h-school/tests/HSchool.People.Tests/ApplicantPoolTests.cs

namespace HSchool.People.Tests;

public class ApplicantPoolTests
{
    [Fact]
    public void SameSeedAndWeek_YieldTheSamePool()
    {
        var roster = Fixtures.Generate(Fixtures.VanillaMap());
        var a = Create(roster);
        var b = Create(roster);

        Assert.Equal(Snapshot(a), Snapshot(b));
    }

    [Fact]
    public void Advance_KeepsSomePeopleWithTheSameSkillsAndAsk()
    {
        var roster = Fixtures.Generate(Fixtures.VanillaMap());
        var first = Create(roster);
        var next = first.Advance(Fixtures.Catalog(), roster, Fixtures.SchoolSeed, "Slavic", Fixtures.AsOf.AddDays(7));

        Assert.NotEqual(first.Week, next.Week);
        var stayed = first.Applicants
            .Join(
                next.Applicants,
                applicant => applicant.Person.Id,
                applicant => applicant.Person.Id,
                (before, after) => (before, after),
                StringComparer.Ordinal)
            .ToArray();

        Assert.NotEmpty(stayed);
        foreach (var (before, after) in stayed)
        {
            Assert.Equal(before.HourlyWageAsk, after.HourlyWageAsk);
            Assert.Equal(Skills(before.Person), Skills(after.Person));
            Assert.Equal(before.Person.Name.Full, after.Person.Name.Full);
        }
    }

    [Fact]
    public void FiftyWeeks_StayAtPoolSize()
    {
        var catalog = Fixtures.Catalog();
        var roster = Fixtures.Generate(Fixtures.VanillaMap());
        var size = catalog.StaffingRules!.PoolSize;
        var asOf = Fixtures.AsOf;
        var pool = ApplicantPool.Create(catalog, roster, Fixtures.SchoolSeed, "Slavic", asOf);

        for (var week = 0; week < 50; week++)
        {
            asOf = asOf.AddDays(7);
            pool = pool.Advance(catalog, roster, Fixtures.SchoolSeed, "Slavic", asOf);
            Assert.Equal(size, pool.Applicants.Count);
        }
    }

    [Fact]
    public void StrongerSkills_AskForMore()
    {
        var catalog = Fixtures.Catalog();
        var person = Fixtures.Generate(Fixtures.Classrooms(1)).People.First(candidate => candidate.IsParent);
        var weak = person with { Skills = person.Skills.ToDictionary(pair => pair.Key, _ => 15) };
        var strong = person with { Skills = person.Skills.ToDictionary(pair => pair.Key, _ => 90) };

        Assert.True(ApplicantPool.HourlyAsk(catalog, strong) > ApplicantPool.HourlyAsk(catalog, weak));
    }

    [Fact]
    public void GeneratedApplicants_AreNotOnTheRoster_ParentsKeepTheirId()
    {
        var roster = Fixtures.Generate(Fixtures.VanillaMap());
        ApplicantPool? pool = null;
        for (var seed = 1; seed <= 20 && pool is null; seed++)
        {
            var candidate = Fixtures.Generate(Fixtures.VanillaMap(), seed);
            var created = ApplicantPool.Create(Fixtures.Catalog(), candidate, seed, "Slavic", Fixtures.AsOf);
            if (created.Applicants.Any(applicant => candidate.People.Any(person => person.Id == applicant.Person.Id)))
            {
                roster = candidate;
                pool = created;
            }
        }

        Assert.NotNull(pool);
        var rosterIds = roster.People.Select(person => person.Id).ToHashSet(StringComparer.Ordinal);
        foreach (var applicant in pool.Applicants)
        {
            if (rosterIds.Contains(applicant.Person.Id))
            {
                Assert.Contains(roster.People, person => person.Id == applicant.Person.Id && person.IsParent && !person.IsStaff);
            }
            else
            {
                Assert.StartsWith("a", applicant.Person.Id, StringComparison.Ordinal);
                Assert.False(applicant.Person.IsStaff);
            }
        }
    }

    [Fact]
    public void PeopleJson_RoundTripsThePool()
    {
        var roster = Fixtures.Generate(Fixtures.Classrooms(1));
        var pool = Create(roster);
        var json = RosterJson.Serialize(RosterDocument.From(Fixtures.SchoolSeed, roster, pool));
        var loaded = RosterJson.Parse(json);

        Assert.Equal(Snapshot(pool), Snapshot(loaded.Applicants!));
        Assert.DoesNotContain(loaded.People, person => pool.Applicants.Any(applicant =>
            applicant.Person.Id.StartsWith('a') && applicant.Person.Id == person.Id));
    }

    private static ApplicantPool Create(Roster roster) =>
        ApplicantPool.Create(Fixtures.Catalog(), roster, Fixtures.SchoolSeed, "Slavic", Fixtures.AsOf);

    private static string Snapshot(ApplicantPool pool) =>
        string.Join('\n', pool.Applicants.Select(applicant =>
            $"{pool.Week}|{pool.NextIndex}|{applicant.Person.Id}|{applicant.HourlyWageAsk:0.00}|{applicant.Person.Name.Full}|{Skills(applicant.Person)}"));

    private static string Skills(Person person) =>
        string.Join(',', person.Skills.OrderBy(pair => pair.Key, StringComparer.Ordinal).Select(pair => $"{pair.Key}={pair.Value}"));
}