fix(mongo): stabilize estimated-total pagination

apps/desktop/src/lib/document/documentQueryTotals.ts

@@ -4,7 +4,46 @@ export interface DocumentQueryTotals {
   paginationTotal: number | undefined;
 }
 
-export function resolveDocumentQueryTotals(total: number, totalIsExact: boolean): DocumentQueryTotals {
+export interface DocumentQueryTotalsPageOptions {
+  page?: number;
+  pageSize?: number;
+  rowCount?: number;
+}
+
+export interface DocumentQueryTotalCountRequest {
+  connectionId: string;
+  database: string;
+  collection: string;
+  filter: string | undefined;
+  generation: number;
+}
+
+export function isSameDocumentQueryTotalCountRequest(left: DocumentQueryTotalCountRequest, right: DocumentQueryTotalCountRequest): boolean {
+  return left.connectionId === right.connectionId && left.database === right.database && left.collection === right.collection && left.filter === right.filter && left.generation === right.generation;
+}
+
+/** When the current page is short, the true total is exactly offset + rowCount. */
+export function exactTotalFromIncompleteDocumentPage(options: DocumentQueryTotalsPageOptions): number | undefined {
+  const page = options.page ?? 0;
+  const pageSize = options.pageSize;
+  const rowCount = options.rowCount;
+  if (!Number.isInteger(page) || page < 0 || typeof pageSize !== "number" || !Number.isInteger(pageSize) || pageSize <= 0 || typeof rowCount !== "number" || !Number.isInteger(rowCount) || rowCount < 0 || rowCount >= pageSize || (page > 0 && rowCount === 0)) {
+    return undefined;
+  }
+  return page * pageSize + rowCount;
+}
+
+export function resolveDocumentQueryTotals(total: number, totalIsExact: boolean, pageOptions?: DocumentQueryTotalsPageOptions): DocumentQueryTotals {
+  if (!totalIsExact) {
+    const exactFromPage = exactTotalFromIncompleteDocumentPage(pageOptions ?? {});
+    if (typeof exactFromPage === "number") {
+      return {
+        total: exactFromPage,
+        totalIsExact: true,
+        paginationTotal: exactFromPage,
+      };
+    }
+  }
   return {
     total,
     totalIsExact,