core/runtime/src/main/java/org/apache/polygene/runtime/composite/UsesInstance.java

/*
 *  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.polygene.runtime.composite;

import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import org.apache.polygene.api.common.ConstructionException;
import org.apache.polygene.runtime.PolygeneRuntimeImpl;

/**
 * JAVADOC
 */
public final class UsesInstance
{
    public static final UsesInstance EMPTY_USES;
    private final Set<Object> uses;

    static
    {
        EMPTY_USES = new UsesInstance( new HashSet<>() );
    }

    private UsesInstance( HashSet<Object> uses )
    {
        this.uses = Collections.unmodifiableSet( uses );
    }

    public UsesInstance use( Object... objects )
    {
        // Validate that there are no Composites in the list, since they are possibly not fully initialized yet.
        // TODO: The reason for that is that Composites may not be fully initialized when reaching here, and the hashCode() call later will cause an NPE.
        for( Object obj : objects )
        {
            if( PolygeneRuntimeImpl.isCompositeType( obj ) )
            {
                throw new ConstructionException( "Composites are not allowed as @Uses arguments: " + obj.toString() );
            }
        }
        HashSet<Object> useObjects = new HashSet<>();
        if( !uses.isEmpty() )
        {
            useObjects.addAll( uses );
            for( Object object : objects )
            {
                Object oldUseForType = useForType( object.getClass() );
                if( oldUseForType != null )
                {
                    useObjects.remove( oldUseForType );
                }
            }
        }
        useObjects.addAll( Arrays.asList( objects ) );
        return new UsesInstance( useObjects );
    }

    public Object useForType( Class<?> type )
    {
        // Check instances first
        for( Object use : uses )
        {
            if( type.isInstance( use ) )
            {
                return use;
            }
        }

        return null;
    }

    public Object[] toArray()
    {
        return uses.toArray();
    }

    @Override
    public boolean equals( Object o )
    {
        if( this == o )
        {
            return true;
        }
        if( o == null || getClass() != o.getClass() )
        {
            return false;
        }
        UsesInstance that = (UsesInstance) o;
        return uses.equals( that.uses );
    }

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

    @Override
    public String toString()
    {
        return "UsesInstance{" +
               "uses=" + uses +
               '}';
    }
}