/*
 * Copyright (c) 2015 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.mdsal.binding.api;

import org.eclipse.jdt.annotation.NonNull;
import org.opendaylight.yangtools.concepts.Registration;
import org.opendaylight.yangtools.yang.binding.DataObject;

/**
 * A {@link BindingService} which allows users to register for changes to a subtree.
 */
public interface DataTreeChangeService extends BindingService {
    /**
     * Registers a {@link DataTreeChangeListener} to receive notifications when data changes under a given path in the
     * conceptual data tree.
     *
     * <p>
     * You are able to register for notifications  for any node or subtree which can be represented using
     * {@link DataTreeIdentifier}.
     *
     * <p>
     * You are able to register for data change notifications for a subtree or leaf even if it does not exist. You will
     * receive notification once that node is created.
     *
     * <p>
     * If there is any pre-existing data in the data tree for the path for which you are registering, you will receive
     * an initial data change event, which will contain all pre-existing data, marked as created.
     *
     * <p>
     * This method returns a {@link Registration} object. To "unregister" your listener for changes call the
     * {@link Registration#close()} method on the returned object.
     *
     * <p>
     * You MUST explicitly unregister your listener when you no longer want to receive
     * notifications. This is especially true in OSGi environments, where failure to
     * do so during bundle shutdown can lead to stale listeners being still registered.
     *
     * @param treeId Data tree identifier of the subtree which should be watched for changes
     * @param listener Listener instance which is being registered
     * @return a Registration object, which may be used to unregister your listener using {@link Registration#close()}
     *         to stop delivery of change events.
     */
    <T extends DataObject> @NonNull Registration registerDataTreeChangeListener(@NonNull DataTreeIdentifier<T> treeId,
        @NonNull DataTreeChangeListener<T> listener);

    /**
     * Registers a {@link DataTreeChangeListener} to receive
     * notifications when data changes under a given path in the conceptual data tree.
     *
     * <p>
     * You are able to register for notifications  for any node or subtree
     * which can be represented using {@link DataTreeIdentifier}.
     *
     * <p>
     * This method returns a {@link Registration} object. To
     * "unregister" your listener for changes call the {@link Registration#close()}
     * method on the returned object.
     *
     * <p>
     * You MUST explicitly unregister your listener when you no longer want to receive
     * notifications. This is especially true in OSGi environments, where failure to
     * do so during bundle shutdown can lead to stale listeners being still registered.
     * @implSpec This method provides {@link DataListenerAdapter} as listener during
     *      the registration of {@link DataTreeChangeListener}. This would allow users
     *      to know the last state of data instead of getting details about what changed
     *      in the entire tree.
     * @param treeId Data tree identifier of the subtree which should be watched for
     *            changes.
     * @param listener Listener instance which is being registered
     * @return Listener registration object, which may be used to unregister
     *         your listener using {@link Registration#close()} to stop
     *         delivery of change events.
     */
    default <T extends DataObject> @NonNull Registration registerDataListener(
            final @NonNull DataTreeIdentifier<T> treeId, final @NonNull DataListener<T> listener) {
        return registerDataTreeChangeListener(checkNotWildcard(treeId), new DataListenerAdapter<>(listener));
    }

    /**
     * Registers a {@link DataTreeChangeListener} to receive
     * notifications about the last data state when it changes under a given path in the conceptual data
     * tree.
     *
     * <p>
     * You are able to register for notifications  for any node or subtree
     * which can be represented using {@link DataTreeIdentifier}.
     *
     * <p>
     * This method returns a {@link Registration} object. To
     * "unregister" your listener for changes call the {@link Registration#close()}
     * method on the returned object.
     *
     * <p>
     * You MUST explicitly unregister your listener when you no longer want to receive
     * notifications. This is especially true in OSGi environments, where failure to
     * do so during bundle shutdown can lead to stale listeners being still registered.
     *
     * @implSpec This method provides {@link DataChangeListenerAdapter} as listener during
     *      the registration of {@link DataTreeChangeListener}, which provides a comparison
     *      of before-value and after-value.
     *
     * @param treeId Data tree identifier of the subtree which should be watched for
     *            changes.
     * @param listener Listener instance which is being registered
     * @return Listener registration object, which may be used to unregister
     *         your listener using {@link Registration#close()} to stop
     *         delivery of change events.
     */
    default <T extends DataObject> @NonNull Registration registerDataChangeListener(
            final @NonNull DataTreeIdentifier<T> treeId, final @NonNull DataChangeListener<T> listener) {
        return registerDataTreeChangeListener(checkNotWildcard(treeId), new DataChangeListenerAdapter<>(listener));
    }

    private static <T extends DataObject> @NonNull DataTreeIdentifier<T> checkNotWildcard(
            final DataTreeIdentifier<T> treeId) {
        final var instanceIdentifier = treeId.path();
        if (instanceIdentifier.isWildcarded()) {
            throw new IllegalArgumentException("Cannot register listener for wildcard " + instanceIdentifier);
        }
        return treeId;
    }
}