/*
 * ================================================================================
 * Copyright (c) 2018 AT&T Intellectual Property. All rights reserved.
 * ================================================================================
 * 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.onap.dcae.analytics.web.spring;

import java.time.Duration;
import java.util.Arrays;
import java.util.Collections;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Collectors;

import org.onap.dcae.analytics.model.AnalyticsProfile;
import org.onap.dcae.analytics.model.configbindingservice.ConfigBindingServiceConstants;
import org.onap.dcae.analytics.model.util.function.JsonStringToMapFunction;
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.CbsClientConfiguration;
import org.onap.dcaegen2.services.sdk.rest.services.cbs.client.model.CbsRequest;
import org.onap.dcaegen2.services.sdk.rest.services.model.logging.RequestDiagnosticContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.env.EnvironmentPostProcessor;
import org.springframework.core.Ordered;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.MapPropertySource;
import org.springframework.core.env.MutablePropertySources;
import org.springframework.core.env.PropertySource;
import org.springframework.core.env.StandardEnvironment;
import org.springframework.util.ClassUtils;
import org.springframework.web.context.support.StandardServletEnvironment;

import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

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

/**
 * A custom spring framework environment post processor which can fetch and populate spring context with
 * Config Binding Service application properties.
 * <p>
 * Activated only when config binding service profile is active.
 *
 * @author Rajiv Singla
 */
public class ConfigBindingServiceEnvironmentPostProcessor implements EnvironmentPostProcessor, Ordered {

    private static final Logger logger = LoggerFactory.getLogger(ConfigBindingServiceEnvironmentPostProcessor.class);
    private static final String SERVLET_ENVIRONMENT_CLASS =
            "org.springframework.web.context.support.StandardServletEnvironment";

    private static final int DEFAULT_ORDER = Ordered.HIGHEST_PRECEDENCE;

    private Disposable refreshConfigTask = null;

    private ConfigurableEnvironment env = null;

    private Map<String, Object> filterKeyMap = null;

    private String configServicePropertiesKey =
            ConfigBindingServiceConstants.CONFIG_BINDING_SERVICE_PROPERTIES_KEY;

    @Override
    public void postProcessEnvironment(final ConfigurableEnvironment environment,
            final SpringApplication application) {

        final boolean isConfigServiceProfilePresent = Arrays.stream(environment.getActiveProfiles())
                .anyMatch(p -> p.equalsIgnoreCase(AnalyticsProfile.CONFIG_BINDING_SERVICE_PROFILE_NAME));

        if (!isConfigServiceProfilePresent) {
            logger.info("Config Binding Service Profile is not active. "
                    + "Skipping Adding config binding service properties");
            return;
        }

        logger.info("Config Binding Service Profile is active. "
                + "Application properties will be fetched from config binding service");

        env = environment;
        initialize();

    }

    @Override
    public int getOrder() {
        return DEFAULT_ORDER;
    }

    public synchronized void addJsonPropertySource(final MutablePropertySources sources,
            final PropertySource<?> source) {
        final String name = findPropertySource(sources);
        if (sources.contains(name)) {
            sources.addBefore(name, source);
        } else {
            sources.addFirst(source);
        }
    }

    private String findPropertySource(final MutablePropertySources sources) {
        if (ClassUtils.isPresent(SERVLET_ENVIRONMENT_CLASS, null)
                && sources.contains(StandardServletEnvironment.JNDI_PROPERTY_SOURCE_NAME)) {
            return StandardServletEnvironment.JNDI_PROPERTY_SOURCE_NAME;

        }
        return StandardEnvironment.SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME;
    }

    /**
     *
     * Fetch the configuration.
     *
     */
    public void initialize() {
        stop();

        refreshConfigTask = createRefreshTask() //
                .subscribe(e -> logger.info("Refreshed configuration data"),
                        throwable -> logger.error("Configuration refresh terminated due to exception", throwable),
                        () -> logger.error("Configuration refresh terminated"));
    }

    /**
     * Fetch the configuration task from CBS.
     *
     */
    private Flux<String> createRefreshTask() {
        return readEnvironmentVariables() //
                .flatMap(this::createCbsClient) //
                .flatMapMany(this::periodicConfigurationUpdates) //
                .map(this::parseTcaConfig) //
                .onErrorResume(this::onErrorResume);
    }

    /**
     * periodicConfigurationUpdates.
     *
     * @param cbsClient cbsClient
     * @return configuration refreshed
     *
     */
    public Flux<JsonObject> periodicConfigurationUpdates(CbsClient cbsClient) {
        final Duration initialDelay = Duration.ZERO;
        final Duration refreshPeriod =
                 Duration.ofMinutes(ConfigBindingServiceConstants.CONFIG_SERVICE_REFRESHPERIOD);
        final CbsRequest getConfigRequest = CbsRequests.getAll(RequestDiagnosticContext.create());
        return cbsClient.updates(getConfigRequest, initialDelay, refreshPeriod);
    }

    /**
     *
     * get environment variables.
     *
     * @return environment properties.
     *
     */
    public Mono<CbsClientConfiguration> readEnvironmentVariables() {
        logger.trace("Loading configuration from system environment variables");
        CbsClientConfiguration cbsClientConfiguration = CbsClientConfiguration.fromEnvironment();
        return Mono.just(cbsClientConfiguration);
    }

    /**
     * Stops the refreshing of the configuration.
     *
     */
    public void stop() {
        if (refreshConfigTask != null) {
            refreshConfigTask.dispose();
            refreshConfigTask = null;
        }
    }

    /**
     * periodicConfigurationUpdates.
     *
     * @param throwable throwable
     * @return Mono
     *
     */
    private <R> Mono<R> onErrorResume(Throwable throwable) {
        logger.error("Could not refresh application configuration {}", throwable.toString());
        return Mono.empty();
    }

    /**
     * create CbsClient.
     *
     * @param cbsClientConfiguration cbs configuration
     * @return cbsclient
     *
     */
    public Mono<CbsClient> createCbsClient(CbsClientConfiguration cbsClientConfiguration) {
        return CbsClientFactory.createCbsClient(cbsClientConfiguration);
    }

    /**
     * Parse configuration.
     *
     * @param jsonObject the TCA service's configuration
     * @return this
     *
     */
    public String parseTcaConfig(JsonObject jsonObject) {

        JsonElement jsonConfig = jsonObject.get(ConfigBindingServiceConstants.CONFIG);

        Optional<String> configServiceJsonOptional = Optional.of(jsonConfig.toString());

        // convert fetch config binding service json string to Map of property key and
        // values
        Map<String, Object> configPropertiesMap = configServiceJsonOptional
                .map(new JsonStringToMapFunction(configServicePropertiesKey)).orElse(Collections.emptyMap());

        if (configPropertiesMap.isEmpty()) {

            logger.warn("No properties found in config binding service");

        } else {

            // remove config service key prefix on spring reserved property key prefixes
            final Set<String> springKeyPrefixes =
                    ConfigBindingServiceConstants.getSpringReservedPropertiesKeyPrefixes();
            final Set<String> springKeys = springKeyPrefixes.stream()
                    .map(springKeyPrefix -> configServicePropertiesKey + "." + springKeyPrefix)
                    .collect(Collectors.toSet());

            filterKeyMap = configPropertiesMap.entrySet().stream()
                    .collect(Collectors.toMap((Map.Entry<String, Object> e) -> springKeys.stream()
                            .anyMatch(springKey -> e.getKey().startsWith(springKey))
                                    ? e.getKey().substring(configServicePropertiesKey.toCharArray().length + 1)
                                    : e.getKey(),
                            Map.Entry::getValue));

            filterKeyMap.forEach((key, value) -> logger
                    .info("Adding property from config service in spring context: {} -> {}", key, value));
            MutablePropertySources sources = env.getPropertySources();
            addJsonPropertySource(sources, new MapPropertySource(configServicePropertiesKey, filterKeyMap));

        }
        return configServiceJsonOptional.get();
    }

}