/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF 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.apache.sshd.client.channel;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Collection;
import java.util.Set;

import org.apache.sshd.client.future.OpenFuture;
import org.apache.sshd.common.channel.Channel;
import org.apache.sshd.common.io.IoInputStream;
import org.apache.sshd.common.io.IoOutputStream;

/**
 * A client channel used to communicate with the SSH server.  Client channels can be shells,
 * simple commands or subsystems. <B>Note:</B> client channels may be associated with a
 * <U>server</U> session if they are opened by the server - e.g., for agent proxy, port
 * forwarding, etc..
 *
 * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
 */
public interface ClientChannel extends Channel {
    enum Streaming {
        Async,
        Sync
    }

    Streaming getStreaming();

    void setStreaming(Streaming streaming);

    IoOutputStream getAsyncIn();

    IoInputStream getAsyncOut();

    IoInputStream getAsyncErr();

    /**
     * Access to an output stream to send data directly to the remote channel.
     * This can be used instead of using {@link #setIn(java.io.InputStream)} method
     * and having the channel polling for data in that stream.
     *
     * @return an OutputStream to be used to send data
     */
    OutputStream getInvertedIn();

    InputStream getInvertedOut();

    InputStream getInvertedErr();

    /**
     * Set an input stream that will be read by this channel and forwarded to
     * the remote channel.  Note that using such a stream will create an additional
     * thread for pumping the stream which will only be able to end when that stream
     * is actually closed or some data is read.  It is recommended to use the
     * {@link #getInvertedIn()} method instead and write data directly.
     *
     * @param in an InputStream to be polled and forwarded
     */
    void setIn(InputStream in);

    void setOut(OutputStream out);

    void setErr(OutputStream err);

    OpenFuture open() throws IOException;

    /**
     * @return A snapshot of the current channel state
     * @see #waitFor(Collection, long)
     */
    Set<ClientChannelEvent> getChannelState();

    /**
     * Waits until any of the specified events in the mask is signaled
     *
     * @param mask The {@link ClientChannelEvent}s mask
     * @param timeout The timeout to wait (msec.) - if non-positive then forever
     * @return The actual signaled event - includes {@link ClientChannelEvent#TIMEOUT}
     * if timeout expired before the expected event was signaled
     */
    Set<ClientChannelEvent> waitFor(Collection<ClientChannelEvent> mask, long timeout);

    /**
     * @return The signaled exit status via "exit-status" request
     * - {@code null} if not signaled
     */
    Integer getExitStatus();

    /**
     * @return The signaled exit signal via "exit-signal"
     * - {@code null} if not signaled
     */
    String getExitSignal();
}