#include <iostream>
#include <vector>

class env_Env {

  public:  
           env_Env( int users, int channels, float load );
           float rate( int i, int j ) { return (currentRateMatrix[i][j]); };
           float arrival( int i ) { return currentArrivalVector[i]; };
           float occupancy( int i ) { return currentOccupancyVector[i]; };
           void transmit( vector<int> schedule );
           void tick();
           void print();
           int numUsers;
           int numChannels;

  private: 

     float avgLoad;
     vector< vector<float> > currentRateMatrix;
     vector<float> currentArrivalVector;
     vector<float> currentOccupancyVector;
     int bernoulli( float avgLoad );
};


env_Env::env_Env( 
  int users,
  int channels,
  float load )
{

  numUsers = users;
  numChannels = channels;
  avgLoad = load;

  for (int i = 0 ; i < numUsers; i++ ) {

    currentArrivalVector.push_back( 0.0 );
    currentOccupancyVector.push_back( 0.0 );

    currentRateMatrix.push_back( *( new vector<float> ) );
    for ( int j = 0 ; j < numChannels ; j++ ) {
      currentRateMatrix[i].push_back( 0.0 );
    }

  }

}


void env_Env::tick()
{
  for (int i = 0 ; i < numUsers; i++ ) {
    for ( int j = 0 ; j < numChannels ; j++ ) {
      currentRateMatrix[i][j] = numUsers * bernoulli( avgLoad );
    }
    currentArrivalVector[i] = bernoulli( avgLoad );
    currentOccupancyVector[i] += currentArrivalVector[i];
  }
}


int env_Env::bernoulli( float prob )
{
  float foo = (float) rand();
  float randmax = (float) RAND_MAX ;
  float bar =  foo / randmax;

  return ( bar  < prob ) ? 1 : 0;
}

           
void 
env_Env::transmit( vector<int> schedule )
{
  for (int i = 0; i < numChannels ; i++ ) {
    currentOccupancyVector[schedule[i]] -= currentRateMatrix[schedule[i]][i];
    if ( currentOccupancyVector[schedule[i]] < 0 ) { 
      currentOccupancyVector[schedule[i]] = 0; 
    }
  }
}


void 
env_Env::print()
{
  cout << "Current state:" << endl;
  for (int i = 0; i < numUsers ; i++ ) {
    cout << "User " << i << " Q length " <<  currentOccupancyVector[i] << endl;
  }
 
}


int main()
{
  int numCycles = 100;
  env_Env cell(2, 1, 0.49);

  vector<int> schedule;
  schedule.push_back(0);
  
  for ( int i = 0; i < numCycles ; i++ ) {

    schedule[0] = 0;
    for ( int j = 0 ; j < cell.numUsers; j++ ) {
      if (  cell.occupancy( j ) > 0 &&
            ( cell.rate( j, 0) > cell.rate( schedule[0], 0 ) ) ) {
        schedule[0] = j;
      }
    }
      
    
    cell.transmit( schedule );
    cell.print();

    cell.tick();
  }

  return 0;
    
}