/*
 * Created by Zhongyi on 06/11/2016.
 * TicTacToe with multiple-step undo and redo.
 * Example code for Lab 7.
 */
import java.util.Scanner;
/**
 * Class TicTacToe is the entry point of the game.
 */
public class TicTacToe {
 public static void main(String[] args) {
 char[][][] boardHistory = new char[10][][];
 // What are these variables used for? Attach your answer as part of the code review.
 int currentStep = 0, lastStep = 0;
 Scanner scanner = new Scanner(System.in);
 // Initial state of the game, as step 0
 boardHistory[0] = new char[][]{{'.', '.', '.'}, {'.', '.', '.'}, {'.', '.', '.'}};
 /*
 * In an legal game, there shall be up to nine steps.
 * Considering the initial state, the step varies from 0 to 9, inclusively.
 */
 while (currentStep <= 9) {
 printBoard(boardHistory[currentStep]);
 String nextMove = scanner.next();
 /*
 * If the input is an undo or redo command, its length is the steps to jump.
 * We can calculate the nextStep based on that.
 * */
 int nextStep;
 if (nextMove.charAt(0) == 'r') {
 // Redo
 nextStep = currentStep + nextMove.length();
 currentStep = redo(currentStep, lastStep, nextStep);
 } else if (nextMove.charAt(0) == 'u') {
 // Undo
 nextStep = currentStep - nextMove.length();
 currentStep = undo(currentStep, nextStep);
 } else {
 // Drop a new piece.
 // Parse the input string to integer to get the position to drop the piece.
 int nextPosition = Integer.parseInt(nextMove);
 // Update lastStep as long as currentStep
 lastStep = ++currentStep;
 // Store the current state into boardHistory,
 // by deep copying the previous state and substitute the position with new piece.
 boardHistory[currentStep] = copyBoard(boardHistory[currentStep - 1]);
 boardHistory[currentStep][nextPosition / 3][nextPosition % 3] = (currentStep % 2 != 0) ? 'O' : 'X';
 }
 }
 }
 /**
 * Redo from currentStep to nextStep.
 * Throw an error message to stdout if the move is illegal.
 *
 * @param currentStep the step to jump from
 * @param nextStep the step to jump to
 * @param lastStep the maximum step to jump
 * @return update currentStep to nextStep, if the move is legal; or change nothing
 */
 private static int redo(int currentStep, int lastStep, int nextStep) {
 if (nextStep <= lastStep) {
 currentStep = nextStep;
 } else {
 System.out.println("Invalid redo.");
 }
 return currentStep;
 }
 /**
 * Undo from currentStep to nextStep.
 * Throw an error message to stdout if the move is illegal.
 *
 * @param currentStep the step to jump from
 * @param nextStep the step to jump to
 * @return update currentStep to nextStep, if the move is legal; or change nothing
 */
 private static int undo(int currentStep, int nextStep) {
 if (nextStep >= 0) {
 currentStep = nextStep;
 } else {
 System.out.println("Invalid undo.");
 }
 return currentStep;
 }
 /**
 * Iterate over the two dimensional array, to print the board.
 * Then, prompt a message to ask user for the next input.
 */
 private static void printBoard(char[][] board) {
 for (int i = 0; i < 3; i++) {
 for (int j = 0; j < 3; j++) {
 System.out.print(board[i][j]);
 }
 System.out.println();
 }
 System.out.print("Next move: ");
 }
 /**
 * Use a nested iteration to deep copy a 2D array, i.e. the board.
 */
 private static char[][] copyBoard(char[][] array) {
 char[][] newArray = new char[3][3];
 for (int i = 0; i < 3; i++) {
 for (int j = 0; j < 3; j++) {
 newArray[i][j] = array[i][j];
 }
 }
 return newArray;
 }
}