001/*
002 * Copyright (C) 2012 eXo Platform SAS.
003 *
004 * This is free software; you can redistribute it and/or modify it
005 * under the terms of the GNU Lesser General Public License as
006 * published by the Free Software Foundation; either version 2.1 of
007 * the License, or (at your option) any later version.
008 *
009 * This software is distributed in the hope that it will be useful,
010 * but WITHOUT ANY WARRANTY; without even the implied warranty of
011 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
012 * Lesser General Public License for more details.
013 *
014 * You should have received a copy of the GNU Lesser General Public
015 * License along with this software; if not, write to the Free
016 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
017 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
018 */
019package org.crsh.shell.impl.command.spi;
020
021import org.crsh.command.CommandContext;
022import org.crsh.keyboard.KeyHandler;
023import org.crsh.stream.Filter;
024import org.crsh.text.ScreenContext;
025
026import java.io.IOException;
027
028/**
029 * A command invoker is a filter for a {@link org.crsh.command.CommandContext} kind of consumer.
030 *
031 * @param <C> the consumed element generic type
032 * @param <P> the produced element generic type
033 */
034public abstract class CommandInvoker<C, P> implements Filter<C, P, CommandContext<? super P>> {
035
036  /**
037   * Invoke the command.
038   *
039   * @param consumer the consumer for this invocation
040   * @throws IOException any io exception
041   * @throws CommandException anything command exception
042   */
043  public final void invoke(CommandContext<? super P> consumer) throws IOException, CommandException {
044    try {
045      open(consumer);
046    }
047    finally {
048      try {
049        flush();
050      }
051      finally {
052        close();
053      }
054    }
055  }
056
057  @Override
058  public abstract void flush() throws IOException;
059
060  @Override
061  public abstract void provide(C element) throws IOException, CommandException;
062
063  @Override
064  public abstract void open(CommandContext<? super P> consumer) throws IOException, CommandException;
065
066  @Override
067  public abstract void close() throws IOException, CommandException;
068
069  /**
070   * Provide an opportunity for the command to implement screen context.
071   *
072   * @return the screen context
073   */
074  public ScreenContext getScreenContext() {
075    return null;
076  }
077
078  /**
079   * Return the key handler or null if the invoker cannot handler key events.
080   *
081   * @return the key handler
082   */
083  public KeyHandler getKeyHandler() {
084    return null;
085  }
086}