Holochain websocket's wrapper as an Angular service (original code in https://github.com/holochain/hc-web-client)

holochain.service.ts

import { Injectable } from '@angular/core';
import { Client } from 'rpc-websockets';

export const connect = url =>
  new Promise((fulfill, reject) => {
    const ws = new Client(url);
    ws.on('open', () => {
      const call = (dnaHash, zome, capability, func) => params => {
        return ws.call(`${dnaHash}/${zome}/${capability}/${func}`, params);
      };
      const close = ws.close;
      fulfill({ call, close, ws });
    });
  });

@Injectable({
  providedIn: 'root'
})
export class HolochainService {
  protected _call;

  constructor() {}

  /**
   * Necessary initialize function
   * @param url
   * @param dna
   * @param capabilities
   */
  public init(url: string, dna: string, zome: string, capabilities: string) {
    connect(url)
      .then(
        ({ call }) =>
          (this._call = function_name =>
            call(dna, zome, capabilities, function_name))
      )
      .catch(console.error);
  }
  
  /**
   * Generic call function to any method of the DNA
   * @param function_name
   * @param data
   */
  public call(function_name: string, data: any): Promise<any> {
    return this._call(function_name)(data);
  }
}