@parity/api/src/pubsub/pubsub.js

The Parity Promise-based API library for interfacing with Ethereum over RPC

// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity.

// Parity is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity.  If not, see <http://www.gnu.org/licenses/>.

const Eth = require('./eth');
const Parity = require('./parity');
const Net = require('./net');
const Signer = require('./signer');

const { isFunction } = require('../util/types');

class PubSub {
  constructor (provider) {
    if (!provider || !isFunction(provider.subscribe)) {
      throw new Error('Pubsub API needs transport with subscribe() function defined. (WebSocket)');
    }

    this._eth = new Eth(provider);
    this._net = new Net(provider);
    this._parity = new Parity(provider);
    this._signer = new Signer(provider);
  }

  get net () {
    return this._net;
  }

  get eth () {
    return this._eth;
  }

  get parity () {
    return this._parity;
  }

  get signer () {
    return this._signer;
  }

  unsubscribe (subscriptionIds) {
    // subscriptions are namespace independent. Thus we can simply removeListener from any.
    return this._parity.removeListener(subscriptionIds);
  }

  subscribeAndGetResult (f, callback) {
    return new Promise((resolve, reject) => {
      let isFirst = true;
      let onSubscription = (error, data) => {
        const p1 = error ? Promise.reject(error) : Promise.resolve(data);
        const p2 = p1.then(callback);

        if (isFirst) {
          isFirst = false;
          p2
            .then(resolve)
            .catch(reject);
        }
      };

      try {
        f.call(this, onSubscription).catch(reject);
      } catch (err) {
        reject(err);
      }
    });
  }
}

module.exports = PubSub;