// Written By: Biplav Chapagain
// Date: 2019-09-19
// This program reads data from a .csv file and interpolates the data.
#include <iostream>
#include <vector>
#include <fstream>
#include <string>
#include <sstream>


using namespace std;
struct Data
{
    float t, x;
};

int size = 10;
Data A[10];

int read2DimData(int size) { //function to read data from a file
   ifstream ip("Prob2-2.csv");
   if (!ip.is_open()) std::cout << "ERROR: File is Open" << '\n';
   string st;
   string sx;
   float t[size];
   float x[size];
   int i=0;

   while (ip.good()&& (i < size)) {
	   	getline(ip, st, ',');
	   	getline (ip, sx, '\n');
	    stringstream convertt(st);
	   	convertt >> t[i];
	   	A[i].t= t[i];
	   	stringstream convertx(sx);
	   	convertx >> x[i];
	   	A[i].x= x[i];
	   	i++;
   }
   ip.close();
   return 0;
}

float polynomialInterpolate(Data D[], float ti, int n) {
	float answer =0;
	for (int i=0; i < n; i++){
		float holdert = 1;
		for (int j=0; j < n; j++)
		{
			if (j!=i) {
				holdert= holdert* ((ti- (A[j].t))/((A[i].t)-(A[j].t)));
			}
		}

		answer= answer+ holdert* A[i].x;
		//cout << answer<< endl;
	}
	return answer;
}

int main() {
	float t;
	int check=0;
	float answer;
	read2DimData(size);
	cout << "The Data read from the file is below: " << endl;
	for (int i =0; i < size; i++) {
		cout <<A [i].t<< " , "<< A [i].x << endl ;
	}
	cout << ""<< endl;
	cout << "Enter the value of t you wish to calculate" << endl;
	while (check ==0){
		check =1;
		cin >> t;
		if ((t < A[0].t) || (t > A[size-1].t)) {
			cout << "Please enter a value of t within [" << A[0].t << " , " << A[size-1].t << "]" << endl;
			check =0;
		}
	}
	answer = polynomialInterpolate(A, t, size);
	cout << "The value of x corresponding to t= " << t << " is: "<< answer << endl;

	return 0;
}