#define MAXX 100
#define MAXY 100
#define KMOLLA 0.4
#define DT .05
#define G 5

#include "TCanvas.h"
#include "TH2F.h"
#include "TLine.h"

#include <iostream>

using namespace std;

class Palla{
  public:
    Palla(float x, float y, float m);
    void evolvi(const Palla& altraPalla);

    float x() const{
      return xPos;
    }
    float y() const{
      return yPos;
    }
    float vx() const{
      return velX;
    }
    float vy() const{
      return velY;
    }
    float m() const{
      return massa;
    }

  private:
    float dist(const Palla&) const;
    float cosX(const Palla&) const;
    float cosY(const Palla&) const;

    float xPos, yPos, massa;
    float velX, velY;
};

Palla::Palla(float x, float y, float m){
  xPos = x;
  yPos = y;
  massa = m;
  velX=0;
  velY=0;
}


float Palla::dist(const Palla& p) const {
  return (sqrt((xPos-p.x())*(xPos-p.x())+
               (xPos-p.y())*(xPos-p.y())));
}


float Palla::cosX(const Palla& p) const {
  return (xPos-p.x())/dist(p);
}

float Palla::cosY(const Palla& p) const {
  return (yPos-p.y())/dist(p);
}

void Palla::evolvi(const Palla& p){
  float d = dist(p);
  float ax = -(d-5)/massa*KMOLLA*cosX(p); 
  float ay = -(d-5)/massa*KMOLLA*cosY(p)-G;

  velX += ax*DT; 
  velY += ay*DT; 

  xPos+=velX*DT;
  yPos+=velY*DT;
  //
  // controlla il bordo
  //
  if (xPos <= 0) {
    xPos=0;
    velX= -velX;
  }
  if (xPos >= MAXX) {
    xPos=MAXX;
    velX= -velX;
  }
  if (yPos <= 0) {
    yPos=0;
    velY= -velY;
  }
  if (yPos >= MAXY) {
    yPos=MAXY;
    velY= -velY;
  }
}

void display(Palla p1, Palla p2){
  static TCanvas * canvas = new TCanvas;
  TH2F histo("fff","Tavolo",40,0,100,40,0,100);
  histo.Fill(p1.x(), p1.y(), p1.m());
  histo.Fill(p2.x(), p2.y(), p2.m());
  histo.DrawCopy("zcol");
  static TLine* theSpring = 0;
  delete theSpring;
  theSpring = new TLine(p1.x(), p1.y(), p2.x(), p2.y());
  theSpring->Draw();
  canvas->Update();

}

int rimbalzo2(int maxIter= 100){
  Palla palla1 (1000,10,2);
  Palla palla2 (60,80,20);

  int i=0;
  while(i < maxIter){
    palla1.evolvi(palla2);
    palla2.evolvi(palla1);    
    //    cout <<" PALLA 1 "<<palla1.x()<<" "<< palla1.y()<<" =V= "<<palla1.vx()<<" "<< palla1.vy()<<endl;
    //    cout <<" PALLA 2 "<<palla2.x()<<" "<< palla2.y()<<" =V= "<<palla2.vx()<<" "<< palla2.vy()<<endl;
    display(palla1, palla2);
    i++;
  }
  return 0;
}