PRESIM Backend

The API server for PRESIM — a scenario-based public speaking rehearsal platform that places users inside a lifelike virtual environment with responsive AI audience behaviour.

Tech Stack

• NestJS + TypeScript (strict mode)
• PostgreSQL — relational database
• TypeORM — ORM with migrations
• ULID — sortable unique identifiers for primary keys
• Swagger — auto-generated API documentation
• Jest — unit and e2e testing
• Helmet — security headers
• class-validator — request validation

Project Structure

src/
├── common/
│   └── filters/            # Global exception filter
├── config/
│   └── database.config.ts  # TypeORM async configuration
├── database/
│   ├── data-source.ts      # Standalone DataSource for TypeORM CLI
│   ├── migrations/         # Database migrations
│   └── seeds/              # Seed data scripts
├── health/
│   ├── health.controller.ts
│   └── health.module.ts
├── scenarios/
│   ├── dto/                # Request/response DTOs with validation
│   ├── entities/           # TypeORM entity definitions
│   ├── scenarios.controller.ts
│   ├── scenarios.service.ts
│   └── scenarios.module.ts
├── app.module.ts
└── main.ts

API Endpoints

Method	Path	Description
GET	/api/v1/scenarios	List all scenarios (optional ?category= filter)
GET	/api/v1/scenarios/:slug	Get a single scenario by slug
GET	/api/v1/health	Health check
GET	/api/docs	Swagger API documentation

Getting Started

Prerequisites

• Node.js 22+
• PostgreSQL (pgAdmin or psql)

Database Setup

1. Create the database:

CREATE DATABASE presim;

2. Copy environment variables:

cp .env.example .env

3. Update .env with your PostgreSQL credentials.

4. Run migrations:

npm run migration:run

5. Seed data:

npm run seed

Running the Server

# Install dependencies
npm install

# Development (watch mode)
npm run start:dev

# Production
npm run build
npm run start:prod

The API will be available at http://localhost:3000. Swagger docs at http://localhost:3000/api/docs.

Environment Variables

Variable	Description	Default
NODE_ENV	Environment mode	development
API_PORT	Server port	3000
DATABASE_HOST	PostgreSQL host	localhost
DATABASE_PORT	PostgreSQL port	5432
DATABASE_NAME	Database name	presim
DATABASE_USER	Database user	postgres
DATABASE_PASSWORD	Database password	postgres
CORS_ORIGINS	Allowed origins (comma-separated)	http://localhost:5173

Scripts

Command	Description
npm run start:dev	Start in development watch mode
npm run start:prod	Start production build
npm run build	Compile TypeScript
npm run test	Run unit tests
npm run test:watch	Run tests in watch mode
npm run test:cov	Run tests with coverage report
npm run test:e2e	Run end-to-end tests
npm run migration:run	Run pending database migrations
npm run migration:revert	Revert last migration
npm run seed	Seed the database with scenario data
npm run lint	Lint with ESLint

Testing

# Unit tests
npm run test

# With coverage
npm run test:cov

# E2E tests
npm run test:e2e

Test Coverage

• Scenarios Service — findAll, findAll with category filter, findOne, 404 handling
• Scenarios Controller — GET /scenarios, GET /scenarios/:slug, query passthrough, error propagation
• Health Controller — status response with timestamp
• Global Exception Filter — HttpException handling, unknown error handling, response shape

Security

• Helmet — security headers (X-Content-Type-Options, X-Frame-Options, etc.)
• CORS — restricted to configured origins
• Rate Limiting — 100 requests per minute per IP
• Input Validation — class-validator with whitelist (strips unknown fields)
• SQL Injection Prevention — TypeORM parameterized queries
• No Secrets in Code — all configuration via environment variables

Database Design

The scenarios table uses ULID primary keys and JSONB columns for nested data:

Column	Type	Notes
id	varchar(26)	ULID primary key
slug	varchar(64)	Unique human-readable identifier
audience_roles	jsonb	Array of role objects
behaviour_rules	jsonb	Array of rule objects
audience_size_range	jsonb	[min, max] tuple
duration_options	jsonb	Array of duration integers
*_id columns	varchar	FK references to future tables