package class8_1_Lab_Command_inClass_start;

import java.util.Stack;

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

    /**
     * tells this to execute its Command immediately
     */
    public void invoke(Command cmd) {
        cmd.execute();
        doneStack.push(cmd);
        undoneStack.clear();
    }

    /**
     * tells this to undo the last Command (if possible)
     */
    public void undo() {
        if (!doneStack.isEmpty()) {
            Command cmd = doneStack.pop();
            cmd.unexecute();
            undoneStack.push(cmd);
        }
    }

    /**
     *
     */
    public void redo() {
        if (!undoneStack.isEmpty()) {
            Command cmd = undoneStack.pop();
            cmd.execute();
            doneStack.push(cmd);
        }
    }

}