# All files / microservices/server server-grpc.ts

88% Statements 66/75
75% Branches 12/16
91.3% Functions 21/23
87.5% Lines 63/72

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     import { fromEvent } from 'rxjs';
    import { takeUntil } from 'rxjs/operators';
    import { CANCEL_EVENT, GRPC_DEFAULT_URL } from '../constants';
    import { InvalidGrpcPackageException } from '../exceptions/errors/invalid-grpc-package.exception';
    import { InvalidProtoDefinitionException } from '../exceptions/errors/invalid-proto-definition.exception';
    import { CustomTransportStrategy } from '../interfaces';
    import {
      GrpcOptions,
      MicroserviceOptions,
    } from '../interfaces/microservice-configuration.interface';
    import { Server } from './server';

    let grpcPackage: any = {};
    let grpcProtoLoaderPackage: any = {};

    export class ServerGrpc extends Server implements CustomTransportStrategy {
      private readonly url: string;
      private grpcClient: any;

      constructor(private readonly options: MicroserviceOptions['options']) {
        super();
        this.url =
          this.getOptionsProp<GrpcOptions>(options, 'url') || GRPC_DEFAULT_URL;

        grpcPackage = this.loadPackage('grpc', ServerGrpc.name);
        grpcProtoLoaderPackage = this.loadPackage(
          '@grpc/proto-loader',
          ServerGrpc.name,
        );
      }

      public async listen(callback: () => void) {
        this.grpcClient = this.createClient();
        await this.start(callback);
      }

      public async start(callback?: () => void) {
        await this.bindEvents();
        this.grpcClient.start();
        callback();
      }

      public async bindEvents() {
        const grpcContext = this.loadProto();
        const packageName = this.getOptionsProp<GrpcOptions>(
          this.options,
          'package',
        );
        const grpcPkg = this.lookupPackage(grpcContext, packageName);
        if (!grpcPkg) {
          const invalidPackageError = new InvalidGrpcPackageException();
          this.logger.error(invalidPackageError.message, invalidPackageError.stack);
          throw invalidPackageError;
        }
        for (const name of this.getServiceNames(grpcPkg)) {
          this.grpcClient.addService(
            grpcPkg[name].service,
            await this.createService(grpcPkg[name], name),
          );
        }
      }

      public getServiceNames(grpcPkg: any) {
        return Object.keys(grpcPkg).filter(name => grpcPkg[name].service);
      }

      public async createService(grpcService: any, name: string) {
        const service = {};

        // tslint:disable-next-line:forin
        for (const methodName in grpcService.prototype) {
          const methodHandler = this.messageHandlers[
            this.createPattern(name, methodName)
          ];
          if (!methodHandler) {
            continue;
          }
          service[methodName] = await this.createServiceMethod(
            methodHandler,
            grpcService.prototype[methodName],
          );
        }
        return service;
      }

      public createPattern(service: string, methodName: string): string {
        return JSON.stringify({
          service,
          rpc: methodName,
        });
      }

      public createServiceMethod(
        methodHandler: Function,
        protoNativeHandler: any,
      ): Function {
        return protoNativeHandler.responseStream
          ? this.createStreamServiceMethod(methodHandler)
          : this.createUnaryServiceMethod(methodHandler);
      }

      public createUnaryServiceMethod(methodHandler): Function {
        return async (call, callback) => {
          const handler = methodHandler(call.request, call.metadata);
          this.transformToObservable(await handler).subscribe(
            data => callback(null, data),
            err => callback(err),
          );
        };
      }

      public createStreamServiceMethod(methodHandler): Function {
        return async (call, callback) => {
          const handler = methodHandler(call.request, call.metadata);
          const result$ = this.transformToObservable(await handler);
          await result$
            .pipe(takeUntil(fromEvent(call, CANCEL_EVENT)))
            .forEach(data => call.write(data));
          call.end();
        };
      }

      public close() {
        this.grpcClient && this.grpcClient.forceShutdown();
        this.grpcClient = null;
      }

      public deserialize(obj): any {
        try {
          return JSON.parse(obj);
        } catch (e) {
          return obj;
        }
      }

      public createClient(): any {
        const server = new grpcPackage.Server();
        const credentials = this.getOptionsProp<GrpcOptions>(
          this.options,
          'credentials',
        );
        server.bind(
          this.url,
          credentials || grpcPackage.ServerCredentials.createInsecure(),
        );
        return server;
      }

      public lookupPackage(root: any, packageName: string) {
        /** Reference: https://github.com/kondi/rxjs-grpc */
        let pkg = root;
        for (const name of packageName.split(/\./)) {
          pkg = pkg[name];
        }
        return pkg;
      }

      public loadProto(): any {
        try {
          const file = this.getOptionsProp<GrpcOptions>(this.options, 'protoPath');
          const loader = this.getOptionsProp<GrpcOptions>(this.options, 'loader');

          const packageDefinition = grpcProtoLoaderPackage.loadSync(file, loader);
          const packageObject = grpcPackage.loadPackageDefinition(
            packageDefinition,
          );
          return packageObject;
        } catch (err) {
          const invalidProtoError = new InvalidProtoDefinitionException();
          const message =
            err && err.message ? err.message : invalidProtoError.message;

          this.logger.error(message, invalidProtoError.stack);
          throw invalidProtoError;
        }
      }
    }