Checkout

Components

• Go HTTP server exposing a RESTful API built with httprouter.
• Multiple DB support: SQLite (in-memory and file store), Postgres (for production use)
• Dedicated promotions engine for applying promotions/deals to purchases
• Prometheus metrics server endpoint.

System Design

The Checkout server is a stateless web server (microservice) exposing a RESTful HTTP interface.

Code layout

.
├── main.go      // main application entrypoint
├── build        // stores generated binary and code coverage data
├── client       // HTTP client wrappers for interacting with the server REST API
├── cmd          // CLI command package (cobra/viper)
├── constants    // Contains embedded version, service name and other global constants
├── database     // Multiple database driver implementations using GORM
├── docs
│   ├── openapi  // OpenAPI/Swagger docs that can be imported into Postman
│   └── markdown // Additional documentation
├── integration  // Integration testing
├── model        // Database and API model
├── promotions   // Engine with composable promotions strategy implementations
└── server       // HTTP server built with httprouter (high performance, panic recovery, concurrency)

REST API Endpoints

1. Status

• Endpoint: GET /status
• Description: Returns the status of the service.
• Response:

  {
    "message": "OK",
    "version": "1.0.0",
    "service": "checkout-svc"
  }

---

2. Health

• Endpoint: GET /health
• Description: Checks the health of the service and its dependencies.
• Response:

  {
    "version": "1.0.0",
    "service": "checkout-svc",
    "failures": []
  }

---

3. Get Item Price

• Endpoint: GET /v0/inventory/item/price/:key
• Description: Get price information for a single item by SKU or name.
• Parameters:
  • key (path): The SKU or name of the item.
• Response:

  {
    "items": [
      {
        "name": "Item1",
        "sku": "SKU1",
        "price": 10.99,
        "inventory_quantity": 100
      }
    ],
    "total": 10.99,
    "total_with_discount": 10.99
  }

---

4. Get Items Price

• Endpoint: POST /v0/inventory/items/price
• Description: Get total price for a batch of items by SKUs.
• Request Body:

  {
    "skus": ["SKU1", "SKU2"]
  }

• Response:

  {
    "items": [
      {
        "name": "Item1",
        "sku": "SKU1",
        "price": 10.99,
        "inventory_quantity": 100
      },
      {
        "name": "Item2",
        "sku": "SKU2",
        "price": 20.99,
        "inventory_quantity": 200
      }
    ],
    "total": 31.98,
    "total_with_discount": 31.98
  }

---

5. Purchase Items

• Endpoint: POST /v0/inventory/items/purchase
• Description: Execute a purchase order for the supplied item list.
• Request Body:

  {
    "skus": ["SKU1", "SKU2"]
  }

• Response:

  {
    "order_reference": "ORD-12345",
    "cost": 31.98
  }

6. Get Orders

• Endpoint: GET /v0/orders
• Description: List all purchase orders.
• Authentication: Required.
• Response:

  [
    {
      "reference": "ORD-12345",
      "skus": ["SKU1", "SKU2"],
      "cost": 31.98
    }
  ]

7. Add Items

• Endpoint: POST /v0/inventory/items
• Description: Add new or updated items to the inventory.
• Authentication: Required.
• Request Body:

  {
    "items": [
      {
        "name": "Item1",
        "sku": "SKU1",
        "price": 10.99,
        "inventory_quantity": 100
      }
    ]
  }

• Response:

  {
    "items": [
      {
        "id": 1,
        "name": "Item1",
        "sku": "SKU1",
        "price": 10.99,
        "inventory_quantity": 100
      }
    ]
  }

Authentication

• Endpoints requiring authentication:
  • GET /v0/orders
  • POST /v0/inventory/items
• Authentication Method: Include a valid password in the X-Auth-Password header.

Error Responses

All endpoints return the following error response in case of failure:

{
  "error": "Error message"
}

Getting started

Usage

$ make build
$ ./build/checkout --help   
checkout server command line interface.

VERSION:
  semver: v0.0.1-1-g0ab807f
  commit: 0ab807f7b986bd8cfa4b593e97b02da62bc4ba92
  compilation date: 2025-02-19 22:08:26

Usage:
  checkout [subcommand] [flags]
  checkout [command]

Available Commands:
  completion  Generate the autocompletion script for the specified shell
  help        Help about any command
  run         Start the checkout server
  version     Print version details

Flags:
  -h, --help   help for checkout

Use "checkout [command] --help" for more information about a command.

Run the checkout server with in-memory DB

$ make run

Run with SQLite

$ make build
$ ./build/checkout run --sqlite data/db --log-level debug --password 1234

Run with connection to Postgres

Ensure that you have a Postgres instance listening on <DB_HOST>:<DB_PORT> ready to accept connection.

$ make build
$ ./build/checkout run --db-host <DB_HOST> --db-port <DB_PORT> --db-user <DB_USER> --db-password <DB_PASSWORD> --password 1234

Run package tests

$ make test