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package org.zodic.kubernetes.leader;

import io.fabric8.kubernetes.api.model.ConfigMap;
import io.fabric8.kubernetes.client.KubernetesClient;
import io.fabric8.kubernetes.client.Watch;
import io.fabric8.kubernetes.client.Watcher;
import io.fabric8.kubernetes.client.WatcherException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class LeaderRecordWatcher implements Watcher {

    private static final Logger LOGGER = LoggerFactory.getLogger(LeaderRecordWatcher.class);

    private final Object lock = new Object();

    private final LeadershipController leadershipController;

    private final LeaderInfo leaderInfo;

    private final KubernetesClient kubernetesClient;

    private Watch watch;

    public LeaderRecordWatcher(LeaderInfo leaderInfo, LeadershipController leadershipController,
        KubernetesClient kubernetesClient) {
        this.leadershipController = leadershipController;
        this.leaderInfo = leaderInfo;
        this.kubernetesClient = kubernetesClient;
    }

    public void start() {
        if (this.watch == null) {
            synchronized (this.lock) {
                if (this.watch == null) {
                    LOGGER.debug("Starting leader record watcher");
                    this.watch = this.kubernetesClient.configMaps()
                        .inNamespace(this.leaderInfo.getNamespace(this.kubernetesClient.getNamespace()))
                        .withName(this.leaderInfo.getConfigMapName()).watch(this);
                }
            }
        }
    }

    public void stop() {
        if (this.watch != null) {
            synchronized (this.lock) {
                if (this.watch != null) {
                    LOGGER.debug("Stopping leader record watcher");
                    this.watch.close();
                    this.watch = null;
                }
            }
        }
    }

    @Override
    public void eventReceived(Action action, ConfigMap configMap) {
        LOGGER.debug("'{}' event received, triggering leadership update", action);

        if (!Action.ERROR.equals(action)) {
            this.leadershipController.update();
        }
    }

    @Override
    public void onClose(WatcherException cause) {
        if (cause != null) {
            synchronized (this.lock) {
                LOGGER.warn("Watcher stopped unexpectedly, will restart", cause);
                this.watch = null;
                start();
            }
        }
    }

}