/*
 * Copyright 2002-2017 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
 *
 *      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.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(Object other) {
			if (this == other) {
				return true;
			}
			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;
		}
	}

}
