#include<iostream>
#include <cstdlib> 
#include<fstream>
#include<iomanip>
#include<cmath>
#include<vector>
using namespace std;

vector<double> currentHistogramValues;

int main(int argc, char* argv[]) {

  int c;	
  string usage = "standard-deviation -l <list-of-files> -i <input-path> -o <output-file> -t <type>";
  string inputFileListName;
  string inputPath;
  string outputFileName;
  string distributionType;
  string inputFileList;
  string currentFileName;

  while ((c = getopt (argc, argv, "i:o:l:t:h")) != -1)
    switch (c)
    {
      case 'l':
        inputFileListName = optarg;
        break;
      case 'i':
        inputPath = optarg;
        break;
      case 'o':
        outputFileName = optarg;
        break;
      case 't':
        distributionType = optarg;
        break;
      case 'h':
        cout << usage << endl;
        exit(1);
        break;
      default:
        break;
    }

  if( (inputFileListName.empty())  || (inputPath.empty()) || (distributionType.empty()) || (outputFileName.empty()) ) {
    cerr << usage << endl;
    exit(1);
  }	

  ifstream inputFileNames(inputFileListName.c_str());
  ofstream outputFile(outputFileName.c_str());
  string prefixPath(inputPath.c_str());
  string metricName(distributionType.c_str());

  if (inputFileNames.fail() == true) {
    cout << "Input File can not be opened"<<endl;
    exit(0);
  }

  outputFile<<left<<setw(30)<<"File Name"<<left<<setw(20)<<"Standard deviation"<<left<<setw(20)<<"Mean"<<endl;

  while(inputFileNames>>currentFileName) {

    string currentFileWithExtension = prefixPath + currentFileName + "/" + currentFileName + "_"+ metricName +".txt";
    cout<<"File: "<<currentFileWithExtension<<endl;
    ifstream currentFile(currentFileWithExtension.c_str());
    if (currentFile.fail() == true) {
      cout << currentFileName + " cannot be opened"<<endl;
      exit(0);
    }

    // N = sum(H_i) for i = 0 to M-1, M = number of samples in the histogram
    // mean = 1/N*(sum(i*H_i)) for i = 0 to M-1
    double currentValueOfHistogram;
    double sumOfValues = 0.0;
    currentHistogramValues.clear();
    double i = 0.0;
    double N = 0.0;
    double M = 0.0;
    while (currentFile >> currentValueOfHistogram) {
      sumOfValues = sumOfValues + i*currentValueOfHistogram;
      currentHistogramValues.push_back(currentValueOfHistogram);

      N = N + currentValueOfHistogram;
      i=i+1.0;
    }

    M = currentHistogramValues.size();
    // mean
    double mean = sumOfValues/N;

    // sigma^2 = (sum( (i-mean)^2*H_i ) )/(N-1) for i = 0 to M-1
    double standardDev = 0.0;
    double sumSquaredResults = 0.0;
    int j = 0;
    for (i=0.0; i<M; i=i+1.0) {
      sumSquaredResults += pow((i-mean), 2.0)*currentHistogramValues[j];
      j++;
    }

    // standard deviation
    standardDev = sumSquaredResults/(N-1);
    standardDev = sqrt(standardDev);

    outputFile<<left<<setw(30)<<currentFileName<<left<<setw(20)<<standardDev<<left<<setw(20)<<mean<<endl;

    currentFile.close();
  }

  inputFileNames.close();
  outputFile.close();

  return(0);
}