package org.eclipse.aether.util.graph.manager;

/*
 * 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.
 */

import org.eclipse.aether.collection.DependencyCollectionContext;
import org.eclipse.aether.collection.DependencyManagement;
import org.eclipse.aether.collection.DependencyManager;
import org.eclipse.aether.graph.Dependency;

import static java.util.Objects.requireNonNull;

/**
 * A dependency manager that does not do any dependency management.
 */
public final class NoopDependencyManager
    implements DependencyManager
{

    /**
     * A ready-made instance of this dependency manager which can safely be reused throughout an entire application
     * regardless of multi-threading.
     */
    public static final DependencyManager INSTANCE = new NoopDependencyManager();

    /**
     * Creates a new instance of this dependency manager. Usually, {@link #INSTANCE} should be used instead.
     */
    public NoopDependencyManager()
    {
    }

    public DependencyManager deriveChildManager( DependencyCollectionContext context )
    {
        requireNonNull( context, "context cannot be null" );
        return this;
    }

    public DependencyManagement manageDependency( Dependency dependency )
    {
        requireNonNull( dependency, "dependency cannot be null" );
        return null;
    }

    @Override
    public boolean equals( Object obj )
    {
        if ( this == obj )
        {
            return true;
        }
        else if ( null == obj || !getClass().equals( obj.getClass() ) )
        {
            return false;
        }
        return true;
    }

    @Override
    public int hashCode()
    {
        return getClass().hashCode();
    }

}
