/*
 * Copyright 2002-2018 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.web.context.request.async;

import java.util.concurrent.Callable;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.core.task.AsyncTaskExecutor;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.web.context.request.NativeWebRequest;

/**
 * Holder for a {@link Callable}, a timeout value, and a task executor.
 *
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @since 3.2
 * @param <V> the value type
 */
public class WebAsyncTask<V> implements BeanFactoryAware {

        private final Callable<V> callable;

        private Long timeout;

        private AsyncTaskExecutor executor;

        private String executorName;

        private BeanFactory beanFactory;

        private Callable<V> timeoutCallback;

        private Callable<V> errorCallback;

        private Runnable completionCallback;


        /**
         * Create a {@code WebAsyncTask} wrapping the given {@link Callable}.
         * @param callable the callable for concurrent handling
         */
        public WebAsyncTask(Callable<V> callable) {
                Assert.notNull(callable, "Callable must not be null");
                this.callable = callable;
        }

        /**
         * Create a {@code WebAsyncTask} with a timeout value and a {@link Callable}.
         * @param timeout a timeout value in milliseconds
         * @param callable the callable for concurrent handling
         */
        public WebAsyncTask(long timeout, Callable<V> callable) {
                this(callable);
                this.timeout = timeout;
        }

        /**
         * Create a {@code WebAsyncTask} with a timeout value, an executor name, and a {@link Callable}.
         * @param timeout the timeout value in milliseconds; ignored if {@code null}
         * @param executorName the name of an executor bean to use
         * @param callable the callable for concurrent handling
         */
        public WebAsyncTask(@Nullable Long timeout, String executorName, Callable<V> callable) {
                this(callable);
                Assert.notNull(executorName, "Executor name must not be null");
                this.executorName = executorName;
                this.timeout = timeout;
        }

        /**
         * Create a {@code WebAsyncTask} with a timeout value, an executor instance, and a Callable.
         * @param timeout the timeout value in milliseconds; ignored if {@code null}
         * @param executor the executor to use
         * @param callable the callable for concurrent handling
         */
        public WebAsyncTask(@Nullable Long timeout, AsyncTaskExecutor executor, Callable<V> callable) {
                this(callable);
                Assert.notNull(executor, "Executor must not be null");
                this.executor = executor;
                this.timeout = timeout;
        }


        /**
         * Return the {@link Callable} to use for concurrent handling (never {@code null}).
         */
        public Callable<?> getCallable() {
                return this.callable;
        }

        /**
         * Return the timeout value in milliseconds, or {@code null} if no timeout is set.
         */
        @Nullable
        public Long getTimeout() {
                return this.timeout;
        }

        /**
         * A {@link BeanFactory} to use for resolving an executor name.
         * <p>This factory reference will automatically be set when
         * {@code WebAsyncTask} is used within a Spring MVC controller.
         */
        @Override
        public void setBeanFactory(BeanFactory beanFactory) {
                this.beanFactory = beanFactory;
        }

        /**
         * Return the AsyncTaskExecutor to use for concurrent handling,
         * or {@code null} if none specified.
         */
        @Nullable
        public AsyncTaskExecutor getExecutor() {
                if (this.executor != null) {
                        return this.executor;
                }
                else if (this.executorName != null) {
                        Assert.state(this.beanFactory != null, "BeanFactory is required to look up an executor bean by name");
                        return this.beanFactory.getBean(this.executorName, AsyncTaskExecutor.class);
                }
                else {
                        return null;
                }
        }


        /**
         * Register code to invoke when the async request times out.
         * <p>This method is called from a container thread when an async request times
         * out before the {@code Callable} has completed. The callback is executed in
         * the same thread and therefore should return without blocking. It may return
         * an alternative value to use, including an {@link Exception} or return
         * {@link CallableProcessingInterceptor#RESULT_NONE RESULT_NONE}.
         */
        public void onTimeout(Callable<V> callback) {
                this.timeoutCallback = callback;
        }

        /**
         * Register code to invoke for an error during async request processing.
         * <p>This method is called from a container thread when an error occurred
         * while processing an async request before the {@code Callable} has
         * completed. The callback is executed in the same thread and therefore
         * should return without blocking. It may return an alternative value to
         * use, including an {@link Exception} or return
         * {@link CallableProcessingInterceptor#RESULT_NONE RESULT_NONE}.
         * @since 5.0
         */
        public void onError(Callable<V> callback) {
                this.errorCallback = callback;
        }

        /**
         * Register code to invoke when the async request completes.
         * <p>This method is called from a container thread when an async request
         * completed for any reason, including timeout and network error.
         */
        public void onCompletion(Runnable callback) {
                this.completionCallback = callback;
        }

        CallableProcessingInterceptor getInterceptor() {
                return new CallableProcessingInterceptor() {
                        @Override
                        public <T> Object handleTimeout(NativeWebRequest request, Callable<T> task) throws Exception {
                                return (timeoutCallback != null ? timeoutCallback.call() : CallableProcessingInterceptor.RESULT_NONE);
                        }
                        @Override
                        public <T> Object handleError(NativeWebRequest request, Callable<T> task, Throwable t) throws Exception {
                                return (errorCallback != null ? errorCallback.call() : CallableProcessingInterceptor.RESULT_NONE);
                        }
                        @Override
                        public <T> void afterCompletion(NativeWebRequest request, Callable<T> task) throws Exception {
                                if (completionCallback != null) {
                                        completionCallback.run();
                                }
                        }
                };
        }

}