refactor(workspace): sync doc update in background using data source (#4081)

packages/y-provider/src/data-source.ts

@@ -0,0 +1,65 @@
+import type { DocState, StatusAdapter } from './types';
+
+export interface DatasourceDocAdapter extends Partial<StatusAdapter> {
+  /**
+   * request diff update from other clients
+   */
+  queryDocState: (
+    guid: string,
+    options?: {
+      stateVector?: Uint8Array;
+      targetClientId?: number;
+    }
+  ) => Promise<DocState | false>;
+
+  /**
+   * send update to the datasource
+   */
+  sendDocUpdate: (guid: string, update: Uint8Array) => Promise<void>;
+
+  /**
+   * listen to update from the datasource. Returns a function to unsubscribe.
+   * this is optional because some datasource might not support it
+   */
+  onDocUpdate?(
+    callback: (guid: string, update: Uint8Array) => void
+  ): () => void;
+}
+
+/**
+ * query the datasource from source, and save the latest update to target
+ *
+ * @example
+ *  bindDataSource(socketIO, indexedDB)
+ *  bindDataSource(socketIO, sqlite)
+ */
+export async function syncDataSource(
+  listDocGuids: () => string[],
+  remoteDataSource: DatasourceDocAdapter,
+  localDataSource: DatasourceDocAdapter
+) {
+  const guids = listDocGuids();
+  await Promise.all(
+    guids.map(guid => {
+      return localDataSource.queryDocState(guid).then(async docState => {
+        const remoteDocState = await (async () => {
+          if (docState) {
+            return remoteDataSource.queryDocState(guid, {
+              stateVector: docState.state,
+            });
+          } else {
+            return remoteDataSource.queryDocState(guid);
+          }
+        })();
+        if (remoteDocState) {
+          const missing = remoteDocState.missing;
+          if (missing.length === 2 && missing[0] === 0 && missing[1] === 0) {
+            // empty update
+            return;
+          }
+          await localDataSource.sendDocUpdate(guid, remoteDocState.missing);
+        }
+      });
+    })
+  );
+}