Chessistics/chessistics-tests/Rules/CollisionResolverTests.cs

using Chessistics.Engine.Model;
using Chessistics.Engine.Rules;
using Xunit;

namespace Chessistics.Tests.Rules;

public class CollisionResolverTests
{
    [Fact]
    public void NoCollision_PiecesOnDifferentCells()
    {
        var pieces = new List<PieceState>
        {
            new(1, PieceKind.Rook, new Coords(0, 0), new Coords(1, 0), 0) { CurrentCell = new Coords(0, 0) },
            new(2, PieceKind.Rook, new Coords(2, 0), new Coords(3, 0), 1) { CurrentCell = new Coords(2, 0) }
        };

        var results = CollisionResolver.ResolveCollisions(pieces);
        Assert.Empty(results);
    }

    [Fact]
    public void HigherStatus_Survives()
    {
        var cell = new Coords(1, 0);
        var rook = new PieceState(1, PieceKind.Rook, new Coords(0, 0), cell, 0) { CurrentCell = cell };
        var knight = new PieceState(2, PieceKind.Knight, new Coords(2, 0), cell, 1) { CurrentCell = cell };
        var pieces = new List<PieceState> { rook, knight };

        var results = CollisionResolver.ResolveCollisions(pieces);
        Assert.Single(results);
        var (survivor, destroyed, resultCell) = results[0];
        Assert.Equal(rook, survivor);
        Assert.Single(destroyed);
        Assert.Equal(knight, destroyed[0]);
        Assert.Equal(cell, resultCell);
    }

    [Fact]
    public void SameStatusAndLevel_MutualDestruction()
    {
        var cell = new Coords(1, 0);
        var pieces = new List<PieceState>
        {
            new(1, PieceKind.Knight, new Coords(0, 0), cell, 0) { CurrentCell = cell },
            new(2, PieceKind.Bishop, new Coords(2, 0), cell, 1) { CurrentCell = cell }
        };

        var results = CollisionResolver.ResolveCollisions(pieces);
        Assert.Single(results);
        var (survivor, destroyed, _) = results[0];
        Assert.Null(survivor);
        Assert.Equal(2, destroyed.Count);
    }

    [Fact]
    public void HigherLevel_SurvivesWhenSameStatus()
    {
        var cell = new Coords(1, 0);
        var knightL2 = new PieceState(1, PieceKind.Knight, new Coords(0, 0), cell, 0, level: 2) { CurrentCell = cell };
        var knightL1 = new PieceState(2, PieceKind.Knight, new Coords(2, 0), cell, 1, level: 1) { CurrentCell = cell };
        var pieces = new List<PieceState> { knightL1, knightL2 };

        var results = CollisionResolver.ResolveCollisions(pieces);
        Assert.Single(results);
        var (survivor, destroyed, _) = results[0];
        Assert.Equal(knightL2, survivor);
        Assert.Single(destroyed);
        Assert.Equal(knightL1, destroyed[0]);
    }

    [Fact]
    public void ThreePieces_StrongestSurvives_OthersDestroyed()
    {
        var cell = new Coords(1, 0);
        var rook = new PieceState(1, PieceKind.Rook, new Coords(0, 0), cell, 0) { CurrentCell = cell };
        var bishop = new PieceState(2, PieceKind.Bishop, new Coords(2, 0), cell, 1) { CurrentCell = cell };
        var knight = new PieceState(3, PieceKind.Knight, new Coords(3, 0), cell, 2) { CurrentCell = cell };
        var pieces = new List<PieceState> { rook, bishop, knight };

        var results = CollisionResolver.ResolveCollisions(pieces);
        Assert.Single(results);
        var (survivor, destroyed, _) = results[0];
        Assert.Equal(rook, survivor);
        Assert.Equal(2, destroyed.Count);
    }
}