title: System Architecture
aliases: [3netra Architecture, Meta App Architecture]
tags: [3netra/wiki, architecture, diagrams]
product: 3netra Meta Android App
source_repository: 3Netra-ai/3n_meta_android
source_ref: origin/prod
source_revision: b48aada8fd5427b5db0c02945569963c4ae543c8
last_verified: 2026-08-06
up: "[[Home]]"

System Architecture

High-Level System Diagram

flowchart TB
    subgraph HW["Meta Ray-Ban Smart Glasses"]
        CAM[12MP Camera]
        MIC[Mic Array]
        SPK[Open-ear Speakers]
        TAP[Temple Touch Controls]
    end

    subgraph PHONE["3netra Companion App (Kotlin/Compose)"]
        UI[UI Layer — Jetpack Compose]
        BT[BluetoothService — orchestrator]
        WCS[WearableCameraService — Meta MWDAT]
        VLM[Vision Pipeline — SupabaseAiService]
        FACE[FaceNet TFLite + Supabase face_embeddings]
        TTS[TTS — Android TTS; Sarvam path conditional]
        VOICE[VoiceCommandService / AudioTranscriptionService]
    end

    subgraph CLOUD["Cloud"]
        SB[(Supabase — Auth/Postgres/Realtime)]
        EDGE[Supabase Edge Function chat-vision]
        OAI[OpenAI gpt-4o]
        SARVAM[Sarvam.ai — translate/TTS/STT]
        OLLAMA[Ollama LAN — moondream/llava — dev only]
    end

    CAM -->|MWDAT camera session| WCS
    TAP -.gesture callback bridge not found.- BT
    MIC -->|BT SCO| VOICE
    BT --> WCS --> VLM
    VLM -->|Functions invoke| EDGE --> OAI
    BT --> TTS --> SARVAM
    SPK -.audio.- TTS
    UI --> SB
    FACE --> SB
    VLM -.legacy/dev only.- OLLAMA

Service-Oriented App Architecture

flowchart LR
    subgraph UI["UI Layer (Compose screens)"]
        S[Screens + ViewModels]
    end
    subgraph SVC["Service Layer (singletons)"]
        SUP[SupabaseService — auth+DB]
        BLS[BluetoothService — gestures/pipeline/chat]
        AI[SupabaseAiService — Edge Function client]
        SAR[SarvamService — Indic voice]
        WCSV[WearableCameraService — Meta camera]
        FNM[FaceNetModel + Supabase face embeddings]
        EMS[EmergencyAlertManager — SOS]
        MISC[Hallway/Recess/Emotion services — prompt wrappers]
    end
    subgraph EXT["External"]
        SB[Supabase]
        EDGE[Supabase Edge Function]
        SA[Sarvam API]
        META[Meta MWDAT SDK / BLE]
        AND[Android TTS / SpeechRecognizer / CameraX]
    end
    S --> SVC
    SUP --> SB
    BLS --> META
    AI --> EDGE
    SAR --> SA
    WCSV --> META
    EMS --> SB
    MISC --> AWSS
    BLS --> AND

Repository Layout (polyglot)

3nApp-Mobile/
├── src/frontend/                 # ★ PRIMARY — native Kotlin/Compose app (own Gradle build)
│   └── app/src/main/kotlin/com/threenetra/app/
│       ├── MainActivity.kt       # entry: Meta SDK init, auth deep links, start destination
│       ├── MainViewModel.kt      # Supabase auth StateFlow
│       ├── services/ (18)        # Supabase, Bluetooth, AwsBackend, Sarvam, WearableCamera,
│       │                         # VoiceCommand, AudioTranscription, Emotion, Hallway, Recess,
│       │                         # EmergencyAlert, PinManager, SmartCapture, VisionService(Ollama)…
│       ├── ml/FaceNetModel.kt    # TFLite FaceNet embeddings (facenet.tflite asset)
│       ├── ui/                   # Navigation, auth, onboarding, student screens, NetraTheme
│       └── utils/                # EncryptedFaceStorageManager, MediaCompressor, PdfExportManager
├── src/backend/                  # AWS SAM prototype — not referenced by the active app path
├── android/                      # Expo/React Native generated shell (vestigial; no JS sources)
├── app/                          # root-level Kotlin prototype (camera stub, returns null)
├── functions/                    # Firebase Cloud Functions — Resend welcome/notification emails (legacy)
├── api/send-welcome.js           # Vercel serverless — Resend welcome email (legacy)
├── supabase/                     # Supabase CLI local dev config (no migrations/seed committed)
├── docs/                         # 16-file doc suite (architecture, API, VLM, setup, debugging)
├── .agent_docs/                  # PRD (md+pdf), architecture/design prompts, assets
└── skills/                       # agent skills: prod-local-deploy, sync-agent-skills, vlm-providers

Backends

1. Supabase (primary data/auth)

GoTrue auth (email/password, email OTP, Google IDToken), PostgREST, Realtime channel on student_settings. Kotlin SDK io.github.jan-tennert.supabase BOM 2.5.0 + Ktor. See 08-Data-Model-Supabase.

2. Supabase Edge Function (active app call target)

SupabaseAiService invokes chat-vision through the Supabase Functions client. The deployed function source calls OpenAI gpt-4o, but the Android client discards the function response and returns the literal success text "AI response received". Thus capture/chat/summary UI wiring is present, but meaningful model narration is not verified at this ref.

3. AWS SAM "Routing Logic" prototype (not active)

One Lambda (nodejs20.x, 30s/512MB) behind API Gateway catch-all /{proxy+} is implemented, including routes below, but AwsBackendService has no production call sites (only its minimal test).

4. Legacy email paths

Firebase Cloud Functions (sendWelcomeEmail on auth.user onCreate, sendNotificationEmail callable) and Vercel api/send-welcome.js — all via Resend. No firebase.json; Supabase replaced Firebase auth/data.

AI Pipeline (capture → speech)

1. Trigger: UI button, glasses gesture, or voice command
2. WearableCameraService.capturePhoto() — MWDAT device session → 15fps LOW stream → still photo (Bitmap/HEIC → bytes; mutex-guarded)
3. Optional on-device FaceNet calculation followed by Supabase embedding lookup (People/Emotions modes)
4. SupabaseAiService invokes chat-vision; at this ref it replaces the response with a fixed success string
5. logLocalSession() → in-memory history and an attempted Supabase sessions insert
6. Speech is Android TTS in SceneDescriptionScreen; BluetoothService.speak() has a conditional Sarvam path. End-to-end voice/vendor behavior is untested.

See the sequence diagram in 03-Frontend-Navigation#Frontend Flow Chart (core capture loop).

Tech Stack