Proposal: Rewrite Android app in Jetpack Compose

[salmon-21]

Summary

I've rewritten the HCGateway Android app from React Native/Expo to native Jetpack Compose + Kotlin. The rewrite addresses several open issues and brings significant improvements to sync reliability, performance, and UI.

Branch: compose-rewrite

Motivation

The React Native implementation has several fundamental issues:

• Material 3 compliance requires workarounds (custom Switch, SVG icon hacks, color token mapping)
• Expo version compatibility and native rebuild cycles for every dependency
• Android-only app deeply integrated with Android APIs (Health Connect, foreground services, FCM) — React Native bridge layer adds unnecessary complexity

What changed

Architecture

• Jetpack Compose + Kotlin with MVVM, Hilt DI, StateFlow
• DataStore replaces AsyncStorage
• WorkManager replaces rn-foreground-service (OS-managed, Doze-aware)
• OkHttp Authenticator for automatic 403 token refresh
• Health Connect Jetpack SDK directly (no bridge layer)

Sync Performance Improvements

Problem (RN)	Solution (Compose)
Full 30-day re-read every sync	Health Connect Changes API (delta sync)
34 types processed sequentially	Coroutines async/awaitAll (parallel)
HR/Sleep/Speed: 1 POST per record + 3s delay	Batch POST (delay removed)
setTimeout-based queue (unreliable)	Structured coroutines (reliable)

Bug Fixes

• formatDateToISOString timezone bug (fixes Missing data current day #52) — Kotlin uses LocalDate.atStartOfDay(ZoneId.of("UTC")), no local-timezone-to-UTC offset issue
• Sync stops when screen is off (fixes Sync stops when screen is off #37) — WorkManager handles background execution properly
• App loses settings after restart (fixes android app looses settings after restarting #57) — DataStore persistence with proper session management
• readRecords 1000-record pagination limit — All records are now fetched via page tokens

UI/UX

• Material You dynamic colors + light/dark/system theme (instant switch via AppCompatDelegate)
• M3 Expressive components (wavy progress, loading indicator, button shapes)
• Material Shared Axis X transitions (via material-motion-compose)
• Predictive back gesture support
• Sync card with New vs Server record count comparison
• Pull-to-refresh with periodic auto-refresh
• Settings screen: sync mode, interval, auto sync toggle, theme, boot start, Sentry toggle
• Permission onboarding flow (Health Connect, notifications, battery optimization)
• Open source licenses screen
• Connection status card with network monitoring and auto-retry

API Addition

• GET /api/v2/counts endpoint — returns record counts per type for the authenticated user
• API-side bulk_write optimization for handling large record batches without timeout

Screenshots

Setup	Login	Home (not synced)

Syncing	Synced	New data detected

Date Picker	Settings	Custom Interval

Compatibility

• Same package name (dev.shuchir.hcgateway)
• Same API endpoints (v2) — fully backward compatible
• Same Health Connect permissions (34 record types)
• Same Firebase FCM integration
• Same Sentry error reporting (with opt-out toggle)

Open for discussion

I'd love to hear your thoughts on this rewrite. Happy to submit a PR if you're interested in merging it.

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[salmon-21]

API Server Improvements

In addition to the Compose rewrite, I've made several improvements to the API server side:

Changes (api-improvements branch)

1. GET /api/v2/counts endpoint — Returns record counts per collection for the authenticated user. Useful for the app to display sync status.

2. POST /api/v2/sync/<method> — bulk_write optimization — Replaced the per-record insert_one/update_one loop with pymongo.bulk_write(ordered=False) using UpdateOne with upsert=True. This resolves socket timeouts when syncing large batches (3000+ records, e.g. Steps, TotalCaloriesBurned).

3. Fix APP_DEBUG parsing bug — bool(os.environ.get('APP_DEBUG', False)) evaluates bool("False") → True, meaning debug mode was always on regardless of the env var value. Fixed to os.environ.get('APP_DEBUG', '0') == '1'.

4. Removed excessive debug print() statements from the sync endpoint.

These changes are available in my fork and can be included in a PR if there's interest.

[salmon-21]

Update: Added 7 new Health Connect record types + history permission

New record types (34 → 41 types)

Record Type	Description
BodyWaterMassRecord	Body water mass (addresses #59)
HeartRateVariabilityRmssdRecord	Heart rate variability (HRV RMSSD)
MindfulnessSessionRecord	Mindfulness sessions (experimental API)
PlannedExerciseSessionRecord	Planned exercise sessions (with blocks/steps)
SexualActivityRecord	Sexual activity
SkinTemperatureRecord	Skin temperature (with delta samples)
WheelchairPushesRecord	Wheelchair pushes

These are all the remaining record types in Health Connect SDK 1.1.0 that were not previously supported.

PERMISSION_READ_HEALTH_DATA_HISTORY

Added the Health Connect history permission, which allows reading data older than 30 days. Without this permission, only the most recent 30 days of data are accessible.

No server-side changes needed

The API dynamically creates MongoDB collections based on the record type name (/sync/<method>), so new record types work without any server modifications.

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🤖 Generated with Claude Code