mae/mae-api/src/main/java/org/apache/maven/mae/internal/container/InstanceRegistry.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.maven.mae.internal.container;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

public class InstanceRegistry
    implements Iterable<Map.Entry<ComponentKey<?>, Object>>
{

    private final Map<ComponentKey<?>, Object> instances = new HashMap<ComponentKey<?>, Object>();

    public InstanceRegistry()
    {
    }

    public InstanceRegistry( final InstanceRegistry... delegates )
    {
        if ( delegates != null && delegates.length > 0 )
        {
            for ( final InstanceRegistry delegate : delegates )
            {
                overrideMerge( delegate );
            }
        }
    }

    public boolean has( final ComponentKey<?> key )
    {
        if ( key == null )
        {
            return false;
        }

        return instances.containsKey( key );
    }

    public <T> boolean has( final Class<T> role, final String hint )
    {
        return has( new ComponentKey<T>( role, hint ) );
    }

    public <T> T get( final ComponentKey<T> key )
    {
        return key.castValue( instances.get( key ) );
    }

    public <T> T get( final Class<T> role, final String hint )
    {
        return get( new ComponentKey<T>( role, hint ) );
    }

    public <C, T extends C> InstanceRegistry add( final ComponentKey<C> key, final T instance )
    {
        if ( instance != null )
        {
            instances.put( key, instance );
        }
        return this;
    }

    public <C, T extends C> InstanceRegistry add( final Class<C> role, final String hint, final T instance )
    {
        if ( role == null )
        {
            throw new NullPointerException( "Role class is null." );
        }

        if ( instance == null )
        {
            throw new NullPointerException( "Instance is null." );
        }

        if ( !role.isAssignableFrom( instance.getClass() ) )
        {
            throw new IllegalArgumentException( "Instance class: " + instance.getClass().getName()
                + " is not assignable to role: " + role.getClass() );
        }

        return add( new ComponentKey<C>( role, hint ), instance );
    }

    public <C, T extends C> InstanceRegistry add( final Class<C> role, final T instance )
    {
        if ( role == null )
        {
            throw new NullPointerException( "Role class is null." );
        }

        if ( instance == null )
        {
            throw new NullPointerException( "Instance is null." );
        }

        if ( !role.isAssignableFrom( instance.getClass() ) )
        {
            throw new IllegalArgumentException( "Instance class: " + instance.getClass().getName()
                + " is not assignable to role: " + role.getClass() );
        }

        return add( new ComponentKey<C>( role ), instance );
    }

    @SuppressWarnings( { "unchecked", "rawtypes" } )
    public <C, T extends C> InstanceRegistry setVirtualInstance( final ComponentKey<C> key, final T instance )
    {
        final Object virt = instances.get( key );
        if ( virt != null && ( virt instanceof VirtualInstance ) )
        {
            final VirtualInstance vi = (VirtualInstance) virt;
            if ( vi.getVirtualClass().equals( key.getRoleClass() ) && vi.getRawInstance() == null )
            {
                vi.setInstance( instance );
            }
        }

        return this;
    }

    public <C, T extends C> InstanceRegistry setVirtualInstance( final Class<C> role, final String hint,
                                                                 final T instance )
    {
        return setVirtualInstance( new ComponentKey<C>( role, hint ), instance );
    }

    public <C, T extends C> InstanceRegistry setVirtualInstance( final Class<C> role, final T instance )
    {
        return setVirtualInstance( new ComponentKey<C>( role ), instance );
    }

    public <T> InstanceRegistry addVirtual( final ComponentKey<T> key, final VirtualInstance<T> virt )
    {
        instances.put( key, virt );
        return this;
    }

    public <T> InstanceRegistry addVirtual( final String hint, final VirtualInstance<T> instance )
    {
        if ( instance == null )
        {
            throw new NullPointerException( "Instance is null." );
        }

        return addVirtual( new ComponentKey<T>( instance.getVirtualClass(), hint ), instance );
    }

    public <T> InstanceRegistry addVirtual( final VirtualInstance<T> instance )
    {
        if ( instance == null )
        {
            throw new NullPointerException( "Instance is null." );
        }

        return addVirtual( new ComponentKey<T>( instance.getVirtualClass() ), instance );
    }

    public InstanceRegistry overrideMerge( final InstanceRegistry instanceRegistry )
    {
        if ( !instanceRegistry.instances.isEmpty() )
        {
            instances.putAll( instanceRegistry.instances );
        }

        return this;
    }

    public Map<ComponentKey<?>, Object> getInstances()
    {
        return instances;
    }

    @SuppressWarnings( "unchecked" )
    public <T> InstanceRegistry add( final T instance )
    {
        if ( instance == null )
        {
            throw new NullPointerException( "Instance is null." );
        }

        return add( new ComponentKey<T>( (Class<T>) instance.getClass() ), instance );
    }

    @Override
    public Iterator<Entry<ComponentKey<?>, Object>> iterator()
    {
        return new HashSet<Map.Entry<ComponentKey<?>, Object>>( instances.entrySet() ).iterator();
    }

}