package org.apache.maven.graph;

/*
 * 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.Collection;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.Map;

import org.apache.maven.execution.ProjectDependencyGraph;
import org.apache.maven.project.MavenProject;

/**
 * Provides a sub view of another dependency graph.
 *
 * @author Benjamin Bentmann
 */
class FilteredProjectDependencyGraph
    implements ProjectDependencyGraph
{

    private ProjectDependencyGraph projectDependencyGraph;

    private Map<MavenProject, ?> whiteList;

    private List<MavenProject> sortedProjects;

    /**
     * Creates a new project dependency graph from the specified graph.
     *
     * @param projectDependencyGraph The project dependency graph to create a sub view from, must not be {@code null}.
     * @param whiteList The projects on which the dependency view should focus, must not be {@code null}.
     */
    public FilteredProjectDependencyGraph( ProjectDependencyGraph projectDependencyGraph,
                                           Collection<? extends MavenProject> whiteList )
    {
        if ( projectDependencyGraph == null )
        {
            throw new IllegalArgumentException( "project dependency graph missing" );
        }

        this.projectDependencyGraph = projectDependencyGraph;

        this.whiteList = new IdentityHashMap<MavenProject, Object>();

        for ( MavenProject project : whiteList )
        {
            this.whiteList.put( project, null );
        }
    }

    public List<MavenProject> getSortedProjects()
    {
        if ( sortedProjects == null )
        {
            sortedProjects = applyFilter( projectDependencyGraph.getSortedProjects() );
        }

        return new ArrayList<MavenProject>( sortedProjects );
    }

    public List<MavenProject> getDownstreamProjects( MavenProject project, boolean transitive )
    {
        return applyFilter( projectDependencyGraph.getDownstreamProjects( project, transitive ) );
    }

    public List<MavenProject> getUpstreamProjects( MavenProject project, boolean transitive )
    {
        return applyFilter( projectDependencyGraph.getUpstreamProjects( project, transitive ) );
    }

    private List<MavenProject> applyFilter( Collection<? extends MavenProject> projects )
    {
        List<MavenProject> filtered = new ArrayList<MavenProject>( projects.size() );

        for ( MavenProject project : projects )
        {
            if ( whiteList.containsKey( project ) )
            {
                filtered.add( project );
            }
        }

        return filtered;
    }

    @Override
    public String toString()
    {
        return getSortedProjects().toString();
    }

}
