fix: atomic claim prevents scheduled tasks from executing twice (#657)

* fix: atomic claim prevents scheduled tasks from executing twice (#138)

Replace the two-phase getDueTasks() + deferred updateTaskAfterRun() with
an atomic SQLite transaction (claimDueTasks) that advances next_run
BEFORE dispatching tasks to the queue. This eliminates the race window
where subsequent scheduler polls re-discover in-progress tasks.

Key changes:
- claimDueTasks(): SELECT + UPDATE in a single db.transaction(), so no
  poll can read stale next_run values. Once-tasks get next_run=NULL;
  recurring tasks get next_run advanced to the future.
- computeNextRun(): anchors interval tasks to the scheduled time (not
  Date.now()) to prevent cumulative drift. Includes a while-loop to
  skip missed intervals and a guard against invalid interval values.
- updateTaskAfterRun(): simplified to only record last_run/last_result
  since next_run is already handled by the claim.

Closes #138, #211, #300, #578

Co-authored-by: @taslim (PR #601)
Co-authored-by: @baijunjie (Issue #138)
Co-authored-by: @Michaelliv (Issue #300)
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

* style: apply prettier formatting

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: track running task ID in GroupQueue to prevent duplicate execution (#138)

Previous commits implemented an "atomic claim" approach (claimDueTasks)
that advanced next_run before execution. Per Gavriel's review, this
solved the symptom at the wrong layer and introduced crash-recovery
risks for once-tasks.

This commit reverts claimDueTasks and instead fixes the actual bug:
GroupQueue.enqueueTask() only checked pendingTasks for duplicates, but
running tasks had already been shifted out. Adding runningTaskId to
GroupState closes that gap with a 3-line fix at the correct layer.

The computeNextRun() drift fix is retained, applied post-execution
where it belongs.

Closes #138, #211, #300, #578

Co-authored-by: @taslim (PR #601)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* docs: add changelog entry for scheduler duplicate fix

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* docs: add contributors for scheduler race condition fix

Co-Authored-By: Taslim <9999802+taslim@users.noreply.github.com>
Co-Authored-By: BaiJunjie <7956480+baijunjie@users.noreply.github.com>
Co-Authored-By: Michael <13676242+Michaelliv@users.noreply.github.com>
Co-Authored-By: Kyle Zhike Chen <3477852+kk17@users.noreply.github.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: gavrielc <gabicohen22@yahoo.com>
Co-authored-by: Taslim <9999802+taslim@users.noreply.github.com>
Co-authored-by: BaiJunjie <7956480+baijunjie@users.noreply.github.com>
Co-authored-by: Michael <13676242+Michaelliv@users.noreply.github.com>
Co-authored-by: Kyle Zhike Chen <3477852+kk17@users.noreply.github.com>

src/group-queue.ts

@@ -18,6 +18,7 @@ interface GroupState {
   active: boolean;
   idleWaiting: boolean;
   isTaskContainer: boolean;
+  runningTaskId: string | null;
   pendingMessages: boolean;
   pendingTasks: QueuedTask[];
   process: ChildProcess | null;
@@ -41,6 +42,7 @@ export class GroupQueue {
         active: false,
         idleWaiting: false,
         isTaskContainer: false,
+        runningTaskId: null,
         pendingMessages: false,
         pendingTasks: [],
         process: null,
@@ -90,7 +92,11 @@ export class GroupQueue {
 
     const state = this.getGroup(groupJid);
 
-    // Prevent double-queuing of the same task
+    // Prevent double-queuing: check both pending and currently-running task
+    if (state.runningTaskId === taskId) {
+      logger.debug({ groupJid, taskId }, 'Task already running, skipping');
+      return;
+    }
     if (state.pendingTasks.some((t) => t.id === taskId)) {
       logger.debug({ groupJid, taskId }, 'Task already queued, skipping');
       return;
@@ -230,6 +236,7 @@ export class GroupQueue {
     state.active = true;
     state.idleWaiting = false;
     state.isTaskContainer = true;
+    state.runningTaskId = task.id;
     this.activeCount++;
 
     logger.debug(
@@ -244,6 +251,7 @@ export class GroupQueue {
     } finally {
       state.active = false;
       state.isTaskContainer = false;
+      state.runningTaskId = null;
       state.process = null;
       state.containerName = null;
       state.groupFolder = null;