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/lib/tx-state-history-helper.js | 37 ++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100644 app/scripts/lib/tx-state-history-helper.js

(limited to 'app/scripts/lib')

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
-- 
cgit