/*
 * 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.Optional;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import org.apache.camel.CamelContext;
import org.apache.camel.CamelContextAware;
import org.apache.camel.StaticService;
import org.apache.camel.spi.IdAware;
import org.apache.camel.util.ObjectHelper;

/**
 * A registry for health checks.
 */
public interface HealthCheckRegistry extends CamelContextAware, StaticService, IdAware {

    /**
     * Service factory key.
     */
    String FACTORY = "health-check-registry";

    /**
     * Whether Health Check is enabled globally
     */
    boolean isEnabled();

    /**
     * Whether Health Check is enabled globally
     */
    void setEnabled(boolean enabled);

    /**
     * Resolves {@link HealthCheck} or {@link HealthCheckRepository} by id.
     *
     * Will first lookup in this {@link HealthCheckRegistry} and then {@link org.apache.camel.spi.Registry},
     * and lastly do classpath scanning via {@link org.apache.camel.spi.annotations.ServiceFactory}.
     * The classpath scanning is attempted first with id-health-check or id-health-check-repository as the key,
     * and then with id as fallback if not found the first time.
     *
     * @return either {@link HealthCheck} or {@link HealthCheckRepository}, or <tt>null</tt> if none found.
     */
    Object resolveById(String id);

    /**
     * Registers a {@link HealthCheck} or {@link HealthCheckRepository}.
     */
    boolean register(Object obj);

    /**
     * Unregisters a {@link HealthCheck} or {@link HealthCheckRepository}.
     */
    boolean unregister(Object obj);

    /**
     * A collection of health check IDs.
     */
    default Collection<String> getCheckIDs() {
        return stream()
            .map(HealthCheck::getId)
            .collect(Collectors.toList());
    }

    /**
     * Returns the check identified by the given <code>id</code> if available.
     */
    default Optional<HealthCheck> getCheck(String id) {
        return stream()
            .filter(r -> ObjectHelper.equal(r.getId(), id) || ObjectHelper.equal(r.getId().replace("-health-check", ""), id))
            .findFirst();
    }

    /**
     * Returns the repository identified by the given <code>id</code> if available.
     */
    Optional<HealthCheckRepository> getRepository(String id);

    /**
     * Returns an optional {@link HealthCheckRegistry}, by default no registry is
     * present and it must be explicit activated. Components can register/unregister
     * health checks in response to life-cycle events (i.e. start/stop).
     *
     * This registry is not used by the camel context but it is up to the impl to
     * properly use it, i.e.
     *
     * - a RouteController could use the registry to decide to restart a route
     *   with failing health checks
     * - spring boot could integrate such checks within its health endpoint or
     *   make it available only as separate endpoint.
     */
    static HealthCheckRegistry get(CamelContext context) {
        return context.getExtension(HealthCheckRegistry.class);
    }

    /**
     * Returns a sequential {@code Stream} with the known {@link HealthCheck}
     * as its source.
     */
    Stream<HealthCheck> stream();
}
