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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.struts2.rest;

import java.lang.reflect.Method;

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

import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionSupport;

/**
 * Extends {@link ActionSupport} to provides a default implementation of the index method that can be invoked for
 * unknown actions by the {@link com.opensymphony.xwork2.UnknownHandler}.
 */
public class RestActionSupport extends ActionSupport {

	private static final long serialVersionUID = -889518620073576882L;
	
	private static final String DELETE = "DELETE";
	private static final String PUT = "PUT";
	private static final String POST = "POST";
	private static final String GET = "GET";
	private static final String OPTIONS = "OPTIONS";
	private static final String DIVIDER = ", ";

	/**
	 * Default execution.
	 * @return object because it can return string, result or httpHeader.
	 * @throws Exception in case of any error
	 */
    public Object index() throws Exception {
        return execute();
    }
    
	/**
	 * Inspect the implemented methods to know the allowed http methods.
	 * 
	 * @return Include the header "Allow" with the allowed http methods. 
	 */
    public HttpHeaders options() {
    	
    	String methods = OPTIONS;
    	
    	Method[] meths = this.getClass().getDeclaredMethods();
    	for (Method m : meths) {
    		String methodName = m.getName();
    		if (!methods.contains(GET) &&
    				(methodName.equals("index")
    				|| methodName.equals("show")
    				|| methodName.equals("edit")
    				|| methodName.equals("editNew"))) {
    			methods += DIVIDER + GET;
    		} else if (methodName.equals("create")) {
    			methods += DIVIDER + POST;
    		} else if (methodName.equals("update")) {
    			methods += DIVIDER + PUT;
    		}else if (methodName.equals("destroy")) {
    			methods += DIVIDER + DELETE;
    		}
    	}
    	
    	HttpServletRequest request = ServletActionContext.getRequest();
    	HttpServletResponse response = ServletActionContext.getResponse();
    	response.addHeader("Allow", methods);
    	
    	DefaultHttpHeaders httpHeaders = new DefaultHttpHeaders();
    	httpHeaders.apply(request, response, this);
    	httpHeaders.disableCaching().withStatus(HttpServletResponse.SC_OK);
    	
    	return httpHeaders;
	}
    
    /**
     * By default, return continue.
     * Is possible override the method to return expectation failed.
     * 
     * @return continue
     */
    public HttpHeaders createContinue() {
		return new DefaultHttpHeaders()
		    .disableCaching()
		    .withStatus(HttpServletResponse.SC_CONTINUE);
	}
    
    /**
     * By default, return continue.
     * Is possible override the method to return expectation failed.
     * 
     * @return continue
     */
    public HttpHeaders updateContinue() {
		return new DefaultHttpHeaders()
		    .disableCaching()
		    .withStatus(HttpServletResponse.SC_CONTINUE);
	}
}