java-design-patterns/command/src/main/java/com/iluwatar/command/Wizard.java

package com.iluwatar.command;

import java.util.Deque;
import java.util.LinkedList;

/**
 * 
 * Wizard is the invoker of the commands
 *
 */
public class Wizard {

  private Deque<Command> undoStack = new LinkedList<>();
  private Deque<Command> redoStack = new LinkedList<>();

  public Wizard() {}

  /**
   * Cast spell
   */
  public void castSpell(Command command, Target target) {
    System.out.println(this + " casts " + command + " at " + target);
    command.execute(target);
    undoStack.offerLast(command);
  }

  /**
   * Undo last spell
   */
  public void undoLastSpell() {
    if (!undoStack.isEmpty()) {
      Command previousSpell = undoStack.pollLast();
      redoStack.offerLast(previousSpell);
      System.out.println(this + " undoes " + previousSpell);
      previousSpell.undo();
    }
  }

  /**
   * Redo last spell
   */
  public void redoLastSpell() {
    if (!redoStack.isEmpty()) {
      Command previousSpell = redoStack.pollLast();
      undoStack.offerLast(previousSpell);
      System.out.println(this + " redoes " + previousSpell);
      previousSpell.redo();
    }
  }

  @Override
  public String toString() {
    return "Wizard";
  }
}