acdream/tests/AcDream.Core.Tests/Audio/SoundCookbookTests.cs

using System;
using System.Collections.Generic;
using AcDream.Core.Audio;
using DatReaderWriter.DBObjs;
using DRWSoundEntry = DatReaderWriter.Types.SoundEntry;
using DatReaderWriter.Types;
using DRWSound = DatReaderWriter.Enums.Sound;
using Xunit;

namespace AcDream.Core.Tests.Audio;

public sealed class SoundCookbookTests
{
    // Deterministic Random for golden-value tests.
    private static Random Seed(int seed) => new Random(seed);

    [Fact]
    public void Roll_EmptyList_ReturnsNull()
    {
        Assert.Null(SoundCookbook.Roll(new List<DRWSoundEntry>(), Seed(1)));
    }

    [Fact]
    public void Roll_SingleEntry_AlwaysReturnsIt()
    {
        var e = new DRWSoundEntry { Probability = 0.5f, Priority = 4f, Volume = 1f };
        var entries = new List<DRWSoundEntry> { e };
        Assert.Same(e, SoundCookbook.Roll(entries, Seed(1)));
        Assert.Same(e, SoundCookbook.Roll(entries, Seed(999)));
    }

    [Fact]
    public void Roll_WeightedEntries_DistributionMatches()
    {
        // Three entries: 50%, 30%, 20%. Roll 10000 times and verify counts
        // are within 5% of expected.
        var a = new DRWSoundEntry { Probability = 0.5f };
        var b = new DRWSoundEntry { Probability = 0.3f };
        var c = new DRWSoundEntry { Probability = 0.2f };
        var entries = new List<DRWSoundEntry> { a, b, c };

        var rng = new Random(42);
        int countA = 0, countB = 0, countC = 0, countNull = 0;
        for (int i = 0; i < 10000; i++)
        {
            var picked = SoundCookbook.Roll(entries, rng);
            if (ReferenceEquals(picked, a)) countA++;
            else if (ReferenceEquals(picked, b)) countB++;
            else if (ReferenceEquals(picked, c)) countC++;
            else countNull++;
        }

        Assert.InRange(countA, 4500, 5500);
        Assert.InRange(countB, 2500, 3500);
        Assert.InRange(countC, 1500, 2500);
        // Probabilities sum to 1.0 → no null rolls.
        Assert.True(countNull < 100);
    }

    [Fact]
    public void Roll_SilenceTail_ReturnsNullOccasionally()
    {
        // Two entries that only cover 60% of the probability mass — the
        // remaining 40% should roll as "silence" (null return).
        var a = new DRWSoundEntry { Probability = 0.3f };
        var b = new DRWSoundEntry { Probability = 0.3f };
        var entries = new List<DRWSoundEntry> { a, b };

        var rng = new Random(42);
        int nullCount = 0;
        for (int i = 0; i < 10000; i++)
        {
            if (SoundCookbook.Roll(entries, rng) is null)
                nullCount++;
        }
        Assert.InRange(nullCount, 3500, 4500);   // ~40% ± margin
    }

    [Fact]
    public void Roll_WithSoundTable_LooksUpBySound()
    {
        var table = new SoundTable();
        var footstep = new DRWSoundEntry { Probability = 1f, Volume = 0.7f };
        table.Sounds[DRWSound.Footstep1] = new SoundData();
        table.Sounds[DRWSound.Footstep1].Entries.Add(footstep);

        var picked = SoundCookbook.Roll(table, DRWSound.Footstep1, Seed(1));
        Assert.Same(footstep, picked);
    }

    [Fact]
    public void Roll_WithSoundTable_MissingSound_ReturnsNull()
    {
        var table = new SoundTable();   // no entries at all
        Assert.Null(SoundCookbook.Roll(table, DRWSound.Attack1, Seed(1)));
    }
}