using AcDream.UI.Abstractions.Input;

namespace AcDream.UI.Abstractions.Tests.Input;

/// <summary>
/// Phase K.2 — MMB-hold instant mouse-look state machine. While
/// active, mouse-X drives the character's heading (and the chase
/// camera follows automatically because <c>ChaseCamera.Update</c>
/// reads the player yaw). The state machine guards activation on
/// ImGui's <c>WantCaptureMouse</c> so a panel-hovered MMB doesn't
/// hijack the cursor.
/// </summary>
public sealed class MmbMouseLookTests
{
    private sealed class YawSink
    {
        public float Total;
        public int   ApplyCount;
        public void Apply(float d) { Total += d; ApplyCount++; }
    }

    [Fact]
    public void Press_ActivatesAndCapturesCursorPosition()
    {
        var sink = new YawSink();
        var ml = new MouseLookState(sink.Apply);

        ml.Press(cursorX: 320f, cursorY: 240f, wantCaptureMouse: false);

        Assert.True(ml.Active);
        Assert.Equal(320f, ml.CapturedCursorX);
        Assert.Equal(240f, ml.CapturedCursorY);
    }

    [Fact]
    public void Release_DeactivatesWhenActive()
    {
        var sink = new YawSink();
        var ml = new MouseLookState(sink.Apply);
        ml.Press(0f, 0f, wantCaptureMouse: false);

        ml.Release();

        Assert.False(ml.Active);
    }

    [Fact]
    public void Press_WhileImGuiCapturesMouse_DoesNotActivate()
    {
        // Defense in depth — the dispatcher already filters on
        // WantCaptureMouse, but if a binding ever fires through the
        // state machine itself must not turn on.
        var sink = new YawSink();
        var ml = new MouseLookState(sink.Apply);

        ml.Press(0f, 0f, wantCaptureMouse: true);

        Assert.False(ml.Active);
    }

    [Fact]
    public void OnWantCaptureMouseChanged_TrueWhileActive_Deactivates()
    {
        var sink = new YawSink();
        var ml = new MouseLookState(sink.Apply);
        ml.Press(0f, 0f, wantCaptureMouse: false);
        Assert.True(ml.Active);

        // ImGui takes mouse focus mid-hold (e.g. tooltip pop-up over
        // the cursor) → suspend mouse-look so the panel gets the
        // cursor.
        ml.OnWantCaptureMouseChanged(wantCaptureMouse: true);

        Assert.False(ml.Active);
    }

    [Fact]
    public void OnWantCaptureMouseChanged_FalseWhileInactive_NoOp()
    {
        // Going from "ImGui captures" to "ImGui doesn't capture" must
        // NOT auto-reactivate — only an explicit Press does.
        var sink = new YawSink();
        var ml = new MouseLookState(sink.Apply);

        ml.OnWantCaptureMouseChanged(wantCaptureMouse: false);

        Assert.False(ml.Active);
    }

    [Fact]
    public void ApplyDelta_WhileActive_DrivesYawSink()
    {
        var sink = new YawSink();
        var ml = new MouseLookState(sink.Apply) { SensitivityRadiansPerPixel = 0.01f };
        ml.Press(0f, 0f, wantCaptureMouse: false);

        ml.ApplyDelta(dx: 10f, extraSensitivity: 1.0f);

        // Sign: dragging right (positive dx) yaws the character right
        // — by the acdream Yaw convention that's negative yaw delta.
        // Magnitude: 10 * 0.01 * 1.0 = 0.1 rad.
        Assert.Equal(1, sink.ApplyCount);
        Assert.Equal(-0.1f, sink.Total, 5);
    }

    [Fact]
    public void ApplyDelta_WhileInactive_DoesNothing()
    {
        var sink = new YawSink();
        var ml = new MouseLookState(sink.Apply);
        // Never pressed.

        ml.ApplyDelta(dx: 100f, extraSensitivity: 1.0f);

        Assert.Equal(0, sink.ApplyCount);
        Assert.Equal(0f, sink.Total);
    }

    [Fact]
    public void ApplyDelta_AfterRelease_DoesNothing()
    {
        var sink = new YawSink();
        var ml = new MouseLookState(sink.Apply);
        ml.Press(0f, 0f, wantCaptureMouse: false);
        ml.Release();

        ml.ApplyDelta(dx: 50f, extraSensitivity: 1.0f);

        Assert.Equal(0, sink.ApplyCount);
    }

    [Fact]
    public void Press_WhileAlreadyActive_IsIdempotent()
    {
        // Repeated Press calls must not blow away the originally
        // captured cursor position — the cursor-restore-on-release
        // path needs the original anchor.
        var sink = new YawSink();
        var ml = new MouseLookState(sink.Apply);
        ml.Press(100f, 200f, wantCaptureMouse: false);

        ml.Press(999f, 888f, wantCaptureMouse: false);

        Assert.Equal(100f, ml.CapturedCursorX);
        Assert.Equal(200f, ml.CapturedCursorY);
    }

    [Fact]
    public void ApplyDelta_DriverDrivesCharacterAndCameraInOneSink()
    {
        // Combined drive: the test only exposes a single yaw mutator,
        // and that's the design — the yaw mutator GameWindow passes
        // updates _playerController.Yaw, and the chase camera reads
        // the same yaw via ChaseCamera.Update(pos, playerYaw). So a
        // single sink in this test models both behaviors.
        var sink = new YawSink();
        var ml = new MouseLookState(sink.Apply) { SensitivityRadiansPerPixel = 0.005f };
        ml.Press(0f, 0f, wantCaptureMouse: false);

        ml.ApplyDelta(dx:  4f, extraSensitivity: 0.5f);  // -0.01
        ml.ApplyDelta(dx: -2f, extraSensitivity: 0.5f);  // +0.005

        Assert.Equal(2, sink.ApplyCount);
        Assert.Equal(-0.005f, sink.Total, 5);
    }
}