#include "TF1.h"
#include "TCanvas.h"
#include "TLegend.h"
#include "TAxis.h"
   
TF1 *Gks, *Gkf, *eLst, *fInt;

double fint(double *x, double *par) {
   double tp = x[0];
   double lambda = par[0];
   double t = par[1];
   return lambda*Gkf->Eval(tp)*eLst->Eval(tp)*Gks->Eval(t-tp);
}
double gkcalc(double *x, double * /*par*/) {
   double t = x[0];
   fInt->SetParameter(1,t);
   return eLst->Eval(t)*Gkf->Eval(t) +fInt->Integral(0,t);
}

void gks() {
    //Calculate Gks
    //parameter[0] = alpha_k
    //parameter[1] = gamma
    Gks = new TF1("Gks","[0]+(1-[0])*exp(-[1]*x)",0,15);
    Gks->SetParameters(0.221243,0.4);
    //Calculate Gkf
    //parameter[0] = lambda_k
    //parameter[1] = tau_c
    Gkf = new TF1("Gkf","(1-[0]*[1])*exp(-[0]*x)",0,15);
    Gkf->SetParameters(0.172,0.5);
    //Calculate expLamba*t
    double Lambdas = 0.0345;
    //parameter[0] = 1    
    //parameter[1] = Lambda*
    eLst = new TF1("eLst","[0]*exp(-[1]*x)",0,15);
    eLst->SetParameters(1.,Lambdas);
    //calculate teh function to be integrated
    fInt = new TF1("fInt",fint,0,15,2);
    fInt->SetParameter(0,Lambdas);   
    //Combine Gks and Gkf to for Gkcalc
    //TF1 *Gkcalc = new TF1("Gkcalc","Gkf*eLst*[0]*[1]",0,15);  // This is the bit I can't get!!!!!!!!
    TF1 *Gkcalc = new TF1("Gkcalc",gkcalc,0,15,1);  // This is the bit I can't get!!!!!!!!
    
    //Create a canvas to draw Gkcalc
    TCanvas *Gkcalc1 = new TCanvas("Gkcalc1","Gkcalc1",10,10,1400,1200);
    //Draw and format Gkcalc
    Gkcalc->Draw();
    Gkcalc->SetLineWidth(2);
    Gkcalc->SetLineColor(kBlue);
    Gkcalc->GetXaxis()->SetTitle("time");
    Gkcalc->GetYaxis()->SetTitle("G_{k}(t)");
    Gkcalc->SetTitle("G_{k}(t)  = e^{-#Lambda^{*} t}G_{k}^{(fluct.)}(t)+ #int_{0}^{t} #Lambda^{*} G_{k}^{(fluct.)}(t').e^{-#Lambda^{*} t'}G_{k}^{(stat.)} (t-t')dt' ");
    Gkcalc->GetYaxis()->SetLabelFont(22);
    Gkcalc->GetYaxis()->SetTitleFont(22);
    Gkcalc->GetXaxis()->SetLabelFont(22);
    Gkcalc->GetXaxis()->SetTitleFont(22);
    //Add other lines
    Gks->Draw("same");
     Gks->SetLineWidth(2);
    Gks->SetLineColor(kRed);
    Gkf->Draw("same");
     Gkf->SetLineWidth(2);
    Gkf->SetLineColor(kGreen);
    eLst->Draw("same");
     eLst->SetLineWidth(2);
    eLst->SetLineColor(kMagenta);
    TLegend *legend = new TLegend(.75,.80,.95,.95);
    legend->AddEntry(Gkcalc,"G_{k}(t)");
    legend->AddEntry(Gks,"G_{k}^{(stat)}(t)");
    legend->AddEntry(Gkf,"G_{k}^{(fluct)}(t)");
    legend->AddEntry(Gks,"e^{-#Lambda^{*} t}");
    legend->Draw();
  
}