Update staffing management to enhance payroll and hiring functionalities

- Increased the `MonthlyPayrollCap` from 10,000 to 40,000, allowing for greater flexibility in hiring and subject assignments.
- Revised payroll calculation logic to ensure that staff members are compensated based on their actual weekly hours, with a minimum payment reflecting one full rate.
- Updated documentation to clarify the new payroll structure and its implications for hiring and subject assignments.
- Enhanced tests to validate the new payroll cap and ensure proper functionality in staffing scenarios, including the handling of uncovered subjects.
- Improved localization strings to reflect changes in staffing and payroll terminology.

tests/HSchool.People.Tests/StaffingTests.cs

@@ -4,16 +4,22 @@ public class StaffingTests
 {
     private const float Cap = 10_000f;
 
+    /// <summary>
+    /// Price of an hour times the hours carried, with one full rate as the floor: a hired person
+    /// costs something even idle, and loading them past the rate costs more. The number of
+    /// subjects does not enter into it — twenty hours are twenty hours.
+    /// </summary>
     [Fact]
-    public void MonthlyPay_AddsSurchargeAfterTheFirstSubject()
+    public void MonthlyPay_IsHoursTimesTheHourlyAsk_WithAFullRateAsTheFloor()
     {
         var rules = Fixtures.Catalog().StaffingRules!;
 
         Assert.Equal(4_000f, Staffing.MonthlyBase(rules, 50f));
-        Assert.Equal(4_000f, Staffing.MonthlyPay(rules, 50f, 0));
-        Assert.Equal(4_000f, Staffing.MonthlyPay(rules, 50f, 1));
-        Assert.Equal(5_000f, Staffing.MonthlyPay(rules, 50f, 2));
-        Assert.Equal(6_000f, Staffing.MonthlyPay(rules, 50f, 3));
+        Assert.Equal(4_000f, Staffing.MonthlyPay(rules, 50f, 0f));
+        Assert.Equal(4_000f, Staffing.MonthlyPay(rules, 50f, 12f));
+        Assert.Equal(4_000f, Staffing.MonthlyPay(rules, 50f, 20f));
+        Assert.Equal(6_000f, Staffing.MonthlyPay(rules, 50f, 30f));
+        Assert.Equal(7_200f, Staffing.MonthlyPay(rules, 50f, 36f));
     }
 
     [Fact]
@@ -53,25 +59,85 @@ public class StaffingTests
         var hired = Staffing.Hire(catalog, map, roster, pool, first.Person.Id, Staffing.TeacherPosition, Cap);
         Assert.Equal(StaffingError.None, hired.Error);
 
+        // Mathematics is 35 curriculum hours a week, Literature 21. At 37.5 an hour that is
+        // 37.5 × 56 × 4 = 8 400 a month for one person — and no room left for a second.
         var loaded = hired;
-        foreach (var subject in new[] { "Mathematics", "RussianLanguage", "Literature", "History", "Biology", "ForeignLanguage" })
+        foreach (var subject in new[] { "Mathematics", "Literature" })
         {
             loaded = Staffing.AssignSubject(catalog, loaded.Roster, loaded.Pool, first.Person.Id, subject, Cap);
             Assert.Equal(StaffingError.None, loaded.Error);
         }
 
-        Assert.Equal(6_750f, loaded.Payroll);
+        Assert.Equal(8_400f, loaded.Payroll);
 
         var blocked = Staffing.Hire(catalog, map, loaded.Roster, loaded.Pool, second.Person.Id, Staffing.TeacherPosition, Cap);
         Assert.Equal(StaffingError.PayrollExceeded, blocked.Error);
 
-        var dropped = Staffing.UnassignSubject(catalog, loaded.Roster, loaded.Pool, first.Person.Id, "Biology", Cap);
+        var dropped = Staffing.UnassignSubject(catalog, loaded.Roster, loaded.Pool, first.Person.Id, "Literature", Cap);
         Assert.Equal(StaffingError.None, dropped.Error);
-        Assert.Equal(6_000f, dropped.Payroll);
+        Assert.Equal(5_250f, dropped.Payroll);
 
         var fitted = Staffing.Hire(catalog, map, dropped.Roster, dropped.Pool, second.Person.Id, Staffing.TeacherPosition, Cap);
         Assert.Equal(StaffingError.None, fitted.Error);
-        Assert.Equal(10_000f, fitted.Payroll);
+        Assert.Equal(9_250f, fitted.Payroll);
+    }
+
+    /// <summary>
+    /// Two teachers of one subject split its hours, so the second one costs a full rate and makes
+    /// the first cheaper. That is the whole reason hiring another is not simply worse than loading
+    /// the one you have.
+    /// </summary>
+    [Fact]
+    public void TwoTeachersOfASubject_ShareItsHours()
+    {
+        var (catalog, map, roster, pool) = Fresh();
+        var first = WithAsk(pool.Applicants[0], 50f);
+        var second = WithAsk(pool.Applicants[1], 50f);
+        pool = pool with { Applicants = [first, second, .. pool.Applicants.Skip(2)] };
+
+        var one = Staffing.Hire(catalog, map, roster, pool, first.Person.Id, Staffing.TeacherPosition, 50_000f);
+        one = Staffing.AssignSubject(catalog, one.Roster, one.Pool, first.Person.Id, "Mathematics", 50_000f);
+
+        // All 35 hours on one person: 50 × 35 × 4.
+        Assert.Equal(7_000f, one.Payroll);
+
+        var two = Staffing.Hire(catalog, map, one.Roster, one.Pool, second.Person.Id, Staffing.TeacherPosition, 50_000f);
+        two = Staffing.AssignSubject(catalog, two.Roster, two.Pool, second.Person.Id, "Mathematics", 50_000f);
+
+        // 17.5 hours each, which is under a full rate, so both are paid the rate: 4 000 × 2.
+        Assert.Equal(8_000f, two.Payroll);
+        Assert.All(
+            two.Roster.People.Where(person => person.IsStaff),
+            person => Assert.Equal(17.5f, Staffing.WeeklyHours(catalog, two.Roster, person)));
+    }
+
+    /// <summary>
+    /// Primary school is twenty hours a week for each of four classes. One teacher cannot carry
+    /// eighty hours whatever the budget says, so the subject stays on the uncovered list until
+    /// enough people share it.
+    /// </summary>
+    [Fact]
+    public void SubjectNeedingMoreHoursThanOnePersonCarries_StaysUncovered()
+    {
+        var (catalog, map, roster, pool) = Fresh();
+        var rules = catalog.StaffingRules!;
+        Assert.Equal(80f, Staffing.SubjectHours(catalog, roster, "PrimarySchool"));
+        Assert.True(80f > rules.MaxWeeklyHours);
+
+        var outcome = new StaffingOutcome(StaffingError.None, roster, pool, 0, 0, 0, 0);
+        for (var i = 0; i < 3; i++)
+        {
+            var applicant = outcome.Pool.Applicants[0];
+            outcome = Staffing.Hire(catalog, map, outcome.Roster, outcome.Pool, applicant.Person.Id, Staffing.TeacherPosition, 500_000f);
+            Assert.Equal(StaffingError.None, outcome.Error);
+            outcome = Staffing.AssignSubject(catalog, outcome.Roster, outcome.Pool, applicant.Person.Id, "PrimarySchool", 500_000f);
+            Assert.Equal(StaffingError.None, outcome.Error);
+
+            var stillShort = 80f > (i + 1) * rules.MaxWeeklyHours;
+            Assert.Equal(
+                stillShort,
+                Staffing.Uncovered(catalog, outcome.Roster).Any(subject => subject.DefName == "PrimarySchool"));
+        }
     }
 
     [Fact]
@@ -82,23 +148,22 @@ public class StaffingTests
         pool = pool with { Applicants = [applicant, .. pool.Applicants.Skip(1)] };
 
         var hired = Staffing.Hire(catalog, map, roster, pool, applicant.Person.Id, Staffing.TeacherPosition, Cap);
-        var loaded = hired;
-        foreach (var subject in new[] { "Mathematics", "RussianLanguage", "Literature", "History", "Biology", "Physics", "Chemistry" })
-        {
-            loaded = Staffing.AssignSubject(catalog, loaded.Roster, loaded.Pool, applicant.Person.Id, subject, Cap);
-            Assert.Equal(StaffingError.None, loaded.Error);
-        }
+        Assert.Equal(4_000f, hired.Payroll);
 
-        Assert.Equal(10_000f, loaded.Payroll);
+        // Mathematics is 35 hours: 50 × 35 × 4 = 7 000.
+        var loaded = Staffing.AssignSubject(catalog, hired.Roster, hired.Pool, applicant.Person.Id, "Mathematics", Cap);
+        Assert.Equal(StaffingError.None, loaded.Error);
+        Assert.Equal(7_000f, loaded.Payroll);
 
-        var rejected = Staffing.AssignSubject(catalog, loaded.Roster, loaded.Pool, applicant.Person.Id, "Geography", Cap);
+        // Russian adds 28 more. 63 hours at 50 is 12 600 a month — past the 10 000 allocation.
+        var rejected = Staffing.AssignSubject(catalog, loaded.Roster, loaded.Pool, applicant.Person.Id, "RussianLanguage", Cap);
         Assert.Equal(StaffingError.PayrollExceeded, rejected.Error);
-        Assert.Equal(10_000f, rejected.Payroll);
-        Assert.Equal(11_000f, rejected.Attempted);
-        Assert.Equal(0f, rejected.Remaining);
+        Assert.Equal(7_000f, rejected.Payroll);
+        Assert.Equal(12_600f, rejected.Attempted);
+        Assert.Equal(3_000f, rejected.Remaining);
         Assert.DoesNotContain(
             rejected.Roster.People.Single(person => person.Id == applicant.Person.Id).Subjects,
-            name => name == "Geography");
+            name => name == "RussianLanguage");
     }
 
     [Fact]