Basic syncing in the plugin

plugin/src/sync-operations/locks.ts

@@ -0,0 +1,40 @@
+import { RelativePath } from "src/database/document-metadata";
+
+const locked = new Set<RelativePath>();
+const waiters = new Map<RelativePath, Array<() => void>>();
+
+export function tryLockDocument(relativePath: RelativePath): boolean {
+	if (locked.has(relativePath)) {
+		return false;
+	}
+
+	locked.add(relativePath);
+	return true;
+}
+
+export function waitForDocumentLock(relativePath: RelativePath): Promise<void> {
+	if (tryLockDocument(relativePath)) {
+		return Promise.resolve();
+	}
+
+	return new Promise((resolve) => {
+		if (!waiters.has(relativePath)) {
+			waiters.set(relativePath, []);
+		}
+
+		waiters.get(relativePath)!.push(resolve);
+	});
+}
+
+export function unlockDocument(relativePath: RelativePath): void {
+	if (!locked.has(relativePath)) {
+		throw new Error(`Document ${relativePath} is not locked`);
+	}
+
+	const nextWaiting = waiters.get(relativePath)?.shift();
+	if (nextWaiting) {
+		nextWaiting();
+	} else {
+		locked.delete(relativePath);
+	}
+}