/*-
 * ========================LICENSE_START=================================
 * O-RAN-SC
 * %%
 * Copyright (C) 2019 Nordix Foundation
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * ========================LICENSE_END===================================
 */

package org.oransc.policyagent.tasks;

import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import com.google.gson.JsonSyntaxException;
import com.google.gson.TypeAdapterFactory;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.time.Duration;
import java.util.Properties;
import java.util.ServiceLoader;

import javax.validation.constraints.NotNull;

import org.onap.dcaegen2.services.sdk.rest.services.cbs.client.api.CbsClient;
import org.onap.dcaegen2.services.sdk.rest.services.cbs.client.api.CbsClientFactory;
import org.onap.dcaegen2.services.sdk.rest.services.cbs.client.api.CbsRequests;
import org.onap.dcaegen2.services.sdk.rest.services.cbs.client.model.CbsRequest;
import org.onap.dcaegen2.services.sdk.rest.services.cbs.client.model.EnvProperties;
import org.onap.dcaegen2.services.sdk.rest.services.model.logging.RequestDiagnosticContext;
import org.oransc.policyagent.configuration.ApplicationConfig;
import org.oransc.policyagent.configuration.ApplicationConfigParser;
import org.oransc.policyagent.exceptions.ServiceException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

import reactor.core.Disposable;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

/**
 * Regularly refreshes the configuration from Consul.
 */
@Component
public class RefreshConfigTask {

    private static final Logger logger = LoggerFactory.getLogger(RefreshConfigTask.class);

    @Value("#{systemEnvironment}")
    public Properties systemEnvironment;

    private final ApplicationConfig appConfig;
    private Disposable refreshTask = null;

    @Autowired
    public RefreshConfigTask(ApplicationConfig appConfig) {
        this.appConfig = appConfig;
    }

    public void start() {
        logger.debug("Starting refreshConfigTask");
        stop();
        loadConfigurationFromFile();
        refreshTask = createRefreshTask() //
            .subscribe(notUsed -> logger.info("Refreshed configuration data"),
                throwable -> logger.error("Configuration refresh terminated due to exception", throwable),
                () -> logger.error("Configuration refresh terminated"));
    }

    public void stop() {
        if (refreshTask != null) {
            refreshTask.dispose();
            refreshTask = null;
        }
    }

    Flux<ApplicationConfig> createRefreshTask() {
        return getEnvironment(systemEnvironment) //
            .flatMap(this::createCbsClient) //
            .flatMapMany(this::periodicConfigurationUpdates) //
            .map(this::parseRicConfigurationfromConsul) //
            .onErrorResume(this::onErrorResume);
    }

    Mono<EnvProperties> getEnvironment(Properties systemEnvironment) {
        return EnvironmentProcessor.readEnvironmentVariables(systemEnvironment);
    }

    Mono<CbsClient> createCbsClient(EnvProperties env) {
        return CbsClientFactory.createCbsClient(env);
    }

    private Flux<JsonObject> periodicConfigurationUpdates(CbsClient cbsClient) {
        final Duration initialDelay = Duration.ZERO;
        final Duration refreshPeriod = Duration.ofMinutes(1);
        final CbsRequest getConfigRequest = CbsRequests.getAll(RequestDiagnosticContext.create());
        return cbsClient.updates(getConfigRequest, initialDelay, refreshPeriod);
    }

    private <R> Mono<R> onErrorResume(Throwable trowable) {
        logger.error("Could not refresh application configuration {}", trowable.toString());
        return Mono.empty();
    }

    private ApplicationConfig parseRicConfigurationfromConsul(JsonObject jsonObject) {
        try {
            ApplicationConfigParser parser = new ApplicationConfigParser();
            parser.parse(jsonObject);
            this.appConfig.setConfiguration(parser.getRicConfigs(), parser.getDmaapPublisherConfig(),
                parser.getDmaapConsumerConfig());
        } catch (ServiceException e) {
            logger.error("Could not parse configuration {}", e.toString(), e);
        }
        return this.appConfig;
    }

    /**
     * Reads the configuration from file.
     */
    public void loadConfigurationFromFile() {
        String filepath = appConfig.getLocalConfigurationFilePath();
        if (filepath == null) {
            logger.debug("No localconfiguration file used");
            return;
        }
        GsonBuilder gsonBuilder = new GsonBuilder();
        ServiceLoader.load(TypeAdapterFactory.class).forEach(gsonBuilder::registerTypeAdapterFactory);

        try (InputStream inputStream = createInputStream(filepath)) {
            JsonObject rootObject = getJsonElement(inputStream).getAsJsonObject();
            if (rootObject == null) {
                throw new JsonSyntaxException("Root is not a json object");
            }
            ApplicationConfigParser appParser = new ApplicationConfigParser();
            appParser.parse(rootObject);
            appConfig.setConfiguration(appParser.getRicConfigs(), appParser.getDmaapPublisherConfig(),
                appParser.getDmaapConsumerConfig());
            logger.info("Local configuration file loaded: {}", filepath);
        } catch (JsonSyntaxException | ServiceException | IOException e) {
            logger.trace("Local configuration file not loaded: {}", filepath, e);
        }
    }

    JsonElement getJsonElement(InputStream inputStream) {
        return JsonParser.parseReader(new InputStreamReader(inputStream));
    }

    InputStream createInputStream(@NotNull String filepath) throws IOException {
        return new BufferedInputStream(new FileInputStream(filepath));
    }
}