using System.Numerics;
using AcDream.App.Rendering;
using Xunit;

namespace AcDream.App.Tests.Rendering;

/// <summary>
/// Pure (no dat access) tests for <see cref="ChargenPreviewRotationController"/>
/// — the port of <c>gmCGAppearancePage::Rotate</c>/<c>DoRotation</c>
/// (<c>0x0047CB50</c>/<c>0x0047CA80</c>).
/// </summary>
public sealed class ChargenPreviewRotationControllerTests
{
    [Fact]
    public void Toggle_StartsRotatingInTheGivenDirection()
    {
        var controller = new ChargenPreviewRotationController();
        controller.Toggle(ChargenRotateDirection.Clockwise);

        Assert.True(controller.IsRotating);
        Assert.Equal(ChargenRotateDirection.Clockwise, controller.Direction);
    }

    [Fact]
    public void Toggle_SameDirectionWhileRotating_Stops()
    {
        var controller = new ChargenPreviewRotationController();
        controller.Toggle(ChargenRotateDirection.Clockwise);
        controller.Toggle(ChargenRotateDirection.Clockwise);

        Assert.False(controller.IsRotating);
    }

    [Fact]
    public void Toggle_OppositeDirectionWhileRotating_SwitchesDirectionAndKeepsRotating()
    {
        var controller = new ChargenPreviewRotationController();
        controller.Toggle(ChargenRotateDirection.Clockwise);
        controller.Toggle(ChargenRotateDirection.CounterClockwise);

        Assert.True(controller.IsRotating);
        Assert.Equal(ChargenRotateDirection.CounterClockwise, controller.Direction);
    }

    [Fact]
    public void Tick_WhileNotRotating_IsANoOp()
    {
        var controller = new ChargenPreviewRotationController();
        controller.Tick(100.0);

        Assert.Equal(0f, controller.HeadingDegrees);
    }

    [Fact]
    public void Tick_FirstCallAfterToggle_ContributesZeroDelta()
    {
        // Rotate() invalidates m_dLastRotateTime so the very first DoRotation
        // tick resets it to "now" rather than computing a huge jump from a
        // stale/never-set timestamp.
        var controller = new ChargenPreviewRotationController();
        controller.Toggle(ChargenRotateDirection.Clockwise);
        controller.Tick(1000.0);

        Assert.Equal(0f, controller.HeadingDegrees);
    }

    [Fact]
    public void Tick_ClockwiseAdvance_AddsTheExactPerTickFormula()
    {
        // deltaDegrees = ((now - last) / RotationSecondsPerRevolution) * 360.
        // Seed "now" nonzero (0.0 collides with the <= 0 reset-if-invalid
        // guard, same as retail's own sentinel check would if Timer::cur_time
        // could ever read exactly zero — never in practice, so tests avoid
        // it too).
        var controller = new ChargenPreviewRotationController();
        controller.Toggle(ChargenRotateDirection.Clockwise);
        controller.Tick(10.0);  // seeds lastRotateTime = 10, zero delta.
        controller.Tick(11.5);  // half a revolution at 3 s/rev.

        Assert.Equal(180f, controller.HeadingDegrees, 3);
    }

    [Fact]
    public void Tick_CounterClockwiseAdvance_SubtractsAndWrapsPositive()
    {
        var controller = new ChargenPreviewRotationController();
        controller.Toggle(ChargenRotateDirection.CounterClockwise);
        controller.Tick(10.0);
        controller.Tick(11.5); // would go to -180, wraps to +180.

        Assert.Equal(180f, controller.HeadingDegrees, 3);
    }

    [Fact]
    public void Tick_AccumulatesAcrossMultipleTicks()
    {
        var controller = new ChargenPreviewRotationController();
        controller.Toggle(ChargenRotateDirection.Clockwise);
        controller.Tick(10.0);
        controller.Tick(10.5); // +60 deg.
        controller.Tick(11.0); // +60 deg more.

        Assert.Equal(120f, controller.HeadingDegrees, 3);
    }

    /// <summary>
    /// F7: exercises the <c>&gt;360 -&gt; -360</c> clamp arm (pseudo-C
    /// ~0x0047cb1e-0x0047cb31), the one with readable decomp polarity —
    /// unlike the CCW-branch FPU-stack artifact F3 documents, this branch's
    /// test/subtract shape is unambiguous. One large clockwise tick pushes
    /// heading past 360 in a single call.
    /// </summary>
    [Fact]
    public void Tick_ClockwiseAdvancePast360_ClampsBackBySubtracting360()
    {
        var controller = new ChargenPreviewRotationController();
        controller.Toggle(ChargenRotateDirection.Clockwise);
        controller.Tick(10.0);       // seeds lastRotateTime = 10, zero delta.
        controller.Tick(10.0 + 3.5); // 3.5s at 3s/rev = 420 deg -> 420, clamped to 60.

        Assert.Equal(60f, controller.HeadingDegrees, 3);
    }

    [Fact]
    public void ToOrientation_AtZeroHeading_IsIdentity()
    {
        var controller = new ChargenPreviewRotationController();
        Quaternion orientation = controller.ToOrientation();

        Assert.Equal(Quaternion.Identity.X, orientation.X, 4);
        Assert.Equal(Quaternion.Identity.Y, orientation.Y, 4);
        Assert.Equal(Quaternion.Identity.Z, orientation.Z, 4);
        Assert.Equal(Quaternion.Identity.W, orientation.W, 4);
    }
}