/*
 * This file is part of Nuts Framework.
 * Copyright(C) 2009-2012 Nuts Develop Team.
 *
 * Nuts Framework is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License any later version.
 * 
 * Nuts Framework is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Nuts Framework. If not, see <http://www.gnu.org/licenses/>.
 */
package nuts.core.lang;

import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Collections;
import java.util.Map;
import java.util.WeakHashMap;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * utility class for Method
 */
@SuppressWarnings("unchecked")
public class MethodUtils {
    private static Log log = LogFactory.getLog(MethodUtils.class);
    
    /** 
     * Only log warning about accessibility work around once.
     * <p>
     * Note that this is broken when this class is deployed via a shared
     * classloader in a container, as the warning message will be emitted
     * only once, not once per webapp. However making the warning appear
     * once per webapp means having a map keyed by context classloader
     * which introduces nasty memory-leak problems. As this warning is
     * really optional we can ignore this problem; only one of the webapps
     * will get the warning in its logs but that should be good enough.
     */
    private static boolean loggedAccessibleWarning = false;
    
    /** 
     * Indicates whether methods should be cached for improved performance.
     * <p>
     * Note that when this class is deployed via a shared classloader in
     * a container, this will affect all webapps. However making this
     * configurable per webapp would mean having a map keyed by context classloader
     * which may introduce memory-leak problems.
     */
    private static boolean CACHE_METHODS = true;

    /** An empty class array */
    private static final Class[] EMPTY_CLASS_PARAMETERS = new Class[0];
    /** An empty object array */
    private static final Object[] EMPTY_OBJECT_ARRAY = new Object[0];

    /**
     * Stores a cache of MethodDescriptor -> Method in a WeakHashMap.
     * <p>
     * The keys into this map only ever exist as temporary variables within
     * methods of this class, and are never exposed to users of this class.
     * This means that the WeakHashMap is used only as a mechanism for 
     * limiting the size of the cache, ie a way to tell the garbage collector
     * that the contents of the cache can be completely garbage-collected 
     * whenever it needs the memory. Whether this is a good approach to
     * this problem is doubtful; something like the commons-collections
     * LRUMap may be more appropriate (though of course selecting an
     * appropriate size is an issue).
     * <p>
     * This static variable is safe even when this code is deployed via a
     * shared classloader because it is keyed via a MethodDescriptor object
     * which has a Class as one of its members and that member is used in
     * the MethodDescriptor.equals method. So two components that load the same
     * class via different classloaders will generate non-equal MethodDescriptor
     * objects and hence end up with different entries in the map.
     */
    private static final Map cache = Collections.synchronizedMap(new WeakHashMap());
    
    // --------------------------------------------------------- Public Methods

    /**
     * Set whether methods should be cached for greater performance or not,
     * default is <code>true</code>.
     *
     * @param cacheMethods <code>true</code> if methods should be
     * cached for greater performance, otherwise <code>false</code>
     * @since 1.8.0
     */
    public static synchronized void setCacheMethods(boolean cacheMethods) {
        CACHE_METHODS = cacheMethods;
        if (!CACHE_METHODS) {
            clearCache();
        }
    }

    /**
     * Clear the method cache.
     * @return the number of cached methods cleared
     * @since 1.8.0
     */
    public static synchronized int clearCache() {
        int size = cache.size();
        cache.clear();
        return size;
    }
    
    /**
     * <p>Invoke a named method whose parameter type matches the object type.</p>
     *
     * <p>The behaviour of this method is less deterministic 
     * than <code>invokeExactMethod()</code>.
     * It loops through all methods with names that match
     * and then executes the first it finds with compatable parameters.</p>
     *
     * <p>This method supports calls to methods taking primitive parameters 
     * via passing in wrapping classes. So, for example, a <code>Boolean</code> class
     * would match a <code>boolean</code> primitive.</p>
     *
     * <p> This is a convenient wrapper for
     * {@link #invokeMethod(Object object,String methodName,Object [] args)}.
     * </p>
     *
     * @param object invoke method on this object
     * @param methodName get method with this name
     * @param arg use this argument
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     */
    public static Object invokeMethod(
            Object object,
            String methodName,
            Object arg)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {

        Object[] args = {arg};
        return invokeMethod(object, methodName, args);

    }


    /**
     * <p>Invoke a named method whose parameter type matches the object type.</p>
     *
     * <p>The behaviour of this method is less deterministic 
     * than {@link #invokeExactMethod(Object object,String methodName,Object [] args)}. 
     * It loops through all methods with names that match
     * and then executes the first it finds with compatable parameters.</p>
     *
     * <p>This method supports calls to methods taking primitive parameters 
     * via passing in wrapping classes. So, for example, a <code>Boolean</code> class
     * would match a <code>boolean</code> primitive.</p>
     *
     * <p> This is a convenient wrapper for
     * {@link #invokeMethod(Object object,String methodName,Object [] args,Class[] parameterTypes)}.
     * </p>
     *
     * @param object invoke method on this object
     * @param methodName get method with this name
     * @param args use these arguments - treat null as empty array
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     */
    public static Object invokeMethod(
            Object object,
            String methodName,
            Object[] args)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {
        
        if (args == null) {
            args = EMPTY_OBJECT_ARRAY;
        }  
        int arguments = args.length;
        Class[] parameterTypes = new Class[arguments];
        for (int i = 0; i < arguments; i++) {
            parameterTypes[i] = args[i].getClass();
        }
        return invokeMethod(object, methodName, args, parameterTypes);

    }


    /**
     * <p>Invoke a named method whose parameter type matches the object type.</p>
     *
     * <p>The behaviour of this method is less deterministic 
     * than {@link 
     * #invokeExactMethod(Object object,String methodName,Object [] args,Class[] parameterTypes)}. 
     * It loops through all methods with names that match
     * and then executes the first it finds with compatable parameters.</p>
     *
     * <p>This method supports calls to methods taking primitive parameters 
     * via passing in wrapping classes. So, for example, a <code>Boolean</code> class
     * would match a <code>boolean</code> primitive.</p>
     *
     *
     * @param object invoke method on this object
     * @param methodName get method with this name
     * @param args use these arguments - treat null as empty array
     * @param parameterTypes match these parameters - treat null as empty array
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     */
    public static Object invokeMethod(
            Object object,
            String methodName,
            Object[] args,
            Class[] parameterTypes)
                throws
                    NoSuchMethodException,
                    IllegalAccessException,
                    InvocationTargetException {
                    
        if (parameterTypes == null) {
            parameterTypes = EMPTY_CLASS_PARAMETERS;
        }        
        if (args == null) {
            args = EMPTY_OBJECT_ARRAY;
        }  

        Method method = getMatchingAccessibleMethod(
                object.getClass(),
                methodName,
                parameterTypes);
        if (method == null) {
            throw new NoSuchMethodException("No such accessible method: " +
                    methodName + "() on object: " + object.getClass().getName());
        }
        return method.invoke(object, args);
    }


    /**
     * <p>Invoke a method whose parameter type matches exactly the object
     * type.</p>
     *
     * <p> This is a convenient wrapper for
     * {@link #invokeExactMethod(Object object,String methodName,Object [] args)}.
     * </p>
     *
     * @param object invoke method on this object
     * @param methodName get method with this name
     * @param arg use this argument
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     */
    public static Object invokeExactMethod(
            Object object,
            String methodName,
            Object arg)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {

        Object[] args = {arg};
        return invokeExactMethod(object, methodName, args);

    }


    /**
     * <p>Invoke a method whose parameter types match exactly the object
     * types.</p>
     *
     * <p> This uses reflection to invoke the method obtained from a call to
     * <code>getAccessibleMethod()</code>.</p>
     *
     * @param object invoke method on this object
     * @param methodName get method with this name
     * @param args use these arguments - treat null as empty array
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     */
    public static Object invokeExactMethod(
            Object object,
            String methodName,
            Object[] args)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {
        if (args == null) {
            args = EMPTY_OBJECT_ARRAY;
        }  
        int arguments = args.length;
        Class[] parameterTypes = new Class[arguments];
        for (int i = 0; i < arguments; i++) {
            parameterTypes[i] = args[i].getClass();
        }
        return invokeExactMethod(object, methodName, args, parameterTypes);

    }


    /**
     * <p>Invoke a method whose parameter types match exactly the parameter
     * types given.</p>
     *
     * <p>This uses reflection to invoke the method obtained from a call to
     * <code>getAccessibleMethod()</code>.</p>
     *
     * @param object invoke method on this object
     * @param methodName get method with this name
     * @param args use these arguments - treat null as empty array
     * @param parameterTypes match these parameters - treat null as empty array
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     */
    public static Object invokeExactMethod(
            Object object,
            String methodName,
            Object[] args,
            Class[] parameterTypes)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {
        
        if (args == null) {
            args = EMPTY_OBJECT_ARRAY;
        }  
                
        if (parameterTypes == null) {
            parameterTypes = EMPTY_CLASS_PARAMETERS;
        }

        Method method = getAccessibleMethod(
                object.getClass(),
                methodName,
                parameterTypes);
        if (method == null) {
            throw new NoSuchMethodException("No such accessible method: " +
                    methodName + "() on object: " + object.getClass().getName());
        }
        return method.invoke(object, args);

    }

    /**
     * <p>Invoke a static method whose parameter types match exactly the parameter
     * types given.</p>
     *
     * <p>This uses reflection to invoke the method obtained from a call to
     * {@link #getAccessibleMethod(Class, String, Class[])}.</p>
     *
     * @param objectClass invoke static method on this class
     * @param methodName get method with this name
     * @param args use these arguments - treat null as empty array
     * @param parameterTypes match these parameters - treat null as empty array
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     * @since 1.8.0
     */
    public static Object invokeExactStaticMethod(
            Class objectClass,
            String methodName,
            Object[] args,
            Class[] parameterTypes)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {
        
        if (args == null) {
            args = EMPTY_OBJECT_ARRAY;
        }  
                
        if (parameterTypes == null) {
            parameterTypes = EMPTY_CLASS_PARAMETERS;
        }

        Method method = getAccessibleMethod(
                objectClass,
                methodName,
                parameterTypes);
        if (method == null) {
            throw new NoSuchMethodException("No such accessible method: " +
                    methodName + "() on class: " + objectClass.getName());
        }
        return method.invoke(null, args);

    }

    /**
     * <p>Invoke a named static method whose parameter type matches the object type.</p>
     *
     * <p>The behaviour of this method is less deterministic 
     * than {@link #invokeExactMethod(Object, String, Object[], Class[])}. 
     * It loops through all methods with names that match
     * and then executes the first it finds with compatable parameters.</p>
     *
     * <p>This method supports calls to methods taking primitive parameters 
     * via passing in wrapping classes. So, for example, a <code>Boolean</code> class
     * would match a <code>boolean</code> primitive.</p>
     *
     * <p> This is a convenient wrapper for
     * {@link #invokeStaticMethod(Class objectClass,String methodName,Object [] args)}.
     * </p>
     *
     * @param objectClass invoke static method on this class
     * @param methodName get method with this name
     * @param arg use this argument
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     * @since 1.8.0
     */
    public static Object invokeStaticMethod(
            Class objectClass,
            String methodName,
            Object arg)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {

        Object[] args = {arg};
        return invokeStaticMethod (objectClass, methodName, args);

    }


    /**
     * <p>Invoke a named static method whose parameter type matches the object type.</p>
     *
     * <p>The behaviour of this method is less deterministic 
     * than {@link #invokeExactMethod(Object object,String methodName,Object [] args)}. 
     * It loops through all methods with names that match
     * and then executes the first it finds with compatable parameters.</p>
     *
     * <p>This method supports calls to methods taking primitive parameters 
     * via passing in wrapping classes. So, for example, a <code>Boolean</code> class
     * would match a <code>boolean</code> primitive.</p>
     *
     * <p> This is a convenient wrapper for
     * {@link #invokeStaticMethod(Class objectClass,String methodName,Object [] args,Class[] parameterTypes)}.
     * </p>
     *
     * @param objectClass invoke static method on this class
     * @param methodName get method with this name
     * @param args use these arguments - treat null as empty array
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     * @since 1.8.0
     */
    public static Object invokeStaticMethod(
            Class objectClass,
            String methodName,
            Object[] args)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {
        
        if (args == null) {
            args = EMPTY_OBJECT_ARRAY;
        }  
        int arguments = args.length;
        Class[] parameterTypes = new Class[arguments];
        for (int i = 0; i < arguments; i++) {
            parameterTypes[i] = args[i].getClass();
        }
        return invokeStaticMethod (objectClass, methodName, args, parameterTypes);

    }


    /**
     * <p>Invoke a named static method whose parameter type matches the object type.</p>
     *
     * <p>The behaviour of this method is less deterministic 
     * than {@link 
     * #invokeExactStaticMethod(Class objectClass,String methodName,Object [] args,Class[] parameterTypes)}. 
     * It loops through all methods with names that match
     * and then executes the first it finds with compatable parameters.</p>
     *
     * <p>This method supports calls to methods taking primitive parameters 
     * via passing in wrapping classes. So, for example, a <code>Boolean</code> class
     * would match a <code>boolean</code> primitive.</p>
     *
     *
     * @param objectClass invoke static method on this class
     * @param methodName get method with this name
     * @param args use these arguments - treat null as empty array
     * @param parameterTypes match these parameters - treat null as empty array
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     * @since 1.8.0
     */
    public static Object invokeStaticMethod(
            Class objectClass,
            String methodName,
            Object[] args,
            Class[] parameterTypes)
                throws
                    NoSuchMethodException,
                    IllegalAccessException,
                    InvocationTargetException {
                    
        if (parameterTypes == null) {
            parameterTypes = EMPTY_CLASS_PARAMETERS;
        }        
        if (args == null) {
            args = EMPTY_OBJECT_ARRAY;
        }  

        Method method = getMatchingAccessibleMethod(
                objectClass,
                methodName,
                parameterTypes);
        if (method == null) {
            throw new NoSuchMethodException("No such accessible method: " +
                    methodName + "() on class: " + objectClass.getName());
        }
        return method.invoke(null, args);
    }


    /**
     * <p>Invoke a static method whose parameter type matches exactly the object
     * type.</p>
     *
     * <p> This is a convenient wrapper for
     * {@link #invokeExactStaticMethod(Class objectClass,String methodName,Object [] args)}.
     * </p>
     *
     * @param objectClass invoke static method on this class
     * @param methodName get method with this name
     * @param arg use this argument
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     * @since 1.8.0
     */
    public static Object invokeExactStaticMethod(
            Class objectClass,
            String methodName,
            Object arg)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {

        Object[] args = {arg};
        return invokeExactStaticMethod (objectClass, methodName, args);

    }


    /**
     * <p>Invoke a static method whose parameter types match exactly the object
     * types.</p>
     *
     * <p> This uses reflection to invoke the method obtained from a call to
     * {@link #getAccessibleMethod(Class, String, Class[])}.</p>
     *
     * @param objectClass invoke static method on this class
     * @param methodName get method with this name
     * @param args use these arguments - treat null as empty array
     * @return The value returned by the invoked method
     *
     * @throws NoSuchMethodException if there is no such accessible method
     * @throws InvocationTargetException wraps an exception thrown by the
     *  method invoked
     * @throws IllegalAccessException if the requested method is not accessible
     *  via reflection
     * @since 1.8.0
     */
    public static Object invokeExactStaticMethod(
            Class objectClass,
            String methodName,
            Object[] args)
            throws
            NoSuchMethodException,
            IllegalAccessException,
            InvocationTargetException {
        if (args == null) {
            args = EMPTY_OBJECT_ARRAY;
        }  
        int arguments = args.length;
        Class[] parameterTypes = new Class[arguments];
        for (int i = 0; i < arguments; i++) {
            parameterTypes[i] = args[i].getClass();
        }
        return invokeExactStaticMethod(objectClass, methodName, args, parameterTypes);

    }


    /**
     * <p>Return an accessible method (that is, one that can be invoked via
     * reflection) with given name and a single parameter.  If no such method
     * can be found, return <code>null</code>.
     * Basically, a convenience wrapper that constructs a <code>Class</code>
     * array for you.</p>
     *
     * @param clazz get method from this class
     * @param methodName get method with this name
     * @param parameterType taking this type of parameter
     * @return The accessible method
     */
    public static Method getAccessibleMethod(
            Class clazz,
            String methodName,
            Class parameterType) {

        Class[] parameterTypes = {parameterType};
        return getAccessibleMethod(clazz, methodName, parameterTypes);

    }


    /**
     * <p>Return an accessible method (that is, one that can be invoked via
     * reflection) with given name and parameters.  If no such method
     * can be found, return <code>null</code>.
     * This is just a convenient wrapper for
     * {@link #getAccessibleMethod(Method method)}.</p>
     *
     * @param clazz get method from this class
     * @param methodName get method with this name
     * @param parameterTypes with these parameters types
     * @return The accessible method
     */
    public static Method getAccessibleMethod(
            Class clazz,
            String methodName,
            Class[] parameterTypes) {

        try {
            MethodDescriptor md = new MethodDescriptor(clazz, methodName, parameterTypes, true);
            // Check the cache first
            Method method = getCachedMethod(md);
            if (method != null) {
                return method;
            }
            
            method =  getAccessibleMethod
                    (clazz, clazz.getMethod(methodName, parameterTypes));
            cacheMethod(md, method);
            return method;
        } catch (NoSuchMethodException e) {
            return (null);
        }

    }


    /**
     * <p>Return an accessible method (that is, one that can be invoked via
     * reflection) that implements the specified Method.  If no such method
     * can be found, return <code>null</code>.</p>
     *
     * @param method The method that we wish to call
     * @return The accessible method
     */
    public static Method getAccessibleMethod(Method method) {

        // Make sure we have a method to check
        if (method == null) {
            return (null);
        }

        return getAccessibleMethod(method.getDeclaringClass(), method);

    }



    /**
     * <p>Return an accessible method (that is, one that can be invoked via
     * reflection) that implements the specified Method.  If no such method
     * can be found, return <code>null</code>.</p>
     *
     * @param clazz The class of the object
     * @param method The method that we wish to call
     * @return The accessible method
     * @since 1.8.0
     */
    public static Method getAccessibleMethod(Class clazz, Method method) {

        // Make sure we have a method to check
        if (method == null) {
            return (null);
        }

        // If the requested method is not public we cannot call it
        if (!Modifier.isPublic(method.getModifiers())) {
            return (null);
        }

        boolean sameClass = true;
        if (clazz == null) {
            clazz = method.getDeclaringClass();
        } else {
            sameClass = clazz.equals(method.getDeclaringClass());
            if (!method.getDeclaringClass().isAssignableFrom(clazz)) {
                throw new IllegalArgumentException(clazz.getName() +
                        " is not assignable from " + method.getDeclaringClass().getName());
            }
        }

        // If the class is public, we are done
        if (Modifier.isPublic(clazz.getModifiers())) {
            if (!sameClass && !Modifier.isPublic(method.getDeclaringClass().getModifiers())) {
                setMethodAccessible(method); // Default access superclass workaround
            }
            return (method);
        }

        String methodName      = method.getName();
        Class[] parameterTypes = method.getParameterTypes();

        // Check the implemented interfaces and subinterfaces
        method =
                getAccessibleMethodFromInterfaceNest(clazz,
                        methodName,
                        parameterTypes);

        // Check the superclass chain
        if (method == null) {
            method = getAccessibleMethodFromSuperclass(clazz,
                        methodName,
                        parameterTypes);
        }

        return (method);

    }


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

    /**
     * <p>Return an accessible method (that is, one that can be invoked via
     * reflection) by scanning through the superclasses. If no such method
     * can be found, return <code>null</code>.</p>
     *
     * @param clazz Class to be checked
     * @param methodName Method name of the method we wish to call
     * @param parameterTypes The parameter type signatures
     */
    private static Method getAccessibleMethodFromSuperclass
            (Class clazz, String methodName, Class[] parameterTypes) {

        Class parentClazz = clazz.getSuperclass();
        while (parentClazz != null) {
            if (Modifier.isPublic(parentClazz.getModifiers())) {
                try {
                    return parentClazz.getMethod(methodName, parameterTypes);
                } catch (NoSuchMethodException e) {
                    return null;
                }
            }
            parentClazz = parentClazz.getSuperclass();
        }
        return null;
    }

    /**
     * <p>Return an accessible method (that is, one that can be invoked via
     * reflection) that implements the specified method, by scanning through
     * all implemented interfaces and subinterfaces.  If no such method
     * can be found, return <code>null</code>.</p>
     *
     * <p> There isn't any good reason why this method must be private.
     * It is because there doesn't seem any reason why other classes should
     * call this rather than the higher level methods.</p>
     *
     * @param clazz Parent class for the interfaces to be checked
     * @param methodName Method name of the method we wish to call
     * @param parameterTypes The parameter type signatures
     */
    private static Method getAccessibleMethodFromInterfaceNest
            (Class clazz, String methodName, Class[] parameterTypes) {

        Method method = null;

        // Search up the superclass chain
        for (; clazz != null; clazz = clazz.getSuperclass()) {

            // Check the implemented interfaces of the parent class
            Class[] interfaces = clazz.getInterfaces();
            for (int i = 0; i < interfaces.length; i++) {

                // Is this interface public?
                if (!Modifier.isPublic(interfaces[i].getModifiers())) {
                    continue;
                }

                // Does the method exist on this interface?
                try {
                    method = interfaces[i].getDeclaredMethod(methodName,
                            parameterTypes);
                } catch (NoSuchMethodException e) {
                    /* Swallow, if no method is found after the loop then this
                     * method returns null.
                     */
                }
                if (method != null) {
                    return method;
                }

                // Recursively check our parent interfaces
                method =
                        getAccessibleMethodFromInterfaceNest(interfaces[i],
                                methodName,
                                parameterTypes);
                if (method != null) {
                    return method;
                }

            }

        }

        // We did not find anything
        return (null);

    }

    /**
     * <p>Find an accessible method that matches the given name and has compatible parameters.
     * Compatible parameters mean that every method parameter is assignable from 
     * the given parameters.
     * In other words, it finds a method with the given name 
     * that will take the parameters given.<p>
     *
     * <p>This method is slightly undeterminstic since it loops 
     * through methods names and return the first matching method.</p>
     * 
     * <p>This method is used by 
     * {@link 
     * #invokeMethod(Object object,String methodName,Object [] args,Class[] parameterTypes)}.
     *
     * <p>This method can match primitive parameter by passing in wrapper classes.
     * For example, a <code>Boolean</code> will match a primitive <code>boolean</code>
     * parameter.
     *
     * @param clazz find method in this class
     * @param methodName find method with this name
     * @param parameterTypes find method with compatible parameters 
     * @return The accessible method
     */
    public static Method getMatchingAccessibleMethod(
                                                Class clazz,
                                                String methodName,
                                                Class[] parameterTypes) {
        // trace logging
        if (log.isTraceEnabled()) {
            log.trace("Matching name=" + methodName + " on " + clazz);
        }
        MethodDescriptor md = new MethodDescriptor(clazz, methodName, parameterTypes, false);
        
        // see if we can find the method directly
        // most of the time this works and it's much faster
        try {
            // Check the cache first
            Method method = getCachedMethod(md);
            if (method != null) {
                return method;
            }

            method = clazz.getMethod(methodName, parameterTypes);
            if (log.isTraceEnabled()) {
                log.trace("Found straight match: " + method);
                log.trace("isPublic:" + Modifier.isPublic(method.getModifiers()));
            }
            
            setMethodAccessible(method); // Default access superclass workaround

            cacheMethod(md, method);
            return method;
            
        } catch (NoSuchMethodException e) { /* SWALLOW */ }
        
        // search through all methods 
        int paramSize = parameterTypes.length;
        Method bestMatch = null;
        Method[] methods = clazz.getMethods();
        float bestMatchCost = Float.MAX_VALUE;
        float myCost = Float.MAX_VALUE;
        for (int i = 0, size = methods.length; i < size ; i++) {
            if (methods[i].getName().equals(methodName)) {
                // log some trace information
                if (log.isTraceEnabled()) {
                    log.trace("Found matching name:");
                    log.trace(methods[i]);
                }                
                
                // compare parameters
                Class[] methodsParams = methods[i].getParameterTypes();
                int methodParamSize = methodsParams.length;
                if (methodParamSize == paramSize) {          
                    boolean match = true;
                    for (int n = 0 ; n < methodParamSize; n++) {
                        if (log.isTraceEnabled()) {
                            log.trace("Param=" + parameterTypes[n].getName());
                            log.trace("Method=" + methodsParams[n].getName());
                        }
                        if (!isAssignmentCompatible(methodsParams[n], parameterTypes[n])) {
                            if (log.isTraceEnabled()) {
                                log.trace(methodsParams[n] + " is not assignable from " 
                                            + parameterTypes[n]);
                            }    
                            match = false;
                            break;
                        }
                    }
                    
                    if (match) {
                        // get accessible version of method
                        Method method = getAccessibleMethod(clazz, methods[i]);
                        if (method != null) {
                            if (log.isTraceEnabled()) {
                                log.trace(method + " accessible version of " 
                                            + methods[i]);
                            }
                            setMethodAccessible(method); // Default access superclass workaround
                            myCost = getTotalTransformationCost(parameterTypes,method.getParameterTypes());
                            if ( myCost < bestMatchCost ) {
                               bestMatch = method;
                               bestMatchCost = myCost;
                            }
                        }
                        
                        log.trace("Couldn't find accessible method.");
                    }
                }
            }
        }
        if ( bestMatch != null ){
                 cacheMethod(md, bestMatch);
        } else {
        // didn't find a match
               log.trace("No match found.");
        }
        
        return bestMatch;                                        
    }

    /**
     * Try to make the method accessible
     * @param method The source arguments
     */
    private static void setMethodAccessible(Method method) {
        try {
            //
            // XXX Default access superclass workaround
            //
            // When a public class has a default access superclass
            // with public methods, these methods are accessible.
            // Calling them from compiled code works fine.
            //
            // Unfortunately, using reflection to invoke these methods
            // seems to (wrongly) to prevent access even when the method
            // modifer is public.
            //
            // The following workaround solves the problem but will only
            // work from sufficiently privilages code. 
            //
            // Better workarounds would be greatfully accepted.
            //
            if (!method.isAccessible()) {
                method.setAccessible(true);
            }
            
        } catch (SecurityException se) {
            // log but continue just in case the method.invoke works anyway
            if (!loggedAccessibleWarning) {
                boolean vulnerableJVM = false;
                try {
                    String specVersion = System.getProperty("java.specification.version");
                    if (specVersion.charAt(0) == '1' && 
                            (specVersion.charAt(2) == '0' ||
                             specVersion.charAt(2) == '1' ||
                             specVersion.charAt(2) == '2' ||
                             specVersion.charAt(2) == '3')) {
                             
                        vulnerableJVM = true;
                    }
                } catch (SecurityException e) {
                    // don't know - so display warning
                    vulnerableJVM = true;
                }
                if (vulnerableJVM) {
                    log.warn(
                        "Current Security Manager restricts use of workarounds for reflection bugs "
                        + " in pre-1.4 JVMs.");
                }
                loggedAccessibleWarning = true;
            }
            log.debug("Cannot setAccessible on method. Therefore cannot use jvm access bug workaround.", se);
        }
    }

    /**
     * Returns the sum of the object transformation cost for each class in the source
     * argument list.
     * @param srcArgs The source arguments
     * @param destArgs The destination arguments
     * @return The total transformation cost
     */
    private static float getTotalTransformationCost(Class[] srcArgs, Class[] destArgs) {

        float totalCost = 0.0f;
        for (int i = 0; i < srcArgs.length; i++) {
            Class srcClass, destClass;
            srcClass = srcArgs[i];
            destClass = destArgs[i];
            totalCost += getObjectTransformationCost(srcClass, destClass);
        }

        return totalCost;
    }
    
    /**
     * Gets the number of steps required needed to turn the source class into the 
     * destination class. This represents the number of steps in the object hierarchy 
     * graph.
     * @param srcClass The source class
     * @param destClass The destination class
     * @return The cost of transforming an object
     */
    private static float getObjectTransformationCost(Class srcClass, Class destClass) {
        float cost = 0.0f;
        while (destClass != null && !destClass.equals(srcClass)) {
            if (destClass.isInterface() && isAssignmentCompatible(destClass,srcClass)) {
                // slight penalty for interface match. 
                // we still want an exact match to override an interface match, but  
                // an interface match should override anything where we have to get a 
                // superclass.
                cost += 0.25f;
                break;
            }
            cost++;
            destClass = destClass.getSuperclass();
        }

        /*
         * If the destination class is null, we've travelled all the way up to 
         * an Object match. We'll penalize this by adding 1.5 to the cost.
         */
        if (destClass == null) {
            cost += 1.5f;
        }

        return cost;
    }
    
    
    /**
     * <p>Determine whether a type can be used as a parameter in a method invocation.
     * This method handles primitive conversions correctly.</p>
     *
     * <p>In order words, it will match a <code>Boolean</code> to a <code>boolean</code>,
     * a <code>Long</code> to a <code>long</code>,
     * a <code>Float</code> to a <code>float</code>,
     * a <code>Integer</code> to a <code>int</code>,
     * and a <code>Double</code> to a <code>double</code>.
     * Now logic widening matches are allowed.
     * For example, a <code>Long</code> will not match a <code>int</code>.
     *
     * @param parameterType the type of parameter accepted by the method
     * @param parameterization the type of parameter being tested 
     *
     * @return true if the assignement is compatible.
     */
    public static final boolean isAssignmentCompatible(Class parameterType, Class parameterization) {
        // try plain assignment
        if (parameterType.isAssignableFrom(parameterization)) {
            return true;
        }
        
        if (parameterType.isPrimitive()) {
            // this method does *not* do widening - you must specify exactly
            // is this the right behaviour?
            Class parameterWrapperClazz = ClassUtils.primitive2Wrapper(parameterType);
            if (parameterWrapperClazz != null) {
                return parameterWrapperClazz.equals(parameterization);
            }
        }
        
        return false;
    }
    

    /**
     * Return the method from the cache, if present.
     *
     * @param md The method descriptor
     * @return The cached method
     */
    private static Method getCachedMethod(MethodDescriptor md) {
        if (CACHE_METHODS) {
            Reference methodRef = (Reference)cache.get(md);
            if (methodRef != null) {
                return (Method)methodRef.get();
            }
        }
        return null;
    }

    /**
     * Add a method to the cache.
     *
     * @param md The method descriptor
     * @param method The method to cache
     */
    private static void cacheMethod(MethodDescriptor md, Method method) {
        if (CACHE_METHODS) {
            if (method != null) {
                cache.put(md, new WeakReference(method));
            }
        }
    }

    /**
     * Represents the key to looking up a Method by reflection.
     */
    private static class MethodDescriptor {
        private Class cls;
        private String methodName;
        private Class[] paramTypes;
        private boolean exact;
        private int hashCode;

        /**
         * The sole constructor.
         *
         * @param cls  the class to reflect, must not be null
         * @param methodName  the method name to obtain
         * @param paramTypes the array of classes representing the paramater types
         * @param exact whether the match has to be exact.
         */
        public MethodDescriptor(Class cls, String methodName, Class[] paramTypes, boolean exact) {
            if (cls == null) {
                throw new IllegalArgumentException("Class cannot be null");
            }
            if (methodName == null) {
                throw new IllegalArgumentException("Method Name cannot be null");
            }
            if (paramTypes == null) {
                paramTypes = EMPTY_CLASS_PARAMETERS;
            }

            this.cls = cls;
            this.methodName = methodName;
            this.paramTypes = paramTypes;
            this.exact= exact;

            this.hashCode = methodName.length();
        }
        /**
         * Checks for equality.
         * @param obj object to be tested for equality
         * @return true, if the object describes the same Method.
         */
        public boolean equals(Object obj) {
            if (!(obj instanceof MethodDescriptor)) {
                return false;
            }
            MethodDescriptor md = (MethodDescriptor)obj;

            return (
                exact == md.exact &&
                methodName.equals(md.methodName) &&
                cls.equals(md.cls) &&
                java.util.Arrays.equals(paramTypes, md.paramTypes)
            );
        }
        /**
         * Returns the string length of method name. I.e. if the
         * hashcodes are different, the objects are different. If the
         * hashcodes are the same, need to use the equals method to
         * determine equality.
         * @return the string length of method name.
         */
        public int hashCode() {
            return hashCode;
        }
    }

    /**
	 * <p>
	 * Invoke a named method.
	 * </p>
	 * 
	 * @param object object
	 * @param methodName get method with this name
	 * @return The value returned by the invoked method
	 * @throws NoSuchMethodException if there is no such accessible method
	 * @throws InvocationTargetException wraps an exception thrown by the method invoked
	 * @throws IllegalAccessException if the requested method is not accessible via reflection
	 */
	public static Object invokeMethod(Object object, String methodName)
			throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
		return invokeMethod(object, methodName, new Object[0]);
	}

	/**
	 * <p>
	 * Invoke a named static method.
	 * </p>
	 * 
	 * @param cls invoke static method on this class
	 * @param methodName get method with this name
	 * @return The value returned by the invoked method
	 * @throws NoSuchMethodException if there is no such accessible method
	 * @throws InvocationTargetException wraps an exception thrown by the method invoked
	 * @throws IllegalAccessException if the requested method is not accessible via reflection
	 */
	public static Object invokeStaticMethod(Class cls, String methodName)
			throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
		return invokeStaticMethod(cls, methodName, new Object[0]);
	}

	/**
	 * <p>
	 * Invoke a named static method.
	 * </p>
	 * 
	 * @param method the method such as java.util.Calendar@getInstance
	 * @return The value returned by the invoked method
	 * @throws NoSuchMethodException if there is no such accessible method
	 * @throws InvocationTargetException wraps an exception thrown by the method invoked
	 * @throws IllegalAccessException if the requested method is not accessible via reflection
	 * @throws ClassNotFoundException if the class is not found
	 */
	public static Object invokeStaticMethod(String method)
			throws NoSuchMethodException, IllegalAccessException,
			InvocationTargetException, ClassNotFoundException {
		String[] ss = method.split("@");
		Class cls = ClassUtils.getClass(ss[0]);
		return invokeStaticMethod(cls, ss[1]);
	}

}
