import java.util.Scanner;

public class KnightMoves
{

    static Scanner sc = new Scanner(System.in);

    // the following static array represents the 8
    // possible moves a knight can make

    // this is an 8 x 2 array
    static int[][] moves = { {-2, +1}, {-1, +2}, {+1, +2}, {+2, +1}, {+2, -1}, {+1, -2}, {-1, -2}, {-2, -1} };

    public static void main(String[] args)
    {
        System.out.println("Welcome to the " + "Knight Move calculator.\n");
        do
        {
            showKnightMoves();                                             
        }
        while (getYorN("Do it again?"));
    }

    public static void showKnightMoves()                                   
    {
        // The first dimension is the file (a, b, c, etc.)
        // The second dimension is the rank (1, 2, 3, etc.)
        // Thus, board[3][4] is square d5.
        // A value of 0 means the square is empty
        // 1 means the knight is in the square
        // 2 means the knight could move to the square
        int[][] board = new int[8][8];                                  
        String kSquare; // the knight's position as a square
        Pos kPos;       // the knight's position as a Pos

        // get the knight's initial position
        do                                                              
        {
            System.out.print("Enter knight's position: ");
            kSquare = sc.nextLine();
            kPos = convertSquareToPos(kSquare);
        } while (kPos == null);

        board[kPos.x][kPos.y] = 1;                                      
        System.out.println("\nThe knight is at square " + convertPosToSquare(kPos));
        System.out.println("From here the knight can move to:");

        for (int move = 0; move < moves.length; move ++)                
        {
            int x, y;
            x = moves[move][0];  // the x for this move
            y = moves[move][1];  // the y for this move
            Pos p = calculateNewPos(kPos, x, y);
            if (p != null)
            {
                System.out.println(convertPosToSquare(p));
                board[p.x][p.y] = 2;
            }

        }

        printBoard(board);                                              
    }

    // this method converts squares such as a1 or d5 to
    // x, y coordinates such as [0][0] or [3][4]
    public static Pos convertSquareToPos(String square)                    
    {
        int x = -1;
        int y = -1;
        char rank, file;

        file = square.charAt(0);
        if (file == 'a') x = 0;
        if (file == 'b') x = 1;
        if (file == 'c') x = 2;
        if (file == 'd') x = 3;
        if (file == 'e') x = 4;
        if (file == 'f') x = 5;
        if (file == 'g') x = 6;
        if (file == 'h') x = 7; 

        rank = square.charAt(1);
        if (rank == '1') y = 0;
        if (rank == '2') y = 1;
        if (rank == '3') y = 2;
        if (rank == '4') y = 3;
        if (rank == '5') y = 4;
        if (rank == '6') y = 5;
        if (rank == '7') y = 6;
        if (rank == '8') y = 7;

        if (x == -1 || y == -1)
        {
            return null;
        }
        else
            return new Pos(x, y);
    }

    // this method converts x, y coordinates such as
    // [0][0] or [3][4] to squares such as a1 or d5.
    public static String convertPosToSquare(Pos p)                        
    {
        String file = "";

        if (p.x == 0) file = "a";
        if (p.x == 1) file = "b";
        if (p.x == 2) file = "c";
        if (p.x == 3) file = "d";
        if (p.x == 4) file = "e";
        if (p.x == 5) file = "f";
        if (p.x == 6) file = "g";
        if (p.x == 7) file = "h";

        return file + (p.y + 1);

    }

    // this method calculates a new Pos given a
    // starting Pos, an x move, and a y move
    // it returns null if the resulting move would
    // be off the board.
    public static Pos calculateNewPos(Pos p, int x, int y)             
    {
        // rule out legal moves
        if (p.x + x < 0) return null;
        if (p.x + x > 7) return null;
        if (p.y + y < 0) return null;
        if (p.y + y > 7) return null;

        // return new position
        return new Pos(p.x + x, p.y + y);
    }

    public static void printBoard(int[][] b)                           
    {
        for (int y = 7; y >= 0; y--)
        {
            for (int x = 0; x < 8; x++)
            {
                if (b[x][y] == 1) System.out.print(" X ");
                else if (b[x][y] == 2) System.out.print(" ? ");
                else System.out.print(" - ");
            }
            System.out.println();
        }
    }

    public static boolean getYorN(String prompt)                       
    {
        while (true)
        {
            String answer;
            System.out.print("\n" + prompt + " (Y or N) ");
            answer = sc.nextLine();
            if (answer.equalsIgnoreCase("Y")) return true;
            else if (answer.equalsIgnoreCase("N")) return false;
        }
    }
}

// this class represents x, y coordinates on the board
class Pos                                                                 
{
    public int x;

    public int y;

    public Pos(int x, int y)
    {
        this.x = x;
        this.y = y;
    }
}