# 16. Backend Router — VoicePrint (Voice Cloning Detection)

meta:
  id: shieldai-unified-restructure-16
  feature: shieldai-unified-restructure
  priority: P1
  depends_on: [shieldai-unified-restructure-12, shieldai-unified-restructure-13, shieldai-unified-restructure-14]
  tags: [backend, trpc, voiceprint, ml, api]

objective:
- Build the tRPC router for VoicePrint, the AI voice cloning detection service. Port all logic from `services/voiceprint/` and `packages/api/src/routes/voiceprint.routes.ts` into a unified `voiceprint` router and service layer.

deliverables:
- `web/src/server/api/routers/voiceprint.ts` — VoicePrint router:
  - `voiceprint.getEnrollments` — `protectedProcedure` returning voice enrollments
  - `voiceprint.createEnrollment` — `protectedProcedure` uploading and processing voice sample
  - `voiceprint.deleteEnrollment` — `protectedProcedure` removing enrollment
  - `voiceprint.analyzeAudio` — `protectedProcedure` analyzing audio for synthetic voice detection
  - `voiceprint.getAnalyses` — `protectedProcedure` returning analysis history
  - `voiceprint.getAnalysisResult` — `protectedProcedure` returning detailed analysis results
  - `voiceprint.getJobStatus` — `protectedProcedure` checking batch analysis job status
- `web/src/server/services/voiceprint.service.ts` — Core business logic:
  - `createEnrollment(userId, name, audioBuffer, metadata)` — save audio, generate embedding hash
  - `deleteEnrollment(userId, enrollmentId)` — remove audio file and DB record
  - `analyzeAudio(userId, audioBuffer, enrollmentId?)` — run ML detection:
    - Preprocess audio (VAD, noise reduction)
    - Run ECAPA-TDNN model for synthetic detection
    - If enrollment provided, run FAISS vector matching
    - Return confidence score and verdict
  - `getAnalyses(userId, filters?)` — query analysis history
  - `createBatchJob(userId, audioFilePath)` — create analysis job for async processing
- `web/src/server/services/voiceprint/ml.engine.ts` — ML inference:
  - `preprocessAudio(audioBuffer)` — VAD, resampling, noise reduction
  - `detectSynthetic(audioFeatures)` — ECAPA-TDNN inference
  - `matchVoice(embedding, enrollmentId)` — FAISS vector index search
  - `generateEmbedding(audioFeatures)` — create voice embedding vector
- `web/src/server/services/voiceprint/storage.ts` — Audio file storage:
  - `saveAudio(userId, audioBuffer)` — save to local disk or S3-compatible storage
  - `getAudioUrl(userId, audioHash)` — generate signed URL for retrieval
  - `deleteAudio(audioHash)` — remove file

steps:
1. Create `web/src/server/api/routers/voiceprint.ts`.
2. Define Zod schemas:
   - `createEnrollmentSchema`: `name: z.string().min(1)`, `audioBase64: z.string()` (or multipart handling)
   - `analyzeAudioSchema`: `audioBase64: z.string()`, `enrollmentId: z.string().uuid().optional()`
   - `analysisFilterSchema`: `page`, `limit`, `verdict` optional
3. Implement router procedures:
   - Enrollment CRUD with user ownership
   - Audio analysis with optional enrollment matching
   - Job status queries
4. Create `web/src/server/services/voiceprint.service.ts`:
   - Port from `services/voiceprint/src/voiceprint.service.ts`
   - Handle audio preprocessing pipeline
   - Integrate with ML engine
5. Create ML engine:
   - `preprocessAudio`: use WebRTC VAD logic or a Node.js equivalent (e.g., `node-vad`)
   - `detectSynthetic`: placeholder for ECAPA-TDNN model integration. If model is not available in JS, create a Python microservice bridge or use ONNX Runtime.
   - `matchVoice`: placeholder for FAISS integration. If FAISS is not available in JS, use `faiss-node` or a Python bridge.
   - `generateEmbedding`: create embedding vector for storage
6. Create storage module:
   - For local dev: save to `uploads/voiceprint/{userId}/{hash}.wav`
   - For production: integrate with S3, R2, or similar
   - Generate presigned URLs for client retrieval
7. Implement analysis pipeline:
   - Save audio → preprocess → run detection → store result → create alert if synthetic detected
   - If enrollment provided, also run matching and include similarity score
8. Wire router into `web/src/server/api/root.ts`.
9. Write unit tests for service functions (mock ML engine).

steps:
- Unit: `createEnrollment` saves audio and creates DB record
- Unit: `analyzeAudio` returns verdict and confidence
- Unit: `matchVoice` returns similarity score for enrolled voice
- Unit: Storage module saves and retrieves files correctly
- Unit: ML engine placeholders return mock results
- Integration: tRPC procedures enforce user ownership of enrollments

acceptance_criteria:
- [ ] Voice enrollments can be created, listed, and deleted per user
- [ ] Audio analysis returns synthetic/natural/uncertain verdict with confidence score
- [ ] If enrollment is provided, analysis includes voice matching similarity
- [ ] Analysis history is queryable with pagination
- [ ] Batch jobs can be created and their status tracked
- [ ] Audio files are stored securely with user-scoped access
- [ ] Synthetic voice detection triggers an alert notification

validation:
- Upload a test audio file via tRPC client, verify enrollment created
- Request analysis on test audio, verify result structure (verdict, confidence, metadata)
- Verify that user A cannot access user B's enrollments or analyses
- Run `cd web && pnpm test` for VoicePrint unit tests

notes:
- Reference legacy: `services/voiceprint/src/`, `packages/api/src/routes/voiceprint.routes.ts`
- The ECAPA-TDNN and FAISS components may require Python or compiled native modules. If they cannot run in the Node.js monolith:
  - Option A: Create a lightweight Python gRPC/HTTP service for ML inference, call it from the monolith
  - Option B: Use ONNX Runtime Node.js bindings if a converted model is available
  - Option C: Keep the Python service separate but unify the API layer in tRPC (the monolith calls the Python service internally)
- For this task, implement the service layer with a pluggable ML engine interface. Use mock/stub implementations if native ML is not yet available.
- Audio files can be large. Consider streaming uploads instead of base64 encoding for production.
- The analysis pipeline should be idempotent: analyzing the same audio twice should return cached results.