tax-calculator-example

TAX CALCULATOR EXAMPLE

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How to run

You can easily run this by running using docker-compose up command. It will pull and run PostgreSQL too.

You need this environment variable:

ADDRESS=localhost:9000 [where this application should exposed to the world]
DEBUG=true [set the application debug, such as request log and query log]
DB_SYNC_MIGRATION=true [sync the migration needed by this application into database]
DB_MASTER_URL=postgres://my_user:my_database@postgresql-master/my_database?sslmode=disable [your master postgreSQL database]
DB_SLAVES_URL=postgres://my_user:my_database@postgresql-slave/my_database?sslmode=disable [your slave replica of postgreSQL database, you can use many slave by separate them by semicolon]

Then access your swagger docs at http://localhost:9000/swagger/index.html

About the project

This project is written in Golang, and using following the structure https://github.com/golang-standards/project-layout. It will separates the code by the function/role of a package.

For example, the package or class (or struct in Go), which can be accessed outside this project should be put in pkg directory. And code inside internal must only be accessed from this project. This follows Open/closed principle rule in SOLID princriples.

In this project I create the db package that located in pkg/db which managing master and slave connection. In pkg directory, I also create the validator package. Both on those packages, I create an interface and implement it using 3rd party library. This makes us easy to change to another package if we want to change those 3rd party package.

For database connection, I use github.com/go-pg/pg, while gopkg.in/go-playground/validator.v9 for validator package. Both of this package is based on Dependency inversion principle.

In addition, to implement Single responsibility principle, I separates the User and Tax in different package inside the internal/pkg/repo directory. This makes us easier to understand that all data source related to user rely on internal/pkg/repo/user, while tax on internal/pkg/repo/user. But, since both of them fetch the data from same database, it shares the same database connection that can be get from conn package (it will and MUST be set in main function when application starts).

REST API

This project only contains 4 (four) end-point, that is (you can also read documentation in Swagger version):

Register new user

Path: POST /api/v1/register

Request parameter:

• username: string, required
• password: string, required

Request example:

{
  "password": "secret",
  "username": "john_doe"
}

Response example:

{
  "authentication_token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJ0YXgtY2FsY3VsYXRvci1leGFtcGxlIiwic3ViIjoiMyIsImF1ZCI6InVzZXIiLCJleHAiOjE1NzAzNzg0NjYsIm5iZiI6MTUzOTI3NDQ2NiwiaWF0IjoxNTM5Mjc0NDY2LCJqdGkiOiIzIn0.h6Ri_KeJWil2ol8y8qoKWgWaWEtDX-Brs0QIIXXAD3U",
  "user": {
    "id": 1,
    "username": "john_doe"
  }
}

Login user

Path: POST /api/v1/login

Request parameter:

• username: string, required
• password: string, required

Request example:

{
  "password": "secret",
  "username": "john_doe"
}

Response example:

{
  "authentication_token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJ0YXgtY2FsY3VsYXRvci1leGFtcGxlIiwic3ViIjoiMSIsImF1ZCI6InVzZXIiLCJleHAiOjE1NzAzNzg1NDgsIm5iZiI6MTUzOTI3NDU0OCwiaWF0IjoxNTM5Mjc0NTQ4LCJqdGkiOiIxIn0.O-mdAdBGToU3boo_MYMaJq_zUrtCROZiWGi4b4xgua0",
  "user": {
    "id": 1,
    "username": "john_doe"
  }
}

Add new task related to current user

Path: POST /api/v1/tax

Request header:

• Authentication-Token: string JWT token from the login

Request parameter:

• name: string, required, name of the item
• price: integer, required, price of the item should be equal or larger than 0
• tax_code: integer, required, the permitted value is:
  • 1 for Food and beverage
  • 2 for Tobacco
  • 3 for Entertainment

Request example:

{
  "name": "Big Mac",
  "price": 1000,
  "tax_code": 1
}

Response example:

{
  "name": "Big Mac",
  "tax_code": 1,
  "type": "Food & Beverage",
  "price": 1000,
  "tax": "100.000000",
  "amount": "1100.000000",
  "refundable": true
}

Get All Bill

Path: GET /api/v1/tax

Request header:

• Authentication-Token: string JWT token from the login

No request parameter needed.

Response example:

{
  "price_sub_total": 1000,
  "tax_sub_total": "100.000000",
  "grand_total": "1100.000000",
  "taxes": [
    {
      "name": "Big Mac",
      "tax_code": 1,
      "type": "Food & Beverage",
      "price": 1000,
      "tax": "100.000000",
      "amount": "1100.000000",
      "refundable": true
    }
  ]
}

Documentation

You can access the Swagger documentation which generated on the fly using https://github.com/swaggo/swag in http://localhost/swagger/index.html.