//-------------------------------------------------
//
// A very small predator/prey example.
//
// We have a grid world on which there lives a rabbit and
// a fox, which move about randomly.
//
// Simon Parsons
// March 14th 2007
//
//-------------------------------------------------

// Include C++ library definitions

#include <iostream> // For cin cout
#include <cstdlib>  // For rand
#include <cmath>    // For sqrt
#include <ctime>    // For time

using namespace std;

//-------------------------------------------------
//
// Declare methods


// Make a random movement. Either go forwards, go backwards
// or do not move.

int makeRandomMove(void)
{

  int movement;

  movement = rand() % 3;

  if(movement == 0)
    {
      return 0;
    }

  if(movement == 1)
    {
      return 1;
    }

  if(movement == 2)
    {
      return -1;
    }
}

// Keep the fox and the rabbit in a 10 by 10 grid

int wrapAround(int coordinate)
{
  if(coordinate > 10)
    {
      return 0;
    }
  else
  if(coordinate < 0)
    {
      return 10;
    }
  else
    {
      return coordinate;
    }
}

// Give the position of the fox and the rabbit.

void displayPosition(int xF, int yF, int xR, int yR)
{
  cout << "The fox is at:    (" << xF << ", " << yF << ")" << endl;
  cout << "The rabbit is at: (" << xR << ", " << yR << ")" << endl;
}

//------------------------------------------------
//
// The main body of the program

int main()

{

    // Declare variables

    int xFox;          // Fox's x position
    int yFox;          // Fox's y position
    int xRabbit;       // Rabbit's x position
    int yRabbit;       // Rabbit's y position
    char c;            // User's input
    bool quit = false; // Do we want to quit?

  // Initialisation. Pick locations of fox and rabiit randomly

  srand(time(NULL));    // Set the random seed

  xFox    = rand() % 11;
  yFox    = rand() % 11;
  xRabbit = rand() % 11;
  yRabbit = rand() % 11;

  while(!quit)
  {

    // Move both fox and rabbit randomly, using wrapAround to make
    // sure that they stay within the grid.

    xFox    = wrapAround(xFox + makeRandomMove());
    yFox    = wrapAround(yFox + makeRandomMove());
    xRabbit = wrapAround(xRabbit + makeRandomMove());
    yRabbit = wrapAround(yRabbit + makeRandomMove());

    displayPosition(xFox, yFox, xRabbit, yRabbit);

    // Get input from user

    cout << endl << "Enter y to quit, n to continue ";
    cin  >> c;

    if (c=='y')
    {
        quit = true;
    }

  }

  cout << "Bye" << endl;

  return 0;
}