/*  The game of Tic Tac Toe using a 2-D array.  Users will enter their choice as a 1-9 which must be
 *  translated to a 0-2,0-2 coordinate value.  Input will be data verified to make sure that the
 *  grid location is within bounds and not currently used.  This is a human-vs-human game.  To make
 *  it a human-vs-computer game, we have to change things up so that O is generated by computer logic. */

import java.util.Scanner;					

public class TicTacToe
{
	public static void main(String[] args)
	{
		char[][] grid = new char[3][3];			// create the 3x3 grid and fill each location with ' '
		for(int i=0;i<3;i++)
			for(int j=0;j<3;j++)
				grid[i][j] = ' ';				// initialize tic tac toe grid to all blanks
		char winner = playGame(grid);			// play the game and get the winner ('X', 'O' or ' ' for draw)
		display(grid);							// display the final grid
		if(winner=='X') System.out.println("Congratulations, you win!");	// output the winner
		else if(winner=='O') System.out.println("Sorry, but I win!");
		else System.out.println("How predictable, its a draw");
	}
	
	//  This method is the main engine for the game.  It will repeat until either someone has won the game or 
	//  count is 9 (a draw) alternating 'X' and 'O' turns
	
	public static char playGame(char[][] g)
	{
		Scanner in = new Scanner(System.in);		
		int count = 0;							// count number of turns, if it becomes 9 its a draw
		char winner = ' ';						// no one has won yet
		int choice;								// user input choice of grid number to insert into (1-9)
		char turn = 'X';						// X goes first, alternate X and O
		while(winner!='X'&&winner!='O'&&count<9)	// while no one has won and not yet a draw
		{
			display(g);							// display the tic tac toe grid
			choice = getChoice(g, turn, in);	// get user's choice, data verified
			g[(choice)/3][(choice)%3] = turn;	// fill in the user's choice with the appropriate letter ('X' or 'O')
			winner = checkForWinner(g);			// now see if anyone has won yet, checkForWinner returns 'X', 'O' or ' '
			count++;							// we have now done 1 more turn, count is used to determine draws
			if(turn=='X') turn = 'O';			// change the player from 'X' to 'O' or 'O' to 'X'
			else turn = 'X';
		}
		return winner;
	}
	
	public static char checkForWinner(char[][] g)		// there are 8 possible winners, we check to see if the character in any row, column or diagonal is the same and not ' '
	{													// if the character is ' ' then its not a winner because any ' ' entries are empty squares
		if(g[0][0]==g[0][1]&&g[0][1]==g[0][2]&&g[0][0]!=' ') return g[0][0];		// upon a match, return the character found in one of those squares
		else if(g[1][0]==g[1][1]&&g[1][1]==g[1][2]&&g[1][0]!=' ') return g[1][0];
		else if(g[2][0]==g[2][1]&&g[2][1]==g[2][2]&&g[2][0]!=' ') return g[2][0];
		else if(g[0][0]==g[1][0]&&g[1][0]==g[2][0]&&g[0][0]!=' ') return g[0][0];
		else if(g[0][1]==g[1][1]&&g[1][1]==g[2][1]&&g[0][1]!=' ') return g[0][1];
		else if(g[0][2]==g[1][2]&&g[1][2]==g[2][2]&&g[0][2]!=' ') return g[0][2];
		else if(g[0][0]==g[1][1]&&g[1][1]==g[2][2]&&g[0][0]!=' ') return g[0][0];
		else if(g[0][2]==g[1][1]&&g[1][1]==g[2][0]&&g[0][2]!=' ') return g[0][2];
		else return ' ';								// noone has won yet
	}
	
	public static void display(char[][] g)				// display the 3x3 grid in a somewhat formatted way
	{
		System.out.println(" "+g[0][0]+" | "+g[0][1]+" | "+g[0][2]);
		System.out.println("-----------");
		System.out.println(" "+g[1][0]+" | "+g[1][1]+" | "+g[1][2]);
		System.out.println("-----------");
		System.out.println(" "+g[2][0]+" | "+g[2][1]+" | "+g[2][2]);
	}
	
	public static int getChoice(char[][]g, char t, Scanner in)		// get the user's choice (1-9), data verify that the choice is legal, and return the value-1 so that
	{																// we can adjust it to be "carved up" into [0-2][0-2] for array access
		int input;
		do {
			System.out.print("Its " + t + "'s turn, enter your grid coordinate from 1-9   ");
			input = in.nextInt();
		}while(input<1||input>9||g[(input-1)/3][(input-1)%3]!=' ');	// illegal if out of bounds (<1, >9) or the grid location is already filled (not blank)
		return input-1;												// adjust the choice to be on a 0-8 scale instead of 1-9 for easier computation
	}
}