fix(generate): fix incorrect rollover handling (#6)

src/generate.ts

@@ -31,9 +31,9 @@ import { stringify } from "./_stringify.ts";
  */
 export function generate(timestamp?: number): string {
   const uuid = new Uint8Array(16);
-  const tm = timestamp ?? Date.now();
+  const now = timestamp ?? Date.now();
   const rand = crypto.getRandomValues(new Uint8Array(10));
-  const seq = getSeq(tm, rand);
+  const [seq, tm] = getState(now, rand);
 
   // [octets 0-5]: timestamp (48 bits)
   uuid[0] = (tm / 0x10000000000) & 0xff;
@@ -65,23 +65,23 @@ export function generate(timestamp?: number): string {
 }
 
 // The last time the function was called
-let _lastTime = -Infinity;
+let lastTime = -Infinity;
 // The sequence number (18 bits)
-let _seq = 0;
+let seq = 0;
 
-function getSeq(now: number, rand: Uint8Array): number {
-  if (now > _lastTime) {
-    _seq = ((rand[7] & 0x03) << 16) | (rand[8] << 8) | rand[9];
-    _lastTime = now;
+function getState(now: number, rand: Uint8Array): [number, number] {
+  if (now > lastTime) {
+    seq = ((rand[7] & 0x03) << 16) | (rand[8] << 8) | (rand[9]);
+    lastTime = now;
 
-    return _seq;
+    return [seq, lastTime];
   }
 
-  _seq = (_seq + 1) & 0x3ffff;
+  seq = (seq + 1) & 0x3ffff;
 
-  if (_seq === 0) {
-    ++_lastTime;
+  if (seq === 0) {
+    ++lastTime;
   }
 
-  return _seq;
+  return [seq, lastTime];
 }