SwimBuddy

Swimming workout tracker with Apple Watch companion app. Expo 57 + React Native 0.86 + NativeWind v5 + Drizzle ORM + Swift Watch target.

Commands

npx expo start              # Dev server
npx expo run:ios            # Build & run on iOS
npx expo prebuild -p ios    # Regenerate ios/ dir (safe — targets/ persists)
npx drizzle-kit generate    # Regenerate SQL migrations after schema changes

No npm test or lint scripts exist yet. No babel.config.js — NativeWind v5 uses CSS-first config.

Project Structure

src/
  features/<name>/screens/   # Screen components (registered in navigators)
  features/<name>/components/# Feature-specific UI
  features/<name>/hooks/     # Feature-specific hooks
  components/                # Shared UI primitives (flat)
  hooks/                     # Shared hooks
  navigation/                # React Navigation (RootNav, TabNav, feature stacks)
  db/                        # Drizzle schema, client, relations, operations
  providers/                 # DatabaseProvider, SettingsProvider (MMKV)
  utils/                     # formatTime, calculateSwolf, uuid, etc.
  constants/                 # strokes, poolLengths, colors
  types/                     # workout.ts, common.ts
  modules/watch-connectivity/# Expo native module bridging WCSession
targets/watch/               # Apple Watch app (Swift/SwiftUI) — survives prebuild

Key Conventions

Path aliases: @/, @features/, @components/, @db/, etc. (tsconfig.json)
Feature-based folder structure with type-based shared layer
NativeWind v5: className prop, no babel config, CSS-first. Use className not StyleSheet
className types: nativewind-env.d.ts at root — don't delete
lightningcss pinned to 1.30.1 in package.json overrides — required by NativeWind v5

Watch Target

Lives in targets/watch/, NOT in ios/ — survives expo prebuild --clean
Config: targets/watch/expo-target.config.js
Build: open ios/SwimBuddy.xcworkspace in Xcode, select Watch scheme
Uses App Groups (group.nl.guido-it.swimbuddy) for data sharing
WCSession for real-time messaging, transferUserInfo for reliable offline sync
HealthKit for swim workout tracking (indoor swimming)
Swift types StoredWorkout, StoredSet, CompletedLap in WorkoutManager.swift

Database

expo-sqlite + Drizzle ORM (SQLite dialect, expo driver)
Schema: src/db/schema.ts — tables: templates, workouts, sets, laps
Relations: src/db/relations.ts
CRUD: src/db/operations.ts
Client: src/db/client.ts — exports db and DATABASE_NAME
Migrations in drizzle/ — generated by npx drizzle-kit generate

WCSession Gotchas (Critical)

These are hard-won bugs that will waste hours if rediscovered:

NSNull crashes sendMessage: JS null becomes NSNull in ObjC, causing WCErrorCodePayloadUnsupportedTypes (Code 7010). Always strip null/undefined values before sending via cleanForWCSession().
Two delegate methods conflict: Having both session(_:didReceiveMessage:) AND session(_:didReceiveMessage:replyHandler:) on the same delegate causes iOS to deliver neither. Watch uses didReceiveMessage (no replyHandler); phone uses didReceiveMessage:replyHandler: for bidirectional sync.
isReachable is unreliable: Only true when both apps are foreground. Check session.activationState == .activated instead for connection readiness.
Phone sendMessage must use replyHandler: nil: Otherwise JS thread blocks waiting for a reply that watch never sends. Use fire-and-forget for workout plans; use transferUserInfo for data sync.
Watch suiteName vs UserDefaults.standard: Watch only needs local storage, so use UserDefaults.standard — the App Groups suite name is only needed for phone↔watch shared data.
Phone pendingEvents polling: Phone polls pollEvents() every 2s because Expo Modules' sendEvent API doesn't work on AppContext. Watch data arrives via didReceiveUserInfo delegate → stored in pendingEvents array.

Watch ↔ Phone Data Flow

Phone → Watch: sendMessage with workout plan (fire-and-forget, promise resolves immediately with ["status":"sent"])
Watch → Phone: transferUserInfo with completed workout data (reliable, works in background)
Phone receives: pollEvents() called from JS every 2s, saveWatchCompletedWorkout() writes to SQLite

UI Conventions

Swipe-to-delete on lists uses SwipeableRow component (react-native-gesture-handler)
BuilderScreen pool length is a 25m/50m toggle (not read-only from settings)
Templates and Stats features removed from navigation (DB schema preserved but UI deleted)
Ionicons used for bottom tab icons (@expo/vector-icons)

NativeWind v5 TextInput Crash

react-native-css has a bug where the textAlign mapping on TextInput causes a crash (path.split on boolean true). The fix is in src/utils/ — don't remove the workaround without testing TextInput rendering.

Gotchas

metro.config.js has .sql in sourceExts — required for Drizzle migration imports
expo prebuild clears and regenerates ios/ by default. Use --no-clean to preserve
Watch target compiles as separate Xcode target — not a RN module
react-native-css is a NativeWind v5 peer dependency — don't remove
@bacons/apple-targets plugin must be in app.json plugins array

Expo Docs

Expo SDK 57: https://docs.expo.dev/versions/v57.0.0/

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