package org.oxerr.spring.security.wechat.web.authentication;
   
   import java.io.IOException;
   
   import javax.servlet.FilterChain;
   import javax.servlet.ServletException;
   import javax.servlet.ServletRequest;
   import javax.servlet.ServletResponse;
   import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.oxerr.spring.security.wechat.authentication.WeChatAuthenticationToken;
  import org.oxerr.spring.security.wechat.core.AuthDenyException;
  import org.springframework.security.core.Authentication;
  import org.springframework.security.core.AuthenticationException;
  import org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter;
  import org.springframework.security.web.util.matcher.AntPathRequestMatcher;
  import org.springframework.util.Assert;
  
  public class WeChatAuthenticationFilter extends AbstractAuthenticationProcessingFilter {
  
  	private final String AUTH_DENY_ATTRIBUTE_NAME = this.getClass().getName() + ".AuthDeny";
  	private final WeChatService weChatService;
  
  	public WeChatAuthenticationFilter(WeChatService weChatService) {
  		super(new AntPathRequestMatcher("/login/wechat", "GET"));
  		this.weChatService = weChatService;
  	}
  
  	/**
  	 * {@inheritDoc}
  	 */
  	@Override
  	public void doFilter(ServletRequest req, ServletResponse res,
  			FilterChain chain) throws IOException, ServletException {
  		HttpServletRequest request = (HttpServletRequest) req;
  		HttpServletResponse response = (HttpServletResponse) res;
  
  		if (request.getSession().getAttribute(AUTH_DENY_ATTRIBUTE_NAME) == null
  				&& isInWeChat(request)) {
  			super.doFilter(request, response, chain);
  		} else {
  			chain.doFilter(request, response);
  		}
  	}
  
  	/**
  	 * {@inheritDoc}
  	 */
  	@Override
  	public Authentication attemptAuthentication(HttpServletRequest request,
  			HttpServletResponse response)
  			throws AuthenticationException, IOException, ServletException {
  		final Authentication authentication;
  
  		final String code = request.getParameter("code");
  
  		if (code == null) {
  			this.weChatService.redirectToAuthorize(request, response);
  			authentication = null;
  		} else {
  			final WeChatAuthenticationToken authenticationToken = new WeChatAuthenticationToken(code);
  
  			// delegate to the authentication provider
  			try {
  				authentication = this.getAuthenticationManager().authenticate(authenticationToken);
  			} catch (AuthDenyException e) {
  				request.getSession().setAttribute(AUTH_DENY_ATTRIBUTE_NAME, e);
  				throw e;
  			}
  		}
  
  		return authentication;
  	}
  
  	/**
  	 * {@inheritDoc}
  	 */
  	@Override
  	public void afterPropertiesSet() {
  		super.afterPropertiesSet();
  
  		Assert.notNull(this.weChatService, "A weChatService must be set.");
  	}
  
  	protected boolean isInWeChat(HttpServletRequest request) throws IOException {
  		final String userAgent = request.getHeader("user-agent");
  		return userAgent != null && userAgent.contains("MicroMessenger/");
  	}
  
  }