/*
    * Copyright 2002-2012 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.filter;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.nio.charset.Charset;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.Enumeration;
  import java.util.LinkedHashMap;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import javax.servlet.FilterChain;
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletRequestWrapper;
  import javax.servlet.http.HttpServletResponse;
  
  import org.springframework.http.HttpInputMessage;
  import org.springframework.http.MediaType;
  import org.springframework.http.converter.FormHttpMessageConverter;
  import org.springframework.http.converter.support.AllEncompassingFormHttpMessageConverter;
  import org.springframework.http.server.ServletServerHttpRequest;
  import org.springframework.util.LinkedMultiValueMap;
  import org.springframework.util.MultiValueMap;
  
  /**
   * {@link javax.servlet.Filter} that makes form encoded data available through
   * the {@code ServletRequest.getParameter*()} family of methods during HTTP PUT
   * or PATCH requests.
   *
   * <p>The Servlet spec requires form data to be available for HTTP POST but
   * not for HTTP PUT or PATCH requests. This filter intercepts HTTP PUT and PATCH
   * requests where content type is {@code 'application/x-www-form-urlencoded'},
   * reads form encoded content from the body of the request, and wraps the ServletRequest
   * in order to make the form data available as request parameters just like
   * it is for HTTP POST requests.
   *
   * @author Rossen Stoyanchev
   * @since 3.1
   */
  public class HttpPutFormContentFilter extends OncePerRequestFilter {
  
  	private final FormHttpMessageConverter formConverter = new AllEncompassingFormHttpMessageConverter();
  
  	/**
  	 * The default character set to use for reading form data.
  	 */
  	public void setCharset(Charset charset) {
  		this.formConverter.setCharset(charset);
  	}
  
  	@Override
  	protected void doFilterInternal(final HttpServletRequest request, HttpServletResponse response,
  			FilterChain filterChain) throws ServletException, IOException {
  
  		if (("PUT".equals(request.getMethod()) || "PATCH".equals(request.getMethod())) && isFormContentType(request)) {
  			HttpInputMessage inputMessage = new ServletServerHttpRequest(request) {
  				@Override
  				public InputStream getBody() throws IOException {
  					return request.getInputStream();
  				}
  			};
  			MultiValueMap<String, String> formParameters = formConverter.read(null, inputMessage);
  			HttpServletRequest wrapper = new HttpPutFormContentRequestWrapper(request, formParameters);
  			filterChain.doFilter(wrapper, response);
  		}
  		else {
  			filterChain.doFilter(request, response);
  		}
  	}
  
  	private boolean isFormContentType(HttpServletRequest request) {
  		String contentType = request.getContentType();
  		if (contentType != null) {
  			try {
  				MediaType mediaType = MediaType.parseMediaType(contentType);
  				return (MediaType.APPLICATION_FORM_URLENCODED.includes(mediaType));
  			}
  			catch (IllegalArgumentException ex) {
  				return false;
 			}
 		}
 		else {
 			return false;
 		}
 	}
 
 	private static class HttpPutFormContentRequestWrapper extends HttpServletRequestWrapper {
 
 		private MultiValueMap<String, String> formParameters;
 
 		public HttpPutFormContentRequestWrapper(HttpServletRequest request, MultiValueMap<String, String> parameters) {
 			super(request);
 			this.formParameters = (parameters != null) ? parameters : new LinkedMultiValueMap<String, String>();
 		}
 
 		@Override
 		public String getParameter(String name) {
 			String queryStringValue = super.getParameter(name);
 			String formValue = this.formParameters.getFirst(name);
 			return (queryStringValue != null) ?  queryStringValue : formValue;
 		}
 
 		@Override
 		public Map<String, String[]> getParameterMap() {
 			Map<String, String[]> result = new LinkedHashMap<String, String[]>();
 			Enumeration<String> names = this.getParameterNames();
 			while (names.hasMoreElements()) {
 				String name = names.nextElement();
 				result.put(name, this.getParameterValues(name));
 			}
 			return result;
 		}
 
 		@Override
 		public Enumeration<String> getParameterNames() {
 			Set<String> names = new LinkedHashSet<String>();
 			names.addAll(Collections.list(super.getParameterNames()));
 			names.addAll(this.formParameters.keySet());
 			return Collections.enumeration(names);
 		}
 
 		@Override
 		public String[] getParameterValues(String name) {
 			String[] queryStringValues = super.getParameterValues(name);
 			List<String> formValues = this.formParameters.get(name);
 			if (formValues == null) {
 				return queryStringValues;
 			}
 			else if (queryStringValues == null) {
 				return formValues.toArray(new String[formValues.size()]);
 			}
 			else {
 				List<String> result = new ArrayList<String>();
 				result.addAll(Arrays.asList(queryStringValues));
 				result.addAll(formValues);
 				return result.toArray(new String[result.size()]);
 			}
 		}
 	}
 
 }