openethereum/js/src/util/subscribe-to-events.js

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// Copyright 2015-2017 Parity Technologies (UK) Ltd.
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// 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/>.
import EventEmitter from 'eventemitter3';
const defaults = {
from: 0,
to: 'latest',
interval: 5000,
filter: () => true
};
const subscribeToEvents = (contract, events, opt = {}) => {
const { api } = contract;
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opt = Object.assign({}, defaults, opt);
let filter = null;
let interval = null;
const unsubscribe = () => {
if (filter) {
filter
.then((filterId) => {
return api.eth.uninstallFilter(filterId);
})
.catch((err) => {
emitter.emit('error', err);
});
filter = null;
}
if (interval) {
clearInterval(interval);
interval = null;
}
};
const emitter = new EventEmitter();
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emitter.unsubscribe = unsubscribe;
const fetcher = (method, filterId) => () => {
api
.eth[method](filterId)
.then((logs) => {
logs = contract.parseEventLogs(logs);
for (let log of logs) {
if (opt.filter(log)) {
emitter.emit('log', log);
emitter.emit(log.event, log);
}
}
})
.catch((err) => {
emitter.emit('error', err);
});
};
const signatures = events
.filter((event) => contract.instance[event])
.map((event) => contract.instance[event].signature);
filter = api.eth
.newFilter({
fromBlock: opt.from, toBlock: opt.to,
address: contract.address,
topics: [signatures]
})
.then((filterId) => {
fetcher('getFilterLogs', filterId)(); // fetch immediately
const fetchChanges = fetcher('getFilterChanges', filterId);
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interval = setInterval(fetchChanges, opt.interval);
return filterId;
})
.catch((err) => {
emitter.emit('error', err);
throw err; // reject Promise
});
return emitter;
};
export default subscribeToEvents;