fix: reconcile concurrent Draft saves (Closes #857)

frontend/index.html

@@ -252,6 +252,7 @@
     <div class="small" id="notification-page-status" aria-live="polite"></div>
     <button class="load-more-notifications" id="load-more-notifications" type="button" hidden>Load older updates</button>
     <div class="small" id="my-work-action-status" aria-live="assertive"></div>
+    <button class="retry-work-route" id="retry-unfiled-draft-sync" type="button" hidden>Retry Draft sync</button>
     <div class="small" id="today-sync-status" aria-live="polite">Today is saved on this device.</div>
     <div class="small" id="later-sync-status" aria-live="polite">Later is saved on this device.</div>
     <button class="retry-work-route" id="retry-work-route" type="button" hidden>Retry shared work item</button>

frontend/unfiled-draft-sync.js

@@ -6,12 +6,13 @@
   function createUnfiledDraftSync(options, mountedFetch) {
     if (mountedFetch) return createUnfiledDraftSync.mount(options, mountedFetch);
     const {
-      captures, fetchJson, storage, getLogin = () => '', onState = () => {},
+      captures, fetchJson, storage, getLogin = () => '', onState = () => {}, maxConflictRetries = 2,
       createConflictId = () => 'conflict-' + (globalThis.crypto?.randomUUID?.() || Date.now().toString(36)),
     } = options;
     const key = 'stackchain.unfiled-draft-sync.v1';
     let inFlight = null;
     let rerun = false;
+    let queuedOwner = '';
 
     function read(login) {
       try {
@@ -33,8 +34,8 @@
       storage?.setItem(key, JSON.stringify(state.all));
     }
 
-    function publish(status, message) {
-      onState({status, ...(message ? {message} : {})});
+    function publish(status, message, details = {}) {
+      onState({status, ...(message ? {message} : {}), ...details});
       const visibleStatus = globalThis.document?.querySelector?.('#my-work-action-status');
       if (message && visibleStatus) visibleStatus.textContent = message;
     }
@@ -131,9 +132,7 @@
           : 'Drafts synced across devices.');
         return true;
       } catch (error) {
-        if (error?.status === 409) {
-          publish('conflict', 'Drafts changed on another device. Sync again to combine them.');
-        } else {
+        if (error?.status !== 409) {
           publish('pending', 'Saved on this device · sync pending');
         }
         throw error;
@@ -145,13 +144,32 @@
       if (!owner) return Promise.resolve(false);
       if (inFlight) {
         rerun = true;
+        queuedOwner = owner;
         return inFlight;
       }
       inFlight = (async () => {
         let result = false;
+        let conflictRetries = 0;
+        let activeOwner = owner;
         do {
           rerun = false;
-          result = await runSync(owner);
+          try {
+            result = await runSync(activeOwner);
+          } catch (error) {
+            if (error?.status !== 409) throw error;
+            if (conflictRetries >= maxConflictRetries) {
+              publish('conflict', 'Draft sync needs attention. Retry when your devices finish saving.', {retryable:true});
+              throw error;
+            }
+            conflictRetries += 1;
+            rerun = true;
+          }
+          if (queuedOwner) {
+            if (queuedOwner !== activeOwner) conflictRetries = 0;
+            activeOwner = queuedOwner;
+            queuedOwner = '';
+            rerun = true;
+          }
         } while (rerun);
         return result;
       })().finally(() => { inFlight = null; });
@@ -168,16 +186,29 @@
       return sync(owner);
     }
 
+    function retry() {
+      return sync(getLogin());
+    }
+
     captures.subscribe?.((id, removed) => {
       const login = getLogin();
       if (login) void (removed ? remove(id, login) : sync(login)).catch(() => {});
     });
 
-    return {sync, remove};
+    return {sync, remove, retry};
   }
   createUnfiledDraftSync.mount = (captures, fetchJson) => {
     const getLogin = captures.currentLogin;
-    const controller = createUnfiledDraftSync({captures, fetchJson, storage:globalThis.localStorage, getLogin});
+    const retryButton = globalThis.document?.querySelector?.('#retry-unfiled-draft-sync');
+    const controller = createUnfiledDraftSync({
+      captures, fetchJson, storage:globalThis.localStorage, getLogin,
+      onState:state => { if (retryButton) retryButton.hidden = !state.retryable; },
+    });
+    retryButton?.addEventListener?.('click', async () => {
+      retryButton.disabled = true;
+      try { await controller.retry(); } catch (_error) { /* state remains actionable */ }
+      finally { retryButton.disabled = false; }
+    });
     const connect = () => {
       const login = getLogin();
       if (login) void controller.sync(login).catch(() => {});