/*******************************************************************************
 * Copyright 2019 Graz University of Technology
 * MOA ZS has been developed in a cooperation between EGIZ
 * and Graz University of Technology.
 * Licensed under the EUPL, Version 1.2 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * https://joinup.ec.europa.eu/news/understanding-eupl-v12
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 *
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 *******************************************************************************/
package at.gv.egiz.moazs.backend;

import at.gv.egiz.moazs.MoaZSException;
import at.gv.egiz.moazs.preprocess.MzsDeliveryRequestValidator;
import at.gv.egiz.moazs.repository.DeliveryRepository;
import at.gv.egiz.moazs.scheme.MsgResponse;
import at.gv.egiz.moazs.service.MsgService;
import at.gv.zustellung.app2mzs.xsd.ConfigType;
import at.gv.zustellung.app2mzs.xsd.DeliveryRequestType;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import java.util.Map;
import java.util.function.Consumer;
import java.util.function.Supplier;

import static at.gv.egiz.moazs.MoaZSException.*;
import static at.gv.egiz.moazs.preprocess.ConfigProfileGenerator.DEFAULT_CONFIG_KEY;
import static at.gv.zustellung.app2mzs.xsd.DeliveryRequestType.deliveryRequestTypeBuilder;
import static java.lang.String.format;
import static java.util.concurrent.CompletableFuture.supplyAsync;

/**
 * @author Christof Rabensteiner
 *
 */
@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. " +
            "Falling Back to Default Configuration.";

    private final DeliveryRepository repository;
    private final Consumer<byte[]> signatureVerifier;
    private final MsgResponseSinkHub hub;
    private final Map<String, ConfigType> deliveryRequestConfigs;
    private final MzsDeliveryRequestValidator validator;

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

    /**
     * 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 config = repository
                .retrieveDeliveryRequest(appDeliveryID)
                .orElseGet(supplyRequestWithDefaultConfig(appDeliveryID))
                .getConfig();

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

    private Supplier<DeliveryRequestType> supplyRequestWithDefaultConfig(String appDeliveryID) {
        return () -> {
            log.warn(format(REQUEST_MISSING_ERROR_MSG, appDeliveryID));
            var defaultConfig = deliveryRequestConfigs.get(DEFAULT_CONFIG_KEY);
            validator.areSinksConfigured(defaultConfig.getMsgResponseSinks());
            return deliveryRequestTypeBuilder()
                    .withConfig(defaultConfig)
                    .build();
        };
    }

}