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const EthQuery = require('ethjs-query')
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
await this.lockMap[address]
// take lock
const releaseLock = this._takeLock(address)
// calculate next nonce
const currentBlock = await this._getCurrentBlock()
const blockNumber = currentBlock.number
const pendingTransactions = this.getPendingTransactions(address)
const baseCount = await this.ethQuery.getTransactionCount(address, blockNumber)
const nextNonce = baseCount + pendingTransactions
// 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)
})
}
_takeLock(lockId) {
let releaseLock = null
// create and store lock
const lock = new Promise((reject, resolve) => { releaseLock = resolve })
this.lockMap[lockId] = lock
// setup lock teardown
lock.then(() => delete this.lockMap[lockId])
return releaseLock
}
}
module.exports = NonceTracker
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