using EnvelopeRenderer.Desktop.Core.Design;

namespace EnvelopeRenderer.Desktop.Tests;

public class SelectionCyclerTests
{
    private static readonly Guid A = Guid.Parse("00000000-0000-0000-0000-00000000000a");
    private static readonly Guid B = Guid.Parse("00000000-0000-0000-0000-00000000000b");
    private static readonly Guid C = Guid.Parse("00000000-0000-0000-0000-00000000000c");

    private static SelectionCycler.Item[] Items() => new[]
    {
        new SelectionCycler.Item(C, ZOrder: 2, X: 0, Y: 0),
        new SelectionCycler.Item(A, ZOrder: 0, X: 0, Y: 0),
        new SelectionCycler.Item(B, ZOrder: 1, X: 0, Y: 0),
    };

    [Fact]
    public void Forward_WalksBottomToTopByZOrder_AndWraps()
    {
        Assert.Equal(A, SelectionCycler.Next(Items(), null, forward: true));
        Assert.Equal(B, SelectionCycler.Next(Items(), A, forward: true));
        Assert.Equal(C, SelectionCycler.Next(Items(), B, forward: true));
        Assert.Equal(A, SelectionCycler.Next(Items(), C, forward: true));
    }

    [Fact]
    public void Backward_WalksTopToBottom_AndWraps_StartingAtTheLastItem()
    {
        Assert.Equal(C, SelectionCycler.Next(Items(), null, forward: false));
        Assert.Equal(B, SelectionCycler.Next(Items(), C, forward: false));
        Assert.Equal(A, SelectionCycler.Next(Items(), B, forward: false));
        Assert.Equal(C, SelectionCycler.Next(Items(), A, forward: false));
    }

    [Fact]
    public void SameZOrder_VisitsTopToBottomThenLeftToRight()
    {
        var items = new[]
        {
            new SelectionCycler.Item(A, 0, X: 50, Y: 10),
            new SelectionCycler.Item(B, 0, X: 10, Y: 100),
            new SelectionCycler.Item(C, 0, X: 10, Y: 10),
        };

        Assert.Equal(B, SelectionCycler.Next(items, null, forward: true)); // highest on the page first
        Assert.Equal(C, SelectionCycler.Next(items, B, forward: true));    // then the lower-left one
        Assert.Equal(A, SelectionCycler.Next(items, C, forward: true));
    }

    [Fact]
    public void UnknownCurrentSelection_BehavesLikeNoSelection()
        => Assert.Equal(A, SelectionCycler.Next(Items(), Guid.NewGuid(), forward: true));

    [Fact]
    public void NoItems_ReturnsNull()
        => Assert.Null(SelectionCycler.Next(Array.Empty<SelectionCycler.Item>(), null, forward: true));

    [Fact]
    public void SingleItem_StaysOnIt()
    {
        var items = new[] { new SelectionCycler.Item(A, 0, 0, 0) };

        Assert.Equal(A, SelectionCycler.Next(items, A, forward: true));
        Assert.Equal(A, SelectionCycler.Next(items, A, forward: false));
    }
}