/*
 * 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.eclipse.aether.util.repository;

import org.eclipse.aether.repository.Proxy;
import org.eclipse.aether.repository.ProxySelector;
import org.eclipse.aether.repository.RemoteRepository;

/**
 * A proxy selector that delegates to another selector but only if a repository has no proxy yet. If a proxy has already
 * been assigned to a repository, that is selected.
 */
public final class ConservativeProxySelector
    implements ProxySelector
{

    private final ProxySelector selector;

    /**
     * Creates a new selector that delegates to the specified selector.
     * 
     * @param selector The selector to delegate to in case a repository has no proxy yet, must not be {@code null}.
     */
    public ConservativeProxySelector( ProxySelector selector )
    {
        if ( selector == null )
        {
            throw new IllegalArgumentException( "no proxy selector specified" );
        }
        this.selector = selector;
    }

    public Proxy getProxy( RemoteRepository repository )
    {
        Proxy proxy = repository.getProxy();
        if ( proxy != null )
        {
            return proxy;
        }
        return selector.getProxy( repository );
    }

}