/*
 * This program plays Tic-Tac-Toe against the user!
 * The program uses a specified, not-perfect strategy.
 * The code uses only basic programming concepts.
 * Written by: Carl Sable
 */

#include <stdio.h>
#include "globals.h"
#include "ttt.h"
#include "player.h"
#include "computer.h"

/* 
 * Initialize the board, ask who goes first, play a game,
 * ask if user wants to play again.
 */
int main(void)
{
  while(1)
  {
    init_board();
    if (user_first())
    {
      computer = 'O';
      user = 'X';
    }
    else
    {
      computer = 'X';
      user = 'O';
    }
    play_game();
    if (!play_again())
      break;
  }
  return 0;
}

/* Make sure board starts off empty. */
void init_board(void)
{
  int row, col;

  for (row = 0; row < 3; row++)
    for (col = 0; col < 3; col++)
      board[row][col] = ' ';

  return;
}

/* Display the board to standard output. */
void draw_board(void)
{
  int row, col;

  printf("\n");
  for (row = 0; row < 3; row++)
  {
    printf("   *   *   \n");
    printf(" %c * %c * %c \n",
	   board[row][0], board[row][1], board[row][2]);
    printf("   *   *   \n");
    if (row != 2)
      printf("***********\n");
  }
  printf("\n");

  return;
}

/*
 * Ask if user wants to go first.
 * Returns 1 if yes, 0 if no.
 */
int user_first(void)
{
  char response;

  printf("Do you want to go first? (y/n) ");
  do
  {
    response = getchar();
  } while ((response != 'y') && (response != 'Y') &&
	   (response != 'n') && (response != 'N'));

  if ((response == 'y') || (response == 'Y'))
    return 1;
  else
    return 0;
}

/*
 * Ask if user wants to play again.
 * Returns 1 if yes, 0 if no.
 */
int play_again(void)
{
  char response;

  printf("Do you want to play again? (y/n) ");
  do
  {
    response = getchar();
  } while ((response != 'y') && (response != 'Y') &&
	   (response != 'n') && (response != 'N'));

  if ((response == 'y') || (response == 'Y'))
    return 1;
  else
    return 0;
}

/* Loop through 9 turns or until somebody wins. */
void play_game(void)
{
  int turn;

  for (turn = 1; turn <= 9; turn++)
  {
    /* Check if turn is even or odd 
       to determine which player should move. */
    if (turn % 2 == 1)
    {
      if (computer == 'X')
        computer_move();
      else
        player_move();
    }
    else
    {
      if (computer == 'O')
        computer_move();
      else
        player_move();
    }

    draw_board();

    if (symbol_won(computer)) {
      printf("\nI WIN!!!\n\n");
      return;
    }
    else if (symbol_won(user)) {
      printf("\nCongratulations, you win!\n\n");
      return;
    }
  }

  printf("\nThe game is a draw.\n\n");
  return;
}