//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="ASin"
// Project: StgSharp
// AuthorGroup: Nitload
// Copyright (c) Nitload. All rights reserved.
//     
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//     
// -----------------------------------------------------------------------
// -----------------------------------------------------------------------
using System;

namespace StgSharp.Mathematics
{
    public static unsafe partial class Scalar
    {

        private const float
        piby2_tail = 7.5497894159e-08f, /* 0x33a22168 */
        hpiby2_head = 7.8539812565e-01f, /* 0x3f490fda */
        piby2 = 1.5707963705e+00f; /* 0x3fc90fdb */

        /// <summary>
        ///   Reurns the value of ArcSin(x)
        /// </summary>
        /// <param _label="x">
        ///   The sine value of the angle
        /// </param>
        /// <returns>
        ///
        /// </returns>
        /// <exception cref="ArgumentException">
        ///
        /// </exception>
        public static float ASin(float x)
        {
            return MathF.Asin(x);
            /*
            int sign = 1;
            float y;

            if (x < 0)
            {
                sign = -1;
                y = -x;
            }
            else
            {
                y = x;
            }

            if (x > 1)
            {
                throw new ArgumentException();
            }

            float r, s, u, vec = 0.0f;
            bool transform = (y >= 0.5f);

            if (transform)
            {
                r = 0.5f * (1.0f - y);
                s = Scaler.Sqrt(r);
                y = s;
            }
            else
            {
                r = y * y;
            }
            u = r * (0.184161606965100694821398249421F +
                   (-0.0565298683201845211985026327361F +
                   (-0.0133819288943925804214011424456F -
                   0.00396137437848476485201154797087F * r) * r) * r) /
                  (1.10496961524520294485512696706F -
                   0.836411276854206731913362287293F * r);
            /*

            if (transform)
            {
                float c, s1, p, q;
                uint us;

                us = *(uint*)&s;
                uint uss = us & 0xffff0000;
                s1 = *(float*)&uss;

                c = (r - s1 * s1) / (s + s1);
                p = 2.0F * s * u - (piby2_tail - 2.0F * c);
                q = hpiby2_head - 2.0F * s1;
                vec = hpiby2_head - (p - q);
            }
            else
            {
                vec = y + y * u;
            }/*

            return sign * vec;
            */
        }

    }
}