/*
 * 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.struts2.jasper.runtime;

import java.util.HashMap;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedExceptionAction;
import java.security.PrivilegedActionException;
import java.lang.reflect.Method;
import javax.servlet.jsp.el.FunctionMapper;

import org.apache.struts2.jasper.security.SecurityUtil;

/**
 * Maps EL functions to their Java method counterparts. Keeps the actual Method
 * objects protected so that JSP pages can't indirectly do reflection.
 * 
 * @author Mark Roth
 * @author Kin-man Chung
 */
public final class ProtectedFunctionMapper extends javax.el.FunctionMapper
        implements FunctionMapper {

    /**
     * Maps "prefix:name" to java.lang.Method objects.
     */
    private HashMap fnmap = null;

    /**
     * If there is only one function in the map, this is the Method for it.
     */
    private Method theMethod = null;

    /**
     * Constructor has protected access.
     */
    private ProtectedFunctionMapper() {
    }

    /**
     * Generated Servlet and Tag Handler implementations call this method to
     * retrieve an instance of the ProtectedFunctionMapper. This is necessary
     * since generated code does not have access to create instances of classes
     * in this package.
     * 
     * @return A new protected function mapper.
     */
    public static ProtectedFunctionMapper getInstance() {
        ProtectedFunctionMapper funcMapper;
        if (SecurityUtil.isPackageProtectionEnabled()) {
            funcMapper = (ProtectedFunctionMapper) AccessController
                    .doPrivileged(new PrivilegedAction() {
                        public Object run() {
                            return new ProtectedFunctionMapper();
                        }
                    });
        } else {
            funcMapper = new ProtectedFunctionMapper();
        }
        funcMapper.fnmap = new java.util.HashMap();
        return funcMapper;
    }

    /**
     * Stores a mapping from the given EL function prefix and name to the given
     * Java method.
     * 
     * @param fnQName
     *            The EL function qualified name (including prefix)
     * @param c
     *            The class containing the Java method
     * @param methodName
     *            The name of the Java method
     * @param args
     *            The arguments of the Java method
     * @throws RuntimeException
     *             if no method with the given signature could be found.
     */
    public void mapFunction(String fnQName, final Class c,
            final String methodName, final Class[] args) {
        java.lang.reflect.Method method;
        if (SecurityUtil.isPackageProtectionEnabled()) {
            try {
                method = (java.lang.reflect.Method) AccessController
                        .doPrivileged(new PrivilegedExceptionAction() {

                            public Object run() throws Exception {
                                return c.getDeclaredMethod(methodName, args);
                            }
                        });
            } catch (PrivilegedActionException ex) {
                throw new RuntimeException(
                        "Invalid function mapping - no such method: "
                                + ex.getException().getMessage());
            }
        } else {
            try {
                method = c.getDeclaredMethod(methodName, args);
            } catch (NoSuchMethodException e) {
                throw new RuntimeException(
                        "Invalid function mapping - no such method: "
                                + e.getMessage());
            }
        }

        this.fnmap.put(fnQName, method);
    }

    /**
     * Creates an instance for this class, and stores the Method for the given
     * EL function prefix and name. This method is used for the case when there
     * is only one function in the EL expression.
     * 
     * @param fnQName
     *            The EL function qualified name (including prefix)
     * @param c
     *            The class containing the Java method
     * @param methodName
     *            The name of the Java method
     * @param args
     *            The arguments of the Java method
     *
     * @return function mapper
     *
     * @throws RuntimeException
     *             if no method with the given signature could be found.
     */
    public static ProtectedFunctionMapper getMapForFunction(String fnQName,
            final Class c, final String methodName, final Class[] args) {
        java.lang.reflect.Method method;
        ProtectedFunctionMapper funcMapper;
        if (SecurityUtil.isPackageProtectionEnabled()) {
            funcMapper = (ProtectedFunctionMapper) AccessController
                    .doPrivileged(new PrivilegedAction() {
                        public Object run() {
                            return new ProtectedFunctionMapper();
                        }
                    });

            try {
                method = (java.lang.reflect.Method) AccessController
                        .doPrivileged(new PrivilegedExceptionAction() {

                            public Object run() throws Exception {
                                return c.getDeclaredMethod(methodName, args);
                            }
                        });
            } catch (PrivilegedActionException ex) {
                throw new RuntimeException(
                        "Invalid function mapping - no such method: "
                                + ex.getException().getMessage());
            }
        } else {
            funcMapper = new ProtectedFunctionMapper();
            try {
                method = c.getDeclaredMethod(methodName, args);
            } catch (NoSuchMethodException e) {
                throw new RuntimeException(
                        "Invalid function mapping - no such method: "
                                + e.getMessage());
            }
        }
        funcMapper.theMethod = method;
        return funcMapper;
    }

    /**
     * Resolves the specified local name and prefix into a Java.lang.Method.
     * Returns null if the prefix and local name are not found.
     * 
     * @param prefix
     *            the prefix of the function
     * @param localName
     *            the short name of the function
     * @return the result of the method mapping. Null means no entry found.
     */
    public Method resolveFunction(String prefix, String localName) {
        if (this.fnmap != null) {
            return (Method) this.fnmap.get(prefix + ":" + localName);
        }
        return theMethod;
    }
}
