/*
 * 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.contribution.osgi.impl;

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

import org.apache.tuscany.sca.contribution.Contribution;
import org.apache.tuscany.sca.contribution.Import;
import org.apache.tuscany.sca.contribution.resolver.ClassReference;
import org.apache.tuscany.sca.contribution.resolver.ModelResolver;
import org.apache.tuscany.sca.core.ExtensionPointRegistry;
import org.apache.tuscany.sca.osgi.runtime.OSGiRuntime;
import org.osgi.framework.Bundle;

/**
 * A Model Resolver for ClassReferences.
 *
 * @version $Rev$ $Date$
 */
public class OSGiClassReferenceModelResolver implements ModelResolver {
    private Contribution contribution;
    private Map<String, ClassReference> map = new HashMap<String, ClassReference>();
    private Bundle bundle;
    private boolean initialized;
    private boolean useOSGi;

    public OSGiClassReferenceModelResolver(Contribution contribution, ExtensionPointRegistry registry) {
        this.contribution = contribution;
    }

    public void addModel(Object resolved) {
        ClassReference clazz = (ClassReference)resolved;
        map.put(clazz.getClassName(), clazz);
    }

    public Object removeModel(Object resolved) {
        return map.remove(((ClassReference)resolved).getClassName());
    }

    /**
     * Handle artifact resolution when the specific class reference is imported from another contribution
     * @param unresolved
     * @return
     */
    private ClassReference resolveImportedModel(ClassReference unresolved) {
        ClassReference resolved = unresolved;

        if (this.contribution != null) {
            for (Import import_ : this.contribution.getImports()) {

                if (resolved == unresolved && bundle != null) {
                    resolved = import_.getModelResolver().resolveModel(ClassReference.class, unresolved);
                    if (resolved != unresolved)
                        break;
                }
            }

        }
        return resolved;
    }

    public <T> T resolveModel(Class<T> modelClass, T unresolved) {
        Object resolved = map.get(unresolved);

        if (resolved != null) {
            return modelClass.cast(resolved);
        }
        initialize();
        if (!useOSGi)
            return unresolved;

        //Load a class on demand
        Class clazz = null;
        if (bundle != null) {
            try {
                clazz = bundle.loadClass(((ClassReference)unresolved).getClassName());
            } catch (Exception e) {
                // we will later try to delegate to imported model resolvers
            }
        }

        if (clazz != null) {
            //if we load the class            
            // Store a new ClassReference wrapping the loaded class
            ClassReference classReference = new ClassReference(clazz);
            map.put(getPackageName(classReference), classReference);

            // Return the resolved ClassReference
            return modelClass.cast(classReference);
        } else {
            //delegate resolution of the class
            resolved = this.resolveImportedModel((ClassReference)unresolved);
            return modelClass.cast(resolved);
        }

    }

    /***************
     * Helper methods
     ***************/

    private String getPackageName(ClassReference clazz) {
        int pos = clazz.getClassName().lastIndexOf(".");
        return clazz.getClassName().substring(0, pos - 1);
    }

    private void initialize() {
        if (initialized)
            return;

        initialized = true;
        try {
            bundle = OSGiRuntime.findInstalledBundle(contribution.getLocation());
            useOSGi = bundle != null;
        } catch (Throwable e) {
            // Ignore errors, default to ClassReferenceModelResolver
        }
    }
}