From fdffb6fedc6a29a2f952f7db669bdc2907afb854 Mon Sep 17 00:00:00 2001
From: kumavis <aaron@kumavis.me>
Date: Mon, 14 Aug 2017 18:46:04 -0700
Subject: introduce tx-state-history-helper and diff-based history

---
 app/scripts/controllers/transactions.js    | 34 +++++++++++++++------------
 app/scripts/lib/tx-state-history-helper.js | 37 ++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+), 15 deletions(-)
 create mode 100644 app/scripts/lib/tx-state-history-helper.js

(limited to 'app')

diff --git a/app/scripts/controllers/transactions.js b/app/scripts/controllers/transactions.js
index 58c468e22..872d11b50 100644
--- a/app/scripts/controllers/transactions.js
+++ b/app/scripts/controllers/transactions.js
@@ -8,6 +8,7 @@ const TxProviderUtil = require('../lib/tx-utils')
 const PendingTransactionTracker = require('../lib/pending-tx-tracker')
 const createId = require('../lib/random-id')
 const NonceTracker = require('../lib/nonce-tracker')
+const txStateHistoryHelper = require('../lib/tx-state-history-helper')
 
 module.exports = class TransactionController extends EventEmitter {
   constructor (opts) {
@@ -128,19 +129,17 @@ module.exports = class TransactionController extends EventEmitter {
 
   updateTx (txMeta) {
     // create txMeta snapshot for history
-    const txMetaForHistory = clone(txMeta)
-    // dont include previous history in this snapshot
-    delete txMetaForHistory.history
-    // add snapshot to tx history
-    if (!txMeta.history) txMeta.history = []
-    txMeta.history.push(txMetaForHistory)
-
+    const currentState = txStateHistoryHelper.snapshotFromTxMeta(txMeta)
+    // recover previous tx state obj
+    const previousState = txStateHistoryHelper.replayHistory(txMeta.history)
+    // generate history entry and add to history
+    const entry = txStateHistoryHelper.generateHistoryEntry(previousState, currentState)
+    txMeta.history.push(entry)
+
+    // commit txMeta to state
     const txId = txMeta.id
     const txList = this.getFullTxList()
     const index = txList.findIndex(txData => txData.id === txId)
-    if (!txMeta.history) txMeta.history = []
-    txMeta.history.push(txMetaForHistory)
-
     txList[index] = txMeta
     this._saveTxList(txList)
     this.emit('update')
@@ -148,16 +147,22 @@ module.exports = class TransactionController extends EventEmitter {
 
   // Adds a tx to the txlist
   addTx (txMeta) {
-    const txCount = this.getTxCount()
-    const network = this.getNetwork()
-    const fullTxList = this.getFullTxList()
-    const txHistoryLimit = this.txHistoryLimit
+    // initialize history
+    txMeta.history = []
+    // capture initial snapshot of txMeta for history
+    const snapshot = txStateHistoryHelper.snapshotFromTxMeta(txMeta)
+    txMeta.history.push(snapshot)
 
     // checks if the length of the tx history is
     // longer then desired persistence limit
     // and then if it is removes only confirmed
     // or rejected tx's.
     // not tx's that are pending or unapproved
+    const txCount = this.getTxCount()
+    const network = this.getNetwork()
+    const fullTxList = this.getFullTxList()
+    const txHistoryLimit = this.txHistoryLimit
+
     if (txCount > txHistoryLimit - 1) {
       const index = fullTxList.findIndex((metaTx) => ((metaTx.status === 'confirmed' || metaTx.status === 'rejected') && network === txMeta.metamaskNetworkId))
       fullTxList.splice(index, 1)
@@ -206,7 +211,6 @@ module.exports = class TransactionController extends EventEmitter {
       status: 'unapproved',
       metamaskNetworkId: this.getNetwork(),
       txParams: txParams,
-      history: [],
     }
     // add default tx params
     await this.addTxDefaults(txMeta)
diff --git a/app/scripts/lib/tx-state-history-helper.js b/app/scripts/lib/tx-state-history-helper.js
new file mode 100644
index 000000000..87b9a1d63
--- /dev/null
+++ b/app/scripts/lib/tx-state-history-helper.js
@@ -0,0 +1,37 @@
+const jsonDiffer = require('fast-json-patch')
+const clone = require('clone')
+
+module.exports = {
+  generateHistoryEntry,
+  replayHistory,
+  snapshotFromTxMeta,
+  migrateFromSnapshotsToDiffs,
+}
+
+
+function migrateFromSnapshotsToDiffs(longHistory) {
+  return (
+    longHistory
+    // convert non-initial history entries into diffs
+    .map((entry, index) => {
+      if (index === 0) return entry
+      return generateHistoryEntry(longHistory[index-1], entry)
+    })
+  )
+}
+
+function generateHistoryEntry(previousState, newState) {
+  return jsonDiffer.compare(previousState, newState)
+}
+
+function replayHistory(shortHistory) {
+  return shortHistory.reduce((val, entry) => jsonDiffer.applyPatch(val, entry).newDocument)
+}
+
+function snapshotFromTxMeta(txMeta) {
+  // create txMeta snapshot for history
+  const snapshot = clone(txMeta)
+  // dont include previous history in this snapshot
+  delete snapshot.history
+  return snapshot
+}
\ No newline at end of file
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