/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package org.jboss.netty.channel;

import java.net.SocketAddress;

/**
 * The current or future state of a {@link Channel}.
 * <p>
 * The state of a {@link Channel} is interpreted differently depending on the
 * {@linkplain ChannelStateEvent#getValue() value} of a {@link ChannelStateEvent}
 * and the direction of the event in a {@link ChannelPipeline}:
 *
 * <table border="1" cellspacing="0" cellpadding="6">
 * <tr>
 * <th>Direction</th><th>State</th><th>Value</th><th>Meaning</th>
 * </tr>
 * <tr>
 * <td>Upstream</td><td>{@link #OPEN}</td>
 * <td>{@code true}</td><td>The channel is open.</td>
 * </tr>
 * <tr>
 * <td>Upstream</td><td>{@link #OPEN}</td>
 * <td>{@code false}</td><td>The channel is closed.</td>
 * </tr>
 * <tr>
 * <td>Upstream</td><td>{@link #BOUND}</td>
 * <td>{@link SocketAddress}</td><td>The channel is bound to a local address.</td>
 * </tr>
 * <tr>
 * <td>Upstream</td><td>{@link #BOUND}</td>
 * <td>{@code null}</td><td>The channel is unbound to a local address.</td>
 * </tr>
 * <tr>
 * <td>Upstream</td><td>{@link #CONNECTED}</td>
 * <td>{@link SocketAddress}</td><td>The channel is connected to a remote address.</td>
 * </tr>
 * <tr>
 * <td>Upstream</td><td>{@link #CONNECTED}</td>
 * <td>{@code null}</td><td>The channel is disconnected from a remote address.</td>
 * </tr>
 * <tr>
 * <td>Upstream</td><td>{@link #INTEREST_OPS}</td>
 * <td>an integer</td><td>The channel interestOps has been changed.</td>
 * </tr>
 * <tr>
 * <td>Downstream</td><td>{@link #OPEN}</td>
 * <td>{@code true}</td><td>N/A</td>
 * </tr>
 * <tr>
 * <td>Downstream</td><td>{@link #OPEN}</td>
 * <td>{@code false}</td><td>Close the channel.</td>
 * </tr>
 * <tr>
 * <td>Downstream</td><td>{@link #BOUND}</td>
 * <td>{@link SocketAddress}</td><td>Bind the channel to the specified local address.</td>
 * </tr>
 * <tr>
 * <td>Downstream</td><td>{@link #BOUND}</td>
 * <td>{@code null}</td><td>Unbind the channel from the current local address.</td>
 * </tr>
 * <tr>
 * <td>Downstream</td><td>{@link #CONNECTED}</td>
 * <td>{@link SocketAddress}</td><td>Connect the channel to the specified remote address.</td>
 * </tr>
 * <tr>
 * <td>Downstream</td><td>{@link #CONNECTED}</td>
 * <td>{@code null}</td><td>Disconnect the channel from the current remote address.</td>
 * </tr>
 * <tr>
 * <td>Downstream</td><td>{@link #INTEREST_OPS}</td>
 * <td>an integer</td><td>Change the interestOps of the channel.</td>
 * </tr>
 * </table>
 * <p>
 * To see how an event is interpreted further, please refer to {@link ChannelEvent}.
 */
public enum ChannelState {
    /**
     * Represents a {@link Channel}'s {@link Channel#isOpen() open} property
     */
    OPEN,

    /**
     * Represents a {@link Channel}'s {@link Channel#isBound() bound} property
     */
    BOUND,

    /**
     * Represents a {@link Channel}'s {@link Channel#isConnected() connected}
     * property
     */
    CONNECTED,

    /**
     * Represents a {@link Channel}'s {@link Channel#getInterestOps() interestOps}
     * property
     */
    INTEREST_OPS;
}
