From dab2fccc78ad76095cc12ce0a1056d9b7a9d6001 Mon Sep 17 00:00:00 2001
From: kumavis <aaron@kumavis.me>
Date: Wed, 14 Jun 2017 22:16:14 -0700
Subject: introduce nonce-tracker

---
 app/scripts/lib/nonce-tracker.js | 49 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 app/scripts/lib/nonce-tracker.js

diff --git a/app/scripts/lib/nonce-tracker.js b/app/scripts/lib/nonce-tracker.js
new file mode 100644
index 000000000..6e9d094bc
--- /dev/null
+++ b/app/scripts/lib/nonce-tracker.js
@@ -0,0 +1,49 @@
+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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