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const EthQuery = require('eth-query')
const assert = require('assert')
const Mutex = require('await-semaphore').Mutex
class NonceTracker {
constructor ({ blockTracker, provider, getPendingTransactions }) {
this.blockTracker = blockTracker
this.ethQuery = new EthQuery(provider)
this.getPendingTransactions = getPendingTransactions
this.lockMap = {}
}
// releaseLock must be called
// releaseLock must be called after adding signed tx to pending transactions (or discarding)
async getNonceLock (address) {
// await lock free, then take lock
const releaseLock = await this._takeMutex(address)
// calculate next nonce
// we need to make sure our base count
// and pending count are from the same block
const currentBlock = await this._getCurrentBlock()
const pendingTransactions = this.getPendingTransactions(address)
const pendingCount = pendingTransactions.length
assert(Number.isInteger(pendingCount), 'nonce-tracker - pendingCount is an integer')
const baseCountHex = await this._getTxCount(address, currentBlock)
const baseCount = parseInt(baseCountHex, 16)
assert(Number.isInteger(baseCount), 'nonce-tracker - baseCount is an integer')
const nextNonce = baseCount + pendingCount
assert(Number.isInteger(nextNonce), 'nonce-tracker - nextNonce is an integer')
// return next nonce and release cb
return { nextNonce, releaseLock }
}
async _getCurrentBlock () {
const currentBlock = this.blockTracker.getCurrentBlock()
if (currentBlock) return currentBlock
return await Promise((reject, resolve) => {
this.blockTracker.once('latest', resolve)
})
}
_lookupMutex (lockId) {
let mutex = this.lockMap[lockId]
if (!mutex) {
mutex = new Mutex()
this.lockMap[lockId] = mutex
}
return mutex
}
async _takeMutex (lockId) {
const mutex = this._lookupMutex(lockId)
const releaseLock = await mutex.acquire()
return releaseLock
}
async _getTxCount (address, currentBlock) {
const blockNumber = currentBlock.number
return new Promise((resolve, reject) => {
this.ethQuery.getTransactionCount(address, blockNumber, (err, result) => {
err ? reject(err) : resolve(result)
})
})
}
}
module.exports = NonceTracker
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