/*
 * Copyright 2006-2019 DLR, Germany
 * 
 * SPDX-License-Identifier: EPL-1.0
 * 
 * https://rcenvironment.de/
 */

package de.rcenvironment.core.communication.management;

import java.util.Set;

import de.rcenvironment.core.communication.common.InstanceNodeSessionId;
import de.rcenvironment.core.communication.spi.NetworkTopologyChangeListener;

/**
 * Reports changes to the set of reachable nodes that have declared themselves to be "workflow hosts".
 * 
 * @author Robert Mischke
 */
// FIXME temporary package location to simplify migration; move to "de.rcenvironment.core.component.workflow.spi"
// when complete - misc_ro
public interface WorkflowHostSetListener {

    /**
     * Reports a change to the set of reachable "workflow host" nodes. As a convenience, the difference to the previous state is provided as
     * well.
     * 
     * Typically, new listeners will receive a custom {@link #onReachableWorkflowHostsChanged()} callback on subscription that allows them
     * to easily initialize to the current observed state. From the listener's perspective, the call will contain parameters as if the last
     * observed set of nodes was empty, and all current nodes just became available.
     * 
     * Note that this listener interface is intentionally similar to {@link NetworkTopologyChangeListener}, as their behaviour is almost the
     * same, except that the sets reported by this listener have filtering applied to them.
     * 
     * @param reachableWfHosts the new set of reachable workflow host nodes
     * @param addedWfHosts workflow host nodes that have been added by this change
     * @param removedWfHosts workflow host nodes that have been removed by this change
     */
    void onReachableWorkflowHostsChanged(Set<InstanceNodeSessionId> reachableWfHosts, Set<InstanceNodeSessionId> addedWfHosts,
        Set<InstanceNodeSessionId> removedWfHosts);
}
