#include "TROOT.h"
#include "TStyle.h"
#include "TCanvas.h"
#include "TView.h"
#include "TPolyLine3D.h"
#include "TLatex.h"

void cir_solid_angle_cal(){
  gROOT->SetStyle("Plain");
  gStyle->SetTextFont(132);

  Double_t cwidth  = 400;
  Double_t cheight = 400;
  TCanvas* c1 = new TCanvas("c1", "c1", cwidth, cheight);
  c1->SetWindowSize(cwidth + (cwidth - c1->GetWw()), cheight + (cheight - c1->GetWh()));

  c1->SetTheta(20.);
  c1->SetPhi(-125.);
  TView *view = TView::CreateView(1);
  Double_t view_size = 1.5;
  view->SetRange(-view_size*1.0,-view_size*1.0,-view_size*1.0,
		  view_size*1.0, view_size*1.0, view_size*1.0);

  const Int_t nPolyLine3D = 20;
  TPolyLine3D *guide[nPolyLine3D];
  for (Int_t i = 0; i<nPolyLine3D; i++){
    guide[i]=new TPolyLine3D();
  }

  Double_t pi = acos(-1.);
  Int_t    n = 60;
  Double_t theta0 = pi/5.0;
  Double_t x0 =  2.*tan(theta0);
  Double_t r0 =  2./cos(theta0);
  std::cout << x0 << r0 << std::endl;

  guide[0]->SetNextPoint(-2,-x0,0);
  guide[0]->SetNextPoint(-2,x0,0);
  guide[1]->SetNextPoint(-2,0,-x0);
  guide[1]->SetNextPoint(-2,0,x0);
  guide[2]->SetNextPoint(-2,0,0);
  guide[2]->SetNextPoint(-r0,0,0);
  guide[0]->SetLineStyle(2);
  guide[1]->SetLineStyle(2);
  guide[2]->SetLineStyle(2);

  for (Int_t i=0;i<=n;i++) {
    Double_t r = 0.6;
    Double_t theta = -i*theta0/n+pi;
    guide[4]->SetNextPoint(r*cos(theta),r*sin(theta),0);
  }

  for (Int_t i=0;i<=n;i++) {
    Double_t r = x0;
    Double_t theta = i*2.*pi/n;
    guide[5]->SetNextPoint(-2.0,r*cos(theta),r*sin(theta));
  }

  for (Int_t i=0;i<=n;i++) {
    Double_t r = r0;
    Double_t theta = i*2.*pi/n;
    guide[6]->SetNextPoint(r*cos(theta),r*sin(theta),0);
    guide[7]->SetNextPoint(r*cos(theta),0,r*sin(theta));
  }
  guide[6]->SetLineStyle(2);
  guide[7]->SetLineStyle(2);


  Double_t gtheta = -c1->GetTheta()*pi/180.;
  Double_t gphi   = -c1->GetPhi()*pi/180.;
  
  for (Int_t i=0;i<=n;i++) {
    Double_t r = r0;
    Double_t theta = i*2.*pi/n;
    Double_t x = r*cos(theta);
    Double_t z = r*sin(theta);
    guide[8]->SetNextPoint(x*cos(gphi)+z*sin(gtheta)*sin(gphi),
			   x*sin(gphi)-z*sin(gtheta)*cos(gphi),
			   z*cos(gtheta));
  }

  guide[9]->SetNextPoint(-2.,x0,0);
  guide[9]->SetNextPoint(0,0,0);
  guide[9]->SetNextPoint(-2.,0,0);

  Double_t virlen = 0.2;
  guide[10]->SetNextPoint(-2.,-virlen,0);
  guide[10]->SetNextPoint(-2.+virlen,-virlen,0);
  guide[10]->SetNextPoint(-2.+virlen,0,0);
  guide[10]->SetNextPoint(-2.+virlen,0,-virlen);
  guide[10]->SetNextPoint(-2.,0,-virlen);

  for (Int_t i = 0; i<nPolyLine3D; i++){
    guide[i]->Draw();
  }

  Double_t xx[3],xxt[3];
  TLatex Tl;
  Tl.SetTextSize(0.06);
  xx[0]=0.1; xx[1]=0.0; xx[2]=-0.25; view->WCtoNDC(xx,xxt);
  Tl.DrawLatex(xxt[0],xxt[1],"O");
  //xx[0]=-2.00; xx[1]=0.05; xx[2]=-0.3; view->WCtoNDC(xx,xxt);
  //Tl.DrawLatex(xxt[0],xxt[1],"C");
  xx[0]=-0.6; xx[1]=0.25; xx[2]=0.00; view->WCtoNDC(xx,xxt);
  Tl.DrawLatex(xxt[0],xxt[1],"#it{#alpha}");
  xx[0]=-0.6; xx[1]=-0.1; xx[2]=0.00; view->WCtoNDC(xx,xxt);
  Tl.SetTextAngle(25);
  Tl.DrawLatex(xxt[0],xxt[1],"cos#it{#alpha}");
}