Merge branch 'pr-6' into single-source

src/storage/contract.js

@@ -294,6 +294,7 @@ function runStorageContract(name, factory) {
     describe('subscribeCollection queryConstraints', () => {
       const orderByC = (field, dir) => ({ __type: 'orderBy', field, dir });
       const limitC = (n) => ({ __type: 'limit', n });
+      const offsetC = (n) => ({ __type: 'offset', offset: n });
 
       beforeEach(async () => {
         // seed 5 log docs, timestamps out of order
@@ -324,6 +325,23 @@ function runStorageContract(name, factory) {
         });
         expect(result).toHaveLength(5);
       });
+
+      // Log page pagination (LogsView pageQuery): orderBy + limit + offset.
+      // Server pushes offset to SQL; firebase adapter emulates (widen limit,
+      // slice). Both MUST return the same page.
+      test('offset skips first N after ordering (pagination)', async () => {
+        const result = await new Promise((resolve) => {
+          storage.subscribeCollection('logs', resolve, [orderByC('timestamp', 'desc'), limitC(2), offsetC(2)]);
+        });
+        expect(result.map(d => d.msg)).toEqual(['two', 'four']);
+      });
+
+      test('offset past end returns empty page', async () => {
+        const result = await new Promise((resolve) => {
+          storage.subscribeCollection('logs', resolve, [orderByC('timestamp', 'desc'), limitC(2), offsetC(10)]);
+        });
+        expect(result).toEqual([]);
+      });
     });
   });
 }

src/storage/firebase.js

@@ -71,6 +71,27 @@ export function getAuthInstance() { return authInstance; }
 // App.js can now import { storage } and call storage.setDoc(path, data).
 // Hooks (useFirestoreDocument etc) still use SDK directly for now.
 
+// Translate neutral {__type} constraints (src/storage/index.js builders) to
+// SDK builders. The client SDK has no offset, so emulate it: widen limit to
+// offset+limit and report offsetN for the caller to slice off the leading
+// docs. Read cost matches native offset (admin SDK also bills skipped docs);
+// the server adapter pushes offset into SQL instead. Unknown constraint types
+// are dropped — a raw object handed to query() throws and white-screens.
+function toSdkConstraints(queryConstraints) {
+  let offsetN = 0;
+  let limitN = null;
+  const fbConstraints = [];
+  for (const c of queryConstraints || []) {
+    if (!c || !c.__type) continue;
+    if (c.__type === 'where') fbConstraints.push(where(c.field, c.op, c.value));
+    else if (c.__type === 'orderBy') fbConstraints.push(orderBy(c.field, c.dir || 'asc'));
+    else if (c.__type === 'limit') limitN = c.n;
+    else if (c.__type === 'offset') offsetN = c.offset || 0;
+  }
+  if (limitN !== null) fbConstraints.push(limit(limitN + offsetN));
+  return { fbConstraints, offsetN };
+}
+
 export function createFirebaseStorage() {
   const db = dbInstance;
   if (!db) throw new Error('Firestore not initialized. Call initFirebase() first.');
@@ -101,18 +122,10 @@ export function createFirebaseStorage() {
     },
 
     async getCollection(collectionPath, queryConstraints = []) {
-      // Translate neutral {__type} constraints to firebase SDK builders.
-      const fbConstraints = [];
-      for (const c of queryConstraints || []) {
-        if (!c || !c.__type) continue;
-        if (c.__type === 'where') fbConstraints.push(where(c.field, c.op, c.value));
-        else if (c.__type === 'orderBy') fbConstraints.push(orderBy(c.field, c.dir || 'asc'));
-        else if (c.__type === 'limit') fbConstraints.push(limit(c.n));
-        // firebase SDK has no offset; skip (UI uses server adapter in dev).
-      }
+      const { fbConstraints, offsetN } = toSdkConstraints(queryConstraints);
       const q = fbConstraints.length ? query(collection(db, collectionPath), ...fbConstraints) : collection(db, collectionPath);
       const snapshot = await getDocsReal(q);
-      return snapshot.docs.map(d => ({ id: d.id, ...d.data() }));
+      return snapshot.docs.slice(offsetN).map(d => ({ id: d.id, ...d.data() }));
     },
 
     async countCollection(collectionPath) {
@@ -174,19 +187,12 @@ export function createFirebaseStorage() {
 
     subscribeCollection(collectionPath, cb, queryConstraints = [], errCb) {
       recordAdapterCall({ fn: 'subscribeCollection', path: collectionPath });
-      // queryConstraints = neutral {__type} builders (from index.js).
-      // Translate to SDK orderBy/limit.
-      const sdkConstraints = queryConstraints.map(c => {
-        if (c.__type === 'where') return where(c.field, c.op, c.value);
-        if (c.__type === 'orderBy') return orderBy(c.field, c.dir);
-        if (c.__type === 'limit') return limit(c.n);
-        return c; // pass-through (forward compat)
-      });
-      const q = sdkConstraints.length > 0
-        ? query(collection(db, collectionPath), ...sdkConstraints)
+      const { fbConstraints, offsetN } = toSdkConstraints(queryConstraints);
+      const q = fbConstraints.length > 0
+        ? query(collection(db, collectionPath), ...fbConstraints)
         : collection(db, collectionPath);
       return onSnapshot(q, (snap) => {
-        cb(snap.docs.map(d => ({ id: d.id, ...d.data() })));
+        cb(snap.docs.slice(offsetN).map(d => ({ id: d.id, ...d.data() })));
       }, (err) => {
         console.error(`subscribeCollection ${collectionPath}:`, err);
         if (typeof errCb === 'function') errCb(err);