# All files / microservices/client client-mqtt.ts

90.74% Statements 49/54
81.25% Branches 13/16
87.5% Functions 14/16
90.74% Lines 49/54

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     import { Logger } from '@nestjs/common/services/logger.service';
    import { loadPackage } from '@nestjs/common/utils/load-package.util';
    import { fromEvent, merge, Observable } from 'rxjs';
    import { first, map, share, tap } from 'rxjs/operators';
    import {
      CLOSE_EVENT,
      ERROR_EVENT,
      MESSAGE_EVENT,
      MQTT_DEFAULT_URL,
    } from '../constants';
    import { MqttClient } from '../external/mqtt-client.interface';
    import { MqttOptions, PacketId, ReadPacket, WritePacket } from '../interfaces';
    import { ClientOptions } from '../interfaces/client-metadata.interface';
    import { ClientProxy } from './client-proxy';
    import { ECONNREFUSED } from './constants';

    let mqttPackage: any = {};

    export class ClientMqtt extends ClientProxy {
      protected readonly logger = new Logger(ClientProxy.name);
      protected readonly url: string;
      protected mqttClient: MqttClient;
      protected connection: Promise<any>;

      constructor(protected readonly options: ClientOptions['options']) {
        super();
        this.url =
          this.getOptionsProp<MqttOptions>(this.options, 'url') || MQTT_DEFAULT_URL;

        mqttPackage = loadPackage('mqtt', ClientMqtt.name);
      }
      public getAckPatternName(pattern: string): string {
        return `${pattern}_ack`;
      }

      public getResPatternName(pattern: string): string {
        return `${pattern}_res`;
      }

      public close() {
        this.mqttClient && this.mqttClient.end();
        this.mqttClient = null;
        this.connection = null;
      }

      public connect(): Promise<any> {
        Iif (this.mqttClient) {
          return this.connection;
        }
        this.mqttClient = this.createClient();
        this.handleError(this.mqttClient);

        const connect$ = this.connect$(this.mqttClient);
        this.connection = this.mergeCloseEvent(this.mqttClient, connect$)
          .pipe(
            tap(() =>
              this.mqttClient.on(MESSAGE_EVENT, this.createResponseCallback()),
            ),
            share(),
          )
          .toPromise();
        return this.connection;
      }

      public mergeCloseEvent<T = any>(
        instance: MqttClient,
        source$: Observable<T>,
      ): Observable<T> {
        const close$ = fromEvent(instance, CLOSE_EVENT).pipe(
          map(err => {
            throw err;
          }),
        );
        return merge(source$, close$).pipe(first());
      }

      public createClient(): MqttClient {
        return mqttPackage.connect(this.url, this.options as MqttOptions);
      }

      public handleError(client: MqttClient) {
        client.addListener(
          ERROR_EVENT,
          err => err.code !== ECONNREFUSED && this.logger.error(err),
        );
      }

      public createResponseCallback(): (channel: string, buffer) => any {
        return (channel: string, buffer: Buffer) => {
          const { err, response, isDisposed, id } = JSON.parse(
            buffer.toString(),
          ) as WritePacket & PacketId;

          const callback = this.routingMap.get(id);
          Iif (!callback) {
            return undefined;
          }
          if (isDisposed || err) {
            return callback({
              err,
              response: null,
              isDisposed: true,
            });
          }
          callback({
            err,
            response,
          });
        };
      }

      protected publish(
        partialPacket: ReadPacket,
        callback: (packet: WritePacket) => any,
      ): Function {
        try {
          const packet = this.assignPacketId(partialPacket);
          const pattern = this.normalizePattern(partialPacket.pattern);
          const responseChannel = this.getResPatternName(pattern);

          this.mqttClient.subscribe(responseChannel, err => {
            Iif (err) {
              return;
            }
            this.routingMap.set(packet.id, callback);
            this.mqttClient.publish(
              this.getAckPatternName(pattern),
              JSON.stringify(packet),
            );
          });
          return () => {
            this.mqttClient.unsubscribe(responseChannel);
            this.routingMap.delete(packet.id);
          };
        } catch (err) {
          callback({ err });
        }
      }
    }