migration 18 - move to diff-based history

app/scripts/migrations/018.js

@@ -0,0 +1,52 @@
+const version = 18
+
+/*
+
+This migration updates "transaction state history" to diffs style
+
+*/
+
+const clone = require('clone')
+const txStateHistoryHelper = require('../tx-state-history-helper')
+
+
+module.exports = {
+  version,
+
+  migrate: function (originalVersionedData) {
+    const versionedData = clone(originalVersionedData)
+    versionedData.meta.version = version
+    try {
+      const state = versionedData.data
+      const newState = transformState(state)
+      versionedData.data = newState
+    } catch (err) {
+      console.warn(`MetaMask Migration #${version}` + err.stack)
+    }
+    return Promise.resolve(versionedData)
+  },
+}
+
+function transformState (state) {
+  const newState = state
+  const transactions = newState.TransactionController.transactions
+  newState.TransactionController.transactions = transactions.map((txMeta) => {
+    // no history: initialize
+    if (!txMeta.history || tx.history.length === 0) {
+      const snapshot = txStateHistoryHelper.snapshotFromTxMeta(txMeta)
+      txMeta.history = [snapshot]
+      return txMeta
+    }
+    // has history: migrate
+    const newHistory = (
+      txStateHistoryHelper.migrateFromSnapshotsToDiffs(txMeta.history)
+      // remove empty diffs
+      .filter((entry) => {
+        return !Array.isArray(entry) || entry.length > 0
+      })
+    )
+    txMeta.history = newHistory
+    return txMeta
+  })
+  return newState
+}