package org.apache.maven.extension.internal;

/*
 * 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.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Collection;
import java.util.Enumeration;
import java.util.LinkedHashSet;
import java.util.Set;

import org.apache.maven.project.ExtensionDescriptor;
import org.apache.maven.project.ExtensionDescriptorBuilder;
import org.codehaus.plexus.classworlds.realm.ClassRealm;
import org.codehaus.plexus.util.IOUtil;

import com.google.common.collect.ImmutableSet;

/**
 * Provides information about artifacts (identified by groupId:artifactId string key) and classpath elements exported by
 * Maven core itself or a Maven core extension.
 * 
 * @since 3.3.0
 */
public class CoreExtensionEntry
{
    private final ClassRealm realm;

    private final Set<String> artifacts;

    private final Set<String> packages;

    public CoreExtensionEntry( ClassRealm realm, Collection<String> artifacts, Collection<String> packages )
    {
        this.realm = realm;
        this.artifacts = ImmutableSet.copyOf( artifacts );
        this.packages = ImmutableSet.copyOf( packages );
    }

    /**
     * Returns ClassLoader used to load extension classes.
     */
    public ClassRealm getClassRealm()
    {
        return realm;
    }

    /**
     * Returns artifacts exported by the extension, identified by groupId:artifactId string key.
     */
    public Set<String> getExportedArtifacts()
    {
        return artifacts;
    }

    /**
     * Returns classpath elements exported by the extension.
     */
    public Set<String> getExportedPackages()
    {
        return packages;
    }

    private static final ExtensionDescriptorBuilder builder = new ExtensionDescriptorBuilder();

    public static CoreExtensionEntry discoverFrom( ClassRealm loader )
    {
        Set<String> artifacts = new LinkedHashSet<String>();
        Set<String> packages = new LinkedHashSet<String>();

        try
        {
            Enumeration<URL> urls = loader.getResources( builder.getExtensionDescriptorLocation() );
            while ( urls.hasMoreElements() )
            {
                InputStream is = urls.nextElement().openStream();
                try
                {
                    ExtensionDescriptor descriptor = builder.build( is );
                    artifacts.addAll( descriptor.getExportedArtifacts() );
                    packages.addAll( descriptor.getExportedPackages() );
                }
                finally
                {
                    IOUtil.close( is );
                }
            }
        }
        catch ( IOException ignored )
        {
            // exports descriptors are entirely optional
        }

        return new CoreExtensionEntry( loader, artifacts, packages );
    }

    public static CoreExtensionEntry discoverFrom( ClassRealm loader, Collection<File> classpath )
    {
        Set<String> artifacts = new LinkedHashSet<String>();
        Set<String> packages = new LinkedHashSet<String>();

        try
        {
            for ( File entry : classpath )
            {
                ExtensionDescriptor descriptor = builder.build( entry );
                if ( descriptor != null )
                {
                    artifacts.addAll( descriptor.getExportedArtifacts() );
                    packages.addAll( descriptor.getExportedPackages() );
                }
            }
        }
        catch ( IOException ignored )
        {
            // exports descriptors are entirely optional
        }

        return new CoreExtensionEntry( loader, artifacts, packages );
    }

}