/**********************************************************

This software is part of J.-S. Caux's ABACUS library.

Copyright (c) J.-S. Caux.

-----------------------------------------------------------

File:  LiebLin_Fourier_to_t_equal_x.cc

Purpose:  Fourier transform to static space correlator for LiebLin.

***********************************************************/

#include "ABACUS.h"

using namespace std;
using namespace ABACUS;


int main(int argc, char* argv[])
{
  if (argc != 10) { // provide some info

    cout << endl << "Welcome to ABACUS\t(copyright J.-S. Caux)." << endl;
    cout << endl << "Usage of LiebLin_Fourier_to_x_equal_t executable: " << endl;
    cout << endl << "Provide the following arguments:" << endl << endl;
    cout << "char whichDSF \t\t Which structure factor ?  Options are:  d for rho rho, g for psi psi{dagger}, o for psi{dagger} psi" << endl;
    cout << "DP c_int \t\t Value of the interaction parameter" << endl;
    cout << "DP L \t\t\t Length of the system" << endl;
    cout << "int N \t\t\t Number of particles" << endl;
    cout << "int iKmin" << endl << "int iKmax \t\t Min and max momentum integers scanned over" << endl;
    cout << "DP kBT \t\t Temperature" << endl;
    cout << "int Npts_t \t Number of points in time for the Fourier transform" << endl;
    cout << "DP t_max \t Max time to be used" << endl;
  }

  else { // (argc == 10), correct nr of arguments
    char whichDSF = *argv[1];
    DP c_int = atof(argv[2]);
    DP L = atof(argv[3]);
    int N = atoi(argv[4]);
    int iKmin = atoi(argv[5]);
    int iKmax = atoi(argv[6]);
    DP kBT = atof(argv[7]);
    int Npts_t = atoi(argv[8]);
    DP t_max = atof(argv[9]);

    // Momentum business: use symmetry
    if (iKmin != 0) ABACUSerror("LiebLin_Fourier_to_t_equal_x only implemented for raw files with iKmin == 0.");

    stringstream filenameprefix;
    Data_File_Name (filenameprefix, whichDSF, c_int, L, N, iKmin, iKmax, kBT, 0.0, "");
    string prefix = filenameprefix.str();

    stringstream RAW_stringstream;    string RAW_string;
    RAW_stringstream << prefix << ".raw";
    RAW_string = RAW_stringstream.str();    const char* RAW_Cstr = RAW_string.c_str();
    ifstream RAW_infile;
    RAW_infile.open(RAW_Cstr);
    if (RAW_infile.fail()) {
      cout << RAW_Cstr << endl;
      ABACUSerror("Could not open RAW_infile... ");
    }

    // We also read the f-sumrule file, to correct for missing intensity.
    stringstream FSR_stringstream;    string FSR_string;
    FSR_stringstream << prefix << ".fsr";
    FSR_string = FSR_stringstream.str();    const char* FSR_Cstr = FSR_string.c_str();
    ifstream FSR_infile;
    FSR_infile.open(FSR_Cstr);
    if (FSR_infile.fail()) {
      cout << FSR_Cstr << endl;
      ABACUSerror("Could not open FSR_infile... ");
    }

    stringstream SFT_stringstream;    string SFT_string;
    SFT_stringstream << prefix << ".tft";
    SFT_string = SFT_stringstream.str();    const char* SFT_Cstr = SFT_string.c_str();
    ofstream SFT_outfile;
    SFT_outfile.open(SFT_Cstr);
    if (SFT_outfile.fail()) ABACUSerror("Could not open TFT_outfile... ");

    // First compute the static structure factor from the RAW data:

    Vect_DP TSF(0.0, Npts_t);

    DP omega;
    int iK;
    DP FF;
    //int conv;
    DP dev;
    string label;

    // Now define time coordinates: between 0 and t_max
    Vect_DP tlattice(Npts_t);
    for (int i = 0; i < Npts_t; ++i) tlattice[i] = (i + 0.5) * t_max/Npts_t;

    // Now the correlation at t:
    Vect<complex<DP> > FT(0.0, Npts_t);
    Vect_DP FTre(0.0, Npts_t);
    Vect_DP FTim(0.0, Npts_t);

    while (RAW_infile.peek() != EOF) {
      RAW_infile >> omega >> iK >> FF >> dev >> label;
      if (iK == 0)
	for (int it = 0; it < Npts_t; ++it)
	  FT[it] += FF * FF * exp(II * omega * tlattice[it]);
      else
	for (int it = 0; it < Npts_t; ++it)
	  FT[it] += 2.0 * FF * FF * exp(II * omega * tlattice[it]);
    }
    RAW_infile.close();

    // Reset proper normalization:
    for (int it = 0; it < Npts_t; ++it) {
      FTre[it] = real(FT[it]);
      FTim[it] = imag(FT[it]);
    }

    // Output to file:
    for (int it = 0; it < Npts_t; ++it) {
      if (it > 0) SFT_outfile << endl;
      SFT_outfile << tlattice[it] << "\t" << FTre[it] << "\t" << FTim[it];
    }

    SFT_outfile.close();
  }

  return(0);

}