/*
 * 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.io.IOException;
import java.lang.reflect.Constructor;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.tuscany.sca.assembly.Binding;
import org.apache.tuscany.sca.assembly.Implementation;
import org.apache.tuscany.sca.contribution.util.ServiceConfigurationUtil;
import org.apache.tuscany.sca.core.ExtensionPointRegistry;
import org.apache.tuscany.sca.runtime.RuntimeComponent;
import org.apache.tuscany.sca.runtime.RuntimeComponentReference;
import org.apache.tuscany.sca.runtime.RuntimeComponentService;

/**
 * Default implementation of a provider factory extension point.
 *
 * @version $Rev$ $Date$
 */
public class DefaultProviderFactoryExtensionPoint implements ProviderFactoryExtensionPoint {
    
    private ExtensionPointRegistry registry;
    private final Map<Class<?>, ProviderFactory> providerFactories = new HashMap<Class<?>, ProviderFactory>();
    private boolean loaded;

    /**
     * The default constructor. Does nothing.
     *
     */
    public DefaultProviderFactoryExtensionPoint(ExtensionPointRegistry registry) {
        this.registry = registry;
    }

    /**
     * Add a provider factory.
     * 
     * @param providerFactory The provider factory
     */
    public void addProviderFactory(ProviderFactory providerFactory) {
        providerFactories.put(providerFactory.getModelType(), providerFactory);
    }
    
    /**
     * Remove a provider factory.
     * 
     * @param providerFactory The provider factory
     */
    public void removeProviderFactory(ProviderFactory providerFactory) {
        providerFactories.remove(providerFactory.getModelType());
    }
    
    /**
     * Returns the provider factory associated with the given model type.
     * @param modelType A model type
     * @return The provider factory associated with the given model type
     */
    public ProviderFactory getProviderFactory(Class<?> modelType) {
        loadProviderFactories();
        
        Class<?>[] classes = modelType.getInterfaces();
        for (Class<?> c : classes) {
            ProviderFactory factory = providerFactories.get(c);
            if (factory != null) {
                return factory;
            }
        }
        return providerFactories.get(modelType);
    }

    /**
     * Load provider factories declared under META-INF/services.
     * @param registry
     */
    private void loadProviderFactories() {
        if (loaded)
            return;

        loadProviderFactories(BindingProviderFactory.class);
        loadProviderFactories(ImplementationProviderFactory.class);
        
        loaded = true;
    }
    
    /**
     * Load provider factories declared under META-INF/services.
     * @param registry
     * @param factoryClass
     * @return
     */
    private List<ProviderFactory> loadProviderFactories(Class<?> factoryClass) {

        // Get the provider factory service declarations
        List<String> factoryDeclarations; 
        try {
            ClassLoader classLoader = factoryClass.getClassLoader();
            factoryDeclarations = ServiceConfigurationUtil.getServiceClassNames(classLoader, factoryClass.getName());
        } catch (IOException e) {
            throw new IllegalStateException(e);
        }
        
        // Get the target extension point
        ProviderFactoryExtensionPoint factoryExtensionPoint = registry.getExtensionPoint(ProviderFactoryExtensionPoint.class);
        List<ProviderFactory> factories = new ArrayList<ProviderFactory>();
        
        for (String factoryDeclaration: factoryDeclarations) {
            Map<String, String> attributes = ServiceConfigurationUtil.parseServiceDeclaration(factoryDeclaration);
            String className = attributes.get("class");
            
            // Load an implementation provider factory
            if (factoryClass == ImplementationProviderFactory.class) {
                String modelTypeName = attributes.get("model");
                
                // Create a provider factory wrapper and register it
                ImplementationProviderFactory factory = new LazyImplementationProviderFactory(registry, modelTypeName, className);
                factoryExtensionPoint.addProviderFactory(factory);
                factories.add(factory);

            } else if (factoryClass == BindingProviderFactory.class) {

                // Load a binding provider factory
                String modelTypeName = attributes.get("model");
                
                // Create a provider factory wrapper and register it
                BindingProviderFactory factory = new LazyBindingProviderFactory(registry, modelTypeName, className);
                factoryExtensionPoint.addProviderFactory(factory);
                factories.add(factory);
            }
        }
        return factories;
    }

    /**
     * A wrapper around an implementation provider factory allowing lazy
     * loading and initialization of implementation providers.
     */
    private static class LazyBindingProviderFactory implements BindingProviderFactory {

        private ExtensionPointRegistry registry;
        private String modelTypeName;
        private String className;
        private BindingProviderFactory factory;
        private Class modelType;
        
        private LazyBindingProviderFactory(ExtensionPointRegistry registry, String modelTypeName, String className) {
            this.registry = registry;
            this.modelTypeName = modelTypeName;
            this.className = className;
        }

        @SuppressWarnings("unchecked")
        private BindingProviderFactory getFactory() {
            if (factory == null) {
                try {
                    ClassLoader classLoader = BindingProviderFactory.class.getClassLoader();
                    Class<BindingProviderFactory> factoryClass = (Class<BindingProviderFactory>)Class.forName(className, true, classLoader);
                    Constructor<BindingProviderFactory> constructor = factoryClass.getConstructor(ExtensionPointRegistry.class);
                    factory = constructor.newInstance(registry);
                } catch (Exception e) {
                    throw new IllegalStateException(e);
                }
            }
            return factory;
        }

        @SuppressWarnings("unchecked")
        public ReferenceBindingProvider createReferenceBindingProvider(RuntimeComponent component, RuntimeComponentReference reference, Binding binding) {
            return getFactory().createReferenceBindingProvider(component, reference, binding);
        }
        
        @SuppressWarnings("unchecked")
        public ServiceBindingProvider createServiceBindingProvider(RuntimeComponent component, RuntimeComponentService service, Binding binding) {
            return getFactory().createServiceBindingProvider(component, service, binding);
        }
        
        public Class getModelType() {
            if (modelType == null) {
                try {
                    ClassLoader classLoader = BindingProviderFactory.class.getClassLoader();
                    modelType = Class.forName(modelTypeName, true, classLoader);
                } catch (Exception e) {
                    throw new IllegalStateException(e);
                }
            }
            return modelType;
        }

    }

    /**
     * A wrapper around an implementation provider factory allowing lazy
     * loading and initialization of implementation providers.
     */
    private class LazyImplementationProviderFactory implements ImplementationProviderFactory {

        private ExtensionPointRegistry registry;
        private String modelTypeName;
        private String className;
        private ImplementationProviderFactory factory;
        private Class modelType;
        
        private LazyImplementationProviderFactory(ExtensionPointRegistry registry, String modelTypeName, String className) {
            this.registry = registry;
            this.modelTypeName = modelTypeName;
            this.className = className;
        }

        @SuppressWarnings("unchecked")
        private ImplementationProviderFactory getFactory() {
            if (factory == null) {
                try {
                    ClassLoader classLoader = ImplementationProviderFactory.class.getClassLoader();
                    Class<ImplementationProviderFactory> factoryClass = (Class<ImplementationProviderFactory>)Class.forName(className, true, classLoader);
                    Constructor<ImplementationProviderFactory> constructor = factoryClass.getConstructor(ExtensionPointRegistry.class);
                    factory = constructor.newInstance(registry);
                } catch (Exception e) {
                    throw new IllegalStateException(e);
                }
            }
            return factory;
        }

        @SuppressWarnings("unchecked")
        public ImplementationProvider createImplementationProvider(RuntimeComponent component, Implementation Implementation) {
            return getFactory().createImplementationProvider(component, Implementation);
        }

        public Class getModelType() {
            if (modelType == null) {
                try {
                    ClassLoader classLoader = ImplementationProviderFactory.class.getClassLoader();
                    modelType = Class.forName(modelTypeName, true, classLoader);
                } catch (Exception e) {
                    throw new IllegalStateException(e);
                }
            }
            return modelType;
        }

    }

}