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'use strict';
/*! * Module dependencies. */
const EventEmitter = require('events').EventEmitter;
/*! * ignore */
class ChangeStream extends EventEmitter {  constructor(changeStreamThunk, pipeline, options) {    super();
    this.driverChangeStream = null;    this.closed = false;    this.bindedEvents = false;    this.pipeline = pipeline;    this.options = options;
    if (options && options.hydrate && !options.model) {      throw new Error(        'Cannot create change stream with `hydrate: true` ' +        'unless calling `Model.watch()`'      );    }
    // This wrapper is necessary because of buffering.    changeStreamThunk((err, driverChangeStream) => {      if (err != null) {        this.emit('error', err);        return;      }
      this.driverChangeStream = driverChangeStream;      this.emit('ready');    });  }
  _bindEvents() {    if (this.bindedEvents) {      return;    }
    this.bindedEvents = true;
    if (this.driverChangeStream == null) {      this.once('ready', () => {        this.driverChangeStream.on('close', () => {          this.closed = true;        });
        ['close', 'change', 'end', 'error'].forEach(ev => {          this.driverChangeStream.on(ev, data => {            if (data != null && data.fullDocument != null && this.options && this.options.hydrate) {              data.fullDocument = this.options.model.hydrate(data.fullDocument);            }            this.emit(ev, data);          });        });      });
      return;    }
    this.driverChangeStream.on('close', () => {      this.closed = true;    });
    ['close', 'change', 'end', 'error'].forEach(ev => {      this.driverChangeStream.on(ev, data => {        this.emit(ev, data);      });    });  }
  hasNext(cb) {    return this.driverChangeStream.hasNext(cb);  }
  next(cb) {    if (this.options && this.options.hydrate) {      if (cb != null) {        const originalCb = cb;        cb = (err, data) => {          if (err != null) {            return originalCb(err);          }          if (data.fullDocument != null) {            data.fullDocument = this.options.model.hydrate(data.fullDocument);          }          return originalCb(null, data);        };      }
      let maybePromise = this.driverChangeStream.next(cb);      if (maybePromise && typeof maybePromise.then === 'function') {        maybePromise = maybePromise.then(data => {          if (data.fullDocument != null) {            data.fullDocument = this.options.model.hydrate(data.fullDocument);          }          return data;        });      }      return maybePromise;    }
    return this.driverChangeStream.next(cb);  }
  on(event, handler) {    this._bindEvents();    return super.on(event, handler);  }
  once(event, handler) {    this._bindEvents();    return super.once(event, handler);  }
  _queue(cb) {    this.once('ready', () => cb());  }
  close() {    this.closed = true;    if (this.driverChangeStream) {      this.driverChangeStream.close();    }  }}
/*! * ignore */
module.exports = ChangeStream;