/* Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
 *
 * Licensed 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.springframework.security.util;

import java.lang.reflect.Method;

import org.aopalliance.intercept.MethodInvocation;
import org.springframework.aop.framework.Advised;
import org.springframework.aop.support.AopUtils;
import org.springframework.util.Assert;


/**
 * Static utility methods for creating <code>MethodInvocation</code>s usable within Spring Security.
 * <p>
 * All methods of this class return a {@link org.springframework.security.util.SimpleMethodInvocation}.
 *
 * @author Ben Alex
 */
public final class MethodInvocationUtils {
    //~ Constructors ===================================================================================================

    private MethodInvocationUtils() {
    }

    //~ Methods ========================================================================================================

    /**
     * Generates a <code>MethodInvocation</code> for specified <code>methodName</code> on the passed object,
     * using the <code>args</code> to locate the method.
     *
     * @param object the object that will be used to find the relevant <code>Method</code>
     * @param methodName the name of the method to find
     * @param args arguments that are required as part of the method signature (can be empty)
     *
     * @return a <code>MethodInvocation</code>, or <code>null</code> if there was a problem
     */
    public static MethodInvocation create(Object object, String methodName, Object... args) {
        Assert.notNull(object, "Object required");

        Class<?>[] classArgs = null;

        if (args != null) {
            classArgs = new Class<?>[args.length];

            for (int i = 0; i < args.length; i++) {
                classArgs[i] = args[i].getClass();
            }
        }

        // Determine the type that declares the requested method, taking into account proxies
        Class<?> target = AopUtils.getTargetClass(object);
        if (object instanceof Advised) {
            Advised a = (Advised) object;
            if (!a.isProxyTargetClass()) {
                Class<?>[] possibleInterfaces = a.getProxiedInterfaces();
                for (Class<?> possibleInterface : possibleInterfaces) {
                    try {
                        possibleInterface.getMethod(methodName, classArgs);
                        // to get here means no exception happened
                        target = possibleInterface;
                        break;
                    } catch (Exception ignored) {
                        // try the next one
                    }
                }
            }
        }

        return createFromClass(object, target, methodName, classArgs, args);
    }

    /**
     * Generates a <code>MethodInvocation</code> for the specified <code>methodName</code> on the passed class.
     *
     * If a method with this name, taking no arguments does not exist, it will check through the declared
     * methods on the class, until one is found matching the supplied name. If more than one method name matches,
     * an <tt>IllegalArgumentException</tt> will be raised.
     *
     * @param clazz the class of object that will be used to find the relevant <code>Method</code>
     * @param methodName the name of the method to find
     *
     * @return a <code>MethodInvocation</code>, or <code>null</code> if there was a problem
     */
    public static MethodInvocation createFromClass(Class<?> clazz, String methodName) {
        MethodInvocation mi = createFromClass(null, clazz, methodName, null, null);

        if (mi == null) {
            for (Method m : clazz.getDeclaredMethods()) {
                if (m.getName().equals(methodName)) {
                    if (mi != null) {
                        throw new IllegalArgumentException("The class " + clazz + " has more than one method named" +
                                " '" + methodName + "'");
                    }
                    mi = new SimpleMethodInvocation(null, m);
                }
            }
        }

        return mi;
    }

    /**
     * Generates a <code>MethodInvocation</code> for specified <code>methodName</code> on the passed class,
     * using the <code>args</code> to locate the method.
     *
     * @param targetObject the object being invoked
     * @param clazz the class of object that will be used to find the relevant <code>Method</code>
     * @param methodName the name of the method to find
     * @param classArgs arguments that are required to locate the relevant method signature
     * @param args the actual arguments that should be passed to SimpleMethodInvocation
     * @return a <code>MethodInvocation</code>, or <code>null</code> if there was a problem
     */
    public static MethodInvocation createFromClass(Object targetObject, Class<?> clazz, String methodName,
            Class<?>[] classArgs, Object[] args) {
        Assert.notNull(clazz, "Class required");
        Assert.hasText(methodName, "MethodName required");

        Method method;

        try {
            method = clazz.getMethod(methodName, classArgs);
        } catch (NoSuchMethodException e) {
            return null;
        }

        return new SimpleMethodInvocation(targetObject, method, args);
    }
}
