From 04eab70e2761925bf4772b2ea72106210f465ab4 Mon Sep 17 00:00:00 2001
From: Lukas Martinelli <me@lukasmartinelli.ch>
Date: Sat, 24 Dec 2016 14:42:25 +0100
Subject: [PATCH] Add missing revision store

---
 src/libs/revisions.js | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 src/libs/revisions.js

diff --git a/src/libs/revisions.js b/src/libs/revisions.js
new file mode 100644
index 0000000..51abcf0
--- /dev/null
+++ b/src/libs/revisions.js
@@ -0,0 +1,35 @@
+export class RevisionStore {
+  constructor(initialRevisions=[]) {
+    this.revisions = initialRevisions
+    this.currentIdx = initialRevisions.length - 1
+  }
+
+  get latest() {
+    return this.revisions[this.revisions.length - 1]
+  }
+
+  get current() {
+    return this.revisions[this.currentIdx]
+  }
+
+  addRevision(revision) {
+    //TODO: compare new revision style id with old ones
+    //and ensure that it is always the same id
+    this.revisions.push(revision)
+    this.currentIdx++
+  }
+
+  undo() {
+    if(this.currentIdx > 0) {
+      this.currentIdx--
+    }
+    return this.current
+  }
+
+  redo() {
+    if(this.currentIdx < this.revisions.length - 1) {
+      this.currentIdx++
+    }
+    return this.current
+  }
+}