exercitationemmaxime/src/NonceTracker.ts

Arkane-enabled Web3 Provider for the web

const inherits = require('util').inherits
const Transaction = require('ethereumjs-tx')
const ethUtil = require('ethereumjs-util')
const Subprovider = require('web3-provider-engine/subproviders/subprovider')
const blockTagForPayload = require('web3-provider-engine/util/rpc-cache-utils').blockTagForPayload

export class NonceTrackerSubprovider extends Subprovider {

    private nonceCache: any;
    private rpcUrl!: string;

    constructor (opts: any) {
        super();
        const self = this;
        self.nonceCache = {};
        self.rpcUrl = opts.rpcUrl;
    }

    public handleRequest(payload: any, next: any, end: any): void {
        const self = this
        switch (payload.method) {

            case 'eth_getTransactionCount':
                var blockTag = blockTagForPayload(payload)
                var address = payload.params[0].toLowerCase()
                var cachedResult = self.nonceCache[self.rpcUrl] && self.nonceCache[self.rpcUrl][address];
                // only handle requests against the 'pending' blockTag
                if (blockTag === 'pending') {
                    // has a result
                    if (cachedResult) {
                        end(null, cachedResult)
                        // fallthrough then populate cache
                    } else {
                        next(function (err: any, result: any, cb: any) {
                            if (err) return cb()
                            if (self.nonceCache[self.rpcUrl] === undefined) {
                                self.nonceCache[self.rpcUrl] = {};
                            }
                            if (self.nonceCache[self.rpcUrl][address] === undefined) {
                                self.nonceCache[self.rpcUrl][address] = result
                            }
                            cb()
                        })
                    }
                } else {
                    next()
                }
                return

            case 'eth_sendRawTransaction':
                // allow the request to continue normally
                next(function (err: any, result: any, cb: any) {
                    // only update local nonce if tx was submitted correctly
                    if (err) return cb()
                    // parse raw tx
                    var rawTx = payload.params[0]
                    var stripped = ethUtil.stripHexPrefix(rawTx)
                    var rawData = new Buffer(ethUtil.stripHexPrefix(rawTx), 'hex')
                    var tx = new Transaction(new Buffer(ethUtil.stripHexPrefix(rawTx), 'hex'))
                    // extract address
                    var address = '0x' + tx.getSenderAddress().toString('hex').toLowerCase()
                    // extract nonce and increment
                    var nonce = ethUtil.bufferToInt(tx.nonce)
                    nonce++
                    // hexify and normalize
                    var hexNonce = nonce.toString(16)
                    if (hexNonce.length % 2) hexNonce = '0' + hexNonce
                    hexNonce = '0x' + hexNonce
                    // dont update our record on the nonce until the submit was successful
                    // update cache
                    if (self.nonceCache[self.rpcUrl] === undefined) {
                        self.nonceCache[self.rpcUrl] = {};
                    }
                    self.nonceCache[self.rpcUrl][address] = hexNonce
                    cb()
                })
                return;

            default:
                next();
                return;

        }
    }
}