feat: converge Today sync across active devices (#361)

frontend/dashboard.js

@@ -156,6 +156,7 @@
             'Today sync unavailable · changes stay on this device.'));
     },
   });
+  todaySync.startLifecycle({ window, document });
   const laterWork = createLaterWork({
     storage: localStorage,
     getLogin: () => planningOwnerLogin,

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-v46';
+const CACHE = 'stackchain-dashboard-shell-v47';
 const OUTAGE_STATUSES = new Set([500, 502, 503, 504]);
 const NAVIGATION_TIMEOUT_MS = self.__STACKCHAIN_NAVIGATION_TIMEOUT_MS || 4000;
 const SHELL = [

frontend/today-sync.js

@@ -1,13 +1,57 @@
-function createTodaySync({ storage, getLogin, fetchJson, onRemoteIds, onStatus, createOperationId }) {
+function createTodaySync({ storage, getLogin, fetchJson, onRemoteIds, onStatus, createOperationId, createChannel }) {
   const prefix = 'stackchain.today-sync.v1.';
   const migrationPrefix = 'stackchain.today-sync-migrated.v1.';
+  const snapshotPrefix = 'stackchain.today-sync-snapshot.v1.';
   let flushing = null;
+  let channel = null;
+  let channelKey = '';
 
   function key() {
     const login = String(getLogin?.() || '').trim().toLowerCase();
     return login ? prefix + encodeURIComponent(login) : '';
   }
 
+  function snapshotKey() {
+    const storageKey = key();
+    return storageKey ? snapshotPrefix + storageKey.slice(prefix.length) : '';
+  }
+
+  function savedRevision() {
+    try {
+      const snapshot = JSON.parse(storage?.getItem(snapshotKey()) || 'null');
+      return Number.isInteger(snapshot?.revision) ? snapshot.revision : -1;
+    } catch (_error) {
+      return -1;
+    }
+  }
+
+  function adopt(plan, broadcast = true) {
+    if (!Number.isInteger(plan?.revision) || !Array.isArray(plan?.ids)) return false;
+    if (plan.revision < savedRevision()) return false;
+    try {
+      storage?.setItem(snapshotKey(), JSON.stringify({ revision: plan.revision, ids: plan.ids }));
+    } catch (_error) {
+      // A storage quota failure must not prevent the current tab from using server truth.
+    }
+    onRemoteIds?.(plan.ids);
+    if (broadcast) channel?.postMessage({ revision: plan.revision, ids: plan.ids });
+    return true;
+  }
+
+  function ensureChannel() {
+    const storageKey = key();
+    if (!storageKey || channelKey === storageKey) return;
+    channel?.close?.();
+    const factory = createChannel || (globalThis.window?.BroadcastChannel
+      ? name => new globalThis.window.BroadcastChannel(name)
+      : null);
+    channelKey = storageKey;
+    channel = factory?.('stackchain-today-' + storageKey.slice(prefix.length)) || null;
+    channel?.addEventListener?.('message', event => {
+      if (key() === storageKey) adopt(event.data, false);
+    });
+  }
+
   function pending() {
     const storageKey = key();
     if (!storageKey || !storage) return [];
@@ -71,6 +115,7 @@ function createTodaySync({ storage, getLogin, fetchJson, onRemoteIds, onStatus,
 
   async function run() {
     if (!key()) return false;
+    ensureChannel();
     try {
       let plan = await fetchJson('api/v1/today');
       const operations = pending();
@@ -85,14 +130,14 @@ function createTodaySync({ storage, getLogin, fetchJson, onRemoteIds, onStatus,
           if (error?.status !== 409) throw error;
           const rejected = pending();
           save(rejected.filter(candidate => candidate.operation_id !== operation.operation_id));
-          onRemoteIds?.(Array.isArray(plan.ids) ? plan.ids : []);
+          adopt(plan);
           onStatus?.('full');
           return false;
         }
         const remaining = pending();
         if (remaining[0]?.operation_id === operation.operation_id) save(remaining.slice(1));
       }
-      onRemoteIds?.(Array.isArray(plan.ids) ? plan.ids : []);
+      adopt(plan);
       onStatus?.(pending().length ? 'pending' : 'saved');
       return true;
     } catch (_error) {
@@ -106,7 +151,14 @@ function createTodaySync({ storage, getLogin, fetchJson, onRemoteIds, onStatus,
     return flushing;
   }
 
-  return { enqueue, migrate, flush, pending };
+  function startLifecycle({ window: windowObject, document: documentObject }) {
+    windowObject?.addEventListener?.('online', flush);
+    documentObject?.addEventListener?.('visibilitychange', () =>
+      documentObject.hidden ? false : flush()
+    );
+  }
+
+  return { enqueue, migrate, flush, pending, startLifecycle };
 }
 
 if (typeof module !== 'undefined' && module.exports) module.exports = createTodaySync;