Tic-Tac-Toe

import std.stdio; //For console I/O
import std.random; //We need this for the randomness of the CPU move
import std.process; //For clearing the console screen - system("cls")

char[3][3] board = [['1','2','3'],['4','5','6'],['7','8','9']]; //The X/O board

struct Player //The player structure. Contains player's mark and win data.
{
    char[1] mark;
    bool winner;
    int inp;
}

void printBoard() //Function to print the board
{
    writeln(" ",board[0][0]," | ",board[0][1]," | ",board[0][2]);
    writeln("---","|","---","|","---");
    writeln(" ",board[1][0]," | ",board[1][1]," | ",board[1][2]);
    writeln("---","|","---","|","---");
    writeln(" ",board[2][0]," | ",board[2][1]," | ",board[2][2]);
}

bool checkWin(Player who) //Function to check the winner
{
    if(board[0][0] == who.mark[0] && board[1][1] == who.mark[0] && board[2][2] == who.mark[0])
    {
        return true;
    }
    else if(board[0][2] == who.mark[0] && board[1][1] == who.mark[0] && board[2][0] == who.mark[0])
    {
        return true;
    }
    else if(board[0][0] == who.mark[0] && board[0][1] == who.mark[0] && board[0][2] == who.mark[0])
    {
        return true;
    }
    else if(board[1][0] == who.mark[0] && board[1][1] == who.mark[0] && board[1][2] == who.mark[0])
    {
        return true;
    }
    else if(board[2][0] == who.mark[0] && board[2][1] == who.mark[0] && board[2][2] == who.mark[0])
    {
        return true;
    }
    else if(board[0][0] == who.mark[0] && board[1][0] == who.mark[0] && board[2][0] == who.mark[0])
    {
        return true;
    }
    else if(board[0][1] == who.mark[0] && board[1][1] == who.mark[0] && board[2][1] == who.mark[0])
    {
        return true;
    }
    else if(board[0][2] == who.mark[0] && board[1][2] == who.mark[0] && board[2][2] == who.mark[0])
    {
        return true;
    }
    else
    {
        return false;
    }
}

int setMark(Player who) //Function to set the mark on the board
{
    int input = who.inp-1;

    switch(input)
    {
        case 0:
            if(board[0][0] == 'X' || board[0][0] == 'O')
            {
                return 1;
            }
            board[0][0] = who.mark[0];
            break;

        case 1:
            if(board[0][1] == 'X' || board[0][1] == 'O')
            {
                return 1;
            }
            board[0][1] = who.mark[0];
            break;

        case 2:
            if(board[0][2] == 'X' || board[0][2] == 'O')
            {
                return 1;
            }
            board[0][2] = who.mark[0];
            break;

        case 3:
            if(board[1][0] == 'X' || board[1][0] == 'O')
            {
                return 1;
            }
            board[1][0] = who.mark[0];
            break;

        case 4:
            if(board[1][1] == 'X' || board[1][1] == 'O')
            {
                return 1;
            }
            board[1][1] = who.mark[0];
            break;

        case 5:
            if(board[1][2] == 'X' || board[1][2] == 'O')
            {
                return 1;
            }
            board[1][2] = who.mark[0];
            break;

        case 6:
            if(board[2][0] == 'X' || board[2][0] == 'O')
            {
                return 1;
            }
            board[2][0] = who.mark[0];
            break;

        case 7:
            if(board[2][1] == 'X' || board[2][1] == 'O')
            {
                return 1;
            }
            board[2][1] = who.mark[0];
            break;

        case 8:
            if(board[2][2] == 'X' || board[2][2] == 'O')
            {
                return 1;
            }
            board[2][2] = who.mark[0];
            break;

        default:
            return 1;
            break;
    }
    return 0;
}

void declareWinner(Player p1, Player p2) //Function to declare winner
{
    if(p1.winner)
    {
        writeln("\n***CONGRATS TO YOU FOR WINNING!***\n");
    }
    else if(p2.winner)
    {
        writeln("\n***CONGRATS TO CPU/P2 FOR WINNING!***\n");
    }
}

int main() //The main function
{
    Player player1; //Set up player 1 variables
    player1.mark[0] = 'X';
    player1.winner = false;
    player1.inp = 12;

    Player cpu; //Set  up player 2 (cpu) variables
    cpu.mark[0] = 'O';
    cpu.winner = false;


    while(true) //Main loop
    {
        system("cls");
        writeln("Copyright(c) 2014 - Ahnaf Tahmid\n");
        writefln("Player 1 (You) = %s, CPU = %s\n",player1.mark[0],cpu.mark[0]);
        printBoard();

        while(setMark(player1) == 1)
        {
            write("\nEnter a position: ");
            readf(" %s", &player1.inp);
            if(setMark(player1) == 1)
            {
                writeln("\nInvalid position!");
            }
            else
            {
                break;
            }
        }

        player1.winner = checkWin(player1);

        if(player1.winner)
        {
            system("cls");
            writeln("Copyright(c) 2014 - Ahnaf Tahmid\n");
            writeln("Player 1 (You) = X, CPU = O\n");
            printBoard();
            declareWinner(player1, cpu);
            break;
        }

        cpu.inp = uniform(0,9)+1;
        int errors = 0; //Draw indicator
        while(setMark(cpu) == 1 && errors < 20)
        {
            cpu.inp = uniform(0,9)+1;
            errors++;
        }

        cpu.winner = checkWin(cpu);

        if(cpu.winner)
        {
            system("cls");
            writeln("Copyright(c) 2014 - Ahnaf Tahmid\n");
            writeln("Player 1 (You) = X, CPU = O\n");
            printBoard();
            declareWinner(player1, cpu);
            break;
        }

        if(errors == 20) //This is actually the real draw handling (not the best one around)
        {
            writeln("\n***ITS A DRAW!***\n");
            break;
        }
    }

    writeln("Enter any number to exit.");

    int dummy_var;
    readf(" %s", &dummy_var);

    return 0;
}