/* Account Tracker
*
* This module is responsible for tracking any number of accounts
* and caching their current balances & transaction counts.
*
* It also tracks transaction hashes, and checks their inclusion status
* on each new block.
*/
const async = require('async')
const EthQuery = require('eth-query')
const ObservableStore = require('obs-store')
const EventEmitter = require('events').EventEmitter
function noop () {}
class AccountTracker extends EventEmitter {
/**
* This module is responsible for tracking any number of accounts and caching their current balances & transaction
* counts.
*
* It also tracks transaction hashes, and checks their inclusion status on each new block.
*
* @typedef {Object} AccountTracker
* @param {Object} opts Initialize various properties of the class.
* @property {Object} store The stored object containing all accounts to track, as well as the current block's gas limit.
* @property {Object} store.accounts The accounts currently stored in this AccountTracker
* @property {string} store.currentBlockGasLimit A hex string indicating the gas limit of the current block
* @property {Object} _provider A provider needed to create the EthQuery instance used within this AccountTracker.
* @property {EthQuery} _query An EthQuery instance used to access account information from the blockchain
* @property {BlockTracker} _blockTracker A BlockTracker instance. Needed to ensure that accounts and their info updates
* when a new block is created.
* @property {Object} _currentBlockNumber Reference to a property on the _blockTracker: the number (i.e. an id) of the the current block
*
*/
constructor (opts = {}) {
super()
const initState = {
accounts: {},
currentBlockGasLimit: '',
}
this.store = new ObservableStore(initState)
this._provider = opts.provider
this._query = new EthQuery(this._provider)
this._blockTracker = opts.blockTracker
// subscribe to latest block
this._blockTracker.on('block', this._updateForBlock.bind(this))
// blockTracker.currentBlock may be null
this._currentBlockNumber = this._blockTracker.currentBlock
}
/**
* Ensures that the locally stored accounts are in sync with a set of accounts stored externally to this
* AccountTracker.
*
* Once this AccountTracker's accounts are up to date with those referenced by the passed addresses, each
* of these accounts are given an updated balance via EthQuery.
*
* @param {array} address The array of hex addresses for accounts with which this AccountTracker's accounts should be
* in sync
*
*/
syncWithAddresses (addresses) {
const accounts = this.store.getState().accounts
const locals = Object.keys(accounts)
const toAdd = []
addresses.forEach((upstream) => {
if (!locals.includes(upstream)) {
toAdd.push(upstream)
}
})
const toRemove = []
locals.forEach((local) => {
if (!addresses.includes(local)) {
toRemove.push(local)
}
})
toAdd.forEach(upstream => this.addAccount(upstream))
toRemove.forEach(local => this.removeAccount(local))
this._updateAccounts()
}
/**
* Adds a new address to this AccountTracker's accounts object, which points to an empty object. This object will be
* given a balance as long this._currentBlockNumber is defined.
*
* @param {string} address A hex address of a new account to store in this AccountTracker's accounts object
*
*/
addAccount (address) {
const accounts = this.store.getState().accounts
accounts[address] = {}
this.store.updateState({ accounts })
if (!this._currentBlockNumber) return
this._updateAccount(address)
}
/**
* Removes an account from this AccountTracker's accounts object
*
* @param {string} address A hex address of a the account to remove
*
*/
removeAccount (address) {
const accounts = this.store.getState().accounts
delete accounts[address]
this.store.updateState({ accounts })
}
/**
* Given a block, updates this AccountTracker's currentBlockGasLimit, and then updates each local account's balance
* via EthQuery
*
* @private
* @param {object} block Data about the block that contains the data to update to.
* @fires 'block' The updated state, if all account updates are successful
*
*/
_updateForBlock (block) {
this._currentBlockNumber = block.number
const currentBlockGasLimit = block.gasLimit
this.store.updateState({ currentBlockGasLimit })
async.parallel([
this._updateAccounts.bind(this),
], (err) => {
if (err) return console.error(err)
this.emit('block', this.store.getState())
})
}
/**
* Calls this._updateAccount for each account in this.store
*
* @param {Function} cb A callback to pass to this._updateAccount, called after each account is successfully updated
*
*/
_updateAccounts (cb = noop) {
const accounts = this.store.getState().accounts
const addresses = Object.keys(accounts)
async.each(addresses, this._updateAccount.bind(this), cb)
}
/**
* Updates the current balance of an account. Gets an updated balance via this._getAccount.
*
* @private
* @param {string} address A hex address of a the account to be updated
* @param {Function} cb A callback to call once the account at address is successfully update
*
*/
_updateAccount (address, cb = noop) {
this._getAccount(address, (err, result) => {
if (err) return cb(err)
result.address = address
const accounts = this.store.getState().accounts
// only populate if the entry is still present
if (accounts[address]) {
accounts[address] = result
this.store.updateState({ accounts })
}
cb(null, result)
})
}
/**
* Gets the current balance of an account via EthQuery.
*
* @private
* @param {string} address A hex address of a the account to query
* @param {Function} cb A callback to call once the account at address is successfully update
*
*/
_getAccount (address, cb = noop) {
const query = this._query
async.parallel({
balance: query.getBalance.bind(query, address),
}, cb)
}
}
module.exports = AccountTracker
