/*
    * Copyright 2002-2014 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.method.annotation;
  
  import java.io.OutputStream;
  import java.io.Writer;
  import java.lang.reflect.Method;
  import javax.servlet.ServletResponse;
  import javax.servlet.http.HttpServletResponse;
  
  import org.springframework.core.MethodParameter;
  import org.springframework.web.bind.support.WebDataBinderFactory;
  import org.springframework.web.context.request.NativeWebRequest;
  import org.springframework.web.method.support.HandlerMethodArgumentResolver;
  import org.springframework.web.method.support.ModelAndViewContainer;
  
  /**
   * Resolves response-related method argument values of types:
   * <ul>
   * <li>{@link ServletResponse}
   * <li>{@link OutputStream}
   * <li>{@link Writer}
   * </ul>
   *
   * @author Arjen Poutsma
   * @author Rossen Stoyanchev
   * @since 3.1
   */
  public class ServletResponseMethodArgumentResolver implements HandlerMethodArgumentResolver {
  
  	@Override
  	public boolean supportsParameter(MethodParameter parameter) {
  		Class<?> paramType = parameter.getParameterType();
  		return (ServletResponse.class.isAssignableFrom(paramType) ||
  				OutputStream.class.isAssignableFrom(paramType) ||
  				Writer.class.isAssignableFrom(paramType));
  	}
  
  	/**
  	 * Set {@link ModelAndViewContainer#setRequestHandled(boolean)} to
  	 * {@code false} to indicate that the method signature provides access
  	 * to the response. If subsequently the underlying method returns
  	 * {@code null}, the request is considered directly handled.
  	 */
  	@Override
  	public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
  			NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
  
  		if (mavContainer != null) {
  			mavContainer.setRequestHandled(true);
  		}
  
  		HttpServletResponse response = webRequest.getNativeResponse(HttpServletResponse.class);
  		Class<?> paramType = parameter.getParameterType();
  
  		if (ServletResponse.class.isAssignableFrom(paramType)) {
  			Object nativeResponse = webRequest.getNativeResponse(paramType);
  			if (nativeResponse == null) {
  				throw new IllegalStateException(
  						"Current response is not of type [" + paramType.getName() + "]: " + response);
  			}
  			return nativeResponse;
  		}
  		else if (OutputStream.class.isAssignableFrom(paramType)) {
  			return response.getOutputStream();
  		}
  		else if (Writer.class.isAssignableFrom(paramType)) {
  			return response.getWriter();
  		}
  		else {
  			// should not happen
  			Method method = parameter.getMethod();
  			throw new UnsupportedOperationException("Unknown parameter type: " + paramType + " in method: " + method);
  		}
  	}
  
  }