Fix: Firestore timestamp precision and offline read error messages (#49)

- fromFirestoreTimestamp() now includes nanoseconds in the milliseconds
  calculation (Math.round(nanoseconds / 1e6)) to avoid precision loss
- getOperationErrorMessage() now accepts an optional context ('load'|'save')
  so network error messages are contextually correct for reads vs writes
- Read error display in App.tsx passes context='load' for a friendlier
  offline message instead of showing raw Firebase error.message

Co-authored-by: theredmoose <theredmoose@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: theredmoose

TODO.md

@@ -72,7 +72,7 @@
 - [x] No validation for negative/zero measurements — MemberForm now validates weight > 0
 - [x] Missing Firebase env var validation — `src/config/firebase.ts` now throws with clear error listing missing vars
 - [ ] No account linking flow — users get stuck signing in with Google after creating email account with same address
-- [ ] No offline error handling — Firebase operations show raw errors when offline
+- [x] No offline error handling — read errors in App.tsx now use `getOperationErrorMessage()` with `'load'` context; network/unavailable codes produce friendly messages
 - [x] Year field in GearForm accepts invalid values — added submit-time validation (1980–currentYear+1); HTML min/max updated to match
 - [x] GearForm numeric fields (tip/waist/tail profile) use parseFloat/parseInt without isNaN guard — fixed: profile only built when all three fields parse to valid integers
 - [x] Foot measurement bounds not validated — MemberForm now validates 12–30 cm range with error message; HTML min/max updated
@@ -82,12 +82,12 @@
 - [x] No date-of-birth bounds validation — MemberForm now rejects future dates and dates > 120 years ago
 - [x] nordic-combi in skillLevels but not in SPORTS array — `SportSizing.tsx` now omits nordic-combi when persisting skill levels
 - [x] US shoe size conversion inconsistency — `sizing.ts` now uses `getShoeSizesFromFootLength()` from shoeSize service
-- [ ] Potential undefined skillLevel access — `skillLevels[currentSport.id]` in SportSizing has no fallback
+- [x] Potential undefined skillLevel access — already handled: `skillLevels` state initialised for all 6 sports with `?? 'intermediate'` fallback on line 68 of SportSizing.tsx
 - [x] No loading state for gear operations — gear delete/submit in App.tsx show no loading indicators; mutations now catch errors and surface a dismissible toast
 - [x] Race condition in useAuth — `setLoading(false)` and `setError()` now guarded by mounted ref
 - [ ] No email verification on signup — email accounts created without verifying address
 - [x] Hockey skate width thresholds (0.36, 0.40) hardcoded without source documentation — added Bauer/CCM fit guide comments to `determineSkateWidth()`
-- [ ] Firestore timestamp conversion drops nanoseconds (`firebase.ts:32`) — minor precision loss
+- [x] Firestore timestamp conversion drops nanoseconds — fixed: now includes `Math.round(nanoseconds / 1e6)` in milliseconds calculation
 
 ## Notes
 - App URL: https://gearguru-b3bc8.web.app

src/App.tsx

@@ -1,9 +1,11 @@
 import { useState } from 'react';
 
-function getOperationErrorMessage(err: unknown): string {
+function getOperationErrorMessage(err: unknown, context: 'load' | 'save' = 'save'): string {
   const code = (err as { code?: string })?.code ?? '';
   if (code === 'unavailable' || code === 'network-request-failed') {
-    return 'Unable to save — check your connection and try again.';
+    return context === 'load'
+      ? 'Unable to load data — check your connection and try again.'
+      : 'Unable to save — check your connection and try again.';
   }
   if (code === 'permission-denied') {
     return 'Permission denied. Please sign out and sign back in.';
@@ -261,7 +263,7 @@ function App() {
 
             <div className="flex-1 overflow-y-auto bg-white px-6 py-6">
               {loading && <p className="loading">Loading...</p>}
-              {error && <p className="error-state">Error: {error.message}</p>}
+              {error && <p className="error-state">{getOperationErrorMessage(error, 'load')}</p>}
 
               {!loading && !error && members.length === 0 && (
                 <p className="empty-state">

src/services/firebase.ts

@@ -29,7 +29,7 @@ async function toFirestoreTimestamp(isoString: string) {
 }
 
 export function fromFirestoreTimestamp(timestamp: FirestoreTimestamp): string {
-  return new Date(timestamp.seconds * 1000).toISOString();
+  return new Date(timestamp.seconds * 1000 + Math.round(timestamp.nanoseconds / 1e6)).toISOString();
 }
 
 function now(): string {