/*
 * Copyright 2002-2020 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.reactive.result.method.annotation;

import java.util.Collections;
import java.util.List;
import java.util.function.Function;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import reactor.core.publisher.Mono;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.ReactiveAdapterRegistry;
import org.springframework.http.codec.HttpMessageReader;
import org.springframework.http.codec.ServerCodecConfigurer;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.web.bind.support.WebBindingInitializer;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.reactive.BindingContext;
import org.springframework.web.reactive.HandlerAdapter;
import org.springframework.web.reactive.HandlerMapping;
import org.springframework.web.reactive.HandlerResult;
import org.springframework.web.reactive.result.method.InvocableHandlerMethod;
import org.springframework.web.server.ServerWebExchange;

/**
 * Supports the invocation of
 * {@link org.springframework.web.bind.annotation.RequestMapping @RequestMapping}
 * handler methods.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public class RequestMappingHandlerAdapter implements HandlerAdapter, ApplicationContextAware, InitializingBean {

        private static final Log logger = LogFactory.getLog(RequestMappingHandlerAdapter.class);


        private List<HttpMessageReader<?>> messageReaders = Collections.emptyList();

        @Nullable
        private WebBindingInitializer webBindingInitializer;

        @Nullable
        private ArgumentResolverConfigurer argumentResolverConfigurer;

        @Nullable
        private ReactiveAdapterRegistry reactiveAdapterRegistry;

        @Nullable
        private ConfigurableApplicationContext applicationContext;

        @Nullable
        private ControllerMethodResolver methodResolver;

        @Nullable
        private ModelInitializer modelInitializer;


        /**
         * Configure HTTP message readers to de-serialize the request body with.
         * <p>By default this is set to {@link ServerCodecConfigurer}'s readers with defaults.
         */
        public void setMessageReaders(List<HttpMessageReader<?>> messageReaders) {
                Assert.notNull(messageReaders, "'messageReaders' must not be null");
                this.messageReaders = messageReaders;
        }

        /**
         * Return the configurer for HTTP message readers.
         */
        public List<HttpMessageReader<?>> getMessageReaders() {
                return this.messageReaders;
        }

        /**
         * Provide a WebBindingInitializer with "global" initialization to apply
         * to every DataBinder instance.
         */
        public void setWebBindingInitializer(@Nullable WebBindingInitializer webBindingInitializer) {
                this.webBindingInitializer = webBindingInitializer;
        }

        /**
         * Return the configured WebBindingInitializer, or {@code null} if none.
         */
        @Nullable
        public WebBindingInitializer getWebBindingInitializer() {
                return this.webBindingInitializer;
        }

        /**
         * Configure resolvers for controller method arguments.
         */
        public void setArgumentResolverConfigurer(@Nullable ArgumentResolverConfigurer configurer) {
                this.argumentResolverConfigurer = configurer;
        }

        /**
         * Return the configured resolvers for controller method arguments.
         */
        @Nullable
        public ArgumentResolverConfigurer getArgumentResolverConfigurer() {
                return this.argumentResolverConfigurer;
        }

        /**
         * Configure the registry for adapting various reactive types.
         * <p>By default this is an instance of {@link ReactiveAdapterRegistry} with
         * default settings.
         */
        public void setReactiveAdapterRegistry(@Nullable ReactiveAdapterRegistry registry) {
                this.reactiveAdapterRegistry = registry;
        }

        /**
         * Return the configured registry for adapting reactive types.
         */
        @Nullable
        public ReactiveAdapterRegistry getReactiveAdapterRegistry() {
                return this.reactiveAdapterRegistry;
        }

        /**
         * A {@link ConfigurableApplicationContext} is expected for resolving
         * expressions in method argument default values as well as for
         * detecting {@code @ControllerAdvice} beans.
         */
        @Override
        public void setApplicationContext(ApplicationContext applicationContext) {
                if (applicationContext instanceof ConfigurableApplicationContext) {
                        this.applicationContext = (ConfigurableApplicationContext) applicationContext;
                }
        }


        @Override
        public void afterPropertiesSet() throws Exception {
                Assert.notNull(this.applicationContext, "ApplicationContext is required");

                if (CollectionUtils.isEmpty(this.messageReaders)) {
                        ServerCodecConfigurer codecConfigurer = ServerCodecConfigurer.create();
                        this.messageReaders = codecConfigurer.getReaders();
                }
                if (this.argumentResolverConfigurer == null) {
                        this.argumentResolverConfigurer = new ArgumentResolverConfigurer();
                }
                if (this.reactiveAdapterRegistry == null) {
                        this.reactiveAdapterRegistry = ReactiveAdapterRegistry.getSharedInstance();
                }

                this.methodResolver = new ControllerMethodResolver(this.argumentResolverConfigurer,
                                this.reactiveAdapterRegistry, this.applicationContext, this.messageReaders);

                this.modelInitializer = new ModelInitializer(this.methodResolver, this.reactiveAdapterRegistry);
        }


        @Override
        public boolean supports(Object handler) {
                return handler instanceof HandlerMethod;
        }

        @Override
        public Mono<HandlerResult> handle(ServerWebExchange exchange, Object handler) {
                HandlerMethod handlerMethod = (HandlerMethod) handler;
                Assert.state(this.methodResolver != null && this.modelInitializer != null, "Not initialized");

                InitBinderBindingContext bindingContext = new InitBinderBindingContext(
                                getWebBindingInitializer(), this.methodResolver.getInitBinderMethods(handlerMethod));

                InvocableHandlerMethod invocableMethod = this.methodResolver.getRequestMappingMethod(handlerMethod);

                Function<Throwable, Mono<HandlerResult>> exceptionHandler =
                                ex -> handleException(ex, handlerMethod, bindingContext, exchange);

                return this.modelInitializer
                                .initModel(handlerMethod, bindingContext, exchange)
                                .then(Mono.defer(() -> invocableMethod.invoke(exchange, bindingContext)))
                                .doOnNext(result -> result.setExceptionHandler(exceptionHandler))
                                .doOnNext(result -> bindingContext.saveModel())
                                .onErrorResume(exceptionHandler);
        }

        private Mono<HandlerResult> handleException(Throwable exception, HandlerMethod handlerMethod,
                        BindingContext bindingContext, ServerWebExchange exchange) {

                Assert.state(this.methodResolver != null, "Not initialized");

                // Success and error responses may use different content types
                exchange.getAttributes().remove(HandlerMapping.PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE);
                exchange.getResponse().getHeaders().clearContentHeaders();

                InvocableHandlerMethod invocable = this.methodResolver.getExceptionHandlerMethod(exception, handlerMethod);
                if (invocable != null) {
                        try {
                                if (logger.isDebugEnabled()) {
                                        logger.debug(exchange.getLogPrefix() + "Using @ExceptionHandler " + invocable);
                                }
                                bindingContext.getModel().asMap().clear();
                                Throwable cause = exception.getCause();
                                if (cause != null) {
                                        return invocable.invoke(exchange, bindingContext, exception, cause, handlerMethod);
                                }
                                else {
                                        return invocable.invoke(exchange, bindingContext, exception, handlerMethod);
                                }
                        }
                        catch (Throwable invocationEx) {
                                if (logger.isWarnEnabled()) {
                                        logger.warn(exchange.getLogPrefix() + "Failure in @ExceptionHandler " + invocable, invocationEx);
                                }
                        }
                }
                return Mono.error(exception);
        }

}