// Reference: https://easings.net

using Syntriax.Engine.Core;

namespace Syntriax.Engine.Systems.Tween;

internal static class EaseConstants
{
    internal const float c1 = 1.70158f;
    internal const float c2 = c1 * 1.525f;
    internal const float c3 = c1 + 1f;
    internal const float c4 = 2f * Math.PI / 3f;
    internal const float c5 = 2f * Math.PI / 4.5f;
}

public abstract class EasingBase<T> where T : IEasing, new() { public static readonly T Instance = new(); }

public class EaseLinear : EasingBase<EaseLinear>, IEasing { public float Evaluate(float x) => x; }

public class EaseInQuad : EasingBase<EaseInQuad>, IEasing { public float Evaluate(float x) => x * x; }
public class EaseOutQuad : EasingBase<EaseOutQuad>, IEasing { public float Evaluate(float x) => 1f - (1f - x) * (1f - x); }
public class EaseInOutQuad : EasingBase<EaseInOutQuad>, IEasing { public float Evaluate(float x) => x < .5f ? 2f * x * x : 1f - Math.Pow(-2f * x + 2f, 2f) * .5f; }

public class EaseInCubic : EasingBase<EaseInCubic>, IEasing { public float Evaluate(float x) => x * x * x; }
public class EaseOutCubic : EasingBase<EaseOutCubic>, IEasing { public float Evaluate(float x) => 1f - Math.Pow(1f - x, 3f); }
public class EaseInOutCubic : EasingBase<EaseInOutCubic>, IEasing { public float Evaluate(float x) => x < .5f ? 4f * x * x * x : 1f - Math.Pow(-2f * x + 2f, 3f) * .5f; }

public class EaseInQuart : EasingBase<EaseInQuart>, IEasing { public float Evaluate(float x) => x * x * x * x; }
public class EaseOutQuart : EasingBase<EaseOutQuart>, IEasing { public float Evaluate(float x) => 1f - Math.Pow(1f - x, 4f); }
public class EaseInOutQuart : EasingBase<EaseInOutQuart>, IEasing { public float Evaluate(float x) => x < .5f ? 8f * x * x * x * x : 1f - Math.Pow(-2f * x + 2f, 4f) * .5f; }

public class EaseInQuint : EasingBase<EaseInQuint>, IEasing { public float Evaluate(float x) => x * x * x * x * x; }
public class EaseOutQuint : EasingBase<EaseOutQuint>, IEasing { public float Evaluate(float x) => 1f - Math.Pow(1f - x, 5f); }
public class EaseInOutQuint : EasingBase<EaseInOutQuint>, IEasing { public float Evaluate(float x) => x < .5f ? 16f * x * x * x * x * x : 1f - Math.Pow(-2f * x + 2f, 5f) * .5f; }

public class EaseInSine : EasingBase<EaseInSine>, IEasing { public float Evaluate(float x) => 1f - Math.Cos(x * Math.PI * .5f); }
public class EaseOutSine : EasingBase<EaseOutSine>, IEasing { public float Evaluate(float x) => Math.Sin(x * Math.PI * .5f); }
public class EaseInOutSine : EasingBase<EaseInOutSine>, IEasing { public float Evaluate(float x) => -(Math.Cos(Math.PI * x) - 1f) * .5f; }

public class EaseInExpo : EasingBase<EaseInExpo>, IEasing { public float Evaluate(float x) => x == 0f ? 0f : Math.Pow(2f, 10f * x - 10f); }
public class EaseOutExpo : EasingBase<EaseOutExpo>, IEasing { public float Evaluate(float x) => x == 1f ? 1f : 1f - Math.Pow(2f, -10f * x); }
public class EaseInOutExpo : EasingBase<EaseInOutExpo>, IEasing { public float Evaluate(float x) => x == 0f ? 0f : x == 1f ? 1f : x < .5f ? Math.Pow(2f, 20f * x - 10f) * .5f : (2f - Math.Pow(2f, -20f * x + 10f)) * .5f; }

public class EaseInCirc : EasingBase<EaseInCirc>, IEasing { public float Evaluate(float x) => 1f - Math.Sqrt(1f - Math.Pow(x, 2f)); }
public class EaseOutCirc : EasingBase<EaseOutCirc>, IEasing { public float Evaluate(float x) => Math.Sqrt(1f - Math.Pow(x - 1f, 2f)); }
public class EaseInOutCirc : EasingBase<EaseInOutCirc>, IEasing { public float Evaluate(float x) => x < .5f ? (1f - Math.Sqrt(1f - Math.Pow(2f * x, 2f))) * .5f : (Math.Sqrt(1f - Math.Pow(-2f * x + 2f, 2f)) + 1f) * .5f; }

public class EaseInBack : EasingBase<EaseInBack>, IEasing { public float Evaluate(float x) => EaseConstants.c3 * x * x * x - EaseConstants.c1 * x * x; }
public class EaseOutBack : EasingBase<EaseOutBack>, IEasing { public float Evaluate(float x) => 1f + EaseConstants.c3 * Math.Pow(x - 1f, 3f) + EaseConstants.c1 * Math.Pow(x - 1f, 2f); }
public class EaseInOutBack : EasingBase<EaseInOutBack>, IEasing { public float Evaluate(float x) => x < .5f ? Math.Pow(2f * x, 2f) * ((EaseConstants.c2 + 1f) * 2f * x - EaseConstants.c2) * .5f : (Math.Pow(2f * x - 2f, 2f) * ((EaseConstants.c2 + 1f) * (x * 2f - 2f) + EaseConstants.c2) + 2f) * .5f; }

public class EaseInElastic : EasingBase<EaseInElastic>, IEasing { public float Evaluate(float x) => x == 0 ? 0 : x == 1f ? 1f : -Math.Pow(2f, 10f * x - 10f) * Math.Sin((x * 10f - 10.75f) * EaseConstants.c4); }
public class EaseOutElastic : EasingBase<EaseOutElastic>, IEasing { public float Evaluate(float x) => x == 0 ? 0 : x == 1f ? 1f : Math.Pow(2f, -10f * x) * Math.Sin((x * 10f - .75f) * EaseConstants.c4) + 1f; }
public class EaseInOutElastic : EasingBase<EaseInOutElastic>, IEasing { public float Evaluate(float x) => x == 0 ? 0 : x == 1f ? 1f : x < .5f ? -(Math.Pow(2f, 20f * x - 10f) * Math.Sin((20f * x - 11.125f) * EaseConstants.c5)) * .5f : Math.Pow(2f, -20f * x + 10f) * Math.Sin((20f * x - 11.125f) * EaseConstants.c5) * .5f + 1f; }

public class EaseInBounce : EasingBase<EaseInBounce>, IEasing { public float Evaluate(float x) => 1f - EaseOutBounce.Instance.Evaluate(1f - x); }
public class EaseOutBounce : EasingBase<EaseOutBounce>, IEasing
{
    public float Evaluate(float x)
    {
        const float n1 = 7.5625f;
        const float d1 = 2.75f;

        if (x < 1f / d1)
            return n1 * x * x;

        if (x < 2f / d1)
            return n1 * (x -= 1.5f / d1) * x + .75f;

        if (x < 2.5f / d1)
            return n1 * (x -= 2.25f / d1) * x + .9375f;

        return n1 * (x -= 2.625f / d1) * x + .984375f;
    }
}
public class EaseInOutBounce : IEasing { public float Evaluate(float x) => x < .5f ? (1f - EaseOutBounce.Instance.Evaluate(1f - 2f * x)) * .5f : (1f + EaseOutBounce.Instance.Evaluate(2f * x - 1f)) * .5f; }