Merge branch 'phase/41-opinions'

# Conflicts:
#	docs/phases/README.md

src/HSchool.Simulation/ApparelWear.cs

@@ -53,9 +53,10 @@ internal static class ApparelWear
         }
 
         var morningChanged = MorningDress.Apply(school);
+        var opinionsChanged = MorningOpinions.Apply(school);
         var ragsReplaced = SchoolDay.IsWorkday(school.Catalog, school.Clock.Time, school.SchoolWeekDays)
             && ReplaceRags(school);
-        return bandCrossed | morningChanged | ragsReplaced;
+        return bandCrossed | morningChanged | opinionsChanged | ragsReplaced;
     }
 
     internal static bool CrossedDayStart(DateTime before, DateTime after)

src/HSchool.Simulation/MorningOpinions.cs

@@ -0,0 +1,66 @@
+using HSchool.Content;
+using HSchool.People;
+
+namespace HSchool.Simulation;
+
+/// <summary>Drifts non-zero opinions toward family basis or zero at six on work mornings.</summary>
+internal static class MorningOpinions
+{
+    public static bool Apply(School school)
+    {
+        if (school.Catalog?.BehaviorRules is not { } rules || school.Roster is null)
+        {
+            return false;
+        }
+
+        if (!SchoolDay.IsWorkday(school.Catalog, school.Clock.Time, school.SchoolWeekDays))
+        {
+            return false;
+        }
+
+        var peopleById = school.Roster.People.ToDictionary(person => person.Id, StringComparer.Ordinal);
+        var changed = false;
+        foreach (var person in school.Roster.People)
+        {
+            changed |= DriftPerson(school.Roster, rules, peopleById, person, rules.OpinionDriftPerMorning);
+        }
+
+        return changed;
+    }
+
+    private static bool DriftPerson(
+        Roster roster,
+        BehaviorDef rules,
+        IReadOnlyDictionary<string, Person> peopleById,
+        Person person,
+        int drift)
+    {
+        if (person.Opinions.Count == 0)
+        {
+            return false;
+        }
+
+        var changed = false;
+        foreach (var (targetId, current) in person.Opinions.ToArray())
+        {
+            if (!peopleById.TryGetValue(targetId, out var target))
+            {
+                changed |= OpinionStore.Remove(person, targetId);
+                continue;
+            }
+
+            var basis = OpinionStore.FamilyBasis(roster, rules, person, target);
+            var next = OpinionStore.MoveToward(current, basis, drift);
+            if (next == 0)
+            {
+                changed |= OpinionStore.Remove(person, targetId);
+            }
+            else
+            {
+                changed |= OpinionStore.Set(person, targetId, next);
+            }
+        }
+
+        return changed;
+    }
+}