/*
    * 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.sockjs.transport.handler;
  
  import java.io.IOException;
  import java.io.UnsupportedEncodingException;
  
  import org.springframework.http.MediaType;
  import org.springframework.http.server.ServerHttpRequest;
  import org.springframework.http.server.ServerHttpResponse;
  import org.springframework.util.MultiValueMap;
  import org.springframework.util.StringUtils;
  import org.springframework.web.socket.WebSocketHandler;
  import org.springframework.web.socket.sockjs.SockJsException;
  import org.springframework.web.socket.sockjs.frame.SockJsFrame;
  import org.springframework.web.socket.sockjs.frame.SockJsFrameFormat;
  import org.springframework.web.socket.sockjs.transport.SockJsSession;
  import org.springframework.web.socket.sockjs.transport.SockJsSessionFactory;
  import org.springframework.web.socket.sockjs.transport.session.AbstractHttpSockJsSession;
  import org.springframework.web.util.UriComponentsBuilder;
  import org.springframework.web.util.UriUtils;
  
  /**
   * Base class for HTTP transport handlers that push messages to connected clients.
   *
   * @author Rossen Stoyanchev
   * @since 4.0
   */
  public abstract class AbstractHttpSendingTransportHandler extends AbstractTransportHandler
  		implements SockJsSessionFactory {
  
  	@Override
  	public final void handleRequest(ServerHttpRequest request, ServerHttpResponse response,
  			WebSocketHandler wsHandler, SockJsSession wsSession) throws SockJsException {
  
  		AbstractHttpSockJsSession sockJsSession = (AbstractHttpSockJsSession) wsSession;
  
  		String protocol = null;  // https://github.com/sockjs/sockjs-client/issues/130
  		sockJsSession.setAcceptedProtocol(protocol);
  
  		// Set content type before writing
  		response.getHeaders().setContentType(getContentType());
  
  		handleRequestInternal(request, response, sockJsSession);
  	}
  
  	protected void handleRequestInternal(ServerHttpRequest request, ServerHttpResponse response,
  			AbstractHttpSockJsSession sockJsSession) throws SockJsException {
  
  		if (sockJsSession.isNew()) {
  			if (logger.isDebugEnabled()) {
  				logger.debug(request.getMethod() + " " + request.getURI());
  			}
  			sockJsSession.handleInitialRequest(request, response, getFrameFormat(request));
  		}
  		else if (sockJsSession.isClosed()) {
  			if (logger.isDebugEnabled()) {
  				logger.debug("Connection already closed (but not removed yet) for " + sockJsSession);
  			}
  			SockJsFrame frame = SockJsFrame.closeFrameGoAway();
  			try {
  				response.getBody().write(frame.getContentBytes());
  			}
  			catch (IOException ex) {
  				throw new SockJsException("Failed to send " + frame, sockJsSession.getId(), ex);
  			}
  		}
  		else if (!sockJsSession.isActive()) {
  			if (logger.isTraceEnabled()) {
  				logger.trace("Starting " + getTransportType() + " async request.");
  			}
  			sockJsSession.handleSuccessiveRequest(request, response, getFrameFormat(request));
  		}
  		else {
  			if (logger.isDebugEnabled()) {
  				logger.debug("Another " + getTransportType() + " connection still open for " + sockJsSession);
  			}
  			String formattedFrame = getFrameFormat(request).format(SockJsFrame.closeFrameAnotherConnectionOpen());
  			try {
  				response.getBody().write(formattedFrame.getBytes(SockJsFrame.CHARSET));
  			}
  			catch (IOException ex) {
  				throw new SockJsException("Failed to send " + formattedFrame, sockJsSession.getId(), ex);
  			}
  		}
 	}
 
 
 	protected abstract MediaType getContentType();
 
 	protected abstract SockJsFrameFormat getFrameFormat(ServerHttpRequest request);
 
 
 	protected final String getCallbackParam(ServerHttpRequest request) {
 		String query = request.getURI().getQuery();
 		MultiValueMap<String, String> params = UriComponentsBuilder.newInstance().query(query).build().getQueryParams();
 		String value = params.getFirst("c");
 		try {
 			return (!StringUtils.isEmpty(value) ? UriUtils.decode(value, "UTF-8") : null);
 		}
 		catch (UnsupportedEncodingException ex) {
 			// should never happen
 			throw new SockJsException("Unable to decode callback query parameter", null, ex);
 		}
 	}
 
 }