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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
 * 
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 * 
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
 * identifying information: "Portions Copyrighted [year]
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 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
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 */

package com.sun.faces.util;

import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * A set of utility methods to make working with
 * Classes and Reflection a little easier.
 */
public final class ReflectionUtils {


    /**
     * Cache
     */
    private static final Map> REFLECTION_CACHE =
          new WeakHashMap>();


    // ------------------------------------------------------------ Constructors


    private ReflectionUtils() { }


    // ---------------------------------------------------------- Public Methods


    /**
     * Clears the cache for the specified ClassLoader.
     * This method MUST be called when ConfigureListener
     * .contextDestroyed() is called.
     * @param loader the ClassLoader whose associated cache
     *  should be cleared
     */
    public static synchronized void clearCache(ClassLoader loader) {

            REFLECTION_CACHE.remove(loader);

    }


    public static synchronized void initCache(ClassLoader loader) {

        if (REFLECTION_CACHE.get(loader) == null) {
            REFLECTION_CACHE.put(loader,
                                 new ConcurrentHashMap());
        }

    }


    /**
     * Returns the Constructor appropriate to the specified
     * Class and parameters.
     * @param clazz the Class of interest
     * @param params the parameters for the constructor of the provided Class
     * @return a Constructor that can be invoked with the specified parameters
     */
    public static Constructor lookupConstructor(
          Class clazz,
          Class... params) {

        ClassLoader loader = Util.getCurrentLoader(clazz);
        if (loader == null) {
            return null;
        }
        
        return getMetaData(loader, clazz).lookupConstructor(params);
        
    }
    
    /**
     * Returns the Method appropriate to the specified
     * Class, method name, and parameters.
     * @param clazz the Class of interest
     * @param methodName the name of the method
     * @param params the parameters for the specified method
     * @return a Method that can be invoked with the specified parameters
     */
    public static Method lookupMethod(
          Class clazz,
          String methodName,
          Class... params) {

        ClassLoader loader = Util.getCurrentLoader(clazz);
        if (loader == null) {
            return null;
        }        
        
        return getMetaData(loader, clazz).lookupMethod(methodName, params);
        
    }


    /**
     * Constructs a new object instance based off the
     * provided class name.
     * @param className the class of the object to instantiate
     * @return a new instances of said class
     * @throws InstantiationException if the class cannot be instantiated
     * @throws IllegalAccessException if there is a security violation
     */
    public static Object newInstance(String className)
    throws InstantiationException, IllegalAccessException {

        ClassLoader loader = Util.getCurrentLoader(null);
        if (loader == null) {
            return null;
        }

        return getMetaData(loader, className).lookupClass().newInstance();
        
    }


    /**
     * Obtain a Class instance based on the provided
     * String name.
     * @param className the class to look up
     * @return the Class corresponding to className
     */
    public static Class lookupClass(String className) {

        ClassLoader loader = Util.getCurrentLoader(null);
        if (loader == null) {
            return null;
        }

        return getMetaData(loader, className).lookupClass();
        
    }


    // --------------------------------------------------------- Private Methods


    /**
     * Return the MetaData for the specified Class.
     * 
     * This will check the cache associated with the specified
     * ClassLoader.  If there is no cache hit, then a new
     * MetaData instance will be created and stored.
     * 
     * @param loader ClassLoader
     * @param clazz the Class of interest
     * @return a MetaData object for the specified Class
     */
    private static MetaData getMetaData(ClassLoader loader, Class clazz) {

        ConcurrentMap cache = REFLECTION_CACHE.get(loader);

        if (cache == null) {
            initCache(loader);
            cache = REFLECTION_CACHE.get(loader);
        }

        MetaData meta = cache.get(clazz.getName());
        if (meta == null) {
            meta = new MetaData(clazz);
            cache.put(clazz.getName(), meta);
        }
       
        return meta;

    }


    /**
     * 
Return the MetaData for the specified className.
     *
     * This will check the cache associated with the specified
     * ClassLoader.  If there is no cache hit, then a new
     * MetaData instance will be created and stored.
     *
     * @param loader ClassLoader
     * @param className the class of interest
     * @return a MetaData object for the specified Class
     */
    private static MetaData getMetaData(ClassLoader loader, String className) {

        ConcurrentMap cache = REFLECTION_CACHE.get(loader);

        if (cache == null) {
            initCache(loader);
            cache = REFLECTION_CACHE.get(loader);
        }

        MetaData meta = cache.get(className);
        if (meta == null) {
            try {
                Class clazz = Util.loadClass(className, cache);
                meta = new MetaData(clazz);
                cache.put(className, meta);
            } catch (ClassNotFoundException cnfe) {
                return null;
            }
        }

        return meta;
    }


    /**
     * 
MetaData contains lookup methods for Constructors and
     * Methods of a particular Class.
     */
    private static final class MetaData {


        Map constructors;
        Map> methods;
        Map> declaredMethods;
        Class clazz;


    // ------------------------------------------------------------ Constructors


        /**
         * 
Constructs a new MetaData instance for the specified
         * class.
         * @param clazz class to construct a new MetaData instance from.
         */
        public MetaData(Class clazz) {

            String name = null;
            this.clazz = clazz;
            Constructor[] ctors = clazz.getConstructors();
            constructors = new HashMap(ctors.length, 1.0f);
            for (int i = 0, len = ctors.length; i < len; i++) {
                constructors.put(getKey(ctors[i].getParameterTypes()),
                                 ctors[i]);
            }
            Method[] meths = clazz.getMethods();
            methods = new HashMap>(meths.length, 1.0f);
            for (int i = 0, len = meths.length; i < len; i++) {
                name = meths[i].getName();
                HashMap methodsMap = methods.get(name);
                if (methodsMap == null) {
                    methodsMap = new HashMap(4, 1.0f);
                    methods.put(name, methodsMap);
                }
                methodsMap.put(getKey(meths[i].getParameterTypes()), meths[i]);
            }
            
            meths = clazz.getDeclaredMethods();
            declaredMethods = new HashMap>(meths.length, 1.0f);
            for (int i = 0, len = meths.length; i < len; i++) {
                name = meths[i].getName();
                HashMap declaredMethodsMap = declaredMethods.get(name);
                if (declaredMethodsMap == null) {
                    declaredMethodsMap = new HashMap(4, 1.0f);
                    declaredMethods.put(name, declaredMethodsMap);
                }
                declaredMethodsMap.put(getKey(meths[i].getParameterTypes()), meths[i]);
            }            

        }


    // ---------------------------------------------------------- Public Methods


        /**
         * Looks up a Constructor based off the specified
         * params.
         * @param params constructor parameters
         * @return the Constructor appropriate to the specified 
         *  parameters or null
         */
        public Constructor lookupConstructor(Class... params) {

            return constructors.get(getKey(params));

        }


        /**
         * Looks up a Method based off the specified method
         * name and params.
         * @param name the name of the Method
         * @param params the Method parameters
         * @return the Method appropriate to the specified 
         *  name and parameters or null
         */
        public Method lookupMethod(String name, Class... params) {

            Map map = methods.get(name);
            Integer key = getKey(params);
            Method result = null;
            if ((null == map) || null == (result = map.get(key))) {
                map = declaredMethods.get(name);
                if (null != map) {
                    result = map.get(key);
                }
            }
            return result;

        }


        /**
         * Looks up the class for this MetaData instance.
         * @return the Class for this MetaData instance
         */
        public Class lookupClass() {

            return clazz;

        }


    // --------------------------------------------------------- Private Methods


        /**
         * Return a hashcode of all the class parameters.
         * @param params the parameters to a Constructor or
         *  a Method instance
         * @return the result of Arrays.deepHashCode
         */
        private static Integer getKey(Class... params) {

            return Arrays.deepHashCode(params);

        }

    }

    
} // END ReflectionUtils