package de.juplo.facebook;
   
   
   import de.juplo.facebook.token.SignedRequestAwareAuthorizationCodeAccessTokenProvider;
   import de.juplo.facebook.client.GraphApiErrorHandler;
   import java.util.Arrays;
   import java.util.LinkedList;
   import java.util.List;
   import javax.annotation.PostConstruct;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.springframework.beans.BeansException;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.beans.factory.config.BeanPostProcessor;
  import org.springframework.context.annotation.Bean;
  import org.springframework.context.annotation.Configuration;
  import org.springframework.security.oauth2.client.OAuth2RestTemplate;
  import org.springframework.security.oauth2.client.http.OAuth2ErrorHandler;
  import org.springframework.security.oauth2.client.token.AccessTokenProvider;
  import org.springframework.security.oauth2.client.token.AccessTokenProviderChain;
  import org.springframework.security.oauth2.client.token.grant.client.ClientCredentialsAccessTokenProvider;
  import org.springframework.security.oauth2.client.token.grant.implicit.ImplicitAccessTokenProvider;
  import org.springframework.security.oauth2.client.token.grant.password.ResourceOwnerPasswordAccessTokenProvider;
  
  
  
  /**
   * This class injects the facebook-utils into the spring-oauth2-configuration
   *
   * @author kai
   */
  @Configuration
  public class FacebookUtils
  {
    private final Logger log = LoggerFactory.getLogger(FacebookUtils.class);
  
  
    @Autowired(required=false)
    private List<AccessTokenProvider> accessTokenProviderChain;
  
  
    @PostConstruct
    public void init()
    {
      if (accessTokenProviderChain == null)
      {
        log.info("no AccessTokenProviderChain configured, creating default-chain");
        accessTokenProviderChain =
            Arrays.<AccessTokenProvider> asList(
                new ImplicitAccessTokenProvider(),
                new ResourceOwnerPasswordAccessTokenProvider(),
                new ClientCredentialsAccessTokenProvider()
                );
      }
    }
  
  
    @Bean
    public BeanPostProcessor getBeanPostProcessor(final String clientSecret)
    {
      log.debug("createing new instance of BeanPostProcessor");
      return new BeanPostProcessor() {
  
        @Override
        public Object postProcessBeforeInitialization(
            Object bean,
            String beanName
            )
            throws
              BeansException
        {
          if (bean instanceof OAuth2RestTemplate)
          {
            log.info("injecting signed_request-aware AccessTokenProviderChain");
            OAuth2RestTemplate template = (OAuth2RestTemplate)bean;
            List<AccessTokenProvider> chain =
                new LinkedList<>(accessTokenProviderChain);
            SignedRequestAwareAuthorizationCodeAccessTokenProvider provider =
                new SignedRequestAwareAuthorizationCodeAccessTokenProvider();
            provider.setSecret(clientSecret);
            chain.add(provider);
            template.setAccessTokenProvider(new AccessTokenProviderChain(chain));
            log.info("injecting GraphApiErrorHandler");
            template.setErrorHandler(
                new GraphApiErrorHandler(
                    (OAuth2ErrorHandler)template.getErrorHandler()
                    )
                );
          }
  
          return bean;
        }
  
        @Override
        public Object postProcessAfterInitialization(
            Object bean,
            String beanName
            )
            throws
             BeansException
       {
         return bean;
       }
     };
   }
 }