
+
   /// Unknown substitution type.
   unknown;
 
   String toDatabaseString() {
     return switch (this) {
       lessonCanceled => 'lessonCanceled',
       locationChanged => 'placeChanged',
+      teacherChanged => 'teacherChanged',
       unknown => 'unknown',
     };
   }
@@ -33,6 +38,7 @@ enum SubstitutionType {
     return switch (value) {
       'lessonCanceled' => lessonCanceled,
       'placeChanged' => locationChanged,
+      'teacherChanged' => teacherChanged,
       _ => unknown,
     };
   }
@@ -94,6 +100,14 @@ sealed class Substitution {
           isDeleted: isDeleted,
           updatedBy: updatedBy,
         ),
+      SubstitutionType.teacherChanged => TeacherChangedSubstitution(
+          id: id,
+          date: Date.parse(data['date'] as String),
+          createdBy: createdBy,
+          newTeacher: data['newTeacher'] as String,
+          isDeleted: isDeleted,
+          updatedBy: updatedBy,
+        ),
       SubstitutionType.unknown => UnknownSubstitution(
           id: id,
           date: Date.parse(data['date'] as String),
@@ -154,6 +168,29 @@ class LocationChangedSubstitution extends Substitution {
   }
 }
 
+class TeacherChangedSubstitution extends Substitution {
+  final String newTeacher;
+
+  const TeacherChangedSubstitution({
+    required super.id,
+    required this.newTeacher,
+    required super.date,
+    required super.createdBy,
+    super.isDeleted,
+    super.updatedBy,
+  }) : super(type: SubstitutionType.teacherChanged);
+
+  @override
+  Map<String, dynamic> toCreateJson({
+    required bool notifyGroupMembers,
+  }) {
+    return {
+      ...super.toCreateJson(notifyGroupMembers: notifyGroupMembers),
+      'newTeacher': newTeacher,
+    };
+  }
+}
+
 class UnknownSubstitution extends Substitution {
   const UnknownSubstitution({
     required super.id,
@@ -163,3 +200,23 @@ class UnknownSubstitution extends Substitution {
     super.updatedBy,
   }) : super(type: SubstitutionType.unknown);
 }
+
+extension SubstitutionList on List<Substitution?> {
+  LocationChangedSubstitution? getLocationChangedSubstitution() {
+    return firstWhereOrNull(
+            (substitution) => substitution is LocationChangedSubstitution)
+        as LocationChangedSubstitution?;
+  }
+
+  TeacherChangedSubstitution? getTeacherChangedSubstitution() {
+    return firstWhereOrNull(
+            (substitution) => substitution is TeacherChangedSubstitution)
+        as TeacherChangedSubstitution?;
+  }
+
+  LessonCanceledSubstitution? getLessonCanceledSubstitution() {
+    return firstWhereOrNull(
+            (substitution) => substitution is LessonCanceledSubstitution)
+        as LessonCanceledSubstitution?;
+  }
+}

app/lib/timetable/timetable_page/lesson/substitution_controller.dart

@@ -83,6 +83,29 @@ class SubstitutionController {
     }));
   }
 
+  void addTeacherSubstitution({
+    required String lessonId,
+    required bool notifyGroupMembers,
+    required Date date,
+    required String newTeacher,
+  }) {
+    final substitution = TeacherChangedSubstitution(
+      id: _generateId(),
+      date: date,
+      createdBy: userId,
+      newTeacher: newTeacher,
+    );
+    gateway.addSubstitutionToLesson(
+      lessonId: lessonId,
+      notifyGroupMembers: notifyGroupMembers,
+      substitution: substitution,
+    );
+    analytics
+        .log(NamedAnalyticsEvent(name: 'substitution_teacher_changed', data: {
+      'notify_group_members': notifyGroupMembers,
+    }));
+  }
+
   void updatePlaceSubstitution({
     required String lessonId,
     required SubstitutionId substitutionId,
@@ -101,6 +124,24 @@ class SubstitutionController {
     }));
   }
 
+  void updateTeacherSubstitution({
+    required String lessonId,
+    required SubstitutionId substitutionId,
+    required bool notifyGroupMembers,
+    required String newTeacher,
+  }) {
+    gateway.updateSubstitutionInLesson(
+      lessonId: lessonId,
+      notifyGroupMembers: notifyGroupMembers,
+      newTeacher: newTeacher,
+      substitutionId: substitutionId,
+    );
+    analytics
+        .log(NamedAnalyticsEvent(name: 'substitution_teacher_changed', data: {
+      'notify_group_members': notifyGroupMembers,
+    }));
+  }
+
   Future<String?> getMemberName(String courseId, UserId userId) async {
     final member = await courseMemberAccessor.getMember(courseId, userId);
     return member?.name;