FXQL Parser

A NestJS-based Foreign Exchange Query Language (FXQL) Statement Parser that processes and stores currency exchange rate information.

Features

• FXQL statement parsing and validation
• Singleton Design
• Response compression
• PostgreSQL database integration
• Rate limiting
• Comprehensive logging
• Docker support
• API documentation (Swagger)
• Unit tests

Prerequisites

• Node.js (v18 or later)
• Docker and Docker Compose
• PostgreSQL (if running locally)

Installation

Using Docker

1. Clone the repository:

git clone https://github.com/yourusername/fxql-parser.git
cd fxql-parser

2. Create a .env file based on the example:

cp .env.example .env

3. Start the application using Docker Compose:

docker-compose -f docker-compose.yml up --build -d

The application will be available at http://127.0.0.1:3000.

Local Development

1. Install dependencies:

npm install

2. Configure environment variables:

cp .env.example .env
# Edit .env with your local database credentials

3. Start the development server:

npm run start:dev

API Documentation

Base URL

http://localhost:3000/api

Endpoints

1. Parse FXQL Statement

• Endpoint: http://localhost:3000/
• Method: POST
• Description: Parses, validates, and saves FXQL statements to the database.

Request

• Content-Type: application/json
• Body:

POST

Parses and stores FXQL statements.

Request Body

{
  "FXQL": "USD-GBP {\n BUY 100\n SELL 200\n CAP 93800\n}"
}

Success Response (200 OK)

{
  "message": "FXQL Statement Parsed Successfully.",
  "code": "FXQL-200",
  "data": [
    {
      "EntryId": 1,
      "SourceCurrency": "USD",
      "DestinationCurrency": "GBP",
      "SellPrice": 200,
      "BuyPrice": 100,
      "CapAmount": 93800
    }
  ]
}

Error Responses

• Status Code: 400 Bad Request

  • Response Body:

  {
    "message": "Invalid FXQL Statement.",
    "code": "FXQL-400"
  }

• Status Code: 429 Too Many Requests

  • Response Body:

  {
    "message": "Rate limit exceeded.",
    "code": "FXQL-429"
  }

Testing

Run the test suite:

npm run test

Run the end-to-end test:

npm run test:e2e

Run tests with coverage:

npm run test:cov

Rate Limiting

The API implements rate limiting with the following default settings:

• 100 requests per minute per IP
• Configurable via environment variables:
  • RATE_LIMIT_TTL: Time window in seconds
  • RATE_LIMIT_LIMIT: Maximum number of requests per window

Logging

The application logs HTTP requests with the following information:

• Method
• URL
• Status code
• Response size
• Response time
• User agent
• IP address

Environment Variables

DATABASE_HOST=localhost
DATABASE_PORT=5432
DATABASE_USERNAME=postgres
DATABASE_PASSWORD=postgres
DATABASE_NAME=fxql_db
RATE_LIMIT_TTL=60
RATE_LIMIT_LIMIT=100