package at.gv.egiz.moazs.backend;

import at.gv.egiz.moazs.MoaZSException;
import at.gv.egiz.moazs.repository.DeliveryRepository;
import at.gv.egiz.moazs.scheme.MsgResponse;
import at.gv.egiz.moazs.service.MsgService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import java.util.function.Consumer;

import static at.gv.egiz.moazs.MoaZSException.*;
import static java.lang.String.format;
import static java.util.concurrent.CompletableFuture.supplyAsync;

@Component
public class MsgResponseBackend implements Consumer<String> {

    private static final Logger log = LoggerFactory.getLogger(MsgService.class);

    public static final String MOASP_SIGNATURE_INVALID_ERROR_MSG = "Signature of Msg Response " +
            "with AppDeliveryID=%s is not valid.";
    public static final String BINARY_RESPONSE_MISSING_ERROR_MSG = "Binary Response is not in repository.";
    public static final String RESPONSE_MISSING_ERROR_MSG = "Response with ResponseID=%s is not in repository.";
    public static final String REQUEST_MISSING_ERROR_MSG = "Request with AppDeliveryID=%s is not in repository.";

    private final DeliveryRepository repository;
    private final Consumer<byte[]> signatureVerifier;
    private final MsgResponseSinkHub hub;

    @Autowired
    public MsgResponseBackend(DeliveryRepository repository,
                              Consumer<byte[]> signatureVerifier,
                              MsgResponseSinkHub hub) {
        this.repository = repository;
        this.signatureVerifier = signatureVerifier;
        this.hub = hub;
    }

    /**
     * Performs all {@code MsgResponse}'s Back-End Tasks, such as verifying
     * its signature and archiving the response.
     *
     * Note: When the signature verification fails, this method will not archive
     * the original response (the one that was received from msg) to the sink,
     * but an error message.
     *
     * @param responseID refers to MsgResponse Object.
     */
    @Override
    public void accept(String responseID) {
        log.info("Backend accepts MsgResponse with responseID={}.", responseID);
        supplyAsync(() -> verifySignature(responseID))
                .thenAcceptAsync(msgResponse -> applySinks(msgResponse))
                .exceptionally(ex -> {
                    log.error(ex.getMessage(), ex);
                    return null;
                });
    }

    private MsgResponse verifySignature(String responseID) {

        var response = repository.retrieveResponse(responseID).orElseThrow(
                ()-> moaZSException(format(RESPONSE_MISSING_ERROR_MSG, responseID)));

        try {
            var binaryResponse = repository.retrieveBinaryResponse(responseID).orElseThrow(
                    () -> moaZSException(BINARY_RESPONSE_MISSING_ERROR_MSG, MoaZSException.ERROR_MZS_BINARY_RESPONSE_MISSING));

            log.info("Verify Signature of msg:{} with AppDeliveryID={}.",
                    response.getRootElementLocalPart(), response.getAppDeliveryID());

            signatureVerifier.accept(binaryResponse);
            return response;
        } catch (MoaZSException ex) {
            log.error(ex.getMessage(), ex);
            var text = format(MOASP_SIGNATURE_INVALID_ERROR_MSG, response.getAppDeliveryID());
            var code = ERROR_MOASP_SIGNATURE_INVALID;
            return response.generateError(text, code);
        }

    }

    private void applySinks(MsgResponse msgResponse) {
        var appDeliveryID = msgResponse.getAppDeliveryID();

        var request = repository.retrieveDeliveryRequest(appDeliveryID).orElseThrow(
                ()-> moaZSException(format(REQUEST_MISSING_ERROR_MSG, appDeliveryID)));

        var sinkParams = request.getConfig().getMsgResponseSinks();
        hub.applySinks(msgResponse, sinkParams);
    }

}