//This was written as an exercise for a friend for a CFD class

using System;
using System.Collections.Generic;
using System.IO;

namespace CenterOfGravity
{
    class Program
    {
        static void Main(string[] args)
        {
			//dataFile is a FileInfo that represent the File at the given Location
            FileInfo dataFile = new FileInfo(@"C:\inputFile.txt");
			//This makes a collection of Particle objects
            List<Particle> particles = new List<Particle>();

			//This part opens the dataFile into fileStream which lets the file be read
            using (StreamReader fileStream = dataFile.OpenText())
            {
				//make a string called line to store each line in as it's read
                string line = "";
				//This makes an array of items to split the file lines along
                string[] splits = new string[1];
                splits[0] = " ";
				//While there are still lines to be read set line equal to that line
                while ((line = fileStream.ReadLine()) != null)
                {
					//split up the current line into a Array of strings
                    string[] part = line.Split(splits, StringSplitOptions.RemoveEmptyEntries);
					//add a new particle to the Collection of particles
					//Set that particles properties equal to the values found in the string array
                    particles.Add(new Particle
                    {
                        Mass = Double.Parse(part[0]),
                        XPosition = Double.Parse(part[1]),
                        YPosition = Double.Parse(part[2]),
                        ZPosition = Double.Parse(part[3])

                    });
                }
			}

			//This part does the math
			double xcenter = 0.0;
			double ycenter = 0.0;
			double zcenter = 0.0;
			double totalMass = 0.0;
			//Loop through all of the particles in the collection of particles and find the total mass
			foreach (Particle particle in particles)
			{
				totalMass += particle.Mass;
			}
			//Perform the summation of the weighted positions
			foreach (Particle particle in particles)
			{
				xcenter += (particle.Mass * particle.XPosition) / totalMass;
				ycenter += (particle.Mass * particle.YPosition) / totalMass;
				zcenter += (particle.Mass * particle.ZPosition) / totalMass;
			}
			//Write Out the output file
			using (StreamWriter outputFile = new StreamWriter(@"C:\output.dat", false))
			{
				outputFile.WriteLine("Total Mass = " + totalMass);
				outputFile.WriteLine("Center of Gravity");
				outputFile.WriteLine("x = " + xcenter);
				outputFile.WriteLine("y = " + ycenter);
				outputFile.WriteLine("z = " + zcenter);
			}
        }
    }
	//A Class representing the particle object.
    class Particle
    {
        public double XPosition { get; set; }
        public double YPosition { get; set; }
        public double ZPosition { get; set; }
        public double Mass { get; set; }
    }
}