/*
* 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.subsystem.sftp;
import java.util.Collection;
import java.util.List;
import java.util.stream.StreamSupport;
import org.apache.sshd.client.session.ClientSession;
import org.apache.sshd.common.util.GenericUtils;
import org.apache.sshd.common.util.NumberUtils;
import org.apache.sshd.common.util.ValidateUtils;
/**
* @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
*/
@FunctionalInterface
public interface SftpVersionSelector {
/**
* An {@link SftpVersionSelector} that returns the current version
*/
SftpVersionSelector CURRENT = new NamedVersionSelector("CURRENT", (session, current, available) -> current);
/**
* An {@link SftpVersionSelector} that returns the maximum available version
*/
SftpVersionSelector MAXIMUM = new NamedVersionSelector("MAXIMUM", (session, current, available) ->
GenericUtils.stream(available).mapToInt(Integer::intValue).max().orElse(current));
/**
* An {@link SftpVersionSelector} that returns the maximum available version
*/
SftpVersionSelector MINIMUM = new NamedVersionSelector("MINIMUM", (session, current, available) ->
GenericUtils.stream(available).mapToInt(Integer::intValue).min().orElse(current));
/**
* @param session The {@link ClientSession} through which the SFTP connection is made
* @param current The current version negotiated with the server
* @param available Extra versions available - may be empty and/or contain
* only the current one
* @return The new requested version - if same as current, then nothing is done
*/
int selectVersion(ClientSession session, int current, List<Integer> available);
/**
* Creates a selector the always returns the requested (fixed version) regardless
* of what the current or reported available versions are. If the requested version
* is not reported as available then an exception will be eventually thrown by the
* client during re-negotiation phase.
*
* @param version The requested version
* @return The {@link SftpVersionSelector}
*/
static SftpVersionSelector fixedVersionSelector(final int version) {
return (session, current, available) -> version;
}
/**
* Selects a version in order of preference - if none of the preferred
* versions is listed as available then an exception is thrown when the
* {@link SftpVersionSelector#selectVersion(ClientSession, int, List)} method is invoked
*
* @param preferred The preferred versions in decreasing order of
* preference (i.e., most preferred is 1st) - may not be {@code null}/empty
* @return A {@link SftpVersionSelector} that attempts to select
* the most preferred version that is also listed as available.
*/
static SftpVersionSelector preferredVersionSelector(final int... preferred) {
return preferredVersionSelector(NumberUtils.asList(preferred));
}
/**
* Selects a version in order of preference - if none of the preferred
* versions is listed as available then an exception is thrown when the
* {@link SftpVersionSelector#selectVersion(ClientSession, int, List)} method is invoked
*
* @param preferred The preferred versions in decreasing order of
* preference (i.e., most preferred is 1st)
* @return A {@link SftpVersionSelector} that attempts to select
* the most preferred version that is also listed as available.
*/
static SftpVersionSelector preferredVersionSelector(final Iterable<? extends Number> preferred) {
ValidateUtils.checkNotNullAndNotEmpty((Collection<?>) preferred, "Empty preferred versions");
return (session, current, available) -> StreamSupport.stream(preferred.spliterator(), false)
.mapToInt(Number::intValue)
.filter(v -> v == current || available.contains(v))
.findFirst()
.orElseThrow(() -> new IllegalStateException("Preferred versions (" + preferred + ") not available: " + available));
}
class NamedVersionSelector implements SftpVersionSelector {
private final String name;
private final SftpVersionSelector selector;
public NamedVersionSelector(String name, SftpVersionSelector selector) {
this.name = name;
this.selector = selector;
}
@Override
public int selectVersion(ClientSession session, int current, List<Integer> available) {
return selector.selectVersion(session, current, available);
}
@Override
public String toString() {
return name;
}
}
}