#include <iostream>
#include <cmath>

#include <TApplication.h>
#include <TGraph.h>
#include <TCanvas.h>
#include <TView.h>
#include <TPolyMarker3D.h>
 #include <TPolyMarker.h>
#include <TSystem.h>

using namespace std;

int main(int argc, char** argv) {
  TApplication app("app",&argc,argv);


  TCanvas *c1 = new TCanvas("c1","",200,10,700,700);
  //TPad *p1 = new TPad("p1","p1",0.05,0.02,0.95,0.82,46,3,1);
  //p1->Draw();
  //p1->cd();
  TPad *p1 = new TPad("p1","p1",0,0,1,1);
		      
  p1->Range(-2,-2,2,2);
  p1->Draw();
  p1->cd();

  //TView *view = TView::CreateView(1);
  // view->SetRange(-3,-3,-3,3,3,-3);
  


  double x,y,t,x0,y0,t0;
  double vx,vy,vx0,vy0;
  double M=2;
  double m=1;

  double G=1;
  double dt=0.01;

  x0=-1;
  y0=0;
  t0=0;
  vx0=0;
  vy0=1;

  x=x0;
  y=y0;
  t=t0;
  vx=vx0;
  vy=vy0;

  double tmax=100;
  double xx[int(tmax/dt)],yy[int(tmax/dt)];
//   TPolyMarker3D *pm3d1 = new TPolyMarker3D(int(tmax/dt));
//   pm3d1->SetMarkerSize(1);
//   pm3d1->SetMarkerColor(2);
//   pm3d1->SetMarkerStyle(8);

  TPolyMarker *pm3d2 = new TPolyMarker(1);
  pm3d2->SetMarkerSize(1);
  pm3d2->SetMarkerColor(2);
  pm3d2->SetMarkerStyle(8);
   TPolyMarker *pm3do = new TPolyMarker(1);
   pm3do->SetMarkerSize(1);
   pm3do->SetMarkerColor(3);
   pm3do->SetMarkerStyle(8);
   pm3do->SetPoint(0,0,0);
   pm3do->Draw();

  int i=0;
  xx[i]=x0;
  yy[i]=y0;
  while(t<tmax) {
    t+=dt;
    i++;
    double ax,ay;
    double xh,yh;
    xh=x+vx/2*dt;
    yh=y+vy/2*dt;
    xh=x;
    yh=y;
    //cout<<x<<" "<<y<<" "<<xh<<" "<<yh<<endl;
    double d2=xh*xh+yh*yh;
    double a=G*M/d2;
    ax=-a*xh/sqrt(d2);
    ay=-a*yh/sqrt(d2);
    vx+=ax*dt;
    vy+=ay*dt;
    double vxo=vx,vyo=vy;
    x+=(vx+vxo)/2*dt;
    y+=(vy+vyo)/2*dt;
    //cout<<x<<" "<<y<<" "<<vx<<" "<<vy<<endl;
    xx[i]=x;
    yy[i]=y;
    pm3d2->SetPoint(0,xx[i],yy[i]);
    pm3d2->Draw();
    c1->Modified();
    c1->Update();
    gSystem->ProcessEvents();
    gSystem->Sleep(10);
  }
  //TGraph g(tmax/dt,xx,yy);
  //g.Draw("ALP");
  app.Run();
}