/*
 * 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.tuscany.sca.provider;

import java.lang.reflect.Constructor;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import org.apache.tuscany.sca.core.ExtensionPointRegistry;
import org.apache.tuscany.sca.extensibility.ServiceDeclaration;
import org.apache.tuscany.sca.extensibility.ServiceDiscovery;

/**
 * Concrete Implementation for the SCADefinitionsProviderExtensionPoint
 *
 * @version $Rev$ $Date$
 */
public class DefaultDefinitionsProviderExtensionPoint implements
    DefinitionsProviderExtensionPoint {

    private ExtensionPointRegistry extensionPointRegistry = null;
    
    private boolean loaded;
    private List<DefinitionsProvider> scaDefnsProviders = new ArrayList<DefinitionsProvider>();
    
    public DefaultDefinitionsProviderExtensionPoint(ExtensionPointRegistry extnPtReg) {
        this.extensionPointRegistry = extnPtReg;
    }

    public void addDefinitionsProvider(DefinitionsProvider provider) {
        scaDefnsProviders.add(provider);
    }

    public void removeDefinitionsProvider(DefinitionsProvider provider) {
        scaDefnsProviders.remove(provider);
    }

    public List<DefinitionsProvider> getDefinitionsProviders() {
        loadProviders();
        return scaDefnsProviders;
    }

    private synchronized void loadProviders() {
        if(loaded) {
            return;
        }
        // Get the provider service declarations
        Collection<ServiceDeclaration> defnProviderDecls;
        DefinitionsProvider aProvider = null;
        Class<?> providerClass = null;
        Constructor<?> constructor = null;

        try {
            defnProviderDecls =
                ServiceDiscovery.getInstance().getServiceDeclarations(DefinitionsProvider.class.getName());
    
            for (ServiceDeclaration aDefnProviderDecl : defnProviderDecls) {
                providerClass = aDefnProviderDecl.loadClass();
            
                try {
                    constructor = providerClass.getConstructor();
                    aProvider = (DefinitionsProvider)constructor.newInstance();
                } catch (NoSuchMethodException e1) {
                        constructor = providerClass.getConstructor(ExtensionPointRegistry.class);
                        aProvider = (DefinitionsProvider)constructor.newInstance(extensionPointRegistry);
                } 
                
                scaDefnsProviders.add(aProvider);
            }
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
        loaded = true;
    }
}