Add sync event queue

frontend/sync-client/src/sync-operations/sync-event-queue.test.ts

@@ -0,0 +1,46 @@
+import { describe, it } from "node:test";
+import assert from "node:assert";
+import { SyncEventQueue, type SyncEvent } from "./sync-event-queue";
+
+describe("SyncEventQueue", () => {
+    it("delete collapses interleaved events for one document while leaving the other intact", () => {
+        const queue = new SyncEventQueue();
+        queue.enqueue({ type: "local-content-update", documentId: "A" });
+        queue.enqueue({ type: "remote-content-update", documentId: "B" });
+        queue.enqueue({ type: "local-content-update", documentId: "A" });
+        queue.enqueue({ type: "move", documentId: "A" });
+        queue.enqueue({ type: "remote-content-update", documentId: "A" });
+        queue.enqueue({ type: "delete", documentId: "A" });
+        queue.enqueue({ type: "local-content-update", documentId: "B" });
+
+        assert.deepStrictEqual(queue.next(), { type: "delete", documentId: "A" });
+        assert.deepStrictEqual(queue.next(), {
+            type: "local-content-update",
+            documentId: "B"
+        });
+        assert.strictEqual(queue.next(), undefined);
+    });
+
+    it("updates coalesce up to a move boundary then post-move events are processed separately", () => {
+        const queue = new SyncEventQueue();
+        queue.enqueue({ type: "local-content-update", documentId: "X" });
+        queue.enqueue({ type: "remote-content-update", documentId: "X" });
+        queue.enqueue({ type: "file-create", path: "new.md" });
+        queue.enqueue({ type: "local-content-update", documentId: "X" });
+        queue.enqueue({ type: "move", documentId: "X" });
+        queue.enqueue({ type: "remote-content-update", documentId: "X" });
+        queue.enqueue({ type: "local-content-update", documentId: "X" });
+
+        assert.deepStrictEqual(queue.next(), {
+            type: "local-content-update",
+            documentId: "X"
+        });
+        assert.deepStrictEqual(queue.next(), { type: "file-create", path: "new.md" });
+        assert.deepStrictEqual(queue.next(), { type: "move", documentId: "X" });
+        assert.deepStrictEqual(queue.next(), {
+            type: "local-content-update",
+            documentId: "X"
+        });
+        assert.strictEqual(queue.next(), undefined);
+    });
+});