NexusTypeCache.java

/**
 * Copyright (c) 2008-2011 Sonatype, Inc.
 * All rights reserved. Includes the third-party code listed at http://www.sonatype.com/products/nexus/attributions.
 *
 * This program is free software: you can redistribute it and/or modify it only under the terms of the GNU Affero General
 * Public License Version 3 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License Version 3
 * for more details.
 *
 * You should have received a copy of the GNU Affero General Public License Version 3 along with this program.  If not, see
 * http://www.gnu.org/licenses.
 *
 * Sonatype Nexus (TM) Open Source Version is available from Sonatype, Inc. Sonatype and Sonatype Nexus are trademarks of
 * Sonatype, Inc. Apache Maven is a trademark of the Apache Foundation. M2Eclipse is a trademark of the Eclipse Foundation.
 * All other trademarks are the property of their respective owners.
 */
package org.sonatype.guice.nexus.scanners;

import java.util.HashMap;
import java.util.Map;

import javax.inject.Singleton;

import org.sonatype.guice.bean.reflect.ClassSpace;
import org.sonatype.guice.bean.scanners.ClassSpaceScanner;
import org.sonatype.guice.bean.scanners.EmptyAnnotationVisitor;
import org.sonatype.guice.bean.scanners.EmptyClassVisitor;
import org.sonatype.guice.bean.scanners.asm.AnnotationVisitor;
import org.sonatype.guice.bean.scanners.asm.ClassVisitor;
import org.sonatype.guice.bean.scanners.asm.Type;
import org.sonatype.nexus.plugins.RepositoryType;
import org.sonatype.plugin.ExtensionPoint;
import org.sonatype.plugin.Managed;

/**
 * Caching {@link ClassVisitor} that maintains a map of interface names to {@link NexusType}s.
 */
final class NexusTypeCache
    extends EmptyClassVisitor
{
    // ----------------------------------------------------------------------
    // Constants
    // ----------------------------------------------------------------------

    private static final String EXTENSION_POINT_DESC = Type.getDescriptor( ExtensionPoint.class );

    private static final String REPOSITORY_TYPE_DESC = Type.getDescriptor( RepositoryType.class );

    private static final String MANAGED_DESC = Type.getDescriptor( Managed.class );

    private static final String SINGLETON_DESC = Type.getDescriptor( Singleton.class );

    // ----------------------------------------------------------------------
    // Implementation fields
    // ----------------------------------------------------------------------

    private final Map<String, NexusType> cachedResults = new HashMap<String, NexusType>();

    private final RepositoryTypeAnnotationVisitor repositoryTypeVisitor = new RepositoryTypeAnnotationVisitor();

    NexusType nexusType;

    private boolean isSingleton;

    // ----------------------------------------------------------------------
    // Public methods
    // ----------------------------------------------------------------------

    /**
     * Attempts to find the {@link NexusType} of a given interface.
     * 
     * @param space The class space
     * @param desc The interface name
     * @return Nexus component type
     */
    public NexusType nexusType( final ClassSpace space, final String name )
    {
        if ( name.startsWith( "java" ) )
        {
            return MarkedNexusTypes.UNKNOWN;
        }
        if ( !cachedResults.containsKey( name ) )
        {
            nexusType = MarkedNexusTypes.UNKNOWN;
            isSingleton = false;

            ClassSpaceScanner.accept( this, space.getResource( name + ".class" ) );

            cachedResults.put( name, nexusType );
        }
        return cachedResults.get( name );
    }

    @Override
    public AnnotationVisitor visitAnnotation( final String desc, final boolean visible )
    {
        if ( EXTENSION_POINT_DESC.equals( desc ) )
        {
            nexusType = MarkedNexusTypes.EXTENSION_POINT;
        }
        else if ( MANAGED_DESC.equals( desc ) )
        {
            nexusType = MarkedNexusTypes.MANAGED;
        }
        else if ( SINGLETON_DESC.equals( desc ) )
        {
            isSingleton = true;
        }
        else if ( REPOSITORY_TYPE_DESC.equals( desc ) )
        {
            repositoryTypeVisitor.reset();
            return repositoryTypeVisitor;
        }
        return null;
    }

    @Override
    public void visitEnd()
    {
        if ( isSingleton )
        {
            nexusType = nexusType.asSingleton();
        }
    }

    // ----------------------------------------------------------------------
    // RepositoryType annotation scanner
    // ----------------------------------------------------------------------

    final class RepositoryTypeAnnotationVisitor
        extends EmptyAnnotationVisitor
    {
        private String pathPrefix;

        private int repositoryMaxInstanceCount;

        public void reset()
        {
            pathPrefix = null;
            repositoryMaxInstanceCount = RepositoryType.UNLIMITED_INSTANCES;
        }

        @Override
        public void visit( final String name, final Object value )
        {
            if ( "pathPrefix".equals( name ) )
            {
                pathPrefix = (String) value;
            }
            else if ( "repositoryMaxInstanceCount".equals( name ) )
            {
                repositoryMaxInstanceCount = ( (Integer) value ).intValue();
            }
        }

        @Override
        public void visitEnd()
        {
            if ( pathPrefix != null )
            {
                nexusType = new DetailedNexusType( new RepositoryTypeImpl( pathPrefix, repositoryMaxInstanceCount ) );
            }
        }
    }
}