fix: keep Later plans conflict-safe across devices (#377)

frontend/dashboard.js

@@ -186,9 +186,10 @@
     },
     onStatus: (state, detail = {}) => {
       qs('#later-sync-status').textContent = state === 'saved' ? 'Later saved to account.' :
-        (state === 'retrying' ? `Later saved on this device · retrying in ${Math.ceil(detail.delayMs / 1000)}s.` :
-          (state === 'pending' ? 'Later saved on this device · sync pending.' :
-            'Later sync unavailable · changes stay on this device.'));
+        (state === 'conflict' ? `Another device changed this Later item${detail.count > 1 ? 's' : ''} · account plan kept.` :
+          (state === 'retrying' ? `Later saved on this device · retrying in ${Math.ceil(detail.delayMs / 1000)}s.` :
+            (state === 'pending' ? 'Later saved on this device · sync pending.' :
+              'Later sync unavailable · changes stay on this device.')));
     },
   });
   laterSync.startLifecycle({ window, document });

frontend/later-sync.js

@@ -115,7 +115,11 @@ function createLaterSync({ storage, getLogin, fetchJson, onRemoteRecords, onStat
         knownOperationKeys.delete(record.recordKey);
       });
       return records.filter(record => latestByItem.get(record.operation.item_id) === record)
-        .map(record => record.operation).filter(operation =>
+        .map(record => ({
+          ...record.operation,
+          base_revision: Number.isInteger(record.operation.base_revision)
+            ? record.operation.base_revision : 0,
+        })).filter(operation =>
           operation && typeof operation.operation_id === 'string' &&
           ['defer', 'restore'].includes(operation.action) && typeof operation.item_id === 'string' &&
           (operation.action === 'restore' || typeof operation.wake_at === 'string'));
@@ -148,7 +152,10 @@ function createLaterSync({ storage, getLogin, fetchJson, onRemoteRecords, onStat
         (action === 'defer' && typeof wakeAt !== 'string')) return false;
     pending().filter(operation => operation.item_id === itemId)
       .forEach(operation => removeOperation(operation.operation_id));
-    const operation = { operation_id: operationId(), action, item_id: itemId, wake_at: wakeAt };
+    const operation = {
+      operation_id: operationId(), action, item_id: itemId, wake_at: wakeAt,
+      base_revision: Math.max(0, savedRevision()),
+    };
     const storageKey = key();
     if (!storageKey || !storage) return false;
     const recordKey = storageKey + '.operation.' + encodeURIComponent(operation.operation_id);
@@ -186,6 +193,7 @@ function createLaterSync({ storage, getLogin, fetchJson, onRemoteRecords, onStat
     try {
       let operations = pending();
       let plan;
+      let conflictCount = 0;
       if (!operations.length) plan = await fetchJson('api/v1/later');
       while (operations.length) {
         if (key() !== ownerKey) return false;
@@ -202,6 +210,8 @@ function createLaterSync({ storage, getLogin, fetchJson, onRemoteRecords, onStat
           ...(plan.duplicate_operation_ids || []),
           ...(plan.rejected_operations || []).map(item => item.operation_id),
         ] : batch.map(item => item.operation_id);
+        conflictCount += (plan.rejected_operations || [])
+          .filter(item => item.reason === 'stale_intent').length;
         for (const operationId of received) {
           if (pending().some(candidate => candidate.operation_id === operationId) &&
               !removeOperation(operationId)) {
@@ -211,7 +221,8 @@ function createLaterSync({ storage, getLogin, fetchJson, onRemoteRecords, onStat
         operations = pending();
       }
       adopt(plan);
-      onStatus?.(pending().length ? 'pending' : 'saved');
+      onStatus?.(pending().length ? 'pending' :
+        (conflictCount ? 'conflict' : 'saved'), conflictCount ? { count: conflictCount } : {});
       retryAttempt = 0;
       cancelRetry();
       return true;

frontend/service-worker.js

@@ -1,6 +1,6 @@
 const BASE = new URL('./', self.location.href).pathname;
 importScripts(BASE + 'static/background-issue-sync.js');
-const CACHE = 'stackchain-dashboard-shell-v54';
+const CACHE = 'stackchain-dashboard-shell-v55';
 const OUTAGE_STATUSES = new Set([500, 502, 503, 504]);
 const NAVIGATION_TIMEOUT_MS = self.__STACKCHAIN_NAVIGATION_TIMEOUT_MS || 4000;
 const SHELL = [