Nitrox/Nitrox.Test/Model/DataStructures/Util/OptionalTest.cs

namespace NitroxModel.DataStructures.Util;

[TestClass]
public class OptionalTest
{
    /// <summary>
    ///     These optional additions should be in <see cref="OptionalHasValueDynamicChecks"/> test method but MSTest
    ///     reuses instances which causes <see cref="Optional{T}.HasValue">Optional{T}.HasValue</see> to be called before the new conditions are added.
    /// </summary>
    [ClassInitialize]
    public static void Init(TestContext _)
    {
        Optional.ApplyHasValueCondition<Base>(v => v.GetType() == typeof(A) || v.Threshold > 200); // Cheat: allow check if type A to do more complex tests on Optional<T>.HasValue
        Optional.ApplyHasValueCondition<A>(v => v.Threshold <= 200);
    }

    [TestMethod]
    public void OptionalGet()
    {
        Optional<string> op = Optional.Of("test");
        op.Value.Should().Be("test");
    }

    [TestMethod]
    public void OptionalIsPresent()
    {
        Optional<string> op = Optional.Of("test");
        op.HasValue.Should().BeTrue();
    }

    [TestMethod]
    public void OptionalIsNotPresent()
    {
        Optional<string> op = Optional.Empty;
        op.HasValue.Should().BeFalse();
    }

    [TestMethod]
    public void OptionalOrElseValidValue()
    {
        Optional<string> op = Optional.Of("test");
        op.OrElse("test2").Should().Be("test");
    }

    [TestMethod]
    public void OptionalOrElseNoValue()
    {
        Optional<string> op = Optional.Empty;
        op.OrElse("test").Should().Be("test");
    }

    [TestMethod]
    public void OptionalEmpty()
    {
        Optional<string> op = Optional.Empty;
        op.HasValue.Should().BeFalse();
    }

    [TestMethod]
    public void OptionalSetValueNull()
    {
        Optional<Random> op = Optional.Of(new Random());
        Assert.IsTrue(op.HasValue);
        Assert.ThrowsException<ArgumentNullException>(() => { op = null; }, "Setting optional to null should not be allowed.");
        op = Optional.Empty;
        Assert.IsFalse(op.HasValue);
    }

    [TestMethod]
    public void OptionalHasValueDynamicChecks()
    {
        Optional<Base> opBase = Optional.Of(new Base());
        opBase.HasValue.Should().BeTrue();
        opBase.Value.Threshold.Should().Be(202);

        Optional<A> a = Optional.Of(new A());
        a.HasValue.Should().BeTrue();

        Optional<A> actuallyB = Optional.Of<A>(new B());
        actuallyB.HasValue.Should().BeFalse();

        Optional<B> b = Optional.Of(new B());
        b.HasValue.Should().BeFalse();

        // A check should still happen on Base because Optional<Base> includes more-specific-than-itself checks.
        Optional<Base> aAsBase = Optional<Base>.Of((Base)a);
        aAsBase.HasValue.Should().BeTrue();
        aAsBase.Value.Threshold.Should().Be(200);

        // Optional<object> should always do all checks because anything can be in it.
        // Note: This test can fail if Optional.ApplyHasValueCondition isn't called early enough. Run this test method directly and it should work.
        Optional<object> bAsObj = Optional<object>.Of(new B());
        bAsObj.HasValue.Should().BeFalse();

        // Type C inheritance doesn't allow for type A. But Optional<object> has the check on A. It should skip the A check on C because inheritance doesn't match up.
        Optional<object> cAsObj = Optional<object>.Of(new C());
        cAsObj.HasValue.Should().BeTrue();
        ((C)cAsObj.Value).Threshold.Should().Be(203);
    }

    [TestMethod]
    public void OptionalEqualsCheck()
    {
        Optional<string> op = Optional.OfNullable<string>(null);
        Optional<string> op1 = Optional.OfNullable<string>(null);
        Optional<string> op2 = Optional.Of("Test");
        Optional<string> op3 = Optional.Of("Test2");
        Optional<string> op4 = Optional.Of("Test");

        Assert.IsFalse(op.Equals(op2));
        Assert.IsFalse(op.Equals(op3));
        Assert.IsFalse(op2.Equals(op3));

        Assert.IsTrue(op.Equals(op1));
        Assert.IsTrue(op2.Equals(op4));

        Assert.IsTrue(op != op2);
        Assert.IsTrue(op2 == op4);
    }

    private class Base
    {
        public virtual int Threshold => 202;
    }

    private class A : Base
    {
        public override int Threshold => 200;
    }

    private class B : A
    {
        public override int Threshold => 201;
    }

    private class C : Base
    {
        public override int Threshold => 203;
    }
}