/*
 * Copyright 2002-2011 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.method.support;

import java.util.Map;

import org.springframework.ui.Model;
import org.springframework.ui.ModelMap;
import org.springframework.validation.support.BindingAwareModelMap;
import org.springframework.web.bind.support.SessionStatus;
import org.springframework.web.bind.support.SimpleSessionStatus;

/**
 * Records model and view related decisions made by 
 * {@link HandlerMethodArgumentResolver}s and 
 * {@link HandlerMethodReturnValueHandler}s during the course of invocation of 
 * a controller method.
 * 
 * <p>The {@link #setRequestHandled} flag can be used to indicate the request
 * has been handled directly and view resolution is not required.
 * 
 * <p>A default {@link Model} is automatically created at instantiation. 
 * An alternate model instance may be provided via {@link #setRedirectModel} 
 * for use in a redirect scenario. When {@link #setRedirectModelScenario} is set 
 * to {@code true} signalling a redirect scenario, the {@link #getModel()} 
 * returns the redirect model instead of the default model.
 * 
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public class ModelAndViewContainer {

	private Object view;
	
	private boolean requestHandled = false;
	
	private final ModelMap defaultModel = new BindingAwareModelMap();

	private ModelMap redirectModel;

	private boolean redirectModelScenario = false;

	private boolean ignoreDefaultModelOnRedirect = false;

	private final SessionStatus sessionStatus = new SimpleSessionStatus();
	
	/**
	 * Create a new instance.
	 */
	public ModelAndViewContainer() {
	}

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

	/**
	 * Return the view name to be resolved by the DispatcherServlet via a 
	 * ViewResolver, or {@code null} if a View object is set.
	 */
	public String getViewName() {
		return (this.view instanceof String ? (String) this.view : null);
	}
	
	/**
	 * Set a View object to be used by the DispatcherServlet. 
	 * Will override any pre-existing view name or View.
	 */
	public void setView(Object view) {
		this.view = view;
	}

	/**
	 * Return the View object, or {@code null} if we using a view name
	 * to be resolved by the DispatcherServlet via a ViewResolver.
	 */
	public Object getView() {
		return this.view;
	}

	/**
	 * Whether the view is a view reference specified via a name to be 
	 * resolved by the DispatcherServlet via a ViewResolver.
	 */
	public boolean isViewReference() {
		return (this.view instanceof String);
	}
	
	/**
	 * Signal a scenario where the request is handled directly. 
	 * <p>A {@link HandlerMethodReturnValueHandler} may use this flag to 
	 * indicate the response has been fully handled and view resolution 
	 * is not required (e.g. {@code @ResponseBody}).
	 * <p>A {@link HandlerMethodArgumentResolver} may also use this flag
	 * to indicate the presence of an argument (e.g. 
	 * {@code ServletResponse} or {@code OutputStream}) that may lead to 
	 * a complete response depending on the method return value.
	 * <p>The default value is {@code true}.
	 */
	public void setRequestHandled(boolean requestHandled) {
		this.requestHandled = requestHandled;
	}
	
	/**
	 * Whether the request is handled directly.
	 */
	public boolean isRequestHandled() {
		return this.requestHandled;
	}

	/**
	 * Return the model to use: the "default" or the "redirect" model.
	 * <p>The default model is used if {@code "redirectModelScenario=false"} or
	 * if the redirect model is {@code null} (i.e. it wasn't declared as a 
	 * method argument) and {@code ignoreDefaultModelOnRedirect=false}.
	 */
	public ModelMap getModel() {
		if (useDefaultModel()) {
			return this.defaultModel;
		}
		else {
			return (this.redirectModel != null) ? this.redirectModel : new ModelMap();
		}
	}
	
	/**
	 * Whether to use the default model or the redirect model.
	 */
	private boolean useDefaultModel() {
		return !this.redirectModelScenario || ((this.redirectModel == null) && !this.ignoreDefaultModelOnRedirect);
	}
	
	/**
	 * Provide a separate model instance to use in a redirect scenario. 
	 * The provided additional model however is not used used unless 
	 * {@link #setRedirectModelScenario(boolean)} gets set to {@code true} to signal
	 * a redirect scenario.
	 */
	public void setRedirectModel(ModelMap redirectModel) {
		this.redirectModel = redirectModel;
	}

	/**
	 * Signal the conditions are in place for using a redirect model.
	 * Typically that means the controller has returned a redirect instruction.
	 */
	public void setRedirectModelScenario(boolean redirectModelScenario) {
		this.redirectModelScenario = redirectModelScenario;
	}

	/**
	 * When set to {@code true} the default model is never used in a redirect
	 * scenario. So if a redirect model is not available, an empty model is 
	 * used instead.
	 * <p>When set to {@code false} the default model can be used in a redirect
	 * scenario if a redirect model is not available.
	 * <p>The default setting is {@code false}.
	 */
	public void setIgnoreDefaultModelOnRedirect(boolean ignoreDefaultModelOnRedirect) {
		this.ignoreDefaultModelOnRedirect = ignoreDefaultModelOnRedirect;
	}

	/**
	 * Return the {@link SessionStatus} instance to use that can be used to 
	 * signal that session processing is complete.
	 */
	public SessionStatus getSessionStatus() {
		return sessionStatus;
	}

	/**
	 * Add the supplied attribute to the underlying model.
	 * @see ModelMap#addAttribute(String, Object)
	 */
	public ModelAndViewContainer addAttribute(String name, Object value) {
		getModel().addAttribute(name, value);
		return this;
	}
	
	/**
	 * Add the supplied attribute to the underlying model.
	 * @see Model#addAttribute(Object)
	 */
	public ModelAndViewContainer addAttribute(Object value) {
		getModel().addAttribute(value);
		return this;
	}

	/**
	 * Copy all attributes to the underlying model.
	 * @see ModelMap#addAllAttributes(Map)
	 */
	public ModelAndViewContainer addAllAttributes(Map<String, ?> attributes) {
		getModel().addAllAttributes(attributes);
		return this;
	}

	/**
	 * Copy attributes in the supplied <code>Map</code> with existing objects of 
	 * the same name taking precedence (i.e. not getting replaced).
	 * @see ModelMap#mergeAttributes(Map)
	 */
	public ModelAndViewContainer mergeAttributes(Map<String, ?> attributes) {
		getModel().mergeAttributes(attributes);
		return this;
	}

	/**
	 * Remove the given attributes from the model.
	 */
	public ModelAndViewContainer removeAttributes(Map<String, ?> attributes) {
		if (attributes != null) {
			for (String key : attributes.keySet()) {
				getModel().remove(key);
			}
		}
		return this;
	}

	/**
	 * Whether the underlying model contains the given attribute name.
	 * @see ModelMap#containsAttribute(String)
	 */
	public boolean containsAttribute(String name) {
		return getModel().containsAttribute(name);
	}

	/**
	 * Return diagnostic information.
	 */
	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder("ModelAndViewContainer: ");
		if (!isRequestHandled()) {
			if (isViewReference()) {
				sb.append("reference to view with name '").append(this.view).append("'");
			}
			else {
				sb.append("View is [").append(this.view).append(']');
			}
			if (useDefaultModel()) {
				sb.append("; default model ");
			}
			else {
				sb.append("; redirect model ");
			}
			sb.append(getModel());
		}
		else {
			sb.append("Request handled directly");
		}
		return sb.toString();
	}
	
}