/*
 * 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;

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
 * @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.
         */
        public void setViewName(@Nullable String viewName) {
                this.view = viewName;
        }

        /**
         * 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
         */
        public void setView(View view) {
                this.view = view;
        }

        /**
         * 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.
         * <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 {@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 {@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.
         */
        public boolean isStatusOnly() {
                return this.statusOnly;
        }


        /**
         * 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();
        }
}