yaris-obd/android/plan.md

yaris-obd Android Companion App — Implementation Plan

Native Android (Kotlin + Jetpack Compose) companion app for the yaris-obd Pi system. Primary goal: dashcam file relay (download from Pi over hotspot WiFi → upload to remote server over cellular, simultaneously) — the one thing the web UI cannot do (see main PLAN.md Phase 11/12 for the platform limitation backstory).

This file is the ground-level implementation plan. The high-level architecture, API surface, and scope decisions live in the main PLAN.md (Phase 28). This file tracks day-to-day progress, per-sub-phase implementation details, and working notes specific to the Android codebase.

Dev environment

• IDE: Android Studio (Ladybug or newer) on Fedora dev machine
• Language: Kotlin 2.x, JDK 17 (Android Studio bundled)
• Build: Gradle with Kotlin DSL, version catalog (gradle/libs.versions.toml)
• Emulator: API 35 AVD, 4GB RAM, 2GB storage — UI/flow testing only (single virtual NIC, can't test dual-network binding)
• Real device: owner's Pixel, USB debugging enabled — required for dual-network tests
• Repo: android/ at project root, part of the same yaris-obd git repo

Project scaffold

android/
├── plan.md                          # this file
├── .gitignore                       # Android-specific ignores
├── build.gradle.kts                 # root build file
├── settings.gradle.kts              # project settings + version catalog
├── gradle/
│   └── libs.versions.toml           # dependency version catalog
├── gradle.properties                # JVM args, AndroidX, Compose compiler
├── gradlew / gradlew.bat            # Gradle wrapper
├── app/
│   ├── build.gradle.kts             # app module build
│   ├── proguard-rules.pro           # R8/ProGuard rules
│   └── src/
│       ├── main/
│       │   ├── AndroidManifest.xml
│       │   ├── java/com/yarisobd/app/
│       │   │   ├── YarisApp.kt              # Application class
│       │   │   ├── MainActivity.kt          # single-activity host
│       │   │   ├── di/                       # manual DI or Hilt modules
│       │   │   ├── data/
│       │   │   │   ├── local/               # Room DB, DAOs, entities
│       │       │   │   ├── remote/           # Retrofit services, DTOs
│       │       │   │   └── repository/       # repository layer
│       │       │   ├── domain/
│       │       │   │   └── model/            # domain models
│       │       │   ├── ui/
│       │       │   │   ├── theme/            # Material 3 theme, colors, typography
│       │       │   │   ├── navigation/       # NavHost, route definitions
│       │       │   │   ├── dashboard/        # live car dashboard screen
│       │       │   │   ├── dashcam/          # file browser + download screen
│       │       │   │   ├── upload/           # upload queue + progress screen
│       │       │   │   ├── trips/            # trip list + route replay screen
│       │       │   │   ├── settings/         # credentials + preferences screen
│       │       │   │   └── components/       # shared composables
│       │       │   └── util/
│       │       │       └── NetworkBinder.kt   # dual-network socket binding
│       │       └── res/
│       │           ├── values/               # strings, colors, themes
│       │           ├── drawable/             # icons, splash
│       │           └── mipmap/               # app launcher icons
│       └── test/                             # unit tests
│       └── androidTest/                      # instrumented tests

Sub-phases

28.1 — Scaffold + networking proof-of-concept ✅ DONE (gate passed 2026-08-12)

28.1.1 — Project creation

• Create Android project in android/ via Android Studio (Empty Activity + Compose)
• Kotlin DSL build files with version catalog
• .gitignore for Android (*.iml, .gradle/, build/, local.properties, .idea/)
• Verify project builds and runs on emulator (needs Android Studio)
• Commit: f1c83a2 init: android project scaffold

28.1.2 — Networking layer

• Add dependencies: OkHttp 4.12, Retrofit 2.11, Kotlinx Serialization 1.7.3
• Create NetworkBinder.kt — discovers WiFi (Pi hotspot) + cellular networks (kept for future use)
• Create Retrofit service interfaces (PiApi.kt, ServerApi.kt) with placeholder endpoints
• Create DTOs: GpsStatus, HealthResponse
• Wire DualNetworkTestScreen.kt with real OkHttp calls + simultaneous "Test Both" button
• Wire MainActivity.kt — simplified to single OkHttpClient, OS routes correctly
• Real-device gate test — PASSED 2026-08-12 on Pixel:
  • "Test Pi" → ✓ Pi OK (200) with live GPS fix data
  • "Test Server" → ✓ Server OK (200) — {"status":"ok"}
  • "Test Both Simultaneously" → ✓ BOTH NETWORKS WORK SIMULTANEOUSLY
  • Key finding: per-socket Network.bindSocket() not needed — Android OS routes 10.42.0.1 through WiFi and yaris.ceaf.dev through cellular automatically
• Commit: 348bfdc feat: Phase 28.1 gate passed

28.1.3 — Credential storage

• Add EncryptedSharedPreferences for server URL, device name, API key
• First-launch screen: text fields for server URL, device name, API key
• "Test connection" button on credentials screen (calls /health on server)
• Persist credentials after successful test
• Commit: feat: encrypted credential storage + first-launch flow

28.2 — Dashcam browser + download ✅ DONE (2026-08-12)

Depends on: 28.1 (networking layer + credentials).

What was built

• Pi API extension (PiApi.kt): listVideos() → VideoListResponse, getVideoFile() (streaming ResponseBody), getThumbnail() (JPEG bytes), deleteVideo()
• DTOs: VideoListResponse, VideoFile (relative_path, size, mtime, sha256, uploaded, thumbnail_url), ConvertProgress
• DashcamScreen: LazyColumn of imported Pi videos with thumbnails via Coil async image loader, file size, date, upload status badge (Uploaded/Pending)
• DashcamViewModel: manages video list state, download to phone storage, delete local copy, conversion progress polling
• Downloads via WorkManager: DownloadWorker foreground service with notification + setProgressAsync() for inline progress bar. ActiveDownload state tracked via WorkManager LiveData observation. Survives screen lock / background. FGS type declared as FOREGROUND_SERVICE_TYPE_DATA_SYNC for Android 14+.
• Downloads tab: progress bar + % for in-flight downloads, downloaded files list
• Bottom navigation: Dashcam tab + Test tab
• Verified: video list loads from real Pi over "yaris 911" hotspot on the owner's Pixel

Commits

• Phase 28.2 — dashcam video browser + WiFi download
• fix: downloads use WorkManager foreground service + inline progress

28.3 — Cellular upload 🚧 IN PROGRESS (2026-08-12)

Depends on: 28.2 (files on phone local storage).

28.3.1 — Server upload data layer ✅ DONE

• Retrofit interface for server chunked upload (data/remote/ServerApi.kt):
  • GET /api/v1/dashcam/upload/status?sha256={hash} → UploadStatus
  • POST /api/v1/dashcam/upload/chunk → multipart (file chunk, sha256, chunk_index, total_chunks)
• Data classes: UploadStatus (already_uploaded, received_chunk_indices, total_chunks)

28.3.2 — Upload worker ✅ DONE

• WorkManager CoroutineWorker (UploadWorker.kt):
  • Input: filename, server URL, device name, API key
  • Step 1: compute SHA256, check /status for already-received chunks
  • Step 2: read file in 40MB chunks (matching DASHCAM_CHUNK_SIZE)
  • Step 3: POST each missing chunk (skips already-received chunks)
  • Step 4: verify server reports already_uploaded after last chunk
• Foreground service notification with live % ("Uploading VID_00234.MOV — 62%")
• Byte-level upload progress via ProgressRequestBody (okio ForwardingSink) — progress reflects actual bytes sent including already-received chunks, not just chunk count
• Robust chunk reads (loop skip()/read() instead of single calls)
• Debug logging (Log.d/Log.e, tag UploadWorker) throughout
• Re-upload guard: skips files already on server (already_uploaded)

28.3.3 — Upload queue UI 🚧 IN PROGRESS

• Downloads screen shows per-file upload status + inline progress bar
• In-app test file generator for upload testing
• "Upload all" button → enqueue all pending files
• Retry button per failed file
• Commit: feat: upload queue screen

28.4 — Live dashboard ⬜ NOT STARTED

Depends on: 28.1 (networking layer). Independent of 28.2/28.3.

28.4.1 — Data layer

• Retrofit interface additions to PiApi:
  • GET /api/gps/status → GpsStatus (has_fix, lat, lon, fix_age_seconds, thread_alive)
  • GET /api/obd/status → ObdStatus (adapter_present, port, car_connected)
  • GET /api/stats → Stats (speed, rpm, coolant_temp, fuel_level, throttle_pos, mil_on, dtc_count, odometer_km)
• Polling scheduler: coroutine while(true) { delay(2000); fetch() } scoped to ViewModel
• Commit: feat: dashboard data polling

28.4.2 — Dashboard UI

• GPS card: MapLibre MapView centered on last fix with car marker
• Speed card: large number (km/h), OBD or GPS source label
• RPM card: gauge or number with color scale (green → yellow → red)
• Engine stats row: coolant temp (°C), fuel level (%), throttle (%)
• MIL/DTC indicator: check-engine icon (green/grey = no MIL, yellow/red = MIL on) with DTC code count badge
• Connection status bar: Pi WiFi icon (green = connected), cellular icon (green = online)
• Auto-refresh every 2s, pause when app is backgrounded
• Commit: feat: live dashboard screen

28.5 — Trip history ⬜ NOT STARTED

Depends on: 28.1. Independent of 28.2–28.4.

28.5.1 — Data layer

• Retrofit interface additions:
  • GET /api/trips → List<TripSummary>
  • GET /api/trip/{id} → TripRoute (list of route points with lat, lon, speed, timestamp)
  • GET /api/geocode?lat={}&lon={} → GeocodeResult (label)
• Room cache: store trip list + last-viewed route for offline viewing
• Commit: feat: trip history data layer

28.5.2 — Trip list UI

• LazyColumn of trips: date, start time, distance (km), duration, start→end locations
• Tap → navigates to route replay
• Sort: by date (default: newest first)
• Commit: feat: trip list screen

28.5.3 — Route replay UI

• MapLibre MapView with route polyline + start/end markers
• Timeline scrubber (slider) with timestamp + speed label
• Play/pause button: animates marker along route
• Geocoded location name below scrubber (debounced while scrubbing)
• Trip stats header: date, distance, duration, avg speed, max speed
• Commit: feat: route replay screen

28.6 — Remote portal direct access ⬜ NOT STARTED

Depends on: 28.1 (credentials). Independent of 28.2–28.5. Stretch goal.

28.6.1 — Auth + data layer

• Retrofit interface for server portal:
  • POST /login → session cookie (or token)
  • GET /api/v1/portal/stats → overview stats
  • GET /api/v1/portal/trips → trip list
  • GET /api/v1/portal/trip/{id} → trip route
  • GET /api/v1/portal/dashcam → dashcam file list
  • GET /api/v1/portal/dashcam/stream/{id} → video stream
• Session persistence: store cookie/token in EncryptedSharedPreferences
• Commit: feat: server portal data layer

28.6.2 — Portal screens

• Reuse trip list + route replay composables from 28.5 (same data shape)
• Reuse dashcam list + player composables (server serves same JSON shape as Pi)
• Login screen (if not already authenticated)
• "Connected to car" vs "Connected to server" mode indicator
• Commit: feat: remote portal screens

28.7 — Polish + distribution ⬜ NOT STARTED

Depends on: 28.1–28.6 (whichever subset ships).

28.7.1 — App polish

• App icon (adaptive icon: foreground + background layers)
• Splash screen (Android 12+ SplashScreen API)
• Dark theme verified on all screens (default, car-friendly)
• Error handling audit: every network call has a user-visible error state + retry
• Accessibility: content descriptions on icons, reasonable touch targets (≥48dp)
• Commit: feat: app polish

28.7.2 — Build + distribution

• Release build signing key (keystore generated, not committed)
• ProGuard/R8 rules verified (Retrofit, OkHttp, Coil, MapLibre keep rules)
• APK output: app/build/outputs/apk/release/app-release.apk
• Self-hosted distribution:
  • Copy APK to Pi: scp app-release.apk [email protected]:~/app/yaris-obd/static/app/
  • Add a lightweight Pi route: GET /app → serves static/app/index.html with download link + install instructions
  • Phone flow: connect to Pi hotspot → open http://yaris.local/app → download APK → install (user must enable "Install unknown apps" once)
• Commit: feat: release build + self-hosted distribution

Working notes

Dual-network binding reference

The key mechanism — from the Android docs and the Phase 11 investigation:

val connectivityManager = context.getSystemService<ConnectivityManager>()

// Find the WiFi network (connected to Pi hotspot)
val wifiNetwork: Network? = connectivityManager.allNetworks
    .firstOrNull { network ->
        val caps = connectivityManager.getNetworkCapabilities(network)
        caps?.hasTransport(NetworkCapabilities.TRANSPORT_WIFI) == true &&
        caps?.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET) == false
        // Pi hotspot has no internet — we WANT this network for local API calls
    }

// Find the cellular network
val cellNetwork: Network? = connectivityManager.allNetworks
    .firstOrNull { network ->
        val caps = connectivityManager.getNetworkCapabilities(network)
        caps?.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) == true
    }

// Create OkHttp clients bound to specific networks
fun OkHttpClient.bindToNetwork(network: Network?): OkHttpClient {
    if (network == null) return this
    return newBuilder()
        .socketFactory(network.socketFactory)
        .dns { network.getAllByName(it) }
        .build()
}

The two clients then share nothing — different socket factories, different DNS resolvers — fully independent network paths.

Pi hotspot info

• SSID: "yaris 911" (WPA2-PSK)
• Subnet: 10.42.0.0/24
• Pi IP: 10.42.0.1
• mDNS: yaris.local (may not resolve on phone hotspot — documented limitation)
• App should use IP 10.42.0.1 directly, not rely on mDNS

Chunked upload protocol (reused from Phase 10)

• Chunk size: 40MB (well under Cloudflare's 100MB free-tier limit)
• /status?sha256=... returns {already_uploaded: true} or {received_chunk_indices: [0,1,3], total_chunks: 8}
• /chunk POST: multipart with file (binary chunk), sha256, chunk_index (0-based), total_chunks
• Server reassembles when all chunks received, verifies SHA256, records in Postgres
• Entirely deduplicated by SHA256 — safe to re-upload chunks, server ignores duplicates

Dependencies (tentative)

[versions]
kotlin = "2.1.0"
compose-bom = "2025.01.00"
okhttp = "4.12.0"
retrofit = "2.11.0"
kotlinx-serialization = "1.7.3"
room = "2.6.1"
workmanager = "2.10.0"
coil = "3.0.4"
maplibre = "11.5.0"
hilt = "2.51.1"

[libraries]
# Compose
compose-bom = { group = "androidx.compose", name = "compose-bom", version.ref = "compose-bom" }
compose-material3 = { group = "androidx.compose.material3", name = "material3" }
compose-navigation = { group = "androidx.navigation", name = "navigation-compose" }

# Network
okhttp = { group = "com.squareup.okhttp3", name = "okhttp", version.ref = "okhttp" }
retrofit = { group = "com.squareup.retrofit2", name = "retrofit", version.ref = "retrofit" }
retrofit-kotlinx-serialization = { group = "com.squareup.retrofit2", name = "converter-kotlinx-serialization", version.ref = "retrofit" }

# Local storage
room-runtime = { group = "androidx.room", name = "room-runtime", version.ref = "room" }
room-ktx = { group = "androidx.room", name = "room-ktx", version.ref = "room" }
room-compiler = { group = "androidx.room", name = "room-compiler", version.ref = "room" }

# Background work
workmanager = { group = "androidx.work", name = "work-runtime-ktx", version.ref = "workmanager" }

# Images
coil-compose = { group = "io.coil-kt.coil3", name = "coil-compose", version.ref = "coil" }

# Maps
maplibre = { group = "org.maplibre.gl", name = "android-sdk", version.ref = "maplibre" }

# Security
security-crypto = { group = "androidx.security", name = "security-crypto", version = "1.1.0-alpha06" }

# DI (optional — manual DI is fine for this scope; add Hilt only if boilerplate gets heavy)
hilt-android = { group = "com.google.dagger", name = "hilt-android", version.ref = "hilt" }
hilt-compiler = { group = "com.google.dagger", name = "hilt-compiler", version.ref = "hilt" }

Real-device testing workflow

1. Build debug APK: ./gradlew assembleDebug
2. Install on Pixel: adb install app/build/outputs/apk/debug/app-debug.apk
3. Connect phone to Pi hotspot
4. Confirm cellular data toggle is ON (Android should show both WiFi and LTE icons)
5. Run the app → check dual-network test screen
6. For upload tests: temporarily pause the Pi's own background uploader (Settings → "Upload dashcam videos" toggle OFF) so the phone's upload isn't racing the Pi's own uploader for the same files

Environment gotchas

• Emulator networking: the Android emulator has its own virtual router. Accessing 10.42.0.1 from the emulator goes through the host machine's network stack — it won't reach the Pi unless the host is also on the Pi's WiFi hotspot. Prefer real-device testing for any network-dependent code.
• Pixel "switch to mobile data automatically": some Android versions have a setting that auto-disables WiFi if it detects no internet. On the Pi hotspot (which has no internet), this could silently drop the WiFi connection. The Phase 11 testing already confirmed this is a hard platform limitation for the web UI; the native app's bindProcessToNetwork() might bypass it. If the OS still kills the WiFi association, the fallback is asking the user to enable "Keep WiFi on when no internet" in Developer Options.
• WorkManager + doze: on Android 6+, WorkManager jobs may be deferred when the device is in Doze mode. For uploads that the user explicitly triggered, consider using a foreground service instead of (or in addition to) WorkManager so uploads continue immediately.
• 40MB chunk memory: the OkHttp MultipartBody will buffer each 40MB chunk in memory before sending. On modern phones with 6GB+ RAM this is fine, but if it becomes an issue, switch to a streaming multipart approach (OkHttp's RequestBody as okio pipe).
• SHA256 of large files: computing SHA256 of a 300MB file on a phone takes a few seconds. Do it once when the download completes, store the result in Room, and reuse for upload. Don't recompute on every upload attempt.