using System;

namespace Science.Mathematics.VectorCalculus
{
    public class TangentPlaneToLevelSurface : Plane
    {
        public TangentPlaneToLevelSurface(Function.ToLastType<double[],double> f,
            double[] at)
        {
            Gradient obj = new Gradient(f, at);
            obj.Compute();
            this.ThroughTip = new Vector(at);
            this.Normal = new Vector(obj.Result);
            if (this.Normal[0] == 0.0)
            {
                this.Direction1 = this.Normal % UnitVector.i;
                this.Direction2 = this.Normal % this.Direction1;
            }
            else if (this.Normal[1] == 0.0)
            {
                this.Direction1 = this.Normal % UnitVector.j;
                this.Direction2 = this.Normal % this.Direction1;
            }
            else
            {
                this.Direction1 = this.Normal % UnitVector.k;
                this.Direction2 = this.Normal % this.Direction1;
            }
        }
    }
}