Add graph ID creation / serialisation (#790)

- Updates UUIDv4 generator
- Adds a unique id & revision support to graphs
- `revision` to be incremented downstream (e.g. on save)
- `id` automatically assigned if not provided

src/utils/uuid.ts

@@ -0,0 +1,29 @@
+export type UUID = `${string}-${string}-${string}-${string}-${string}`
+
+/** Special-case zero-UUID, consisting entirely of zeros. Used as a default value. */
+export const zeroUuid = "00000000-0000-0000-0000-000000000000"
+
+/** Pre-allocated storage for uuid random values. */
+const randomStorage = new Uint32Array(31)
+
+/**
+ * Creates a UUIDv4 string.
+ * @returns A new UUIDv4 string
+ * @remarks
+ * Original implementation from https://gist.github.com/jed/982883?permalink_comment_id=852670#gistcomment-852670
+ *
+ * Prefers the {@link crypto.randomUUID} method if available, falling back to
+ * {@link crypto.getRandomValues}, then finally the legacy {@link Math.random} method.
+ */
+export function createUuidv4(): UUID {
+  if (typeof crypto?.randomUUID === "function") return crypto.randomUUID()
+  // Assertion: `replaceAll` returns `string`; UUID format must be asserted below
+  if (typeof crypto?.getRandomValues === "function") {
+    const random = crypto.getRandomValues(randomStorage)
+    let i = 0
+    return "10000000-1000-4000-8000-100000000000".replaceAll(/[018]/g, a =>
+      (Number(a) ^ ((random[i++] * 3.725_290_298_461_914e-9) >> (Number(a) * 0.25))).toString(16)) as UUID
+  }
+  return "10000000-1000-4000-8000-100000000000".replaceAll(/[018]/g, a =>
+    (Number(a) ^ ((Math.random() * 16) >> (Number(a) * 0.25))).toString(16)) as UUID
+}