/*
 * 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.config.hosts;

import java.io.IOException;

/**
 * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
 */
@FunctionalInterface
public interface HostConfigEntryResolver {

    /**
     * An "empty" implementation that does not resolve any entry
     */
    HostConfigEntryResolver EMPTY = new HostConfigEntryResolver() {
        @Override
        public HostConfigEntry resolveEffectiveHost(String host, int port, String username) throws IOException {
            return null;
        }

        @Override
        public String toString() {
            return "EMPTY";
        }
    };

    /**
     * Invoked when creating a new client session in order to allow for overriding
     * of the original parameters
     *
     * @param host The requested host - never {@code null}/empty
     * @param port The requested port
     * @param username The requested username
     * @return A {@link HostConfigEntry} for the actual target - {@code null} if use
     * original parameters. <B>Note:</B> if any identity files are attached to the
     * configuration then they must point to <U>existing</U> locations. This means
     * that any macros such as <code>~, %d, %h</code>, etc. must be resolved <U>prior</U>
     * to returning the value
     * @throws IOException If failed to resolve the configuration
     */
    HostConfigEntry resolveEffectiveHost(String host, int port, String username) throws IOException;
}