/*
 * 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.context.event;

import java.util.concurrent.Executor;

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

import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.core.ResolvableType;
import org.springframework.lang.Nullable;
import org.springframework.util.ErrorHandler;

/**
 * Simple implementation of the {@link ApplicationEventMulticaster} interface.
 *
 * <p>Multicasts all events to all registered listeners, leaving it up to
 * the listeners to ignore events that they are not interested in.
 * Listeners will usually perform corresponding {@code instanceof}
 * checks on the passed-in event object.
 *
 * <p>By default, all listeners are invoked in the calling thread.
 * This allows the danger of a rogue listener blocking the entire application,
 * but adds minimal overhead. Specify an alternative task executor to have
 * listeners executed in different threads, for example from a thread pool.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @author Stephane Nicoll
 * @see #setTaskExecutor
 */
public class SimpleApplicationEventMulticaster extends AbstractApplicationEventMulticaster {

        @Nullable
        private Executor taskExecutor;

        @Nullable
        private ErrorHandler errorHandler;


        /**
         * Create a new SimpleApplicationEventMulticaster.
         */
        public SimpleApplicationEventMulticaster() {
        }

        /**
         * Create a new SimpleApplicationEventMulticaster for the given BeanFactory.
         */
        public SimpleApplicationEventMulticaster(BeanFactory beanFactory) {
                setBeanFactory(beanFactory);
        }


        /**
         * Set a custom executor (typically a {@link org.springframework.core.task.TaskExecutor})
         * to invoke each listener with.
         * <p>Default is equivalent to {@link org.springframework.core.task.SyncTaskExecutor},
         * executing all listeners synchronously in the calling thread.
         * <p>Consider specifying an asynchronous task executor here to not block the
         * caller until all listeners have been executed. However, note that asynchronous
         * execution will not participate in the caller's thread context (class loader,
         * transaction association) unless the TaskExecutor explicitly supports this.
         * @see org.springframework.core.task.SyncTaskExecutor
         * @see org.springframework.core.task.SimpleAsyncTaskExecutor
         */
        public void setTaskExecutor(@Nullable Executor taskExecutor) {
                this.taskExecutor = taskExecutor;
        }

        /**
         * Return the current task executor for this multicaster.
         */
        @Nullable
        protected Executor getTaskExecutor() {
                return this.taskExecutor;
        }

        /**
         * Set the {@link ErrorHandler} to invoke in case an exception is thrown
         * from a listener.
         * <p>Default is none, with a listener exception stopping the current
         * multicast and getting propagated to the publisher of the current event.
         * If a {@linkplain #setTaskExecutor task executor} is specified, each
         * individual listener exception will get propagated to the executor but
         * won't necessarily stop execution of other listeners.
         * <p>Consider setting an {@link ErrorHandler} implementation that catches
         * and logs exceptions (a la
         * {@link org.springframework.scheduling.support.TaskUtils#LOG_AND_SUPPRESS_ERROR_HANDLER})
         * or an implementation that logs exceptions while nevertheless propagating them
         * (e.g. {@link org.springframework.scheduling.support.TaskUtils#LOG_AND_PROPAGATE_ERROR_HANDLER}).
         * @since 4.1
         */
        public void setErrorHandler(@Nullable ErrorHandler errorHandler) {
                this.errorHandler = errorHandler;
        }

        /**
         * Return the current error handler for this multicaster.
         * @since 4.1
         */
        @Nullable
        protected ErrorHandler getErrorHandler() {
                return this.errorHandler;
        }


        @Override
        public void multicastEvent(ApplicationEvent event) {
                multicastEvent(event, resolveDefaultEventType(event));
        }

        @Override
        public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) {
                ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));
                Executor executor = getTaskExecutor();
                for (ApplicationListener<?> listener : getApplicationListeners(event, type)) {
                        if (executor != null) {
                                executor.execute(() -> invokeListener(listener, event));
                        }
                        else {
                                invokeListener(listener, event);
                        }
                }
        }

        private ResolvableType resolveDefaultEventType(ApplicationEvent event) {
                return ResolvableType.forInstance(event);
        }

        /**
         * Invoke the given listener with the given event.
         * @param listener the ApplicationListener to invoke
         * @param event the current event to propagate
         * @since 4.1
         */
        protected void invokeListener(ApplicationListener<?> listener, ApplicationEvent event) {
                ErrorHandler errorHandler = getErrorHandler();
                if (errorHandler != null) {
                        try {
                                doInvokeListener(listener, event);
                        }
                        catch (Throwable err) {
                                errorHandler.handleError(err);
                        }
                }
                else {
                        doInvokeListener(listener, event);
                }
        }

        @SuppressWarnings({"rawtypes", "unchecked"})
        private void doInvokeListener(ApplicationListener listener, ApplicationEvent event) {
                try {
                        listener.onApplicationEvent(event);
                }
                catch (ClassCastException ex) {
                        String msg = ex.getMessage();
                        if (msg == null || matchesClassCastMessage(msg, event.getClass())) {
                                // Possibly a lambda-defined listener which we could not resolve the generic event type for
                                // -> let's suppress the exception and just log a debug message.
                                Log logger = LogFactory.getLog(getClass());
                                if (logger.isTraceEnabled()) {
                                        logger.trace("Non-matching event type for listener: " + listener, ex);
                                }
                        }
                        else {
                                throw ex;
                        }
                }
        }

        private boolean matchesClassCastMessage(String classCastMessage, Class<?> eventClass) {
                // On Java 8, the message starts with the class name: "java.lang.String cannot be cast..."
                if (classCastMessage.startsWith(eventClass.getName())) {
                        return true;
                }
                // On Java 11, the message starts with "class ..." a.k.a. Class.toString()
                if (classCastMessage.startsWith(eventClass.toString())) {
                        return true;
                }
                // On Java 9, the message used to contain the module name: "java.base/java.lang.String cannot be cast..."
                int moduleSeparatorIndex = classCastMessage.indexOf('/');
                if (moduleSeparatorIndex != -1 && classCastMessage.startsWith(eventClass.getName(), moduleSeparatorIndex + 1)) {
                        return true;
                }
                // Assuming an unrelated class cast failure...
                return false;
        }

}