using System;

namespace Science.Physics.GeneralPhysics
{
	/// <summary>
	/// NewtonEquation is written with Force, Mass, and Acceleration.
	/// </summary>
	public class NewtonEquation
	{
		public NewtonEquation()
		{
		}
		private TotalForce[] f;
		private Mass[] m;
		private Acceleration[] a;
		private ConstraintFunctionToBeZero[] cf;
		private int numcons = 0;

		public NewtonEquation(TotalForce[] ff, Mass[] mm,
			Acceleration[] aa)
		{
			f = ff;
			m = mm;
			a = aa;
		}

		public delegate double ConstraintFunctionToBeZero(TotalForce[] f, Mass[] m, Acceleration[] a);
			
		public void Constraint(ConstraintFunctionToBeZero[] func)
		{
			cf = func;
			numcons = func.Length;
    	}

    	public void Solve()    
		{
			int ndim = 0;
			for(int k = 0; k < m.Length; k++) if(m[k].VariableQ) ndim += 1;
			for(int k = 0; k < a.Length; k++)
			{
				if(a[k].XVariableQ) ndim += 1;
				if(a[k].YVariableQ) ndim += 1;
				if(a[k].ZVariableQ) ndim += 1;
			}
			for(int k = 0; k < f.Length; k++)
			{
				for(int kk = 0; kk < f[k].NumberOfDecomposedForces; kk++)
				{
					if(f[k].DecomposedForce[kk].XVariableQ) ndim += 1;
					if(f[k].DecomposedForce[kk].YVariableQ) ndim += 1;
					if(f[k].DecomposedForce[kk].ZVariableQ) ndim += 1;
				}
			}
            Calculus.Function<double[],double> fun
                = new Calculus.Function<double[], double>(Func);
            double[] c = new double[ndim];
            double[] ans = Calculus.MinimumOfFunction(fun, c, 100.0);
		}
		private double Func(double[] x)
		{
			int i = 0;
			for(int k = 0; k < m.Length; k++) if(m[k].VariableQ) this.m[k].kg = x[i++];
			for(int k = 0; k < a.Length; k++)
			{
				if(a[k].XVariableQ) this.a[k].X = x[i++];
				if(a[k].YVariableQ) this.a[k].Y = x[i++];
				if(a[k].ZVariableQ) this.a[k].Z = x[i++];
			}
			for(int k = 0; k < f.Length; k++)
			{
				for(int kk = 0; kk < f[k].NumberOfDecomposedForces; kk++)
				{
					if(f[k].DecomposedForce[kk].XVariableQ) 
						this.f[k].DecomposedForce[kk].X = x[i++];
					if(f[k].DecomposedForce[kk].YVariableQ)
						this.f[k].DecomposedForce[kk].Y = x[i++];
					if(f[k].DecomposedForce[kk].ZVariableQ) 
						this.f[k].DecomposedForce[kk].Z = x[i++];
				}
			}
			double sum = 0.0;
			for(int k = 0; k < numcons; k++)
			{
				sum += cf[k](this.f,this.m,this.a)*cf[k](this.f,this.m,this.a);
			}
			return BasicConstraint()+sum;
		}	
		private double BasicConstraint()
		{
			double zero = 0.0;
			for(int k = 0; k < this.f.Length; k++)
				zero += (this.f[k].X - this.m[k].kg*this.a[k].X)*
                    (this.f[k].X - this.m[k].kg*this.a[k].X)
					+(this.f[k].Y - this.m[k].kg*this.a[k].Y)*
					(this.f[k].Y - this.m[k].kg*this.a[k].Y)
					+(this.f[k].Z - this.m[k].kg*this.a[k].Z)*
					(this.f[k].Z - this.m[k].kg*this.a[k].Z);
			return zero;
		}	
	}
}