# Intrasys - Internal Transfers System

![Rust](https://img.shields.io/badge/rust-%23000000.svg?logo=rust&logoColor=white)
![PostgreSQL](https://img.shields.io/badge/PostgreSQL-316192?style=for-square&logo=postgresql&logoColor=white)
![Tokio](https://img.shields.io/badge/Tokio-1.46-green?style=for-square)
![Sqlx](https://img.shields.io/badge/Sqlx-0.8-green?style=for-square)
![Axum](https://img.shields.io/badge/Axum-0.8-green?style=for-square)

Intrasys is an internal financial transfers application built with Rust and Axum, providing HTTP endpoints for account management and transaction processing with PostgreSQL as the backing database.

## Features

- Account creation with initial balance
- Account balance queries
- Secure transaction processing between accounts
- Atomic transaction handling with database integrity
- Precise decimal arithmetic for financial amounts

## Prerequisites

- Rust (latest stable version)
- Docker (for database provisioning)
- PostgreSQL client (optional)

## Quick Start

### Using docker compose
Just run

```bash
docker compose up
```

### Build locally

#### Ensure you have rust installed
Follow the steps described [here](https://www.rust-lang.org/tools/install) if you don't

#### Provision PostgreSQL Database

The easiest way is to run a PostgreSQL container with Docker:

```bash
docker run --name intrasys-pg -d -e POSTGRES_PASSWORD=password -p 127.0.0.1:5432:5432 postgres:alpine
```

#### Run the Application

```bash
cargo run
```

The application will be available at `http://localhost:8080`

## API Endpoints

### Account Management

- **Create Account**  
  `POST /accounts`
  ```json
  {
    "account_id": 123,
    "initial_balance": "100.23344"
  }
  ```

- **Get Account Balance**  
  `GET /accounts/{account_id}`  
  Response:
  ```json
  {
    "account_id": 123,
    "balance": "100.23344"
  }
  ```

### Transactions

- **Process Transaction**  
  `POST /transactions`
  ```json
  {
    "source_account_id": 123,
    "destination_account_id": 456,
    "amount": "50.12345"
  }
  ```

## Configuration
The app can be configured using environmental variable that can also be provided through a `.dotenv` file.
The following variables affect the application behavior:

- `INTRASYS_LOG` changes the logging level, can be set to one of `trace`, `debug`, `info`, `warn`, `error`
- `INTRASYS_HOST` is the address the HTTP server will bind to
- `INTRASYS_PORT` is the port the HTTP server will listen to
- any of the environmental variables mentioned [here](https://docs.rs/sqlx/latest/sqlx/postgres/struct.PgConnectOptions.html#method.options) affects the postgres database connection

## Running tests

Make sure you have an available postgres database and edit `DATABASE_URL` variable in the `.env` file accordingly. If you've used the docker command mentioned in the *Quickstart*
section you don't need to change anything.

Then run

```bash
cargo test
```

## Assumptions

- All accounts use the same currency
- No authentication or authorization is implemented
- Decimal precision of 2 decimal places is sufficient for financial amounts, maximum allowed monetary amount is (10^18 -0.01) and the minimum is (-10^18 + 0.01)
- Account IDs are positive integers
- Account creation must NOT be idempotent since it also sets the account balance (creating an account that already exists should fail)
- Transfer money to an account that does not exist should not create a new account, but fail with an error (to prevent users from accidentally locking their money forever)