indexer-core/src/main/java/org/apache/maven/index/AbstractMultiArtifactInfoFilter.java

package org.apache.maven.index;

/*
 * 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 java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import org.apache.maven.index.context.IndexingContext;

/**
 * An abstract helper class for implementing ArtifactInfoFilter that actually aggregates multiple filters into one. It
 * is up to developer to implement how will be they behave ("fail-fast", or "one-vote-enough for passing", etc).
 * 
 * @author cstamas
 */
public abstract class AbstractMultiArtifactInfoFilter
    implements ArtifactInfoFilter
{
    private final List<ArtifactInfoFilter> filters;

    public AbstractMultiArtifactInfoFilter( final List<ArtifactInfoFilter> filters )
    {
        if ( filters == null || filters.isEmpty() )
        {
            this.filters = null;
        }
        else
        {
            this.filters = new ArrayList<>( filters );
        }
    }

    /**
     * Returns an unmodifiable list of filters.
     * 
     * @return
     */
    public List<ArtifactInfoFilter> getFilters()
    {
        if ( filters == null )
        {
            return Collections.emptyList();
        }
        else
        {
            return Collections.unmodifiableList( filters );
        }
    }

    /**
     * The filter's implementation is: if list of filters is empty, the just accept it, otherwise consult the list of
     * filters.
     */
    public boolean accepts( IndexingContext ctx, ArtifactInfo ai )
    {
        if ( this.filters == null )
        {
            return true;
        }
        else
        {
            return accepts( filters, ctx, ai );
        }
    }

    /**
     * It is left to final implementor to implement how we want to decide using filters. This method is called only if
     * we _have_ filters set!
     * 
     * @param filters
     * @param ctx
     * @param ai
     * @return
     */
    protected abstract boolean accepts( List<ArtifactInfoFilter> filters, IndexingContext ctx, ArtifactInfo ai );
}