/*
This file is part of web3.js.
web3.js is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
web3.js 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with web3.js. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @file subscription.js
* @author Fabian Vogelsteller <fabian@ethereum.org>
* @date 2017
*/
"use strict";
var errors = require('web3-core-helpers').errors;
var EventEmitter = require('eventemitter3');
var formatters = require('web3-core-helpers').formatters;
function identity(value) { //used to return the exact same replica of the value given to it as the argument
return value;
}
function Subscription(options) {
EventEmitter.call(this);
this.id = null;
this.callback = identity;
this.arguments = null;
this.lastBlock = null; // "from" block tracker for backfilling events on reconnection
this.options = {
subscription: options.subscription,
type: options.type,
requestManager: options.requestManager
};
}
// INHERIT
Subscription.prototype = Object.create(EventEmitter.prototype);
Subscription.prototype.constructor = Subscription;
/**
* Should be used to extract callback from array of arguments. Modifies input param
*
* @method extractCallback
* @param {Array} arguments
* @return {Function|Null} callback, if exists
*/
Subscription.prototype._extractCallback = function (args) {
if (typeof args[args.length - 1] === 'function') {
return args.pop(); // modify the args array!
}
};
/**
* Should be called to check if the number of arguments is correct
*
* @method validateArgs
* @param {Array} arguments
* @throws {Error} if it is not
*/
Subscription.prototype._validateArgs = function (args) {
var subscription = this.options.subscription;
if(!subscription)
subscription = {};
if(!subscription.params)
subscription.params = 0;
if (args.length !== subscription.params) {
throw errors.InvalidNumberOfParams(
args.length,
subscription.params,
subscription.subscriptionName
);
}
};
/**
* Should be called to format input args of method
*
* @method formatInput
* @param {Array}
* @return {Array}
*/
Subscription.prototype._formatInput = function (args) {
var subscription = this.options.subscription;
if (!subscription) {
return args;
}
if (!subscription.inputFormatter) {
return args;
}
var formattedArgs = subscription.inputFormatter.map(function (formatter, index) {
return formatter ? formatter(args[index]) : args[index];
});
return formattedArgs;
};
/**
* Should be called to format output(result) of method
*
* @method formatOutput
* @param result {Object}
* @return {Object}
*/
Subscription.prototype._formatOutput = function (result) {
var subscription = this.options.subscription;
return (subscription && subscription.outputFormatter && result) ? subscription.outputFormatter(result) : result;
};
/**
* Should create payload from given input args
*
* @method toPayload
* @param {Array} args
* @return {Object}
*/
Subscription.prototype._toPayload = function (args) {
var params = [];
this.callback = this._extractCallback(args) || identity;
if (!this.subscriptionMethod) {
this.subscriptionMethod = args.shift();
// replace subscription with given name
if (this.options.subscription.subscriptionName) {
this.subscriptionMethod = this.options.subscription.subscriptionName;
}
}
if (!this.arguments) {
this.arguments = this._formatInput(args);
this._validateArgs(this.arguments);
args = []; // make empty after validation
}
// re-add subscriptionName
params.push(this.subscriptionMethod);
params = params.concat(this.arguments);
if (args.length) {
throw new Error('Only a callback is allowed as parameter on an already instantiated subscription.');
}
return {
method: this.options.type + '_subscribe',
params: params
};
};
/**
* Unsubscribes and clears callbacks
*
* @method unsubscribe
* @return {Object}
*/
Subscription.prototype.unsubscribe = function(callback) {
this.options.requestManager.removeSubscription(this.id, callback);
this.id = null;
this.lastBlock = null;
this.removeAllListeners();
};
/**
* Subscribes and watches for changes
*
* @method subscribe
* @param {String} subscription the subscription
* @param {Object} options the options object with address topics and fromBlock
* @return {Object}
*/
Subscription.prototype.subscribe = function() {
var _this = this;
var args = Array.prototype.slice.call(arguments);
var payload = this._toPayload(args);
if(!payload) {
return this;
}
// throw error, if provider is not set
if(!this.options.requestManager.provider) {
setTimeout(function(){
var err1 = new Error('No provider set.');
_this.callback(err1, null, _this);
_this.emit('error', err1);
},0);
return this;
}
// throw error, if provider doesnt support subscriptions
if(!this.options.requestManager.provider.on) {
setTimeout(function(){
var err2 = new Error(
'The current provider doesn\'t support subscriptions: ' +
_this.options.requestManager.provider.constructor.name
);
_this.callback(err2, null, _this);
_this.emit('error', err2);
},0);
return this;
}
// Re-subscription only: continue fetching from the last block we received.
// a dropped connection may have resulted in gaps in the logs...
if (this.lastBlock && !!this.options.params && typeof this.options.params === 'object'){
payload.params[1] = this.options.params;
payload.params[1].fromBlock = formatters.inputBlockNumberFormatter(this.lastBlock + 1);
}
// if id is there unsubscribe first
if (this.id) {
this.unsubscribe();
}
// store the params in the options object
this.options.params = payload.params[1];
// get past logs, if fromBlock is available
if(payload.params[0] === 'logs' && !!payload.params[1] && typeof payload.params[1] === 'object' && payload.params[1].hasOwnProperty('fromBlock') && isFinite(payload.params[1].fromBlock)) {
// send the subscription request
// copy the params to avoid race-condition with deletion below this block
var blockParams = Object.assign({}, payload.params[1]);
this.options.requestManager.send({
method: 'eth_getLogs',
params: [blockParams]
}, function (err, logs) {
if(!err) {
logs.forEach(function(log){
var output = _this._formatOutput(log);
_this.callback(null, output, _this);
_this.emit('data', output);
});
// TODO subscribe here? after the past logs?
} else {
setTimeout(function(){
_this.callback(err, null, _this);
_this.emit('error', err);
},0);
}
});
}
// create subscription
// TODO move to separate function? so that past logs can go first?
if(typeof payload.params[1] === 'object')
delete payload.params[1].fromBlock;
this.options.requestManager.send(payload, function (err, result) {
if(!err && result) {
_this.id = result;
_this.method = payload.params[0];
// call callback on notifications
_this.options.requestManager.addSubscription(_this, function(error, result) {
if (!error) {
if (!Array.isArray(result)) {
result = [result];
}
result.forEach(function(resultItem) {
var output = _this._formatOutput(resultItem);
// Track current block (for gaps introduced by dropped connections)
_this.lastBlock = !!output && typeof output === 'object' ? output.blockNumber : null;
if (typeof _this.options.subscription.subscriptionHandler === 'function' ) {
return _this.options.subscription.subscriptionHandler.call(_this, output);
} else {
_this.emit('data', output);
}
// call the callback, last so that unsubscribe there won't affect the emit above
_this.callback(null, output, _this);
});
} else {
_this.callback(error, false, _this);
_this.emit('error', error);
}
});
_this.emit('connected', result);
} else {
setTimeout(function(){
_this.callback(err, false, _this);
_this.emit('error', err);
},0);
}
});
// return an object to cancel the subscription
return this;
};
/**
* Resubscribe
*
* @method resubscribe
*
* @returns {void}
*/
Subscription.prototype.resubscribe = function () {
this.options.requestManager.removeSubscription(this.id); // unsubscribe
this.id = null;
this.subscribe(this.callback);
};
module.exports = Subscription;