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/*
 * Copyright (C)2009 - SSHJ Contributors
 *
 * Licensed 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 net.schmizz.sshj.connection.channel;

import net.schmizz.sshj.common.ErrorNotifiable;
import net.schmizz.sshj.common.LoggerFactory;
import net.schmizz.sshj.common.SSHPacketHandler;
import net.schmizz.sshj.connection.ConnectionException;
import net.schmizz.sshj.transport.TransportException;

import java.io.Closeable;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.charset.Charset;
import java.util.concurrent.TimeUnit;

/**
 * A channel is the basic medium for application-layer data on top of an SSH transport.
 */
public interface Channel extends Closeable, SSHPacketHandler, ErrorNotifiable {

    /**
     * Direct channels are those that are initiated by us.
     */
    interface Direct extends Channel {

        /**
         * Request opening this channel from remote end.
         *
         * @throws OpenFailException   in case the channel open request was rejected
         * @throws ConnectionException other connection-layer error
         * @throws TransportException  error writing packets etc.
         */
        void open() throws ConnectionException, TransportException;

    }

    /**
     * Forwarded channels are those that are initiated by the server.
     */
    interface Forwarded extends Channel {

        /**
         * Confirm {@code CHANNEL_OPEN} request.
         *
         * @throws TransportException error sending confirmation packet
         */
        void confirm() throws TransportException;

        /**
         * @return the IP of where the forwarded connection originates.
         */
        String getOriginatorIP();

        /**
         * @return port from which the forwarded connection originates.
         */
        int getOriginatorPort();

        /**
         * Indicate rejection to remote end.
         *
         * @param reason  indicate {@link OpenFailException.Reason reason} for rejection of the request
         * @param message indicate a message for why the request is rejected
         * @throws TransportException error sending rejection packet
         */
        void reject(OpenFailException.Reason reason, String message) throws TransportException;

    }


    /**
     * Close this channel.
     */
    @Override
    void close() throws TransportException, ConnectionException;

    /**
     * @return whether auto-expansion of local window is set.
     * @see #setAutoExpand(boolean)
     */
    boolean getAutoExpand();

    /**
     * @return the channel ID
     */
    int getID();

    /**
     * @return the {@code InputStream} for this channel.
     */
    InputStream getInputStream();

    /**
     * @return the maximum packet size that we have specified.
     */
    int getLocalMaxPacketSize();

    /**
     * @return the current local window size.
     */
    long getLocalWinSize();

    /**
     * @return an {@code OutputStream} for this channel.
     */
    OutputStream getOutputStream();

    /**
     * @return the channel ID at the remote end.
     */
    int getRecipient();

    /** @return the character set used to communicate with the remote machine for certain strings (like paths). */
    Charset getRemoteCharset();

    /**
     * @return the maximum packet size as specified by the remote end.
     */
    int getRemoteMaxPacketSize();

    /**
     * @return the current remote window size.
     */
    long getRemoteWinSize();

    /**
     * @return the channel type identifier.
     */
    String getType();

    /**
     * @return whether the channel is open.
     */
    boolean isOpen();

    /**
     * Set whether local window should automatically expand when data is received, irrespective of whether data has been
     * read from that stream. This is useful e.g. when a remote command produces a lot of output that would fill the
     * local window but you are not interested in reading from its {@code InputStream}.
     *
     * @param autoExpand whether local windows should automatically expand
     */
    void setAutoExpand(boolean autoExpand);

    void join() throws ConnectionException;

    void join(long timeout, TimeUnit unit) throws ConnectionException;

    /**
     * Returns whether EOF has been received.
     */
    boolean isEOF();

    /**
     * Get the LoggerFactory associated with the SSH client.
     */
    LoggerFactory getLoggerFactory();
}