/*
 * Copyright 2014-2018 the original author or authors.
 *
 * 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.
 */

package de.codecentric.boot.admin.client.registration;

import java.time.Duration;
import java.util.concurrent.ScheduledFuture;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.boot.context.event.ApplicationReadyEvent;
import org.springframework.context.event.ContextClosedEvent;
import org.springframework.context.event.EventListener;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;

/**
 * Listener responsible for starting and stopping the registration task when the application is
 * ready.
 *
 * @author Johannes Edmeier
 */
public class RegistrationApplicationListener implements InitializingBean, DisposableBean {
    private static final Logger LOGGER = LoggerFactory.getLogger(RegistrationApplicationListener.class);
    private final ApplicationRegistrator registrator;
    private final ThreadPoolTaskScheduler taskScheduler;
    private boolean autoDeregister = false;
    private boolean autoRegister = true;
    private Duration registerPeriod = Duration.ofSeconds(10);
    private volatile ScheduledFuture<?> scheduledTask;

    public RegistrationApplicationListener(ApplicationRegistrator registrator) {
        this(registrator, registrationTaskScheduler());
    }

    private static ThreadPoolTaskScheduler registrationTaskScheduler() {
        ThreadPoolTaskScheduler taskScheduler = new ThreadPoolTaskScheduler();
        taskScheduler.setPoolSize(1);
        taskScheduler.setRemoveOnCancelPolicy(true);
        taskScheduler.setThreadNamePrefix("registrationTask");
        return taskScheduler;
    }

    RegistrationApplicationListener(ApplicationRegistrator registrator, ThreadPoolTaskScheduler taskScheduler) {
        this.registrator = registrator;
        this.taskScheduler = taskScheduler;
    }

    @EventListener
    @Order(Ordered.LOWEST_PRECEDENCE)
    public void onApplicationReady(ApplicationReadyEvent event) {
        if (autoRegister) {
            startRegisterTask();
        }
    }

    @EventListener
    @Order(Ordered.LOWEST_PRECEDENCE)
    public void onClosedContext(ContextClosedEvent event) {
        if (event.getApplicationContext().getParent() == null ||
            "bootstrap".equals(event.getApplicationContext().getParent().getId())) {
            stopRegisterTask();

            if (autoDeregister) {
                registrator.deregister();
            }
        }
    }

    public void startRegisterTask() {
        if (scheduledTask != null && !scheduledTask.isDone()) {
            return;
        }

        scheduledTask = taskScheduler.scheduleAtFixedRate(registrator::register, registerPeriod);
        LOGGER.debug("Scheduled registration task for every {}ms", registerPeriod);
    }

    public void stopRegisterTask() {
        if (scheduledTask != null && !scheduledTask.isDone()) {
            scheduledTask.cancel(true);
            LOGGER.debug("Canceled registration task");
        }
    }

    public void setAutoDeregister(boolean autoDeregister) {
        this.autoDeregister = autoDeregister;
    }

    public void setAutoRegister(boolean autoRegister) {
        this.autoRegister = autoRegister;
    }

    public void setRegisterPeriod(Duration registerPeriod) {
        this.registerPeriod = registerPeriod;
    }

    @Override
    public void afterPropertiesSet() {
        taskScheduler.afterPropertiesSet();
    }

    @Override
    public void destroy() {
        taskScheduler.destroy();
    }
}
