IntraPay

IntraPay is a lightweight internal transfer system built in Go. It allows users to register internal accounts, query balances, and process secure transactions between accounts. Designed with simplicity, concurrency safety, and modularity in mind, IntraPay is ideal as a foundational financial microservice in fintech or internal wallet systems.

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Features

• Create account with initial balance
• Get account balance
• Create transaction between two accounts with balance check and rollback
• Safe transactions using FOR UPDATE and retry logic
• Clean architecture: separated API, service, and repository layers
• Full unit test coverage for service and API logic

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API Endpoints

1. Create Account

POST /accounts

Request Body:

{
  "account_id": 123,
  "initial_balance": 100.0
}

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2. Get Account Balance

GET /accounts/{id}

Path Parameter:

• id: integer, account ID

Response:

{
  "account_id": 123,
  "balance": 100.0
}

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3. Create Transaction

POST /transactions

Request Body:

{
  "source_account_id": 1,
  "destination_account_id": 2,
  "amount": 50.0
}

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Setup & Installation

1. Prerequisites

• Docker + Docker Compose
• Go 1.21+ (only needed for development outside containers)

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2. Start the Application

From the root directory, run:

docker-compose up --build

This will:

• Start the PostgreSQL service
• Apply the schema from migrations/001_init.sql
• Start the Go application server

Once complete, the app will be running at: 📍 http://localhost:8080

Note: Make sure Docker and PostgreSQL is running on your system.

3. Test API with curl

Create Account

curl -X POST http://localhost:8080/accounts \
  -H "Content-Type: application/json" \
  -d '{"account_id": 1, "initial_balance": 100}'

Get Account

curl -X GET http://localhost:8080/accounts/1

Create Transaction

 curl -X POST http://localhost:8080/transactions \
 -H "Content-Type: application/json" \
 -d '{"source_account_id": 2, "destination_account_id": 1, "amount": 50}'

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That's a useful command for developers! Here's a clean and general way to include it in your documentation:

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Accessing the PostgreSQL Database

To inspect your database from the terminal, you can run:

docker exec -it intrapay_db psql -U <your_user> -d <your_database>

For example, if you're using the default credentials in .env:

docker exec -it intrapay_db psql -U postgres -d intrapay

Tip: Replace <your_user> and <your_database> with the values from your .env file:

• POSTGRES_USER
• POSTGRES_DB

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Run Tests

To run all unit tests (API + service logic):

go test ./internal/... -v

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Project Structure

.
├── cmd/server             # Application entry point
├── internal
│   ├── api                # HTTP handlers
│   ├── db                 # DB connection setup
│   ├── models             # Request structs
│   ├── service            # Business logic (Service layer)
│   ├── repository         # Data access abstraction
├── migrations             # SQL schema
├── Dockerfile             # Docker image for app
├── docker-compose.yml     # PostgreSQL + app services
├── go.mod / go.sum        # Dependencies
└── README.md

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License

This project is licensed under the MIT License - see the LICENSE.md file for details.