feat: add seating plans for learning groups

LehrerApp.Data/LiteDbContext.cs

@@ -36,6 +36,7 @@ public class LiteDbContext : IDisposable
 
     public ILiteCollection<Student>       Students      => _db.GetCollection<Student>("students");
     public ILiteCollection<LearningGroup> Groups        => _db.GetCollection<LearningGroup>("groups");
+    public ILiteCollection<SeatingPlan>   SeatingPlans  => _db.GetCollection<SeatingPlan>("seating_plans");
     public ILiteCollection<GroupMembership> Memberships => _db.GetCollection<GroupMembership>("group_memberships");
     public ILiteCollection<Exam>          Exams         => _db.GetCollection<Exam>("exams");
     public ILiteCollection<ExamResult>    ExamResults   => _db.GetCollection<ExamResult>("exam_results");
@@ -333,6 +334,7 @@ public class LiteDbContext : IDisposable
         Students.EnsureIndex(x => x.IsActive);
         Groups.EnsureIndex(x => x.SchoolYear);
         Groups.EnsureIndex(x => x.IsActive);
+        SeatingPlans.EnsureIndex(x => x.GroupId);
         Memberships.EnsureIndex(x => x.StudentId);
         Memberships.EnsureIndex(x => x.GroupId);
         Memberships.EnsureIndex("ux_student_group",

LehrerApp.Data/Repositories/AllRepositories.cs

@@ -121,6 +121,9 @@ public class GroupRepository(LiteDbContext db) : IGroupRepository
             foreach (var section in db.ParticipationSections.Find(s => s.GroupId == id).ToList())
                 db.ParticipationSections.Delete(section.Id);
 
+            foreach (var plan in db.SeatingPlans.Find(p => p.GroupId == id).ToList())
+                db.SeatingPlans.Delete(plan.Id);
+
             // Dokumentation und Arbeitszeit sind historische Nachweise. Sie bleiben erhalten,
             // werden aber von der nicht mehr existierenden Lerngruppe entkoppelt.
             foreach (var documentation in db.Documentation.Find(d => d.GroupId == id).ToList())
@@ -148,6 +151,58 @@ public class GroupRepository(LiteDbContext db) : IGroupRepository
     }
 }
 
+public class SeatingPlanRepository(LiteDbContext db) : ISeatingPlanRepository
+{
+    public SeatingPlan? GetById(Guid id) => db.SeatingPlans.FindById(id);
+
+    public List<SeatingPlan> GetByGroup(Guid groupId) =>
+        db.SeatingPlans.Find(p => p.GroupId == groupId)
+            .OrderBy(p => p.Name).ThenBy(p => p.Room).ToList();
+
+    public void Save(SeatingPlan plan)
+    {
+        ArchivedGroupWriteGuard.EnsureActive(db, plan.GroupId);
+        plan.Name = plan.Name.Trim();
+        plan.Room = plan.Room.Trim();
+        if (plan.Name.Length == 0)
+            throw new ArgumentException("Der Name des Sitzplans darf nicht leer sein.");
+        if (plan.Rows is < 1 or > 10 || plan.Columns is < 1 or > 10)
+            throw new ArgumentOutOfRangeException(nameof(plan), "Ein Sitzplan muss zwischen 1 und 10 Reihen und Spalten haben.");
+        if (db.Groups.FindById(plan.GroupId) is null)
+            throw new InvalidOperationException("Die zugehörige Lerngruppe existiert nicht.");
+
+        var duplicateName = db.SeatingPlans.Find(p => p.GroupId == plan.GroupId)
+            .FirstOrDefault(p => p.Id != plan.Id
+                && string.Equals(p.Name, plan.Name, StringComparison.OrdinalIgnoreCase)
+                && string.Equals(p.Room, plan.Room, StringComparison.OrdinalIgnoreCase));
+        if (duplicateName is not null)
+            throw new InvalidOperationException("Für diese Lerngruppe existiert bereits ein gleichnamiger Sitzplan in diesem Raum.");
+
+        plan.Assignments = plan.Assignments
+            .Where(a => a.Row >= 0 && a.Row < plan.Rows && a.Column >= 0 && a.Column < plan.Columns)
+            .ToList();
+        if (plan.Assignments.GroupBy(a => (a.Row, a.Column)).Any(g => g.Count() > 1))
+            throw new InvalidOperationException("Ein Sitzplatz darf nur einmal belegt werden.");
+        if (plan.Assignments.GroupBy(a => a.StudentId).Any(g => g.Count() > 1))
+            throw new InvalidOperationException("Ein Schüler darf in einem Sitzplan nur einmal vorkommen.");
+
+        var memberIds = db.Memberships.Find(m => m.GroupId == plan.GroupId)
+            .Select(m => m.StudentId).ToHashSet();
+        if (plan.Assignments.Any(a => !memberIds.Contains(a.StudentId)))
+            throw new InvalidOperationException("Der Sitzplan enthält einen Schüler, der nicht zur Lerngruppe gehört.");
+
+        plan.UpdatedAt = DateTime.UtcNow;
+        db.SeatingPlans.Upsert(plan);
+    }
+
+    public void Delete(Guid id)
+    {
+        if (db.SeatingPlans.FindById(id) is { } plan)
+            ArchivedGroupWriteGuard.EnsureActive(db, plan.GroupId);
+        db.SeatingPlans.Delete(id);
+    }
+}
+
 public class GroupMembershipRepository(LiteDbContext db) : IGroupMembershipRepository
 {
     public List<GroupMembership> GetByStudent(Guid id) =>