Cache most recent account balances in the account-tracker

app/scripts/lib/account-tracker.js

@@ -36,6 +36,7 @@ class AccountTracker {
   constructor (opts = {}) {
     const initState = {
       accounts: {},
+      cachedAccountBalances: {},
       currentBlockGasLimit: '',
     }
     this.store = new ObservableStore(initState)
@@ -184,12 +185,25 @@ class AccountTracker {
     // query balance
     const balance = await this._query.getBalance(address)
     const result = { address, balance }
-    // update accounts state
-    const { accounts } = this.store.getState()
+    // update accounts and cachedAccountBalances state
+    const { accounts, cachedAccountBalances } = this.store.getState()
     // only populate if the entry is still present
     if (!accounts[address]) return
     accounts[address] = result
-    this.store.updateState({ accounts })
+    this.store.updateState({
+      accounts,
+      cachedAccountBalances: this._generateAccountBalancesToCache(result, cachedAccountBalances),
+    })
+  }
+
+  _generateAccountBalancesToCache ({ address, balance }, cachedAccountBalances) {
+    const accountBalancesToCache = { ...cachedAccountBalances }
+
+    if (balance !== null && balance !== undefined) {
+      accountBalancesToCache[address] = balance
+    }
+
+    return accountBalancesToCache
   }
 
 }

app/scripts/migrations/030.js

@@ -0,0 +1,42 @@
+// next version number
+const version = 30
+
+/*
+
+Adds cachedAccountBalances to the account tracker.
+
+*/
+
+const clone = require('clone')
+
+module.exports = {
+  version,
+
+  migrate: async function (originalVersionedData) {
+    const versionedData = clone(originalVersionedData)
+    versionedData.meta.version = version
+    const state = versionedData.data
+    const newState = transformState(state)
+    versionedData.data = newState
+    return versionedData
+  },
+}
+
+function transformState (state) {
+  if (!state.AccountTracker) {
+    return state
+  }
+
+  const cachedAccountBalances = {}
+  const accounts = state.AccountTracker.accounts
+
+  let balance
+  for (const accountId in state.AccountTracker.accounts) {
+    balance = accounts[accountId].balance
+    if (balance !== null && balance !== undefined) {
+      cachedAccountBalances[accountId] = balance
+    }
+  }
+  state.AccountTracker.cachedAccountBalances = cachedAccountBalances
+  return state
+}

app/scripts/migrations/index.js

@@ -40,4 +40,5 @@ module.exports = [
   require('./027'),
   require('./028'),
   require('./029'),
+  require('./030'),
 ]