import org.apache.commons.lang3.StringUtils;

import com.google.inject.Singleton;

import java.io.IOException;
import java.util.List;
import java.util.Random;

import javax.ws.rs.container.ContainerRequestContext;
import javax.ws.rs.container.ContainerRequestFilter;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.UriInfo;

@Authenticator
@Singleton
public class AuthenticateFilter implements ContainerRequestFilter {

  private static final String PARAM_API_KEY = "apiKey";
  private static final String PARAM_TOKEN = "token";

  @Override
  public void filter(ContainerRequestContext context) throws IOException {
    final String apiKey = extractParam(context, PARAM_API_KEY);
    if (StringUtils.isEmpty(apiKey)) {
      context.abortWith(responseMissingParameter(PARAM_API_KEY));
    }

    final String token = extractParam(context, PARAM_TOKEN);
    if (StringUtils.isEmpty(token)) {
      context.abortWith(responseMissingParameter(PARAM_TOKEN));
    }

    if (!authenticate(apiKey, token)) {
      context.abortWith(responseUnauthorized());
    }
  }

  private String extractParam(ContainerRequestContext context, String param) {
    final UriInfo uriInfo = context.getUriInfo();
    final List<String> paramValues = uriInfo.getQueryParameters().get(param);
    return paramValues != null && !paramValues.isEmpty() ? String.valueOf(paramValues.get(0)) : null;
  }

  private Response responseMissingParameter(String name) {
    return Response.status(Response.Status.BAD_REQUEST)
                     .type(MediaType.TEXT_PLAIN_TYPE)
                     .entity("Parameter '" + name + "' is required.")
                     .build();
  }

  private boolean authenticate(String apiKey, String token) {
    return new Random().nextBoolean();
  }

  private Response responseUnauthorized() {
    return Response.status(Response.Status.UNAUTHORIZED)
        .type(MediaType.TEXT_PLAIN_TYPE)
        .entity("Unauthorized")
        .build();
  }
}