using System.Numerics;
using AcDream.App.UI;
using AcDream.App.UI.Layout;
using Xunit;

namespace AcDream.App.Tests.UI;

/// <summary>
/// Campaign LA gate round 2 (register AD-98): retail renders fixed-canvas
/// pre-world screens (char select, authored 800×600) at authored size and
/// stretches the whole composed frame at presentation — its UI blitter has no
/// stretch mode. acdream's equivalent is <see cref="UiRoot.FixedCanvasSize"/>:
/// draw applies one uniform scale at the renderer's quad chokepoint, and the
/// mouse entry points apply the exact inverse so hit-testing lives in canvas
/// space. These tests pin the scale math and the inverse input mapping — the
/// half that, if wrong, makes the user click on art and hit nothing.
/// </summary>
public class UiRootFixedCanvasTests
{
    [Fact]
    public void CanvasScale_IsOne_WithoutFixedCanvas()
    {
        var root = new UiRoot { Width = 1920f, Height = 1080f };
        Assert.Equal(Vector2.One, root.CanvasScale);
    }

    [Fact]
    public void CanvasScale_IsWindowOverCanvas_WhenFixed()
    {
        var root = new UiRoot
        {
            Width = 1920f,
            Height = 1080f,
            FixedCanvasSize = new Vector2(800f, 600f),
        };
        Assert.Equal(new Vector2(2.4f, 1.8f), root.CanvasScale);
    }

    [Fact]
    public void CanvasScale_IsOne_ForDegenerateCanvasOrWindow()
    {
        var zeroCanvas = new UiRoot
        {
            Width = 1920f,
            Height = 1080f,
            FixedCanvasSize = new Vector2(0f, 600f),
        };
        Assert.Equal(Vector2.One, zeroCanvas.CanvasScale);

        var zeroWindow = new UiRoot
        {
            Width = 0f,
            Height = 0f,
            FixedCanvasSize = new Vector2(800f, 600f),
        };
        Assert.Equal(Vector2.One, zeroWindow.CanvasScale);
    }

    /// <summary>
    /// The load-bearing inverse: a click at WINDOW coordinates must land on the
    /// widget whose authored CANVAS rect the user visually clicked. The button
    /// sits at canvas (300,400)+(120×40); at a 1920×1080 window over an 800×600
    /// canvas it appears at window (720,720)-(1008,792). Clicking window
    /// (860,750) — canvas (358,417) — must click it; clicking window (300,400)
    /// — canvas (125,222), visually empty — must not.
    /// </summary>
    [Fact]
    public void MouseInput_MapsWindowCoordsToCanvasSpace()
    {
        var root = new UiRoot
        {
            Width = 1920f,
            Height = 1080f,
            FixedCanvasSize = new Vector2(800f, 600f),
        };
        int clicks = 0;
        var button = new UiButton(
            new ElementInfo { Width = 120, Height = 40 },
            _ => (0u, 0, 0))
        {
            Left = 300f,
            Top = 400f,
            Width = 120f,
            Height = 40f,
            OnClick = () => clicks++,
        };
        root.AddChild(button);

        // Truncation, not rounding (batch review F6): 860/2.4 = 358.33 → 358,
        // 750/1.8 = 416.67 → 416. Rounding mapped the window's far edge one
        // past the canvas's last valid coordinate (1919 → 800), losing a 1px
        // hit-test band at the right/bottom.
        root.OnMouseDown(UiMouseButton.Left, 860, 750);
        root.OnMouseUp(UiMouseButton.Left, 860, 750);
        Assert.Equal(1, clicks);
        Assert.Equal(358, root.MouseX);
        Assert.Equal(416, root.MouseY);

        // The far window edge maps INSIDE the canvas.
        root.OnMouseMove(1919, 1079);
        Assert.Equal(799, root.MouseX);
        Assert.Equal(599, root.MouseY);

        root.OnMouseDown(UiMouseButton.Left, 300, 400);
        root.OnMouseUp(UiMouseButton.Left, 300, 400);
        Assert.Equal(1, clicks);
    }

    [Fact]
    public void MouseInput_IsUntouched_WithoutFixedCanvas()
    {
        var root = new UiRoot { Width = 1920f, Height = 1080f };
        int clicks = 0;
        var button = new UiButton(
            new ElementInfo { Width = 120, Height = 40 },
            _ => (0u, 0, 0))
        {
            Left = 300f,
            Top = 400f,
            Width = 120f,
            Height = 40f,
            OnClick = () => clicks++,
        };
        root.AddChild(button);

        root.OnMouseDown(UiMouseButton.Left, 360, 420);
        root.OnMouseUp(UiMouseButton.Left, 360, 420);
        Assert.Equal(1, clicks);
    }
}