import {
  CollectionChangeInfo,
  INotifyCollectionChanged,
  ObservableCollection,
  ReflectionHelper,
} from '@mobilize/wms-framework';

/*****************************************************************************
 * Copyright (C) Mobilize.Net <info@mobilize.net> - All Rights Reserved
 *
 * This file is part of the Mobilize Frameworks, which is
 * proprietary and confidential.
 *
 * NOTICE:  All information contained herein is, and remains
 * the property of Mobilize.Net Corporation.
 * The intellectual and technical concepts contained herein are
 * proprietary to Mobilize.Net Corporation and may be covered
 * by U.S. Patents, and are protected by trade secret or copyright law.
 * Dissemination of this information or reproduction of this material
 * is strictly forbidden unless prior written permission is obtained
 * from Mobilize.Net Corporation.
 ******************************************************************************/

/**
 * Provides a helper class that listens for changes a collection that implements {@INotifyCollectionChanged}.  Helper
 * is responsible for keeping track of the registered handler so it can be removed later.
 * Usage is very simple:
 * <ul>
 *  <li>Create a new instance of {@link NotifyCollectionChangedHandler} and set the handler to take action when
 * collection changes </li>
 *  <li>Call the {@link NotifyCollectionChangedHandler#trackCollection} method with the collection to listen
 * changes for.</li>
 * <li>Call the {@link NotifyCollectionChangedHandler#cleaup} method when finishing (on ngDestroy for instance)
 * </ul>
 *
 */
export class NotifyCollectionChangedHandler {
  private collectionHandler: any;
  private collection: INotifyCollectionChanged;

  /**
   * Creates an instance of NotifyCollectionChangedHandler.
   * @param {(e: any, args: CollectionChangeInfo) => void} handler the handler to be called when the collection
   * content changes
   * @memberof NotifyCollectionChangedHandler
   */
  constructor(private handler: (e: any, args: CollectionChangeInfo) => void) {}

  /**
   * Cleans up this instance by removing current attached handler from tracked collection.
   *
   * @memberof NotifyCollectionChangedHandler
   */
  cleanup() {
    if (this.collection && this.collectionHandler) {
      this.collection.CollectionChanged.removeHandler(this.collectionHandler);
      this.collectionHandler = undefined;
    }
  }

  /**
   * Tracks the given collection, once called this method the changes on the new collection will be
   * notified.<p>
   * If a previous collection was being tracked then it gets clean up.
   *
   * @param {*} newCollection
   * @memberof NotifyCollectionChangedHandler
   */
  trackCollection(newCollection: any) {
    this.cleanup();
    /* istanbul ignore else */
    if (this.isINotifyCollection(newCollection)) {
      this.collection = newCollection;
      this.collectionHandler = this.collection.CollectionChanged.addHandler(
        this.handler
      );
    }
  }

  private isINotifyCollection(value: any) {
    return (
      value &&
      (value instanceof ObservableCollection ||
        ReflectionHelper.isInterfaceIsSupported(
          value,
          'System.Collections.Specialized.INotifyCollectionChanged'
        ))
    );
  }
}