import java.util.stream.Collectors;

import javax.annotation.Nullable;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import org.jboss.resteasy.util.GetRestful;

import com.google.inject.Inject;
import com.google.inject.Injector;
import com.typesafe.config.Config;
import com.typesafe.config.ConfigFactory;
import com.wordnik.swagger.config.ScannerFactory;
import com.wordnik.swagger.jaxrs.config.BeanConfig;

/**
 * A context listener that scans for APIs and configures Swagger.
 *
 * @author ben.manes@gmail.com (Ben Manes)
 */
final class SwaggerServletContextListener implements ServletContextListener {
  private final Config config = ConfigFactory.load().getConfig(getClass().getPackage().getName());
  private final Injector injector;

  @Inject
  SwaggerServletContextListener(Injector injector) {
    this.injector = injector;
  }

  @Override
  public void contextInitialized(ServletContextEvent event) {
    BeanConfig beanConfig = getBeanConfig();
    event.getServletContext().setAttribute("reader", beanConfig);
    event.getServletContext().setAttribute("swagger", beanConfig.getSwagger());
    event.getServletContext().setAttribute("scanner", ScannerFactory.getScanner());
  }

  private BeanConfig getBeanConfig() {
    BeanConfig beanConfig = new ResourceConfig();
    beanConfig.setHost(getConfigString("host"));
    beanConfig.setTitle(getConfigString("title"));
    beanConfig.setVersion(getConfigString("version"));
    beanConfig.setContact(getConfigString("contact"));
    beanConfig.setLicense(getConfigString("license"));
    beanConfig.setBasePath(getConfigString("base_path"));
    beanConfig.setLicenseUrl(getConfigString("licenseUrl"));
    beanConfig.setDescription(getConfigString("description"));
    beanConfig.setPrettyPrint(getConfigString("pretty_print"));
    beanConfig.setTermsOfServiceUrl(getConfigString("terms_of_service_url"));

    // Must be called last
    beanConfig.setResourcePackage(resourcePackages());
    beanConfig.setScan(true);

    return beanConfig;
  }

  @Nullable
  private String getConfigString(String path) {
    return config.hasPath(path) ? config.getString(path) : null;
  }

  /** Returns a comma separated list of resource packages. */
  private String resourcePackages() {
    return injector.getBindings().keySet().stream()
        .map(key -> key.getTypeLiteral().getRawType())
        .filter(GetRestful::isRootResource)
        .map(clazz -> clazz.getPackage().getName())
        .distinct()
        .collect(Collectors.joining(","));
  }

  @Override
  public void contextDestroyed(ServletContextEvent event) {}
}