/*
 * 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
 *
 *      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.mvc.method.annotation;

import org.springframework.core.MethodParameter;
import org.springframework.lang.Nullable;
import org.springframework.util.PatternMatchUtils;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
import org.springframework.web.method.support.ModelAndViewContainer;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.SmartView;
import org.springframework.web.servlet.View;

Handles return values of type ModelAndView copying view and model information to the ModelAndViewContainer. 
If the return value is null, the ModelAndViewContainer.setRequestHandled(boolean) flag is set to true to indicate the request was handled directly. 
A ModelAndView return type has a set purpose. Therefore this handler should be configured ahead of handlers that support any return value type annotated with @ModelAttribute or @ResponseBody to ensure they don't take over. 
Author:
Rossen Stoyanchev
Since:
3.1/**
 * Handles return values of type {@link ModelAndView} copying view and model
 * information to the {@link ModelAndViewContainer}.
 *
 * <p>If the return value is {@code null}, the
 * {@link ModelAndViewContainer#setRequestHandled(boolean)} flag is set to
 * {@code true} to indicate the request was handled directly.
 *
 * <p>A {@link ModelAndView} return type has a set purpose. Therefore this
 * handler should be configured ahead of handlers that support any return
 * value type annotated with {@code @ModelAttribute} or {@code @ResponseBody}
 * to ensure they don't take over.
 *
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public class ModelAndViewMethodReturnValueHandler implements HandlerMethodReturnValueHandler {

	@Nullable
	private String[] redirectPatterns;


	
Configure one more simple patterns (as described in PatternMatchUtils.simpleMatch) to use in order to recognize custom redirect prefixes in addition to "redirect:". 
Note that simply configuring this property will not make a custom redirect prefix work. There must be a custom View that recognizes the prefix as well. 
Since:
4.1/**
	 * Configure one more simple patterns (as described in {@link PatternMatchUtils#simpleMatch})
	 * to use in order to recognize custom redirect prefixes in addition to "redirect:".
	 * <p>Note that simply configuring this property will not make a custom redirect prefix work.
	 * There must be a custom {@link View} that recognizes the prefix as well.
	 * @since 4.1
	 */
	public void setRedirectPatterns(@Nullable String... redirectPatterns) {
		this.redirectPatterns = redirectPatterns;
	}

	
Return the configured redirect patterns, if any.
Since:
4.1/**
	 * Return the configured redirect patterns, if any.
	 * @since 4.1
	 */
	@Nullable
	public String[] getRedirectPatterns() {
		return this.redirectPatterns;
	}


	@Override
	public boolean supportsReturnType(MethodParameter returnType) {
		return ModelAndView.class.isAssignableFrom(returnType.getParameterType());
	}

	@Override
	public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,
			ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {

		if (returnValue == null) {
			mavContainer.setRequestHandled(true);
			return;
		}

		ModelAndView mav = (ModelAndView) returnValue;
		if (mav.isReference()) {
			String viewName = mav.getViewName();
			mavContainer.setViewName(viewName);
			if (viewName != null && isRedirectViewName(viewName)) {
				mavContainer.setRedirectModelScenario(true);
			}
		}
		else {
			View view = mav.getView();
			mavContainer.setView(view);
			if (view instanceof SmartView && ((SmartView) view).isRedirectView()) {
				mavContainer.setRedirectModelScenario(true);
			}
		}
		mavContainer.setStatus(mav.getStatus());
		mavContainer.addAllAttributes(mav.getModel());
	}

	
Whether the given view name is a redirect view reference.
The default implementation checks the configured redirect patterns and
also if the view name starts with the "redirect:" prefix.
Params:
viewName – the view name to check, never null
Returns:
"true" if the given view name is recognized as a redirect view
reference; "false" otherwise./**
	 * Whether the given view name is a redirect view reference.
	 * The default implementation checks the configured redirect patterns and
	 * also if the view name starts with the "redirect:" prefix.
	 * @param viewName the view name to check, never {@code null}
	 * @return "true" if the given view name is recognized as a redirect view
	 * reference; "false" otherwise.
	 */
	protected boolean isRedirectViewName(String viewName) {
		return (PatternMatchUtils.simpleMatch(this.redirectPatterns, viewName) || viewName.startsWith("redirect:"));
	}

}