/****************************************************************************
Copyright (c) 2011-2013,WebJet Business Division,CYOU
 
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****************************************************************************/
namespace ScriptRuntime
{
    using System;
    /// <summary>
    /// 数学运算类
    /// </summary>
    public static class MathHelper
    {
        /// <summary>
        /// 数学常数 e
        /// </summary>
        public const float E = 2.718282f;
        /// <summary>
        /// log10 e.
        /// </summary>
        public const float Log10E = 0.4342945f;
        /// <summary>
        /// log2 e.
        /// </summary>
        public const float Log2E = 1.442695f;
        /// <summary>
        /// 圆周率pi
        /// </summary>
        public const float Pi = 3.141593f;
        /// <summary>
        /// 圆周率pi/2
        /// </summary>
        public const float PiOver2 = 1.570796f;
        /// <summary>
        /// 圆周率pi/4
        /// </summary>
        public const float PiOver4 = 0.7853982f;
        /// <summary>
        /// 圆周率pi*2
        /// </summary>
        public const float TwoPi = 6.283185f;
        /// <summary>
        /// 角度转换为弧度所用常量
        /// </summary>
        public const float Deg2Rad = 0.01745329f;
        /// <summary>
        /// 弧度转换为角度所用常量
        /// </summary>
        public const float Rad2Deg = 57.29578f;
        /// <summary>
        /// 一个很小的浮点值
        /// </summary>
        public const float Epsilon = float.Epsilon;
        /// <summary>
        /// 代表正无穷
        /// </summary>
        public const float Infinity = float.PositiveInfinity;
        /// <summary>
        /// 代表负无穷
        /// </summary>
        public const float NegativeInfinity = float.NegativeInfinity;
        /// <summary>
        /// 在规定的范围内限定一个值
        /// </summary>
        /// <param name="value">需要限定的值</param>
        /// <param name="min">最小值</param>
        /// <param name="max">最大值</param>
        /// <returns>返回值</returns>
        public static float Clamp(float value, float min, float max)
        {
            value = (value > max) ? max : value;
            value = (value < min) ? min : value;
            return value;
        }
        /// <summary>
        /// 在规定的范围内限定一个值
        /// </summary>
        /// <param name="value">需要限定的值</param>
        /// <param name="min">最小值</param>
        /// <param name="max">最大值</param>
        /// <returns>返回值</returns>
        public static int Clamp(int value, int min, int max)
        {
            value = (value > max) ? max : value;
            value = (value < min) ? min : value;
            return value;
        }
        /// <summary>
        /// Hermite样条插值
        /// </summary>
        /// <param name="value1">源值</param>
        /// <param name="tangent1">源切线</param>
        /// <param name="value2">源值</param>
        /// <param name="tangent2">源切线</param>
        /// <param name="amount">权重</param>
        /// <returns>Hermite样条插值的结果</returns>
        public static float Hermite(float value1, float tangent1, float value2, float tangent2, float amount)
        {
            float num3 = amount;
            float num = num3 * num3;
            float num2 = num3 * num;
            float num7 = ((2f * num2) - (3f * num)) + 1f;
            float num6 = (-2f * num2) + (3f * num);
            float num5 = (num2 - (2f * num)) + num3;
            float num4 = num2 - num;
            return ((((value1 * num7) + (value2 * num6)) + (tangent1 * num5)) + (tangent2 * num4));
        }
        /// <summary>
        /// 两个向量之间的线性插值
        /// </summary>
        /// <param name="value1">源值</param>
        /// <param name="value2">源值</param>
        /// <param name="amount">表明value2的权重，数字0到1之间</param>
        /// <returns>结果所得值</returns>
        public static float Lerp(float value1, float value2, float amount)
        {
            return (value1 + ((value2 - value1) * amount));
        }
        /// <summary>
        /// 返回较大的值
        /// </summary>
        /// <param name="a">源值</param>
        /// <param name="b">源值</param>
        /// <returns>较大的值</returns>
        public static float Max(float a, float b)
        {
            return ((a <= b) ? b : a);
        }
        /// <summary>
        /// 返回较小的值
        /// </summary>
        /// <param name="a">源值</param>
        /// <param name="b">源值</param>
        /// <returns>较小的值</returns>
        public static float Min(float a, float b)
        {
            return ((a >= b) ? b : a);
        }
        /// <summary>
        /// 返回较大的值 
        /// </summary>
        /// <param name="a">源值</param>
        /// <param name="b">源值</param>
        /// <returns>较大的值</returns>
        public static int Max(int a, int b)
        {
            return ((a <= b) ? b : a);
        }
        /// <summary>
        /// 返回较小的值
        /// </summary>
        /// <param name="a">源值</param>
        /// <param name="b">源值</param>
        /// <returns>较小</returns>
        public static int Min(int a, int b)
        {
            return ((a >= b) ? b : a);
        }
        /// <summary>
        /// 用立方等式在两个值之间插值
        /// </summary>
        /// <param name="value1">源值</param>
        /// <param name="value2">源值</param>
        /// <param name="amount">权重</param>
        /// <returns>插值结果</returns>
        public static float SmoothStep(float value1, float value2, float amount)
        {
            float num = Clamp(amount, 0f, 1f);
            return Lerp(value1, value2, (num * num) * (3f - (2f * num)));
        }
        /// <summary>
        /// 将弧度转换为角度
        /// </summary>
        /// <param name="radians">角的弧度值</param>
        /// <returns>角的角度值</returns>
        public static float RadiansToDegrees(float radians)
        {
            return (radians * 57.29578f);
        }
        /// <summary>
        /// 将弧度转换为角度
        /// </summary>
        /// <param name="degrees">角的角度值</param>
        /// <returns>角的弧度值</returns>
        public static float DegreesToRadians(float degrees)
        {
            return (degrees * 0.01745329f);
        }
        /// <summary>
        /// 指定角的正弦
        /// </summary>
        /// <param name="f">一个角的弧度表示</param>
        /// <returns>角的正弦值，如果角为NaN或者是正无穷或负无穷，返回NaN</returns>
        public static float Sin(float f)
        {
            return (float)Math.Sin((double)f);
        }
        /// <summary>
        /// 指定角的余弦
        /// </summary>
        /// <param name="f">一个角的弧度表示</param>
        /// <returns>角的余弦值</returns>
        public static float Cos(float f)
        {
            return (float)Math.Cos((double)f);
        }
        /// <summary>
        /// 指定角的正切
        /// </summary>
        /// <param name="f">一个角的弧度表示</param>
        /// <returns>角的正切值，如果角为NaN或者是正无穷或负无穷，返回NaN</returns>
        public static float Tan(float f)
        {
            return (float)Math.Tan((double)f);
        }
        /// <summary>
        /// 指定值的反正弦
        /// </summary>
        /// <param name="f">正弦值</param>
        /// <returns>一个角的弧度表示</returns>
        public static float ASin(float f)
        {
            return (float)Math.Asin((double)f);

        }
        /// <summary>
        /// 指定值的反余弦
        /// </summary>
        /// <param name="f">余弦值</param>
        /// <returns>一个角的弧度表示</returns>
        public static float ACos(float f)
        {
            return (float)Math.Acos((double)f);
        }
        /// <summary>
        /// 指定值的反正切
        /// </summary>
        /// <param name="f">正切值</param>
        /// <returns>一个角的弧度表示</returns>
        public static float ATan(float f)
        {
            return (float)Math.Atan((double)f);
        }
        /// <summary>
        /// Returns the angle whose tangent is the quotient of two specified numbers.
        /// </summary>
        /// <param name="a">点的X坐标</param>
        /// <param name="b">点的Y坐标</param>
        /// <returns>一个角的弧度表示, 例如 -π≤θ≤π, 和 tan(θ) = y / x, 点(x, y)在笛卡尔坐标系中.遵守如下规律: 
        ///(x, y)在第一象限 ,0 &lt; θ &lt; π/2.
        ///(x, y)在第二象限 , π/2 &lt; θ≤π.
        ///(x, y)在第三象限 , -π &lt; θ &lt; -π/2.
        ///(x, y)在第四象限 , -π/2 &lt; θ &lt; 0.
        ///如果点在象限边界，值如下：
        ///如果X为0，Y为非负, θ = 0.
        ///如果X为0，Y为负, θ = π.
        ///如果X为负，Y为0, θ = π/2.
        ///如果X为正，Y为0, θ = -π/2.
        ///</returns>
        public static float ATan2(float a, float b)
        {
            return (float)Math.Atan2((double)a, (double)b);
        }
        /// <summary>
        /// 求指定数的平方根
        /// </summary>
        /// <param name="f">指定数值</param>
        /// <returns>零或者正数返回结果，负数返回NaN</returns>
        public static float Sqrt(float f)
        {
            return (float)Math.Sqrt((double)f);
        }
        /// <summary>
        /// 求指定数的绝对值
        /// </summary>
        /// <param name="f">指定数</param>
        /// <returns>绝对值</returns>
        public static float Abs(float f)
        {
            return Math.Abs(f);
        }
        /// <summary>
        /// 求指定数的绝对值
        /// </summary>
        /// <param name="value">指定数</param>
        /// <returns>绝对值</returns>
        public static int Abs(int value)
        {
            return Math.Abs(value);
        }
        /// <summary>
        /// 求指定数的指定次方
        /// </summary>
        /// <param name="fBase">底数</param>
        /// <param name="fExponent">指数 </param>
        /// <returns>结果值</returns>
        public static float Pow(float fBase, float fExponent)
        {
            return (float)Math.Pow((double)fBase, (double)fExponent);
        }
        /// <summary>
        /// 数学常量e的指定次方
        /// </summary>
        /// <param name="power">指数</param>
        /// <returns>结果值</returns>
        public static float Exp(float power)
        {
            return (float)Math.Exp((double)power);
        }
        /// <summary>
        /// 求指定数的对数
        /// </summary>
        /// <param name="f">指定数</param>
        /// <returns>结果</returns>
        public static float Log(float f)
        {
            return (float)Math.Log((double)f);
        }
        /// <summary>
        /// 求指定数的以10为底对数
        /// </summary>
        /// <param name="f">指定数</param>
        /// <returns>结果</returns>
        public static float Log10(float f)
        {
            return (float)Math.Log10((double)f);
        }
        /// <summary>
        /// 求比指定数大或相等的最小整数
        /// </summary>
        /// <param name="f">一个数 </param>
        /// <returns>比指定数大或相等的最小整数</returns>
        public static float Ceil(float f)
        {
            return (float)Math.Ceiling((double)f);
        }
        /// <summary>
        /// 求比指定数小或相等的最大整数
        /// </summary>
        /// <param name="f">一个数 </param>
        /// <returns>比指定数小或相等的最大整数</returns>
        public static float Floor(float f)
        {
            return (float)Math.Floor((double)f);
        }
        /// <summary>
        /// 求距指定数最近的一个整数
        /// </summary>
        /// <param name="f">一个数.</param>
        /// <returns>结果</returns>
        public static float Round(float f)
        {
            return (float)Math.Round((double)f);
        }
        /// <summary>
        /// 求比指定数大或相等的最小整数
        /// </summary>
        /// <param name="f">一个数 </param>
        /// <returns>比指定数大或相等的最小整数</returns>
        public static int ICeil(float f)
        {
            return (int)Math.Ceiling((double)f);
        }
        /// <summary>
        /// 求比指定数小或相等的最大整数
        /// </summary>
        /// <param name="f">一个数</param>
        /// <returns>比指定数小或相等的最大整数</returns>
        public static int IFloor(float f)
        {
            return (int)Math.Floor((double)f);
        }
        /// <summary>
        /// 求距指定数最近的一个整数
        /// </summary>
        /// <param name="f">一个数</param>
        /// <returns>距指定数最近的一个整数</returns>
        public static int IRound(float f)
        {
            return (int)Math.Round((double)f);
        }
        /// <summary>
        /// 检测一个数是否是2的次幂
        /// </summary>
        /// <param name="value">一个数</param>
        /// <returns>是返回true，不是false</returns>
        public static bool IsPowerOfTwo(int value)
        {
            return ((value & (value - 1)) == 0);
        }
        /// <summary>
        /// 求最接近较大的2的次幂
        /// </summary>
        /// <param name="v">一个数</param>
        /// <returns>最接近较大的2的次幂</returns>
        public static int NextPowerOfTwo(int v)
        {
            v -= 1;
            v |= v >> 16;
            v |= v >> 8;
            v |= v >> 4;
            v |= v >> 2;
            v |= v >> 1;
            return v + 1;
        }
    }
}