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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */
package org.apache.camel.health;

import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Map;
import java.util.Optional;
import java.util.function.Function;
import java.util.stream.Collectors;

import org.apache.camel.CamelContext;
import org.apache.camel.util.ObjectHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Helper for invoking {@link HealthCheck}'s.
 *
 * The helper will lookup the {@link HealthCheckRegistry} from {@link CamelContext} and gather all the registered
 * {@link HealthCheck}s and invoke them and gather their responses.
 *
 * The helper allows to filter out unwanted health checks using {@link HealthCheckFilter} or to invoke only readiness or
 * liveness checks.
 */
public final class HealthCheckHelper {
    private static final Logger LOGGER = LoggerFactory.getLogger(HealthCheckHelper.class);

    private HealthCheckHelper() {
    }

    /**
     * Get the group of the given check or an empty string if the group is not set.
     *
     * @param  check the health check
     * @return       the {@link HealthCheck#getGroup()} or an empty string if it is null
     */
    public static String getGroup(HealthCheck check) {
        return ObjectHelper.supplyIfEmpty(check.getGroup(), () -> "");
    }

    /**
     * Invokes the checks and returns a collection of results.
     */
    public static Collection invoke(CamelContext camelContext) {
        return invoke(camelContext, check -> Collections.emptyMap(), check -> false);
    }

    /**
     * Invokes the readiness checks and returns a collection of results.
     */
    public static Collection invokeReadiness(CamelContext camelContext) {
        return invoke(camelContext, check -> Collections.emptyMap(), check -> !check.isReadiness());
    }

    /**
     * Invokes the liveness checks and returns a collection of results.
     */
    public static Collection invokeLiveness(CamelContext camelContext) {
        return invoke(camelContext, check -> Collections.emptyMap(), check -> !check.isLiveness());
    }

    /**
     * Invokes the checks and returns a collection of results.
     */
    public static Collection invoke(
            CamelContext camelContext,
            Function> optionsSupplier) {

        return invoke(camelContext, optionsSupplier, check -> false);
    }

    /**
     * Invokes the checks and returns a collection of results.
     */
    public static Collection invoke(
            CamelContext camelContext,
            HealthCheckFilter filter) {

        return invoke(camelContext, check -> Collections.emptyMap(), filter);
    }

    /**
     * Invokes the checks and returns a collection of results.
     *
     * @param camelContext    the camel context.
     * @param optionsSupplier a supplier for options.
     * @param filter          filter to exclude some checks.
     */
    public static Collection invoke(
            CamelContext camelContext,
            Function> optionsSupplier,
            HealthCheckFilter filter) {

        final HealthCheckRegistry registry = HealthCheckRegistry.get(camelContext);

        if (registry != null) {
            // If no health check service is defined, this endpoint invokes the
            // check one by one.
            return registry.stream()
                    .collect(Collectors.groupingBy(HealthCheckHelper::getGroup))
                    .entrySet().stream()
                    .map(Map.Entry::getValue)
                    .flatMap(Collection::stream)
                    .filter(check -> !filter.test(check))
                    .sorted(Comparator.comparingInt(HealthCheck::getOrder))
                    .distinct()
                    .map(check -> check.call(optionsSupplier.apply(check)))
                    .collect(Collectors.toList());
        } else {
            LOGGER.debug("No health check source found");
        }

        return Collections.emptyList();
    }

    /**
     * Query the status of a check by id. Note that this may result in an effective invocation of the
     * {@link HealthCheck}.
     *
     * @param  camelContext the camel context.
     * @param  id           the check id.
     * @param  options      the check options.
     * @return              an optional {@link HealthCheck.Result}.
     */
    public static Optional query(CamelContext camelContext, String id, Map options) {
        final HealthCheckRegistry registry = HealthCheckRegistry.get(camelContext);

        if (registry != null) {
            return registry.getCheck(id).map(check -> check.call(options));
        } else {
            LOGGER.debug("No health check source found");
        }

        return Optional.empty();
    }

    /**
     * Invoke a check by id.
     *
     * @param  camelContext the camel context.
     * @param  id           the check id.
     * @param  options      the check options.
     * @return              an optional {@link HealthCheck.Result}.
     */
    public static Optional invoke(CamelContext camelContext, String id, Map options) {
        final HealthCheckRegistry registry = HealthCheckRegistry.get(camelContext);

        if (registry != null) {
            return registry.getCheck(id).map(check -> check.call(options));
        } else {
            LOGGER.debug("No health check source found");
        }

        return Optional.empty();
    }
}