// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.container.handler;

import com.yahoo.component.annotation.Inject;
import com.yahoo.component.AbstractComponent;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

/**
 * A component which tracks the up/down status of any clusters which should influence
 * the up down status of this container itself, as well as the separate fact (from config)
 * that such clusters are present. This is a separate fact because we might know we have clusters configured,
 * but we don't have positive information that they are up yet, and in this case we should be down.
 *
 * This is a separate component which has <b>no dependencies</b> such that the status tracked in this
 * will survive reconfiguration events and inform other components even immediately after a reconfiguration
 * (where the true statue of clusters may not yet be available).
 *
 * This is multithread safe.
 *
 * @author bratseth
 */
public class ClustersStatus extends AbstractComponent {

    // NO DEPENDENCIES: Do not add dependencies here
    @Inject
    public ClustersStatus() { }

    public enum Require {ONE, ALL}

    /** Are there any (in-service influencing) clusters in this container? */
    private boolean containerHasClusters;

    private final Object mutex = new Object();

    /** The status of clusters, when known. Note that clusters may exist for which there is no knowledge yet. */
    private final Map<String, Boolean> clusterStatus = new HashMap<>();

    /** Sets the current clusters of this container */
    public void setClusters(Set<String> clusters) {
        synchronized (mutex) {
            this.containerHasClusters = clusters.size() > 0;
            for (Iterator<String> i = clusterStatus.keySet().iterator(); i.hasNext(); ) {
                String existingCluster = i.next();
                if ( ! clusters.contains(existingCluster))
                    i.remove(); // forget clusters which was configured away
            }
        }
    }

    void setUp(String clusterIdentifier) {
        synchronized (mutex) {
            clusterStatus.put(clusterIdentifier, Boolean.TRUE);
        }
    }

    void setDown(String clusterIdentifier) {
        synchronized (mutex) {
            clusterStatus.put(clusterIdentifier, Boolean.FALSE);
        }
    }

    /**
     *  Returns whether this container should receive traffic based on the state of this
     *
     *  @param require requirement for being up, ALL or ONE.
     */
    public boolean containerShouldReceiveTraffic(Require require) {
        synchronized (mutex) {
            if (containerHasClusters) {
                switch (require) {
                    case ONE:
                        // Should receive traffic when at least one cluster is up
                        return clusterStatus.values().stream().anyMatch(status -> status == true);
                    case ALL:
                    default:
                        return !clusterStatus.isEmpty() && clusterStatus.values().stream().allMatch(status -> status == true);
                }
            }
            else {
                return true;
            }
        }
    }

}