Grow lesson skills only when the assigned teacher is standing in the room.

The timetable already named a teacher; learning ignored whether they were in the toilet, still walking, or not a person at all.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/HSchool.Server/mods/core/localizations/en.jsonc

@@ -191,5 +191,6 @@
   "ActionEnded": "finished: {0}",
   "ApparelReplaced": "got a new {0}",
   "ApparelChanged": "changed clothes: {0}",
+  "LessonNoTeacher": "lesson without a teacher: {0}",
   "core": "Core",
 }

src/HSchool.Server/mods/core/localizations/ru.jsonc

@@ -191,5 +191,6 @@
   "ActionEnded": "закончил: {0}",
   "ApparelReplaced": "получил новую {0}",
   "ApparelChanged": "переоделся: {0}",
+  "LessonNoTeacher": "урок без учителя: {0}",
   "core": "Базовая игра",
 }

src/HSchool.Simulation/LessonLearningSystem.cs

@@ -8,10 +8,14 @@ namespace HSchool.Simulation;
 
 /// <summary>
 /// Grows skills for people who are actually in the lesson: at the room, not walking, not off
-/// doing something else. The formula lives in <see cref="HSchool.Ai.LessonLearning"/>.
+/// doing something else, and with the assigned teacher standing there. The formula lives in
+/// <see cref="HSchool.Ai.LessonLearning"/>.
 /// </summary>
 internal static class LessonLearningSystem
 {
+    private static readonly QueryDescription Places =
+        new QueryDescription().WithAll<PersonIdentity, Presence>();
+
     private static readonly QueryDescription People =
         new QueryDescription().WithAll<PersonIdentity, PersonSkills, PersonTraits, PersonNeeds, PersonRoles, Presence, PersonActivity>();
 
@@ -38,11 +42,19 @@ internal static class LessonLearningSystem
         var weekday = SchoolDay.WeekdayIndex(school.Clock.Time);
         var catalog = school.Catalog;
         var world = school.World;
+        var places = new Dictionary<string, Presence>(StringComparer.Ordinal);
+        world.Query(
+            in Places,
+            (ref PersonIdentity identity, ref Presence presence) =>
+            {
+                places[identity.Id] = presence;
+            });
+
         world.Query(
             in People,
             (ref PersonIdentity identity, ref PersonSkills skills, ref PersonTraits traits, ref PersonNeeds needs, ref PersonRoles roles, ref Presence presence, ref PersonActivity activity) =>
             {
-                if (activity.IsActive || presence.NodeId is null || presence.Path.Length > 0 || presence.RemainingMinutes > 0)
+                if (activity.IsActive || !IsStanding(presence))
                 {
                     return;
                 }
@@ -56,12 +68,19 @@ internal static class LessonLearningSystem
 
                 var lesson = CurrentLesson(school, person, weekday, slot.Index);
                 if (lesson is null
+                    || presence.NodeId is null
                     || !presence.NodeId.Equals(lesson.RoomId, StringComparison.Ordinal)
                     || !catalog.Subjects.TryGetValue(lesson.Subject, out var subject))
                 {
                     return;
                 }
 
+                if (!TeacherStandingIn(places, lesson.TeacherId, lesson.RoomId))
+                {
+                    school.TryLogLessonOnce(personId, PersonLogTypes.LessonNoTeacher, lesson.Subject);
+                    return;
+                }
+
                 var hunger = needs.Values.GetValueOrDefault("Hunger", 1f);
                 foreach (var share in subject.Skills)
                 {
@@ -87,6 +106,17 @@ internal static class LessonLearningSystem
             });
     }
 
+    private static bool IsStanding(Presence presence) =>
+        presence.NodeId is not null && presence.Path.Length == 0 && presence.RemainingMinutes <= 0;
+
+    private static bool TeacherStandingIn(
+        Dictionary<string, Presence> places,
+        string teacherId,
+        string roomId) =>
+        places.TryGetValue(teacherId, out var teacher) && IsStanding(teacher)
+            && teacher.NodeId is not null
+            && teacher.NodeId.Equals(roomId, StringComparison.Ordinal);
+
     private static LessonPlacement? CurrentLesson(School school, Person person, int weekday, int period)
     {
         foreach (var lesson in Duty.LessonsToday(person, ClassOf(school, person), school.Timetable, weekday))

src/HSchool.Simulation/PersonLog.cs

@@ -14,6 +14,7 @@ public static class PersonLogTypes
     public const string ActionEnded = "action-ended";
     public const string ApparelReplaced = "apparel-replaced";
     public const string ApparelChanged = "apparel-changed";
+    public const string LessonNoTeacher = "lesson-no-teacher";
 }
 
 /// <summary>
@@ -58,6 +59,14 @@ public sealed record PersonLogEvent(string PersonId, DateTime Time, string Type,
             return string.Format(CultureInfo.InvariantCulture, catalog.Text(locale, key), name);
         }
 
+        if (Type.Equals(PersonLogTypes.LessonNoTeacher, StringComparison.Ordinal))
+        {
+            var name = catalog.Subjects.TryGetValue(ThingDef, out var subject)
+                ? catalog.Label(locale, subject)
+                : ThingDef;
+            return string.Format(CultureInfo.InvariantCulture, catalog.Text(locale, "LessonNoTeacher"), name);
+        }
+
         return Type;
     }
 }

src/HSchool.Simulation/School.cs

@@ -17,6 +17,7 @@ public sealed class School : IDisposable
 
     private bool _disposed;
     private readonly List<PersonLogEvent> _dayLog = [];
+    private readonly HashSet<string> _lessonLogOnce = new(StringComparer.Ordinal);
 
     internal School(int id, string name, DateTime startDate, DefCatalog? catalog, MapLayout? map)
     {
@@ -135,10 +136,26 @@ public sealed class School : IDisposable
     {
         _dayLog.Clear();
         LoggedActivity.Clear();
+        _lessonLogOnce.Clear();
     }
 
     internal void AppendDayLog(PersonLogEvent row) => _dayLog.Add(row);
 
+    /// <summary>
+    /// Lesson-quality rows fire every tick the condition holds. One key per person per day is enough.
+    /// </summary>
+    internal bool TryLogLessonOnce(string personId, string type, string subject)
+    {
+        var key = string.Concat(personId, "\0", type, "\0", subject);
+        if (!_lessonLogOnce.Add(key))
+        {
+            return false;
+        }
+
+        AppendDayLog(new PersonLogEvent(personId, Clock.Time, type, subject));
+        return true;
+    }
+
     public void QueueDecision(string personId)
     {
         ObjectDisposedException.ThrowIf(_disposed, this);