(core) move home server into core

Summary: This moves enough server material into core to run a home server.  The data engine is not yet incorporated (though in manual testing it works when ported).

Test Plan: existing tests pass

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2552

app/server/lib/idUtils.ts

@@ -0,0 +1,48 @@
+import {ForkResult} from 'app/common/ActiveDocAPI';
+import {buildUrlId, parseUrlId} from 'app/common/gristUrls';
+import {padStart} from 'app/common/gutil';
+import {IDocWorkerMap} from 'app/server/lib/DocWorkerMap';
+import * as shortUUID from 'short-uuid';
+
+// make an id that is a standard UUID compressed into fewer characters.
+export function makeId(): string {
+  // Generate a flickr-style id, by converting a regular uuid interpreted
+  // as a hex number (without dashes) into a number expressed in a bigger
+  // base. That number is encoded as characters chosen for url safety and
+  // lack of confusability. The character encoding zero is '1'.  We pad the
+  // result so that the length of the id remains consistent, since there is
+  // routing that depends on the id length exceeding a minimum threshold.
+  return padStart(shortUUID.generate(), 22, '1');
+}
+
+/**
+ * Construct an id for a fork, given the userId, whether the user is the anonymous user,
+ * and the id of a reference document (the trunk).
+ * If the userId is null, the user will be treated as the anonymous user.
+ */
+export function makeForkIds(options: { userId: number|null, isAnonymous: boolean,
+                                       trunkDocId: string, trunkUrlId: string }): ForkResult {
+  const forkId = makeId();
+  const forkUserId = options.isAnonymous ? undefined :
+    (options.userId !== null ? options.userId : undefined);
+  // TODO: we will want to support forks of forks, but for now we do not -
+  // forks are always forks of the trunk.
+  const docId = parseUrlId(options.trunkDocId).trunkId;
+  const urlId = parseUrlId(options.trunkUrlId).trunkId;
+  return {
+    docId: buildUrlId({trunkId: docId, forkId, forkUserId}),
+    urlId: buildUrlId({trunkId: urlId, forkId, forkUserId}),
+  };
+}
+
+// For importing, we can assign any worker to the job.  As a hack, we reuse the document
+// assignment mechanism.  To spread the work around a bit if we have several doc workers,
+// we use a fake document id between import0 and import9.
+// This method takes a DocWorkerMap to allow for something smarter in future.
+export function getAssignmentId(docWorkerMap: IDocWorkerMap, docId: string): string {
+  let assignmentId = docId;
+  if (assignmentId === 'import') {
+    assignmentId = `import${Math.round(Math.random() * 10)}`;
+  }
+  return assignmentId;
+}