using System;
using System.Globalization;


namespace Assets.Scenes.Ride.Scripts
{
    public class Helper
    {
        /// <summary>
        /// 计算速度
        /// 参考 http://bikecalculator.com/index.html
        /// </summary>
        /// <param name="elevationv">海拔</param>
        /// <param name="gradev">坡度%</param>
        /// <param name="powerv">功率</param>
        /// <param name="rweightv">体重</param>
        /// <param name="bweightv">自行车重量</param>
        /// <returns>km/h</returns>
        public static double CalculateSpeed(double elevationv, double gradev, double powerv, double rweightv, double bweightv)
        {
            if (powerv < 0)
            {
                return 0;
            }
            if (gradev < -10)
            {
                gradev = -10;
            }
            var tireValues = new double[] { 0.005, 0.004, 0.012 };
            var aeroValues = new double[] { 0.388, 0.445, 0.420, 0.300, 0.233, 0.200 };
            var units = 0;

            //温度
            var temperaturev = 25;

            //海拔
            //var elevationv = 100;

            //坡度
            //var gradev = 6 * 0.01 * -1;

            //风，转换成m/s
            var headwindv = 0 / 3.6;

            var frontalArea = aeroValues[0];

            var transv = 0.95; // no one knows what this is, so why bother presenting a choice?
            var rollingRes = tireValues[0];

            //应该是空气密度
            var density = (1.293 - 0.00426 * temperaturev) * Math.Exp(-elevationv / 7000.0);


            //全空气阻力参数
            var a2 = 0.5 * frontalArea * density;   // full air resistance parameter
            var twt = 9.8 * (rweightv + bweightv);  // total weight in newtons
            var tres = twt * (gradev * 0.01 + rollingRes); // gravity and rolling resistance

            //var powerv = 195;

            var v = Newton(a2, headwindv, tres, transv, powerv) * 3.6;// convert to km/h

            //Trace.WriteLine($"速度为：{ v }");

            var t1 = makeDecimal2(v * (units == 1 ? 1.609 : 1.0));
            return double.Parse(t1, CultureInfo.InvariantCulture);
        }
        private static double Newton(double aero, double hw, double tr, double tran, double p)
        {
            var vel = 20D;
            var MAX = 10;
            var TOL = 0.05;
            for (int i = 0; i < MAX; i++)
            {
                var tv = vel + hw;
                var aeroEff = (tv > 0.0) ? aero : -aero; // wind in face, must reverse effect
                var f = vel * (aeroEff * tv * tv + tr) - tran * p; // the function
                var fp = aeroEff * (3.0 * vel + hw) * tv + tr;     // the derivative
                var vNew = vel - f / fp;
                if (Math.Abs(vNew - vel) < TOL)
                {
                    return vNew;  // success
                }
                vel = vNew;
            }
            return 0.0;
        }
        private static string makeDecimal2(double value)
        {
            if (value != 0)
            {
                var x = Math.Round(value * 100);
                int d;
                if (x < 100)
                {
                    d = 0;
                }
                else
                {
                    d = Convert.ToInt32(Math.Floor(x / 100), CultureInfo.InvariantCulture);
                };
                var c = x % 100;
                var g = (c >= 10) ? "" : "0";
                return "" + d + "." + g + c;
            }
            return value.ToString(CultureInfo.InvariantCulture);
        }
    }
}