The Ethereum service to manage accounts

eth.service.ts

import { Injectable, Inject } from '@angular/core';
// Web3
import { WEB3 } from './tokens';
import Web3 from 'web3';

// RXJS
import { Observable } from 'rxjs/Observable';
import { bindNodeCallback } from 'rxjs/observable/bindNodeCallback';
import { of } from 'rxjs/observable/of';
import { map, tap, catchError } from 'rxjs/operators';

@Injectable()
export class AccountsService {

    constructor(@Inject(WEB3) private web3: Web3) { }

    /** Returns all accounts available */
    public getAccounts(): Observable<string[]> {
        return bindNodeCallback(this.web3.eth.getAccounts)();
    }

    /** Get the current account */
    public currentAccount(): Observable<string | Error> {
        if (this.web3.eth.defaultAccount) {
            return of(this.web3.eth.defaultAccount);
        } else {
            return this.getAccounts().pipe(
                tap((accounts: string[]) => {
                    if (accounts.length === 0) { throw new Error('No accounts available'); }
                }),
                map((accounts: string[]) => accounts[0]),
                tap((account: string) => this.web3.defaultAccount = account),
                catchError((err: Error) => of(err))
            );
        }
    }
}