package class8_1_RemoteControl.other;

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

/**
 * This is a "helper" class that handles the details of invocation of specific commands
 * @author hornick
 *
 */
public class Invoker {
	private Deque<Command> stack = new LinkedList<Command>();

	/**
	 * constructor
	 */
	public Invoker() {
	}
	
	/**
	 * tells this to execute its Command immediately
	 */
	public boolean invoke( Command command ) {
		if(null == command) {
			System.out.println("Errro!!!!");
		}

		boolean status;
		if(command instanceof UndoCommand) {
			Command lastCommand = stack.pollFirst();
			if(null != lastCommand) {
				status = lastCommand.unexecute();
			} else {
				status = false;
			}
		} else {
			status = command.execute();
			if(status) {
				stack.push(command);
			}
		}
		return status;
	}
}