google_ants/Aim.java at google_v10 · pkmiec/google_ants · GitHub

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import java.util.HashMap;
import java.util.Map;

/**
 * Represents a direction in which to move an ant.
 */
public enum Aim {
    /** North direction, or up. */
    NORTH(-1, 0, 'n'),

    /** East direction or right. */
    EAST(0, 1, 'e'),

    /** South direction or down. */
    SOUTH(1, 0, 's'),

    /** West direction or left. */
    WEST(0, -1, 'w');

    private static final Map<Character, Aim> symbolLookup = new HashMap<Character, Aim>();

    static {
        symbolLookup.put('n', NORTH);
        symbolLookup.put('e', EAST);
        symbolLookup.put('s', SOUTH);
        symbolLookup.put('w', WEST);
    }

    private final int rowDelta;

    private final int colDelta;

    private final char symbol;

    private Aim opposite;

    private Aim[] sideways;

    private Aim[] others;

    Aim(int rowDelta, int colDelta, char symbol) {
        this.rowDelta = rowDelta;
        this.colDelta = colDelta;
        this.symbol = symbol;
    }

    /**
     * Returns rows delta.
     *
     * @return rows delta.
     */
    public int getRowDelta() {
        return rowDelta;
    }

    /**
     * Returns columns delta.
     *
     * @return columns delta.
     */
    public int getColDelta() {
        return colDelta;
    }

    /**
     * Returns symbol associated with this direction.
     *
     * @return symbol associated with this direction.
     */
    public char getSymbol() {
        return symbol;
    }

    /**
     * Returns direction associated with specified symbol.
     *
     * @param symbol <code>n</code>, <code>e</code>, <code>s</code> or <code>w</code> character
     *
     * @return direction associated with specified symbol
     */
    public static Aim fromSymbol(char symbol) {
        return symbolLookup.get(symbol);
    }

    public Aim opposite() {
      if (opposite == null) {
        if (this == Aim.NORTH) {
          opposite = Aim.SOUTH;
        } else if (this == Aim.SOUTH) {
          opposite = Aim.NORTH;
        } else if (this == Aim.WEST) {
          opposite = Aim.EAST;
        } else if (this == Aim.EAST) {
          opposite = Aim.WEST;
        }
      }
      return opposite;
    }

    public Aim[] sideways() {
      if (sideways == null) {
        if (this == Aim.NORTH || this == Aim.SOUTH) {
          sideways = new Aim[] { Aim.WEST, Aim.EAST };
        } else {
          sideways = new Aim[] { Aim.NORTH, Aim.SOUTH };
        }
      }
      return sideways;
    }

    public Aim[] others() {
      if (others == null) {
        if (this == Aim.NORTH) {
          others = new Aim[] { Aim.SOUTH, Aim.WEST, Aim.EAST };
        } else if (this == Aim.SOUTH) {
          others = new Aim[] { Aim.NORTH, Aim.WEST, Aim.EAST };
        } else if (this == Aim.WEST) {
          others = new Aim[] { Aim.NORTH, Aim.SOUTH, Aim.EAST };
        } else if (this == Aim.EAST) {
          others = new Aim[] { Aim.NORTH, Aim.WEST, Aim.SOUTH };
        }
      }
      return others;
    }

}