/*
 * 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.servlet.function.support;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import org.springframework.beans.factory.BeanFactoryUtils;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.core.SpringProperties;
import org.springframework.http.converter.ByteArrayHttpMessageConverter;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.StringHttpMessageConverter;
import org.springframework.http.converter.support.AllEncompassingFormHttpMessageConverter;
import org.springframework.http.converter.xml.SourceHttpMessageConverter;
import org.springframework.lang.Nullable;
import org.springframework.util.CollectionUtils;
import org.springframework.web.servlet.function.RouterFunction;
import org.springframework.web.servlet.function.RouterFunctions;
import org.springframework.web.servlet.function.ServerRequest;
import org.springframework.web.servlet.handler.AbstractHandlerMapping;
import org.springframework.web.util.pattern.PathPatternParser;

HandlerMapping implementation that supports RouterFunctions. 
If no RouterFunction is provided at construction time, this mapping will detect all router functions in the application context, and consult them in order. 
Author:
Arjen Poutsma, Sebastien Deleuze
Since:
5.2/**
 * {@code HandlerMapping} implementation that supports {@link RouterFunction RouterFunctions}.
 *
 * <p>If no {@link RouterFunction} is provided at
 * {@linkplain #RouterFunctionMapping(RouterFunction) construction time}, this mapping
 * will detect all router functions in the application context, and consult them in
 * {@linkplain org.springframework.core.annotation.Order order}.
 *
 * @author Arjen Poutsma
 * @author Sebastien Deleuze
 * @since 5.2
 */
public class RouterFunctionMapping extends AbstractHandlerMapping implements InitializingBean {

	
Boolean flag controlled by a spring.xml.ignore system property that instructs Spring to ignore XML, i.e. to not initialize the XML-related infrastructure. 
The default is "false".
/**
	 * Boolean flag controlled by a {@code spring.xml.ignore} system property that instructs Spring to
	 * ignore XML, i.e. to not initialize the XML-related infrastructure.
	 * <p>The default is "false".
	 */
	private static final boolean shouldIgnoreXml = SpringProperties.getFlag("spring.xml.ignore");


	@Nullable
	private RouterFunction<?> routerFunction;

	private List<HttpMessageConverter<?>> messageConverters = Collections.emptyList();

	private boolean detectHandlerFunctionsInAncestorContexts = false;



	
Create an empty RouterFunctionMapping. 
If this constructor is used, this mapping will detect all RouterFunction instances available in the application context. /**
	 * Create an empty {@code RouterFunctionMapping}.
	 * <p>If this constructor is used, this mapping will detect all
	 * {@link RouterFunction} instances available in the application context.
	 */
	public RouterFunctionMapping() {
	}

	
Create a RouterFunctionMapping with the given RouterFunction. 
If this constructor is used, no application context detection will occur.
Params:
routerFunction – the router function to use for mapping/**
	 * Create a {@code RouterFunctionMapping} with the given {@link RouterFunction}.
	 * <p>If this constructor is used, no application context detection will occur.
	 * @param routerFunction the router function to use for mapping
	 */
	public RouterFunctionMapping(RouterFunction<?> routerFunction) {
		this.routerFunction = routerFunction;
	}

	
Set the router function to map to.
If this property is used, no application context detection will occur.
/**
	 * Set the router function to map to.
	 * <p>If this property is used, no application context detection will occur.
	 */
	public void setRouterFunction(@Nullable RouterFunction<?> routerFunction) {
		this.routerFunction = routerFunction;
	}

	
Return the configured RouterFunction. 
Note: When router functions are detected from the ApplicationContext, this method may return null if invoked prior to afterPropertiesSet(). 
Returns:
the router function or null/**
	 * Return the configured {@link RouterFunction}.
	 * <p><strong>Note:</strong> When router functions are detected from the
	 * ApplicationContext, this method may return {@code null} if invoked
	 * prior to {@link #afterPropertiesSet()}.
	 * @return the router function or {@code null}
	 */
	@Nullable
	public RouterFunction<?> getRouterFunction() {
		return this.routerFunction;
	}

	public void setMessageConverters(List<HttpMessageConverter<?>> messageConverters) {
		this.messageConverters = messageConverters;
	}

	
Set whether to detect handler functions in ancestor ApplicationContexts.
Default is "false": Only handler functions in the current ApplicationContext
will be detected, i.e. only in the context that this HandlerMapping itself
is defined in (typically the current DispatcherServlet's context).
Switch this flag on to detect handler beans in ancestor contexts
(typically the Spring root WebApplicationContext) as well.
/**
	 * Set whether to detect handler functions in ancestor ApplicationContexts.
	 * <p>Default is "false": Only handler functions in the current ApplicationContext
	 * will be detected, i.e. only in the context that this HandlerMapping itself
	 * is defined in (typically the current DispatcherServlet's context).
	 * <p>Switch this flag on to detect handler beans in ancestor contexts
	 * (typically the Spring root WebApplicationContext) as well.
	 */
	public void setDetectHandlerFunctionsInAncestorContexts(boolean detectHandlerFunctionsInAncestorContexts) {
		this.detectHandlerFunctionsInAncestorContexts = detectHandlerFunctionsInAncestorContexts;
	}

	@Override
	public void afterPropertiesSet() throws Exception {
		if (this.routerFunction == null) {
			initRouterFunction();
		}
		if (CollectionUtils.isEmpty(this.messageConverters)) {
			initMessageConverters();
		}
		if (this.routerFunction != null) {
			PathPatternParser patternParser = getPatternParser();
			if (patternParser == null) {
				patternParser = new PathPatternParser();
				setPatternParser(patternParser);
			}
			RouterFunctions.changeParser(this.routerFunction, patternParser);
		}
	}

	
Detect a all router functions in the current application context. /**
	 * Detect a all {@linkplain RouterFunction router functions} in the
	 * current application context.
	 */
	@SuppressWarnings({"rawtypes", "unchecked"})
	private void initRouterFunction() {
		ApplicationContext applicationContext = obtainApplicationContext();
		Map<String, RouterFunction> beans =
				(this.detectHandlerFunctionsInAncestorContexts ?
						BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, RouterFunction.class) :
						applicationContext.getBeansOfType(RouterFunction.class));

		List<RouterFunction> routerFunctions = new ArrayList<>(beans.values());
		if (!CollectionUtils.isEmpty(routerFunctions) && logger.isInfoEnabled()) {
			routerFunctions.forEach(routerFunction -> logger.info("Mapped " + routerFunction));
		}
		this.routerFunction = routerFunctions.stream()
				.reduce(RouterFunction::andOther)
				.orElse(null);
	}

	
Initializes a default set of message converters. /**
	 * Initializes a default set of {@linkplain HttpMessageConverter message converters}.
	 */
	private void initMessageConverters() {
		List<HttpMessageConverter<?>> messageConverters = new ArrayList<>(4);
		messageConverters.add(new ByteArrayHttpMessageConverter());
		messageConverters.add(new StringHttpMessageConverter());

		if (!shouldIgnoreXml) {
			try {
				messageConverters.add(new SourceHttpMessageConverter<>());
			}
			catch (Error err) {
				// Ignore when no TransformerFactory implementation is available
			}
		}
		messageConverters.add(new AllEncompassingFormHttpMessageConverter());

		this.messageConverters = messageConverters;
	}

	@Nullable
	@Override
	protected Object getHandlerInternal(HttpServletRequest servletRequest) throws Exception {
		if (this.routerFunction != null) {
			ServerRequest request = ServerRequest.create(servletRequest, this.messageConverters);
			setAttributes(servletRequest, request);
			return this.routerFunction.route(request).orElse(null);
		}
		else {
			return null;
		}
	}

	private void setAttributes(HttpServletRequest servletRequest, ServerRequest request) {
		servletRequest.removeAttribute(RouterFunctions.MATCHING_PATTERN_ATTRIBUTE);
		servletRequest.setAttribute(RouterFunctions.REQUEST_ATTRIBUTE, request);
	}

}