/*
    * 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.socket.server.standard;
  
  import java.net.InetSocketAddress;
  import java.security.Principal;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Map;
  import javax.servlet.ServletContext;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import javax.websocket.Endpoint;
  import javax.websocket.Extension;
  import javax.websocket.WebSocketContainer;
  import javax.websocket.server.ServerContainer;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import org.springframework.http.HttpHeaders;
  import org.springframework.http.server.ServerHttpRequest;
  import org.springframework.http.server.ServerHttpResponse;
  import org.springframework.http.server.ServletServerHttpRequest;
  import org.springframework.http.server.ServletServerHttpResponse;
  import org.springframework.util.Assert;
  import org.springframework.web.socket.WebSocketExtension;
  import org.springframework.web.socket.WebSocketHandler;
  import org.springframework.web.socket.adapter.standard.StandardToWebSocketExtensionAdapter;
  import org.springframework.web.socket.adapter.standard.StandardWebSocketHandlerAdapter;
  import org.springframework.web.socket.adapter.standard.StandardWebSocketSession;
  import org.springframework.web.socket.adapter.standard.WebSocketToStandardExtensionAdapter;
  import org.springframework.web.socket.server.HandshakeFailureException;
  import org.springframework.web.socket.server.RequestUpgradeStrategy;
  
  /**
   * A base class for {@link RequestUpgradeStrategy} implementations that build
   * on the standard WebSocket API for Java (JSR-356).
   *
   * @author Rossen Stoyanchev
   * @since 4.0
   */
  public abstract class AbstractStandardUpgradeStrategy implements RequestUpgradeStrategy {
  
  	protected final Log logger = LogFactory.getLog(getClass());
  
  	private volatile List<WebSocketExtension> extensions;
  
  
  	protected ServerContainer getContainer(HttpServletRequest request) {
  		ServletContext servletContext = request.getServletContext();
  		String attrName = "javax.websocket.server.ServerContainer";
  		ServerContainer container = (ServerContainer) servletContext.getAttribute(attrName);
  		Assert.notNull(container, "No 'javax.websocket.server.ServerContainer' ServletContext attribute. " +
  				"Are you running in a Servlet container that supports JSR-356?");
  		return container;
  	}
  
  	protected final HttpServletRequest getHttpServletRequest(ServerHttpRequest request) {
  		Assert.isTrue(request instanceof ServletServerHttpRequest);
  		return ((ServletServerHttpRequest) request).getServletRequest();
  	}
  
  	protected final HttpServletResponse getHttpServletResponse(ServerHttpResponse response) {
  		Assert.isTrue(response instanceof ServletServerHttpResponse);
  		return ((ServletServerHttpResponse) response).getServletResponse();
  	}
  
  
  	@Override
  	public List<WebSocketExtension> getSupportedExtensions(ServerHttpRequest request) {
  		if (this.extensions == null) {
  			HttpServletRequest servletRequest = ((ServletServerHttpRequest) request).getServletRequest();
  			this.extensions = getInstalledExtensions(getContainer(servletRequest));
  		}
  		return this.extensions;
  	}
  
  	protected List<WebSocketExtension> getInstalledExtensions(WebSocketContainer container) {
  		List<WebSocketExtension> result = new ArrayList<WebSocketExtension>();
  		for (Extension ext : container.getInstalledExtensions()) {
  			result.add(new StandardToWebSocketExtensionAdapter(ext));
  		}
  		return result;
  	}
 
 
 	@Override
 	public void upgrade(ServerHttpRequest request, ServerHttpResponse response,
 			String selectedProtocol, List<WebSocketExtension> selectedExtensions, Principal user,
 			WebSocketHandler wsHandler, Map<String, Object> attrs) throws HandshakeFailureException {
 
 		HttpHeaders headers = request.getHeaders();
 		InetSocketAddress localAddr = request.getLocalAddress();
 		InetSocketAddress remoteAddr = request.getRemoteAddress();
 
 		StandardWebSocketSession session = new StandardWebSocketSession(headers, attrs, localAddr, remoteAddr, user);
 		StandardWebSocketHandlerAdapter endpoint = new StandardWebSocketHandlerAdapter(wsHandler, session);
 
 		List<Extension> extensions = new ArrayList<Extension>();
 		for (WebSocketExtension extension : selectedExtensions) {
 			extensions.add(new WebSocketToStandardExtensionAdapter(extension));
 		}
 
 		upgradeInternal(request, response, selectedProtocol, extensions, endpoint);
 	}
 
 	protected abstract void upgradeInternal(ServerHttpRequest request, ServerHttpResponse response,
 			String selectedProtocol, List<Extension> selectedExtensions, Endpoint endpoint)
 			throws HandshakeFailureException;
 
 }