// Program to compute mean, standard deviation and standard
// error of the mean electronic charge. Data is read from file.

#include<iostream>
#include<iomanip>
#include<fstream>
#include<cmath>
#include<string>
#include<sstream>

using namespace std;

// Functions to compute mean and standard deviation

double calcmean(double *data){
	double sum{0};
	int length = sizeof(data);
	for (int i = 0; i < length; i++){
		sum += data[i];
	}
	double mean = sum / (length);
	return mean;
}
double calcstddev(double *data){
	double sum{ 0 };
	int length = sizeof(data);
	double sumdev2{ 0 };

	for (int i = 0; i < length; i++){
		sum += data[i];
	}
	double mean = sum / length;
	for (int i = 0;i < length; i++){
		sumdev2 += pow(data[i] - mean, 2);
	}
	double stddev = pow(sumdev2 / (length - 1), 0.5);
	return stddev;
}
double strtodbl(string s) {
	double d;
	stringstream ss(s);
	ss >> d;
	return d;
}
bool linetest(string input){
	stringstream ss(input);
	double d;
	if (!(ss >> d)){
		return 0;
	}
	return 1;
}

// Main function

int main()
{
	int datapoints{0};
	string filename;
	/* Ask user to enter number of data points
	cout << "How many data points does your file contain? "; cin >> datapoints;
	while (cin.fail() || datapoints != floor(datapoints) || datapoints < 0){
		cout << "How many data points does your file contain? "; cin.clear(); cin.ignore() >> datapoints;
	}*/
	// Ask user to enter filename
	cout << "What is the name of your file? "; cin >> filename;

	// Open file and check if successful
	fstream myfile(filename);
	if (!myfile.good()) {
		cout << "Error: File could not be opened." << endl;
	}

	// Allocate memory for data
	double *data;
	data = new double[datapoints];

	// Read data from file, ignoring any additional bad data
	string line;
	while (getline(myfile, line)){
		cout << line << endl;
		if (linetest(line)){
			datapoints++;
		}
	}
	cout << "The file contains " << datapoints << " measurements." << endl;
	/*myfile.clear();
	myfile.seekg((0, ios::beg));
	int i{0};
	while (getline(myfile, line)){
		if (linetest(line)){
				data[i] = strtodbl(line);
				i++;
			}
		else{
			cout << "Error encountered: " << line << " is not a valid input" << endl;
		}
	}

	// Close file
	myfile.close();


	 //Compute mean
	double mean = calcmean(data);

	// Compute standard deviation
	double stddev = calcstddev(data);

	// Compute standard error of mean
	double stderrmean = calcstddev(data) / pow(datapoints, 0.5);

	cout << "The mean value is: " << mean << endl;
	cout << "standard error on the mean is: " << stddev << endl;
	cout << "The standard deviation is: " << stderrmean << endl;

	// Free memory*/
	delete[] data;

	return 0;
}