Task queue pagination by anchor

CHANGELOG.md

@@ -16,6 +16,7 @@ If you are upgrading from v0.16.x, replace the binary (or run `docker pull`). If
   - Invalidate caches when group memberships change on an external directory.
   - Return OIDC errors instead of "failed to decode token".
   - User impersonation.
+- Task queue pagination by anchor.
 - Log viewer: All events show as `INFO`.
 - Registry: Allow changing object variants.
 - Node id renewal.

crates/jmap/src/registry/mapping/task.rs

@@ -457,13 +457,7 @@ pub(crate) async fn task_query(
             _ => false,
         })?;
 
-    if let Some(anchor) = req.request.anchor {
-        let anchor = anchor.id();
-        if anchor > due_from {
-            due_from = anchor;
-        }
-    }
-
+    let anchor_id = req.request.anchor.map(|anchor| anchor.id());
     if req
         .request
         .sort
@@ -480,6 +474,24 @@ pub(crate) async fn task_query(
         .request
         .extract_parameters(req.server.core.jmap.query_max_results, None)?;
 
+    let mut from_id = 0u64;
+    if let Some(anchor_id) = anchor_id
+        && let Some(anchor_task) = req
+            .server
+            .store()
+            .get_value::<Task>(ValueKey::from(ValueClass::TaskQueue(
+                TaskQueueClass::Task { id: anchor_id },
+            )))
+            .await
+            .caused_by(trc::location!())?
+    {
+        let anchor_due = anchor_task.due_timestamp();
+        if anchor_due >= due_from && anchor_due <= due_to {
+            due_from = anchor_due;
+            from_id = anchor_id;
+        }
+    }
+
     // Build response
     let mut response = QueryResponseBuilder::new(
         req.server.core.jmap.query_max_results + 1,
@@ -489,9 +501,8 @@ pub(crate) async fn task_query(
     );
 
     let mut total = 0;
-
     let from_key = ValueKey::from(ValueClass::TaskQueue(TaskQueueClass::Due {
-        id: 0,
+        id: from_id,
         due: due_from,
     }));
     let to_key = ValueKey::from(ValueClass::TaskQueue(TaskQueueClass::Due {