acdream/tests/AcDream.Core.Tests/CharGen/ChargenSkillCreditMathTests.cs

using AcDream.Core.CharGen;

namespace AcDream.Core.Tests.CharGen;

/// <summary>
/// Tests for <see cref="ChargenSkillCreditMath"/> — retail's skill-credit
/// spend port (<c>CharGenState::UpdateRemainingSkillCredits @
/// 0x005C37C0</c>).
/// </summary>
public sealed class ChargenSkillCreditMathTests
{
    private static readonly Dictionary<uint, ChargenSkillCost> Costs = new()
    {
        [1u] = new ChargenSkillCost(1u, NormalCost: 4, PrimaryCost: 12), // Axe
        [11u] = new ChargenSkillCost(11u, NormalCost: 4, PrimaryCost: 12), // Sword
        [24u] = new ChargenSkillCost(24u, NormalCost: 1, PrimaryCost: 3), // Run
        // Deliberately no entry for skill id 2 (Bow) — heritage doesn't offer it.
    };

    [Fact]
    public void ComputeSpent_IgnoresInactiveAndUntrainedSkills()
    {
        var advancement = new ChargenSkillAdvancementSet
        {
            [1u] = ChargenSkillAdvancementClass.Inactive,
            [11u] = ChargenSkillAdvancementClass.Untrained,
        };

        Assert.Equal(0, ChargenSkillCreditMath.ComputeSpent(advancement, Costs));
    }

    [Fact]
    public void ComputeSpent_ChargesNormalCostForTrainedSkills()
    {
        var advancement = new ChargenSkillAdvancementSet { [1u] = ChargenSkillAdvancementClass.Trained };

        Assert.Equal(4, ChargenSkillCreditMath.ComputeSpent(advancement, Costs));
    }

    [Fact]
    public void ComputeSpent_ChargesPrimaryCostInsteadOfNormalCostForSpecializedSkills()
    {
        // Retail adds exactly one of NormalCost/PrimaryCost per skill, never
        // both — PrimaryCost is the TOTAL cost to reach Specialized.
        var advancement = new ChargenSkillAdvancementSet { [1u] = ChargenSkillAdvancementClass.Specialized };

        Assert.Equal(12, ChargenSkillCreditMath.ComputeSpent(advancement, Costs));
    }

    [Fact]
    public void ComputeSpent_SumsAcrossMultipleTrainedAndSpecializedSkills()
    {
        var advancement = new ChargenSkillAdvancementSet
        {
            [1u] = ChargenSkillAdvancementClass.Trained,       // 4
            [11u] = ChargenSkillAdvancementClass.Specialized,  // 12
            [24u] = ChargenSkillAdvancementClass.Trained,      // 1
        };

        Assert.Equal(17, ChargenSkillCreditMath.ComputeSpent(advancement, Costs));
    }

    [Fact]
    public void ComputeSpent_SkillWithNoCostEntryIsSkippedDefensively()
    {
        var advancement = new ChargenSkillAdvancementSet { [2u] = ChargenSkillAdvancementClass.Trained };

        Assert.Equal(0, ChargenSkillCreditMath.ComputeSpent(advancement, Costs));
    }

    [Fact]
    public void RemainingCredits_IsTotalMinusSpent_AndMayGoNegativeUnlikeAttributes()
    {
        var advancement = new ChargenSkillAdvancementSet
        {
            [1u] = ChargenSkillAdvancementClass.Trained,
            [11u] = ChargenSkillAdvancementClass.Specialized,
        };

        Assert.Equal(84, ChargenSkillCreditMath.RemainingCredits(100u, advancement, Costs));
        // Retail's Finish gate never checks remainingSkillCredits, so
        // overspending relative to the (small, synthetic) budget below is a
        // representable state, not a thrown exception.
        Assert.Equal(-16, ChargenSkillCreditMath.RemainingCredits(0u, advancement, Costs));
    }
}