/*
 * Copyright 2002-2019 the original author or authors.
 *
 * 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
 *
 *      https://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.jmx.access;

import java.beans.PropertyDescriptor;
import java.io.IOException;
import java.lang.reflect.Array;
import java.lang.reflect.Method;
import java.net.MalformedURLException;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

import javax.management.Attribute;
import javax.management.InstanceNotFoundException;
import javax.management.IntrospectionException;
import javax.management.JMException;
import javax.management.JMX;
import javax.management.MBeanAttributeInfo;
import javax.management.MBeanException;
import javax.management.MBeanInfo;
import javax.management.MBeanOperationInfo;
import javax.management.MBeanServerConnection;
import javax.management.MBeanServerInvocationHandler;
import javax.management.MalformedObjectNameException;
import javax.management.ObjectName;
import javax.management.OperationsException;
import javax.management.ReflectionException;
import javax.management.RuntimeErrorException;
import javax.management.RuntimeMBeanException;
import javax.management.RuntimeOperationsException;
import javax.management.openmbean.CompositeData;
import javax.management.openmbean.TabularData;
import javax.management.remote.JMXServiceURL;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.core.CollectionFactory;
import org.springframework.core.MethodParameter;
import org.springframework.core.ResolvableType;
import org.springframework.jmx.support.JmxUtils;
import org.springframework.jmx.support.ObjectNameManager;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ReflectionUtils;
import org.springframework.util.StringUtils;

/**
 * {@link org.aopalliance.intercept.MethodInterceptor} that routes calls to an
 * MBean running on the supplied {@code MBeanServerConnection}.
 * Works for both local and remote {@code MBeanServerConnection}s.
 *
 * <p>By default, the {@code MBeanClientInterceptor} will connect to the
 * {@code MBeanServer} and cache MBean metadata at startup. This can
 * be undesirable when running against a remote {@code MBeanServer}
 * that may not be running when the application starts. Through setting the
 * {@link #setConnectOnStartup(boolean) connectOnStartup} property to "false",
 * you can defer this process until the first invocation against the proxy.
 *
 * <p>This functionality is usually used through {@link MBeanProxyFactoryBean}.
 * See the javadoc of that class for more information.
 *
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @since 1.2
 * @see MBeanProxyFactoryBean
 * @see #setConnectOnStartup
 */
public class MBeanClientInterceptor
                implements MethodInterceptor, BeanClassLoaderAware, InitializingBean, DisposableBean {

        /** Logger available to subclasses. */
        protected final Log logger = LogFactory.getLog(getClass());

        @Nullable
        private MBeanServerConnection server;

        @Nullable
        private JMXServiceURL serviceUrl;

        @Nullable
        private Map<String, ?> environment;

        @Nullable
        private String agentId;

        private boolean connectOnStartup = true;

        private boolean refreshOnConnectFailure = false;

        @Nullable
        private ObjectName objectName;

        private boolean useStrictCasing = true;

        @Nullable
        private Class<?> managementInterface;

        @Nullable
        private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();

        private final ConnectorDelegate connector = new ConnectorDelegate();

        @Nullable
        private MBeanServerConnection serverToUse;

        @Nullable
        private MBeanServerInvocationHandler invocationHandler;

        private Map<String, MBeanAttributeInfo> allowedAttributes = Collections.emptyMap();

        private Map<MethodCacheKey, MBeanOperationInfo> allowedOperations = Collections.emptyMap();

        private final Map<Method, String[]> signatureCache = new HashMap<>();

        private final Object preparationMonitor = new Object();


        /**
         * Set the {@code MBeanServerConnection} used to connect to the
         * MBean which all invocations are routed to.
         */
        public void setServer(MBeanServerConnection server) {
                this.server = server;
        }

        /**
         * Set the service URL of the remote {@code MBeanServer}.
         */
        public void setServiceUrl(String url) throws MalformedURLException {
                this.serviceUrl = new JMXServiceURL(url);
        }

        /**
         * Specify the environment for the JMX connector.
         * @see javax.management.remote.JMXConnectorFactory#connect(javax.management.remote.JMXServiceURL, java.util.Map)
         */
        public void setEnvironment(@Nullable Map<String, ?> environment) {
                this.environment = environment;
        }

        /**
         * Allow Map access to the environment to be set for the connector,
         * with the option to add or override specific entries.
         * <p>Useful for specifying entries directly, for example via
         * "environment[myKey]". This is particularly useful for
         * adding or overriding entries in child bean definitions.
         */
        @Nullable
        public Map<String, ?> getEnvironment() {
                return this.environment;
        }

        /**
         * Set the agent id of the {@code MBeanServer} to locate.
         * <p>Default is none. If specified, this will result in an
         * attempt being made to locate the attendant MBeanServer, unless
         * the {@link #setServiceUrl "serviceUrl"} property has been set.
         * @see javax.management.MBeanServerFactory#findMBeanServer(String)
         * <p>Specifying the empty String indicates the platform MBeanServer.
         */
        public void setAgentId(String agentId) {
                this.agentId = agentId;
        }

        /**
         * Set whether or not the proxy should connect to the {@code MBeanServer}
         * at creation time ("true") or the first time it is invoked ("false").
         * Default is "true".
         */
        public void setConnectOnStartup(boolean connectOnStartup) {
                this.connectOnStartup = connectOnStartup;
        }

        /**
         * Set whether to refresh the MBeanServer connection on connect failure.
         * Default is "false".
         * <p>Can be turned on to allow for hot restart of the JMX server,
         * automatically reconnecting and retrying in case of an IOException.
         */
        public void setRefreshOnConnectFailure(boolean refreshOnConnectFailure) {
                this.refreshOnConnectFailure = refreshOnConnectFailure;
        }

        /**
         * Set the {@code ObjectName} of the MBean which calls are routed to,
         * as {@code ObjectName} instance or as {@code String}.
         */
        public void setObjectName(Object objectName) throws MalformedObjectNameException {
                this.objectName = ObjectNameManager.getInstance(objectName);
        }

        /**
         * Set whether to use strict casing for attributes. Enabled by default.
         * <p>When using strict casing, a JavaBean property with a getter such as
         * {@code getFoo()} translates to an attribute called {@code Foo}.
         * With strict casing disabled, {@code getFoo()} would translate to just
         * {@code foo}.
         */
        public void setUseStrictCasing(boolean useStrictCasing) {
                this.useStrictCasing = useStrictCasing;
        }

        /**
         * Set the management interface of the target MBean, exposing bean property
         * setters and getters for MBean attributes and conventional Java methods
         * for MBean operations.
         */
        public void setManagementInterface(@Nullable Class<?> managementInterface) {
                this.managementInterface = managementInterface;
        }

        /**
         * Return the management interface of the target MBean,
         * or {@code null} if none specified.
         */
        @Nullable
        protected final Class<?> getManagementInterface() {
                return this.managementInterface;
        }

        @Override
        public void setBeanClassLoader(ClassLoader beanClassLoader) {
                this.beanClassLoader = beanClassLoader;
        }


        /**
         * Prepares the {@code MBeanServerConnection} if the "connectOnStartup"
         * is turned on (which it is by default).
         */
        @Override
        public void afterPropertiesSet() {
                if (this.server != null && this.refreshOnConnectFailure) {
                        throw new IllegalArgumentException("'refreshOnConnectFailure' does not work when setting " +
                                        "a 'server' reference. Prefer 'serviceUrl' etc instead.");
                }
                if (this.connectOnStartup) {
                        prepare();
                }
        }

        /**
         * Ensures that an {@code MBeanServerConnection} is configured and attempts
         * to detect a local connection if one is not supplied.
         */
        public void prepare() {
                synchronized (this.preparationMonitor) {
                        if (this.server != null) {
                                this.serverToUse = this.server;
                        }
                        else {
                                this.serverToUse = null;
                                this.serverToUse = this.connector.connect(this.serviceUrl, this.environment, this.agentId);
                        }
                        this.invocationHandler = null;
                        if (this.useStrictCasing) {
                                Assert.state(this.objectName != null, "No ObjectName set");
                                // Use the JDK's own MBeanServerInvocationHandler, in particular for native MXBean support.
                                this.invocationHandler = new MBeanServerInvocationHandler(this.serverToUse, this.objectName,
                                                (this.managementInterface != null && JMX.isMXBeanInterface(this.managementInterface)));
                        }
                        else {
                                // Non-strict casing can only be achieved through custom invocation handling.
                                // Only partial MXBean support available!
                                retrieveMBeanInfo(this.serverToUse);
                        }
                }
        }
        /**
         * Loads the management interface info for the configured MBean into the caches.
         * This information is used by the proxy when determining whether an invocation matches
         * a valid operation or attribute on the management interface of the managed resource.
         */
        private void retrieveMBeanInfo(MBeanServerConnection server) throws MBeanInfoRetrievalException {
                try {
                        MBeanInfo info = server.getMBeanInfo(this.objectName);

                        MBeanAttributeInfo[] attributeInfo = info.getAttributes();
                        this.allowedAttributes = new HashMap<>(attributeInfo.length);
                        for (MBeanAttributeInfo infoEle : attributeInfo) {
                                this.allowedAttributes.put(infoEle.getName(), infoEle);
                        }

                        MBeanOperationInfo[] operationInfo = info.getOperations();
                        this.allowedOperations = new HashMap<>(operationInfo.length);
                        for (MBeanOperationInfo infoEle : operationInfo) {
                                Class<?>[] paramTypes = JmxUtils.parameterInfoToTypes(infoEle.getSignature(), this.beanClassLoader);
                                this.allowedOperations.put(new MethodCacheKey(infoEle.getName(), paramTypes), infoEle);
                        }
                }
                catch (ClassNotFoundException ex) {
                        throw new MBeanInfoRetrievalException("Unable to locate class specified in method signature", ex);
                }
                catch (IntrospectionException ex) {
                        throw new MBeanInfoRetrievalException("Unable to obtain MBean info for bean [" + this.objectName + "]", ex);
                }
                catch (InstanceNotFoundException ex) {
                        // if we are this far this shouldn't happen, but...
                        throw new MBeanInfoRetrievalException("Unable to obtain MBean info for bean [" + this.objectName +
                                        "]: it is likely that this bean was unregistered during the proxy creation process",
                                        ex);
                }
                catch (ReflectionException ex) {
                        throw new MBeanInfoRetrievalException("Unable to read MBean info for bean [ " + this.objectName + "]", ex);
                }
                catch (IOException ex) {
                        throw new MBeanInfoRetrievalException("An IOException occurred when communicating with the " +
                                        "MBeanServer. It is likely that you are communicating with a remote MBeanServer. " +
                                        "Check the inner exception for exact details.", ex);
                }
        }

        /**
         * Return whether this client interceptor has already been prepared,
         * i.e. has already looked up the server and cached all metadata.
         */
        protected boolean isPrepared() {
                synchronized (this.preparationMonitor) {
                        return (this.serverToUse != null);
                }
        }


        /**
         * Route the invocation to the configured managed resource..
         * @param invocation the {@code MethodInvocation} to re-route
         * @return the value returned as a result of the re-routed invocation
         * @throws Throwable an invocation error propagated to the user
         * @see #doInvoke
         * @see #handleConnectFailure
         */
        @Override
        @Nullable
        public Object invoke(MethodInvocation invocation) throws Throwable {
                // Lazily connect to MBeanServer if necessary.
                synchronized (this.preparationMonitor) {
                        if (!isPrepared()) {
                                prepare();
                        }
                }
                try {
                        return doInvoke(invocation);
                }
                catch (MBeanConnectFailureException | IOException ex) {
                        return handleConnectFailure(invocation, ex);
                }
        }

        /**
         * Refresh the connection and retry the MBean invocation if possible.
         * <p>If not configured to refresh on connect failure, this method
         * simply rethrows the original exception.
         * @param invocation the invocation that failed
         * @param ex the exception raised on remote invocation
         * @return the result value of the new invocation, if succeeded
         * @throws Throwable an exception raised by the new invocation,
         * if it failed as well
         * @see #setRefreshOnConnectFailure
         * @see #doInvoke
         */
        @Nullable
        protected Object handleConnectFailure(MethodInvocation invocation, Exception ex) throws Throwable {
                if (this.refreshOnConnectFailure) {
                        String msg = "Could not connect to JMX server - retrying";
                        if (logger.isDebugEnabled()) {
                                logger.warn(msg, ex);
                        }
                        else if (logger.isWarnEnabled()) {
                                logger.warn(msg);
                        }
                        prepare();
                        return doInvoke(invocation);
                }
                else {
                        throw ex;
                }
        }

        /**
         * Route the invocation to the configured managed resource. Correctly routes JavaBean property
         * access to {@code MBeanServerConnection.get/setAttribute} and method invocation to
         * {@code MBeanServerConnection.invoke}.
         * @param invocation the {@code MethodInvocation} to re-route
         * @return the value returned as a result of the re-routed invocation
         * @throws Throwable an invocation error propagated to the user
         */
        @Nullable
        protected Object doInvoke(MethodInvocation invocation) throws Throwable {
                Method method = invocation.getMethod();
                try {
                        Object result;
                        if (this.invocationHandler != null) {
                                result = this.invocationHandler.invoke(invocation.getThis(), method, invocation.getArguments());
                        }
                        else {
                                PropertyDescriptor pd = BeanUtils.findPropertyForMethod(method);
                                if (pd != null) {
                                        result = invokeAttribute(pd, invocation);
                                }
                                else {
                                        result = invokeOperation(method, invocation.getArguments());
                                }
                        }
                        return convertResultValueIfNecessary(result, new MethodParameter(method, -1));
                }
                catch (MBeanException ex) {
                        throw ex.getTargetException();
                }
                catch (RuntimeMBeanException ex) {
                        throw ex.getTargetException();
                }
                catch (RuntimeErrorException ex) {
                        throw ex.getTargetError();
                }
                catch (RuntimeOperationsException ex) {
                        // This one is only thrown by the JMX 1.2 RI, not by the JDK 1.5 JMX code.
                        RuntimeException rex = ex.getTargetException();
                        if (rex instanceof RuntimeMBeanException) {
                                throw ((RuntimeMBeanException) rex).getTargetException();
                        }
                        else if (rex instanceof RuntimeErrorException) {
                                throw ((RuntimeErrorException) rex).getTargetError();
                        }
                        else {
                                throw rex;
                        }
                }
                catch (OperationsException ex) {
                        if (ReflectionUtils.declaresException(method, ex.getClass())) {
                                throw ex;
                        }
                        else {
                                throw new InvalidInvocationException(ex.getMessage());
                        }
                }
                catch (JMException ex) {
                        if (ReflectionUtils.declaresException(method, ex.getClass())) {
                                throw ex;
                        }
                        else {
                                throw new InvocationFailureException("JMX access failed", ex);
                        }
                }
                catch (IOException ex) {
                        if (ReflectionUtils.declaresException(method, ex.getClass())) {
                                throw ex;
                        }
                        else {
                                throw new MBeanConnectFailureException("I/O failure during JMX access", ex);
                        }
                }
        }

        @Nullable
        private Object invokeAttribute(PropertyDescriptor pd, MethodInvocation invocation)
                        throws JMException, IOException {

                Assert.state(this.serverToUse != null, "No MBeanServerConnection available");

                String attributeName = JmxUtils.getAttributeName(pd, this.useStrictCasing);
                MBeanAttributeInfo inf = this.allowedAttributes.get(attributeName);
                // If no attribute is returned, we know that it is not defined in the
                // management interface.
                if (inf == null) {
                        throw new InvalidInvocationException(
                                        "Attribute '" + pd.getName() + "' is not exposed on the management interface");
                }

                if (invocation.getMethod().equals(pd.getReadMethod())) {
                        if (inf.isReadable()) {
                                return this.serverToUse.getAttribute(this.objectName, attributeName);
                        }
                        else {
                                throw new InvalidInvocationException("Attribute '" + attributeName + "' is not readable");
                        }
                }
                else if (invocation.getMethod().equals(pd.getWriteMethod())) {
                        if (inf.isWritable()) {
                                this.serverToUse.setAttribute(this.objectName, new Attribute(attributeName, invocation.getArguments()[0]));
                                return null;
                        }
                        else {
                                throw new InvalidInvocationException("Attribute '" + attributeName + "' is not writable");
                        }
                }
                else {
                        throw new IllegalStateException(
                                        "Method [" + invocation.getMethod() + "] is neither a bean property getter nor a setter");
                }
        }

        /**
         * Routes a method invocation (not a property get/set) to the corresponding
         * operation on the managed resource.
         * @param method the method corresponding to operation on the managed resource.
         * @param args the invocation arguments
         * @return the value returned by the method invocation.
         */
        private Object invokeOperation(Method method, Object[] args) throws JMException, IOException {
                Assert.state(this.serverToUse != null, "No MBeanServerConnection available");

                MethodCacheKey key = new MethodCacheKey(method.getName(), method.getParameterTypes());
                MBeanOperationInfo info = this.allowedOperations.get(key);
                if (info == null) {
                        throw new InvalidInvocationException("Operation '" + method.getName() +
                                        "' is not exposed on the management interface");
                }

                String[] signature;
                synchronized (this.signatureCache) {
                        signature = this.signatureCache.get(method);
                        if (signature == null) {
                                signature = JmxUtils.getMethodSignature(method);
                                this.signatureCache.put(method, signature);
                        }
                }

                return this.serverToUse.invoke(this.objectName, method.getName(), args, signature);
        }

        /**
         * Convert the given result object (from attribute access or operation invocation)
         * to the specified target class for returning from the proxy method.
         * @param result the result object as returned by the {@code MBeanServer}
         * @param parameter the method parameter of the proxy method that's been invoked
         * @return the converted result object, or the passed-in object if no conversion
         * is necessary
         */
        @Nullable
        protected Object convertResultValueIfNecessary(@Nullable Object result, MethodParameter parameter) {
                Class<?> targetClass = parameter.getParameterType();
                try {
                        if (result == null) {
                                return null;
                        }
                        if (ClassUtils.isAssignableValue(targetClass, result)) {
                                return result;
                        }
                        if (result instanceof CompositeData) {
                                Method fromMethod = targetClass.getMethod("from", CompositeData.class);
                                return ReflectionUtils.invokeMethod(fromMethod, null, result);
                        }
                        else if (result instanceof CompositeData[]) {
                                CompositeData[] array = (CompositeData[]) result;
                                if (targetClass.isArray()) {
                                        return convertDataArrayToTargetArray(array, targetClass);
                                }
                                else if (Collection.class.isAssignableFrom(targetClass)) {
                                        Class<?> elementType =
                                                        ResolvableType.forMethodParameter(parameter).asCollection().resolveGeneric();
                                        if (elementType != null) {
                                                return convertDataArrayToTargetCollection(array, targetClass, elementType);
                                        }
                                }
                        }
                        else if (result instanceof TabularData) {
                                Method fromMethod = targetClass.getMethod("from", TabularData.class);
                                return ReflectionUtils.invokeMethod(fromMethod, null, result);
                        }
                        else if (result instanceof TabularData[]) {
                                TabularData[] array = (TabularData[]) result;
                                if (targetClass.isArray()) {
                                        return convertDataArrayToTargetArray(array, targetClass);
                                }
                                else if (Collection.class.isAssignableFrom(targetClass)) {
                                        Class<?> elementType =
                                                        ResolvableType.forMethodParameter(parameter).asCollection().resolveGeneric();
                                        if (elementType != null) {
                                                return convertDataArrayToTargetCollection(array, targetClass, elementType);
                                        }
                                }
                        }
                        throw new InvocationFailureException(
                                        "Incompatible result value [" + result + "] for target type [" + targetClass.getName() + "]");
                }
                catch (NoSuchMethodException ex) {
                        throw new InvocationFailureException(
                                        "Could not obtain 'from(CompositeData)' / 'from(TabularData)' method on target type [" +
                                                        targetClass.getName() + "] for conversion of MXBean data structure [" + result + "]");
                }
        }

        private Object convertDataArrayToTargetArray(Object[] array, Class<?> targetClass) throws NoSuchMethodException {
                Class<?> targetType = targetClass.getComponentType();
                Method fromMethod = targetType.getMethod("from", array.getClass().getComponentType());
                Object resultArray = Array.newInstance(targetType, array.length);
                for (int i = 0; i < array.length; i++) {
                        Array.set(resultArray, i, ReflectionUtils.invokeMethod(fromMethod, null, array[i]));
                }
                return resultArray;
        }

        private Collection<?> convertDataArrayToTargetCollection(Object[] array, Class<?> collectionType, Class<?> elementType)
                        throws NoSuchMethodException {

                Method fromMethod = elementType.getMethod("from", array.getClass().getComponentType());
                Collection<Object> resultColl = CollectionFactory.createCollection(collectionType, Array.getLength(array));
                for (int i = 0; i < array.length; i++) {
                        resultColl.add(ReflectionUtils.invokeMethod(fromMethod, null, array[i]));
                }
                return resultColl;
        }


        @Override
        public void destroy() {
                this.connector.close();
        }


        /**
         * Simple wrapper class around a method name and its signature.
         * Used as the key when caching methods.
         */
        private static final class MethodCacheKey implements Comparable<MethodCacheKey> {

                private final String name;

                private final Class<?>[] parameterTypes;

                /**
                 * Create a new instance of {@code MethodCacheKey} with the supplied
                 * method name and parameter list.
                 * @param name the name of the method
                 * @param parameterTypes the arguments in the method signature
                 */
                public MethodCacheKey(String name, @Nullable Class<?>[] parameterTypes) {
                        this.name = name;
                        this.parameterTypes = (parameterTypes != null ? parameterTypes : new Class<?>[0]);
                }

                @Override
                public boolean equals(@Nullable Object other) {
                        if (this == other) {
                                return true;
                        }
                        if (!(other instanceof MethodCacheKey)) {
                                return false;
                        }
                        MethodCacheKey otherKey = (MethodCacheKey) other;
                        return (this.name.equals(otherKey.name) && Arrays.equals(this.parameterTypes, otherKey.parameterTypes));
                }

                @Override
                public int hashCode() {
                        return this.name.hashCode();
                }

                @Override
                public String toString() {
                        return this.name + "(" + StringUtils.arrayToCommaDelimitedString(this.parameterTypes) + ")";
                }

                @Override
                public int compareTo(MethodCacheKey other) {
                        int result = this.name.compareTo(other.name);
                        if (result != 0) {
                                return result;
                        }
                        if (this.parameterTypes.length < other.parameterTypes.length) {
                                return -1;
                        }
                        if (this.parameterTypes.length > other.parameterTypes.length) {
                                return 1;
                        }
                        for (int i = 0; i < this.parameterTypes.length; i++) {
                                result = this.parameterTypes[i].getName().compareTo(other.parameterTypes[i].getName());
                                if (result != 0) {
                                        return result;
                                }
                        }
                        return 0;
                }
        }

}