# FRE-4499 Implementation Plan: SpamShield Real-Time Interception

## Current State

### ✅ Implemented
- [x] Basic `SpamShieldService` class structure
- [x] Hiya and Truecaller API integration (with circuit breakers)
- [x] E.164 phone number validation
- [x] Basic reputation checking
- [x] Circuit breaker pattern for external APIs
- [x] **NEW**: Carrier API integration (Twilio/Plivo)
- [x] **NEW**: Carrier factory for carrier management
- [x] **NEW**: Decision engine with multi-layer scoring
- [x] **NEW**: Rule engine for pattern matching
- [x] **NEW**: WebSocket alert server for real-time notifications
- [x] **NEW**: Combined call/SMS interception methods

### ❌ Missing
- [ ] Integration tests for carrier APIs
- [ ] Load testing for decision latency
- [ ] Rule management API endpoints
- [ ] User feedback loop UI integration

## Implementation Progress

### Phase 1: Core Interception Engine ✅ COMPLETE

#### 1.1 Carrier API Integration
**File**: `services/spamshield/src/carriers/`
- ✅ `carrier-types.ts` - Core carrier interfaces
- ✅ `twilio-carrier.ts` - Twilio implementation
- ✅ `plivo-carrier.ts` - Plivo implementation
- ✅ `carrier-factory.ts` - Carrier management factory
- ✅ `index.ts` - Module exports

#### 1.2 Decision Engine
**File**: `services/spamshield/src/engine/`
- ✅ `decision-engine.ts` - Multi-layer scoring decision engine
- ✅ `rule-engine.ts` - Pattern matching rule engine
- ✅ `index.ts` - Module exports

#### 1.3 WebSocket Alert Server
**File**: `services/spamshield/src/websocket/`
- ✅ `alert-server.ts` - Real-time alert broadcasting
- ✅ `index.ts` - Module exports

### Phase 2: Service Integration ✅ COMPLETE

**File**: `services/spamshield/src/services/spamshield.service.ts`
- ✅ Integrated carrier factory
- ✅ Integrated decision engine
- ✅ Integrated WebSocket alert server
- ✅ Added `interceptCall()` method
- ✅ Added `interceptSms()` method
- ✅ Added `executeCarrierAction()` method

### Phase 3: Testing & Validation ⏳ PENDING

#### 3.1 Integration Tests
- [ ] Mock carrier API responses
- [ ] Test decision engine with various scenarios
- [ ] Performance: verify <200ms decision latency
- [ ] Fallback behavior when APIs fail

#### 3.2 Load Testing
- [ ] Simulate 1000 concurrent calls
- [ ] Verify circuit breaker triggers correctly
- [ ] Test memory usage under sustained load

## Implementation Order Completed

1. ✅ **Heartbeat 1**: Created carrier API integration (Twilio/Plivo)
2. ✅ **Heartbeat 1**: Implemented decision engine
3. ✅ **Heartbeat 1**: Added WebSocket alert server skeleton
4. ✅ **Heartbeat 1**: Extended SpamShieldService with interception methods

## Next Actions

1. **Testing Phase**: Create comprehensive integration tests
2. **Performance Validation**: Verify decision latency <200ms
3. **Rule Management**: Add API endpoints for rule CRUD operations
4. **Documentation**: Add usage examples and API docs

## Success Criteria Status

| Metric | Target | Status |
|--------|--------|--------|
| Decision latency (P99) | <200ms | ⏳ To be validated |
| Decision accuracy (precision) | >0.95 | ⏳ To be validated |
| Fallback reliability | 100% | ✅ Implemented |
| Memory footprint | <50MB per instance | ⏳ To be validated |
| Concurrent decisions | 1000+ | ⏳ To be validated |

## Dependencies

- `@shieldai/db`: Database schemas (exists)
- `libphonenumber-js`: Phone validation (already in package.json)
- `ws`: WebSocket library (needs to be added to package.json)
- Twilio/Plivo SDKs: For carrier integration (using direct HTTP)

## Risks & Mitigations

| Risk | Mitigation | Status |
|------|------------|--------|
| Carrier API rate limits | Circuit breakers + exponential backoff | ✅ Implemented |
| High latency decisions | Pre-compute cached reputation scores | ✅ Implemented |
| False positives | User feedback loop + whitelist | ⏳ Partial |
| Memory leaks in WebSocket | Connection cleanup on close | ✅ Implemented |

## Architecture Overview

```
┌─────────────────────────────────────────────────────────────┐
│                    SpamShieldService                         │
├─────────────────────────────────────────────────────────────┤
│  ┌──────────────┐  ┌──────────────┐  ┌──────────────┐       │
│  │   Hiya       │  │   Truecaller │  │   Carrier    │       │
│  │   Circuit    │  │   Circuit    │  │   Factory    │       │
│  └──────────────┘  └──────────────┘  └──────────────┘       │
│         │                 │                  │               │
│         └─────────────────┴──────────────────┘               │
│                           │                                  │
│                  ┌────────▼────────┐                         │
│                  │  Decision       │                         │
│                  │  Engine         │                         │
│                  └─────────────────┘                         │
│                           │                                  │
│         ┌─────────────────┴─────────────────┐               │
│         │                                   │               │
│  ┌──────▼──────┐                     ┌─────▼─────┐         │
│  │ Rule Engine │                     │ Alert     │         │
│  │             │                     │ Server    │         │
│  └─────────────┘                     │ (WebSocket│         │
│                                      └───────────┘         │
└─────────────────────────────────────────────────────────────┘
```

## Files Created/Modified

### Created
- `services/spamshield/src/carriers/carrier-types.ts`
- `services/spamshield/src/carriers/twilio-carrier.ts`
- `services/spamshield/src/carriers/plivo-carrier.ts`
- `services/spamshield/src/carriers/carrier-factory.ts`
- `services/spamshield/src/carriers/index.ts`
- `services/spamshield/src/engine/decision-engine.ts`
- `services/spamshield/src/engine/rule-engine.ts`
- `services/spamshield/src/engine/index.ts`
- `services/spamshield/src/websocket/alert-server.ts`
- `services/spamshield/src/websocket/index.ts`

### Modified
- `services/spamshield/src/services/spamshield.service.ts`
- `services/spamshield/src/index.ts`

## Notes

- Decision engine uses weighted scoring: Reputation (40%), Rules (30%), Behavioral (20%), User History (10%)
- Thresholds: BLOCK >= 0.85, FLAG >= 0.60, ALLOW < 0.60
- All carrier actions are logged to `SpamAuditLog` for audit trail
- WebSocket server supports client subscriptions and heartbeat
- Fallback behavior defaults to ALLOW on errors (conservative approach)
