package class7_3_RemoteControl_inClass_start.other;

import java.util.LinkedList;

/**
 * This is a "helper" class that handles the details of invocation of specific commands
 * @author hornick
 *
 */
public class Invoker {

	private LinkedList<Command> stackOfExecutedCommands = new LinkedList<>();
	private LinkedList<Command> stackOfUnexecutedCommands = new LinkedList<>();

	/**
	 * constructor
	 */
	public Invoker() {
	}
	
	/**
	 * tells this to execute its Command immediately
	 */
	public boolean invoke( Command cmd ) {
		boolean success = cmd.execute();
		stackOfExecutedCommands.push(cmd);
		stackOfUnexecutedCommands.clear();
		return	success;
	}

	/**
	 * tells this to undo the last Command (if possible)
	 */
	public boolean undo() {
		Command lastCommand = stackOfExecutedCommands.pop();
		boolean success = lastCommand.unexecute();
		if(success) {
			stackOfUnexecutedCommands.push(lastCommand);
		}
		return success;
	}

	public boolean redo() {
		Command nextCommand = stackOfUnexecutedCommands.pop();
		boolean success = nextCommand.execute();
		if(success) {
			stackOfExecutedCommands.push(nextCommand);
		}
		return success;
	}

}