1 files changed, 84 insertions, 0 deletions
diff --git a/app/scripts/lib/nonce-tracker.js b/app/scripts/lib/nonce-tracker.js
new file mode 100644
index 000000000..b76dac4e8
--- /dev/null
+++ b/app/scripts/lib/nonce-tracker.js
@@ -0,0 +1,84 @@
+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 = {}
+  }
+
+  async getGlobalLock () {
+    const globalMutex = this._lookupMutex('global')
+    // await global mutex free
+    const releaseLock = await globalMutex.acquire()
+    return { releaseLock }
+  }
+
+  // releaseLock must be called
+  // releaseLock must be called after adding signed tx to pending transactions (or discarding)
+  async getNonceLock (address) {
+    // await global mutex free
+    await this._globalMutexFree()
+    // 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)
+    })
+  }
+
+  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)
+      })
+    })
+  }
+
+  async _globalMutexFree () {
+    const globalMutex = this._lookupMutex('global')
+    const release = await globalMutex.acquire()
+    release()
+  }
+
+  async _takeMutex (lockId) {
+    const mutex = this._lookupMutex(lockId)
+    const releaseLock = await mutex.acquire()
+    return releaseLock
+  }
+
+  _lookupMutex (lockId) {
+    let mutex = this.lockMap[lockId]
+    if (!mutex) {
+      mutex = new Mutex()
+      this.lockMap[lockId] = mutex
+    }
+    return mutex
+  }
+
+}
+
+module.exports = NonceTracker