/*
 * 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
 *
 *      http://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;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.http.HttpMethod;
import org.springframework.http.HttpStatus;
import org.springframework.lang.Nullable;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.View;
import org.springframework.web.servlet.support.RequestContextUtils;

Trivial controller that always returns a pre-configured view and optionally
sets the response status code. The view and status can be configured using
the provided configuration properties.
Author:
Rod Johnson, Juergen Hoeller, Keith Donald, Rossen Stoyanchev/**
 * Trivial controller that always returns a pre-configured view and optionally
 * sets the response status code. The view and status can be configured using
 * the provided configuration properties.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @author Keith Donald
 * @author Rossen Stoyanchev
 */
public class ParameterizableViewController extends AbstractController {

	@Nullable
	private Object view;

	@Nullable
	private HttpStatus statusCode;

	private boolean statusOnly;


	public ParameterizableViewController() {
		super(false);
		setSupportedMethods(HttpMethod.GET.name(), HttpMethod.HEAD.name());
	}

	
Set a view name for the ModelAndView to return, to be resolved by the
DispatcherServlet via a ViewResolver. Will override any pre-existing
view name or View.
/**
	 * Set a view name for the ModelAndView to return, to be resolved by the
	 * DispatcherServlet via a ViewResolver. Will override any pre-existing
	 * view name or View.
	 */
	public void setViewName(@Nullable String viewName) {
		this.view = viewName;
	}

	
Return the name of the view to delegate to, or null if using a View instance. /**
	 * Return the name of the view to delegate to, or {@code null} if using a
	 * View instance.
	 */
	@Nullable
	public String getViewName() {
		if (this.view instanceof String) {
			String viewName = (String) this.view;
			if (getStatusCode() != null && getStatusCode().is3xxRedirection()) {
				return viewName.startsWith("redirect:") ? viewName : "redirect:" + viewName;
			}
			else {
				return viewName;
			}
		}
		return null;
	}

	
Set a View object for the ModelAndView to return.
Will override any pre-existing view name or View.
Since:
4.1/**
	 * Set a View object for the ModelAndView to return.
	 * Will override any pre-existing view name or View.
	 * @since 4.1
	 */
	public void setView(View view) {
		this.view = view;
	}

	
Return the View object, or null if we are using a view name to be resolved by the DispatcherServlet via a ViewResolver. 
Since:
4.1/**
	 * Return the View object, or {@code null} if we are using a view name
	 * to be resolved by the DispatcherServlet via a ViewResolver.
	 * @since 4.1
	 */
	@Nullable
	public View getView() {
		return (this.view instanceof View ? (View) this.view : null);
	}

	
Configure the HTTP status code that this controller should set on the
response.
When a "redirect:" prefixed view name is configured, there is no need to set this property since RedirectView will do that. However this property may still be used to override the 3xx status code of RedirectView. For full control over redirecting provide a RedirectView instance. 
If the status code is 204 and no view is configured, the request is
fully handled within the controller.
Since:
4.1/**
	 * Configure the HTTP status code that this controller should set on the
	 * response.
	 * <p>When a "redirect:" prefixed view name is configured, there is no need
	 * to set this property since RedirectView will do that. However this property
	 * may still be used to override the 3xx status code of {@code RedirectView}.
	 * For full control over redirecting provide a {@code RedirectView} instance.
	 * <p>If the status code is 204 and no view is configured, the request is
	 * fully handled within the controller.
	 * @since 4.1
	 */
	public void setStatusCode(@Nullable HttpStatus statusCode) {
		this.statusCode = statusCode;
	}

	
Return the configured HTTP status code or null. 
Since:
4.1/**
	 * Return the configured HTTP status code or {@code null}.
	 * @since 4.1
	 */
	@Nullable
	public HttpStatus getStatusCode() {
		return this.statusCode;
	}


	
The property can be used to indicate the request is considered fully handled within the controller and that no view should be used for rendering. Useful in combination with setStatusCode. 
By default this is set to false. 
Since:
4.1/**
	 * The property can be used to indicate the request is considered fully
	 * handled within the controller and that no view should be used for rendering.
	 * Useful in combination with {@link #setStatusCode}.
	 * <p>By default this is set to {@code false}.
	 * @since 4.1
	 */
	public void setStatusOnly(boolean statusOnly) {
		this.statusOnly = statusOnly;
	}

	
Whether the request is fully handled within the controller.
/**
	 * Whether the request is fully handled within the controller.
	 */
	public boolean isStatusOnly() {
		return this.statusOnly;
	}


	
Return a ModelAndView object with the specified view name.
The content of the 
"input" FlashMap is also added to the model. 
See Also:
getViewName()/**
	 * Return a ModelAndView object with the specified view name.
	 * <p>The content of the {@link RequestContextUtils#getInputFlashMap
	 * "input" FlashMap} is also added to the model.
	 * @see #getViewName()
	 */
	@Override
	protected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response)
			throws Exception {

		String viewName = getViewName();

		if (getStatusCode() != null) {
			if (getStatusCode().is3xxRedirection()) {
				request.setAttribute(View.RESPONSE_STATUS_ATTRIBUTE, getStatusCode());
			}
			else {
				response.setStatus(getStatusCode().value());
				if (getStatusCode().equals(HttpStatus.NO_CONTENT) && viewName == null) {
					return null;
				}
			}
		}

		if (isStatusOnly()) {
			return null;
		}

		ModelAndView modelAndView = new ModelAndView();
		modelAndView.addAllObjects(RequestContextUtils.getInputFlashMap(request));
		if (viewName != null) {
			modelAndView.setViewName(viewName);
		}
		else {
			modelAndView.setView(getView());
		}
		return modelAndView;
	}

	@Override
	public String toString() {
		return "ParameterizableViewController [" + formatStatusAndView() + "]";
	}

	private String formatStatusAndView() {
		StringBuilder sb = new StringBuilder();
		if (this.statusCode != null) {
			sb.append("status=").append(this.statusCode);
		}
		if (this.view != null) {
			sb.append(sb.length() != 0 ? ", " : "");
			String viewName = getViewName();
			sb.append("view=").append(viewName != null ? "\"" + viewName + "\"" : this.view);
		}
		return sb.toString();
	}
}