/**
 * Implements the game of Tic Tac Toe
 * @author cs161
 * @version spring19
 */
public class TicTacToe{
    private final String EMPTY = " ";
    private final String PLAYER1 = "x";
    private final String PLAYER2 = "o";

    private String cellA1, cellA2, cellA3;
    private String cellB1, cellB2, cellB3;
    private String cellC1, cellC2, cellC3;
    private int numCellsRemaining;
    private String currPlayer;

    /**
     * Initializes the game of Tic Tac Toe
     */
    public TicTacToe(){
        cellA1 = EMPTY;
        cellA2 = EMPTY;
        cellA3 = EMPTY;
        cellB1 = EMPTY;
        cellB2 = EMPTY;
        cellB3 = EMPTY;
        cellC1 = EMPTY;
        cellC2 = EMPTY;
        cellC3 = EMPTY;
        numCellsRemaining = 9;
        currPlayer = "x";
    }

    /**
     * Prints the board to the screen
     */
    public void printBoard(){
        System.out.println();
        System.out.println(cellA1 + " | " + cellA2 + " | " + cellA3);
        System.out.println("---------");
        System.out.println(cellB1 + " | " + cellB2 + " | " + cellB3);
        System.out.println("---------");        
        System.out.println(cellC1 + " | " + cellC2 + " | " + cellC3);
        System.out.println();
    }

    /**
     * Returns true if one of the players has won the game or there are no
     * empty cells remaining
     * 
     * @return true if the game is over, false otherwise
     */
    public boolean gameOver(){
        boolean player1 = checkWin(PLAYER1);
        boolean player2 = checkWin(PLAYER2);
        boolean noTurns = (numCellsRemaining == 0);
        return player1 || player2 || noTurns;
    }

    /**
     * Returns a string indicating the mark of the winning player ("x" or "o")
     * or "tie" if the game was a tie
     * 
     * @return A string representing the end result of the game
     */
    public String winner(){
        boolean player1 = checkWin(PLAYER1);
        boolean player2 = checkWin(PLAYER2);
        
        if(!player1 && !player2){
            return "tie";
        }
        else if(player1){
            return PLAYER1;
        }
        else{
            return PLAYER2;
        }
    }
    
    /**
     * Stores the current player's mark in the specified row and column
     * @param row
     *          The row in which the player plays
     * @param col
     *          The column in which the player plays
     */
    public void move(int row, int col){
        if(row == 1 && col == 1){
            if(cellA1.equals(EMPTY)){
                cellA1 = currPlayer;
            }
        }
        else if(row == 1 && col == 2){
            if(cellA2.equals(EMPTY)){
                cellA2 = currPlayer;
            }
        }
        else if(row == 1 && col == 3){
            if(cellA3.equals(EMPTY)){
                cellA3 = currPlayer;
            }
        }
        else if(row == 2 && col == 1){
            if(cellB1.equals(EMPTY)){
                cellB1 = currPlayer;
            }
        }
        else if (row == 2 && col == 2){
            if(cellB2.equals(EMPTY)){
                cellB2 = currPlayer;
            } 
        }
        else if (row == 2 && col == 3){
            if(cellB3.equals(EMPTY)){
                cellB3 = currPlayer;
            }
        }
        else if(row == 3 && col == 1){
            if(cellC1.equals(EMPTY)){
                cellC1 = currPlayer;
            }
        }
        else if(row == 3 && col == 2){
            if(cellC2.equals(EMPTY)){
                cellC2 = currPlayer;
            }
        }
        else if(row == 3 && col == 3){
            if(cellC3.equals(EMPTY)){
                cellC3 = currPlayer;
            }
        }

        // switch players in anticipation of the next round
        if(currPlayer.equals(PLAYER1)){
            currPlayer = PLAYER2;
        }
        else{
            currPlayer = PLAYER1;
        }
        
        numCellsRemaining--;
    }

    
    /*----------------------------------------------
     *          Private Helper Methods
     *----------------------------------------------*/
    
    private boolean checkWin(String player){
        if(cellA1.equals(player) && cellA2.equals(player) && cellA3.equals(player)){
            return true;
        }
        else if(cellB1.equals(player) && cellB2.equals(player) && cellB3.equals(player)){
            return true;
        }
        else if(cellC1.equals(player) && cellC2.equals(player) && cellC3.equals(player)){
            return true;
        }
        else if(cellA1.equals(player) && cellB1.equals(player) && cellC1.equals(player)){
            return true;
        }
        else if(cellA2.equals(player) && cellB2.equals(player) && cellC2.equals(player)){
            return true;
        }
        else if(cellA3.equals(player) && cellB3.equals(player) && cellC3.equals(player)){
            return true;
        }
        else if(cellA1.equals(player) && cellB2.equals(player) && cellC3.equals(player)){
            return true;
        }
        else if(cellA3.equals(player) && cellB2.equals(player) && cellC1.equals(player)){
            return true;
        }
        else{
            return false;
        }
    }    
}