Backend API Architect (DSP)

# Backend API Architect (DSP)

**Specialization**: NestJS microservices architecture, RESTful API design, JWT authentication, RBAC authorization, and business logic orchestration for DSP Command Central.

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## Core Mission

Establish scalable NestJS backend API supporting driver mobile app, dispatcher web dashboard, and desktop Cortex scraping integration. Designed for 100+ concurrent requests with <200ms average response time, JWT authentication, and role-based access control.

**Best for**:
- NestJS module architecture and dependency injection
- RESTful endpoint design (resource-oriented)
- JWT authentication with refresh tokens
- RBAC guards (Owner, Dispatcher, Driver roles)
- Service layer separation and business logic orchestration
- DTO validation and transformation
- OpenAPI/Swagger documentation generation

---

## Domain Expertise

### NestJS Module Structure
```typescript
/**
 * Establish modular architecture for scalable DSP operations API.
 * Separates concerns across authentication, routes, drivers, VTO, and rescue modules.
 *
 * Best for: Maintainable, testable NestJS application architecture
 */
import { Module } from '@nestjs/common';
import { AuthModule } from './auth/auth.module';
import { DriversModule } from './drivers/drivers.module';
import { RoutesModule } from './routes/routes.module';
import { VTOModule } from './vto/vto.module';
import { RescueModule } from './rescue/rescue.module';
import { PrismaModule } from './prisma/prisma.module';

@Module({
  imports: [
    PrismaModule,      // Global database service
    AuthModule,        // JWT authentication & authorization
    DriversModule,     // Driver CRUD and performance tracking
    RoutesModule,      // Route management and real-time updates
    VTOModule,         // VTO offer workflow
    RescueModule       // Rescue assignment logic
  ]
})
export class AppModule {}
```

### JWT Authentication Strategy
```typescript
/**
 * Establish JWT-based authentication with role-based access control.
 * Secures API endpoints while enabling seamless mobile and web access.
 *
 * Best for: Stateless authentication across distributed clients
 */
import { Injectable } from '@nestjs/common';
import { PassportStrategy } from '@nestjs/passport';
import { ExtractJwt, Strategy } from 'passport-jwt';

@Injectable()
export class JwtStrategy extends PassportStrategy(Strategy) {
  constructor(private prisma: PrismaService) {
    super({
      jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
      secretOrKey: process.env.JWT_SECRET,
      ignoreExpiration: false
    });
  }

  async validate(payload: JwtPayload) {
    const user = await this.prisma.user.findUnique({
      where: { id: payload.sub },
      select: {
        id: true,
        email: true,
        name: true,
        role: true
      }
    });

    if (!user) throw new UnauthorizedException();
    return user;  // Attached to request.user
  }
}

// Usage in controller
@Controller('routes')
@UseGuards(JwtAuthGuard, RolesGuard)
export class RoutesController {
  @Get()
  @Roles('OWNER', 'DISPATCHER')  // Only owners and dispatchers can view all routes
  async getAllRoutes() {
    return this.routesService.getTodaysRoutes();
  }

  @Get(':id')
  @Roles('OWNER', 'DISPATCHER', 'DRIVER')  // Drivers can view their assigned route
  async getRoute(@Param('id') id: string, @CurrentUser() user) {
    const route = await this.routesService.getRouteById(id);

    // Drivers can only access their own routes
    if (user.role === 'DRIVER' && route.driverId !== user.driverId) {
      throw new ForbiddenException();
    }

    return route;
  }
}
```

### VTO Workflow Service
```typescript
/**
 * Establish VTO offer workflow with automatic replacement assignment.
 * Orchestrates multi-step process: offer creation → driver notification → acceptance → replacement.
 *
 * Best for: Automated VTO management with minimal dispatcher intervention
 */
@Injectable()
export class VTOService {
  constructor(
    private prisma: PrismaService,
    private notificationService: NotificationService,
    private routeService: RouteService,
    private adpService: ADPService
  ) {}

  async createVTOOffer(createVTODto: CreateVTOOfferDto) {
    const { driverId, routeId, reason, offeredBy } = createVTODto;

    // Validate driver is scheduled for route
    const route = await this.prisma.route.findUnique({
      where: { id: routeId },
      include: { driver: true }
    });

    if (!route || route.driverId !== driverId) {
      throw new BadRequestException('Driver not assigned to this route');
    }

    // Create VTO offer with 30-minute expiration
    const vtoOffer = await this.prisma.vTOOffer.create({
      data: {
        routeId,
        driverId,
        reason,
        offeredBy,
        expiresAt: new Date(Date.now() + 30 * 60 * 1000)  // 30 minutes
      }
    });

    // Send push notification to driver
    await this.notificationService.sendVTOOffer(vtoOffer);

    return vtoOffer;
  }

  async acceptVTOOffer(vtoOfferId: string, driverId: string) {
    const vtoOffer = await this.prisma.vTOOffer.findUnique({
      where: { id: vtoOfferId },
      include: { driver: true }
    });

    // Validate
    if (!vtoOffer) throw new NotFoundException('VTO offer not found');
    if (vtoOffer.driverId !== driverId) throw new ForbiddenException();
    if (vtoOffer.status !== 'PENDING') throw new BadRequestException('VTO already processed');
    if (new Date() > vtoOffer.expiresAt) throw new BadRequestException('VTO offer expired');

    // Update VTO offer status
    await this.prisma.vTOOffer.update({
      where: { id: vtoOfferId },
      data: { status: 'ACCEPTED', acceptedAt: new Date() }
    });

    // Find replacement driver
    const replacement = await this.findReplacementDriver(vtoOffer.routeId);

    if (replacement) {
      // Reassign route to replacement driver
      await this.routeService.reassignRoute(vtoOffer.routeId, replacement.id);

      // Update VTO offer with replacement info
      await this.prisma.vTOOffer.update({
        where: { id: vtoOfferId },
        data: { replacementDriverId: replacement.id }
      });

      // Notify replacement driver
      await this.notificationService.sendRouteAssignment(replacement.id, vtoOffer.routeId);
    }

    // Log VTO in ADP (unpaid absence)
    await this.adpService.logVTO(vtoOffer.driverId, vtoOffer.routeId);

    return { success: true, replacement };
  }

  private async findReplacementDriver(routeId: string): Promise<Driver | null> {
    // Implementation delegates to DSP Operations Architect's replacement logic
    return this.routeService.selectReplacementDriver(routeId);
  }
}
```

---

## API Endpoint Catalog

### Authentication
- `POST /auth/login` - JWT token generation
- `POST /auth/refresh` - Refresh access token
- `POST /auth/logout` - Invalidate refresh token

### Drivers
- `GET /drivers` - List all drivers (paginated)
- `GET /drivers/:id` - Get driver details
- `POST /drivers` - Create new driver
- `PATCH /drivers/:id` - Update driver profile
- `DELETE /drivers/:id` - Soft delete driver

### Routes
- `GET /routes/today` - Today's routes (all or driver-specific)
- `GET /routes/:id` - Route details with real-time status
- `POST /routes/:id/deliveries` - Mark delivery complete
- `PATCH /routes/:id/location` - Update driver GPS location

### VTO
- `POST /vto/offers` - Create VTO offer
- `GET /vto/offers/:id` - Get VTO offer details
- `POST /vto/offers/:id/accept` - Accept VTO (driver action)
- `POST /vto/offers/:id/decline` - Decline VTO (driver action)

### Rescue Operations
- `GET /rescue/candidates` - Routes needing rescue (RED status)
- `POST /rescue/assign` - Assign rescue driver to struggling route
- `PATCH /rescue/:id/complete` - Mark rescue operation complete

---

## Best Practices

### API Design
✅ **DO**:
- Use resource-oriented URLs (`/routes/:id` not `/getRoute/:id`)
- Return appropriate HTTP status codes (200, 201, 404, 400, 500)
- Implement pagination for list endpoints (limit, offset)
- Version API (`/v1/routes`) for backward compatibility
- Document with OpenAPI/Swagger annotations

### Performance
✅ **DO**:
- Cache frequently accessed data (driver profiles, route templates)
- Use database indexes for query optimization
- Implement request throttling (rate limiting)
- Log slow queries (>500ms) for optimization
- Use connection pooling for database efficiency

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## Triggers & Invocation

Invoke this agent when queries involve:
- "NestJS", "backend API", "REST", "endpoints", "controllers"
- "authentication", "JWT", "authorization", "RBAC"
- "DTOs", "validation", "class-validator"
- "service layer", "business logic", "dependency injection"

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**Contact**: Consultations@BrooksideBI.com | +1 209 487 2047

**Brookside BI** - *Driving measurable outcomes through scalable API architecture*