//-------------------------------------------------
//
// The basis for a simple pursuer/evader game
//
// We have a grid world on which there lives an evader
// which responds to commands from the user.
//
// Simon Parsons
// November 22nd
//
//-------------------------------------------------

// Include C++ library definitions

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

using namespace std;

//-------------------------------------------------
//
// Function headers

int wrapAround(int coordinate);
void displayPosition(int xE, int yE);
void moveEvader(char move, int &xE, int &yE);

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

int main(){

    // Declare variables

    int xEvader;          // Evader's x position
    int yEvader;          // Evader's y position
    char c;               // User's input
    bool quit = false;    // Do we want to quit?

  // Initialisation. Pick locations of the evader randomly

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

  xEvader    = rand() % 10;
  yEvader    = rand() % 10;
 
  cout << endl << "Your job in this game is to make the evader";
  cout <<  " stay away from the pursuers" << endl;
  cout << "The pursuers will chase you down!" << endl << endl; 

  displayPosition(xEvader, yEvader);

  while(!quit)
  {

    // Get input from user

    cout << endl << "Enter q to quit, or n, s, e or w to have the evader move that way: ";
    cin  >> c;

    if (c=='q'){
        quit = true;
    }
    else{
      moveEvader(c, xEvader, yEvader);
    }

    displayPosition(xEvader, yEvader);
    }
 
  cout << "Bye" << endl;

  return 0;
}

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

// Keep the robots in a 10 by 10 grid

int wrapAround(int coordinate)
{
  if(coordinate > 9)
    {
      return 0;
    }
  else
  if(coordinate < 0)
    {
      return 9;
    }
  else
    {
      return coordinate;
    }
}

// Display the positions of the robots

void displayPosition(int xE, int yE)
{
    int dx;
    int dy;

    for(dy=10; dy>=0; dy--)
    {
        cout << "\n----------------------\n";

        for (dx=0; dx<=10; dx++)
        {
            if((xE == dx) && (yE == dy))
            {
                cout << "|E";
            }
            else
            {
                cout << "| ";
            }
        }
    }

    cout << "\n----------------------\n\n";

}

// Move the evader, using a switch statement and reference parameters

void moveEvader(char move, int &xE, int &yE)
{
  switch(move) {
  case 'n':
    yE = wrapAround(yE + 1);
    break;
  case 's':
    yE = wrapAround(yE - 1);
    break;
  case 'e':
    xE = wrapAround(xE + 1);
    break;
  case 'w':
    xE = wrapAround(xE - 1);
    break;
    
  default:
    cout << "The evader is confused" << endl << endl;
  }
}