feat: add snjs package

packages/snjs/lib/Version.ts

@@ -0,0 +1,40 @@
+import { eq, gt } from 'semver'
+
+/** Declared in webpack config */
+declare const __VERSION__: string
+export const SnjsVersion = __VERSION__
+
+/**
+ * Legacy architecture (pre-3.5 clients)
+ */
+export const PreviousSnjsVersion1_0_0 = '1.0.0'
+
+/**
+ * First release of new architecture, did not automatically store version
+ */
+export const PreviousSnjsVersion2_0_0 = '2.0.0'
+
+/**
+ * Returns true if the version string on the right is greater than the one
+ * on the left. Accepts any format version number, like 2, 2.0, 2.0.0, or even 2.0.0.01
+ */
+export function isRightVersionGreaterThanLeft(left: string, right: string): boolean {
+  return compareSemVersions(left, right) === -1
+}
+
+/**
+ *  -1 if a < b
+ *  0 if a == b
+ *  1 if a > b
+ */
+export function compareSemVersions(left: string, right: string): 1 | -1 | 0 {
+  if (eq(left, right)) {
+    return 0
+  }
+
+  if (gt(left, right)) {
+    return 1
+  }
+
+  return -1
+}