namespace HSchool.People.Tests;

public class SkillGrantTests
{
    [Fact]
    public void FirstYear_HasCoreAndPrimary_ButNotChemistryOrEnglish()
    {
        var roster = Fixtures.Generate(Fixtures.Classrooms(11));
        var pupils = PupilsIn(roster, 1).ToArray();
        Assert.NotEmpty(pupils);
        Assert.All(
            pupils,
            person =>
            {
                Assert.True(person.Skills.ContainsKey("Communication"));
                Assert.True(person.Skills.ContainsKey("RussianLanguage"));
                Assert.True(person.Skills.ContainsKey("Agility"));
                Assert.True(person.Skills.ContainsKey("Hauling"));
                Assert.True(person.Skills.ContainsKey("Mathematics"));
                Assert.False(person.Skills.ContainsKey("Chemistry"));
                Assert.False(person.Skills.ContainsKey("Physics"));
                Assert.False(person.Skills.ContainsKey("English"));
                Assert.False(person.Skills.ContainsKey("German"));
                Assert.False(person.Skills.ContainsKey("Pedagogy"));
            });
    }

    [Fact]
    public void YearFive_HasEnglish_YearEight_HasChemistry()
    {
        var roster = Fixtures.Generate(Fixtures.Classrooms(11));
        Assert.All(
            PupilsIn(roster, 5),
            person =>
            {
                Assert.True(person.Skills.ContainsKey("English"));
                Assert.False(person.Skills.ContainsKey("Chemistry"));
                Assert.False(person.Skills.ContainsKey("German"));
            });
        Assert.All(PupilsIn(roster, 8), person => Assert.True(person.Skills.ContainsKey("Chemistry")));
    }

    [Fact]
    public void Adults_HaveNativeAndCommunication_ButNotEverySkill()
    {
        var catalog = Fixtures.Catalog();
        var roster = Fixtures.Generate(Fixtures.Classrooms(11));
        var adults = roster.People.Where(person => !person.IsStudent).ToArray();
        Assert.NotEmpty(adults);

        var concrete = catalog.Skills.Values.Count(skill => !skill.Abstract);
        Assert.All(
            adults,
            person =>
            {
                Assert.True(person.Skills.ContainsKey("Communication"));
                Assert.True(person.Skills.ContainsKey("RussianLanguage"));
                Assert.True(person.Skills.Count < concrete);
                Assert.InRange(person.Skills.Keys.Count(name => catalog.Skills[name].Work), 0, 2);
            });
        Assert.Contains(
            adults,
            person => person.Skills.Keys.Any(name => catalog.Skills[name].Work));
    }

    [Fact]
    public void BelarusianNative_IsGrantedToEveryone_PupilsStillStudyRussian()
    {
        var catalog = Fixtures.Catalog();
        var roster = RosterGenerator.Generate(
            catalog,
            Fixtures.Classrooms(11),
            Fixtures.SchoolSeed,
            "Russia",
            Fixtures.AsOf,
            "BelarusianLanguage");

        var max = catalog.Countries["Russia"].Names.RelatedLanguageMax;
        Assert.All(
            roster.People,
            person =>
            {
                Assert.True(person.Skills.ContainsKey("BelarusianLanguage"));
                if (person.Skills.TryGetValue("UkrainianLanguage", out var ukrainian))
                {
                    Assert.InRange(ukrainian, 0, max);
                }
            });
        Assert.All(
            roster.People.Where(person => person.IsStudent),
            person => Assert.True(person.Skills.ContainsKey("RussianLanguage")));
        Assert.Contains(
            roster.People.Where(person => person.IsStudent),
            person => person.Skills["RussianLanguage"] > max);
    }

    [Fact]
    public void RelatedLanguages_AreCommonAndStayLow()
    {
        var catalog = Fixtures.Catalog();
        var max = catalog.Countries["Russia"].Names.RelatedLanguageMax;
        var roster = Fixtures.Generate(Fixtures.Classrooms(11));
        Assert.Contains(
            roster.People,
            person =>
                person.Skills.ContainsKey("BelarusianLanguage")
                || person.Skills.ContainsKey("UkrainianLanguage"));
        Assert.Contains(roster.People, person => !person.Skills.ContainsKey("BelarusianLanguage"));
        Assert.Contains(roster.People, person => !person.Skills.ContainsKey("UkrainianLanguage"));
        Assert.True(
            roster.People.Count(person =>
                person.Skills.ContainsKey("BelarusianLanguage")
                || person.Skills.ContainsKey("UkrainianLanguage"))
            > roster.People.Count / 2);

        Assert.All(
            roster.People,
            person =>
            {
                Assert.True(person.Skills.ContainsKey("RussianLanguage"));
                if (person.Skills.TryGetValue("BelarusianLanguage", out var belarusian))
                {
                    Assert.InRange(belarusian, 0, max);
                }

                if (person.Skills.TryGetValue("UkrainianLanguage", out var ukrainian))
                {
                    Assert.InRange(ukrainian, 0, max);
                }
            });
    }

    /// <summary>
    /// A school saved before native languages carries no pick, and the reload path asks for one
    /// with <c>rollIfOmitted: false</c>. The contract is that it takes the first listed language
    /// instead of rolling — a roll would change an existing school's tongue on the next start,
    /// and the intake after it would draw different people.
    /// </summary>
    [Fact]
    public void ReloadWithoutASavedPick_TakesTheFirstLanguageInsteadOfRolling()
    {
        var names = Fixtures.Catalog().Countries["Russia"].Names;
        Assert.True(names.Spoken.Count > 1, "this pins behaviour that only matters for a multi-language set");

        foreach (var seed in new[] { 1, 2, 7, 20260818 })
        {
            Assert.Equal(names.Spoken[0], NativeLanguages.Pick(names, seed, requested: null, rollIfOmitted: false));
        }

        // A new school rolls instead, and the roll is stable for one seed.
        var rolled = NativeLanguages.Pick(names, 7, requested: null, rollIfOmitted: true);
        Assert.Contains(rolled, names.Spoken);
        Assert.Equal(rolled, NativeLanguages.Pick(names, 7, requested: null, rollIfOmitted: true));

        // A saved pick is honoured whichever way it is asked for.
        Assert.Equal(
            names.Spoken[^1],
            NativeLanguages.Pick(names, 7, names.Spoken[^1], rollIfOmitted: false));

        // Anything outside the set comes back null so the create path can answer 400.
        Assert.Null(NativeLanguages.Pick(names, 7, "Klingon", rollIfOmitted: true));
    }

    [Fact]
    public void OmittedNativeLanguage_IsStableForTheSameSeed()
    {
        var map = Fixtures.Classrooms(2);
        var a = RosterGenerator.Generate(Fixtures.Catalog(), map, 7, "Russia", Fixtures.AsOf);
        var b = RosterGenerator.Generate(Fixtures.Catalog(), map, 7, "Russia", Fixtures.AsOf);
        Assert.Equal(
            a.People.Select(person => string.Join(',', person.Skills.Keys.Order(StringComparer.Ordinal))),
            b.People.Select(person => string.Join(',', person.Skills.Keys.Order(StringComparer.Ordinal))));
    }

    [Fact]
    public void Pupils_DoNotRollWorkSkills()
    {
        var catalog = Fixtures.Catalog();
        var roster = Fixtures.Generate(Fixtures.Classrooms(11));
        Assert.All(
            roster.People.Where(person => person.IsStudent),
            person => Assert.DoesNotContain(person.Skills.Keys, name => catalog.Skills[name].Work));
    }

    [Fact]
    public void Intake_YearFourGainsEnglishWithoutRerollingMath()
    {
        var catalog = Fixtures.Catalog();
        var before = Fixtures.Generate(Fixtures.Classrooms(5));
        var year4 = before.Classes.Single(schoolClass => schoolClass.Year == 4);
        var pupil = before.People.First(person => person.Id == year4.PupilIds[0]);
        Assert.False(pupil.Skills.ContainsKey("English"));
        var math = pupil.Skills["Mathematics"];

        var after = YearlyIntake.Apply(
            catalog,
            before,
            Fixtures.SchoolSeed,
            "Russia",
            new DateTime(2012, 9, 1, 0, 0, 0, DateTimeKind.Utc));
        var grown = after.People.First(person => person.Id == pupil.Id);
        Assert.True(grown.ClassId is { } classId && after.Classes.Any(schoolClass =>
            schoolClass.Id.Equals(classId, StringComparison.Ordinal) && schoolClass.Year == 5));
        Assert.True(grown.Skills.ContainsKey("English"));
        Assert.Equal(math, grown.Skills["Mathematics"]);
    }

    private static IEnumerable<Person> PupilsIn(Roster roster, int year)
    {
        var classIds = roster.Classes
            .Where(schoolClass => schoolClass.Year == year)
            .Select(schoolClass => schoolClass.Id)
            .ToHashSet(StringComparer.Ordinal);
        return roster.People.Where(person =>
            person.IsStudent && person.ClassId is { } classId && classIds.Contains(classId));
    }
}