Billing service

Code challange for an interview. Allows creating bills by sending information about the items in json. The application outputs either json or an PDF.

Assumptions made

The application is used in a web context
The application is a microservice
The type of products is known and does need to be parsed from its name
The output can be either PDF or JSON

Implementation

Uses Spring Boot
Architecture is orientated at Ports & Adapters

Running the app

You can run the app using ./gradlew bootRun, Java 18 is required. App needs to be connected to Postgres DB or launched with dev profile (set SPRING_PROFILES_ACTIVE=dev as environment variable).

Docker

Otherwise, install as well docker and docker compose and build with ./gradlew bootBuildImage then run docker compose up -d.

How to communicate

Below you can see request that can be made to the Backend. See insomnia collection import.

Types

Getting all type: Get on /types results in

[
  {
    "id": "other",
    "name": "Other",
    "description": "Products that do not fall into any other category",
    "valueAddedTax": 0.1,
    "customs": 0.05
  },
  {
    "id": "books",
    "name": "Books",
    "description": "Books can be read",
    "valueAddedTax": 0.0,
    "customs": 0.05
  },
  {
    "id": "meds",
    "name": "medical products",
    "description": "Needed for medicine",
    "valueAddedTax": 0.0,
    "customs": 0.05
  },
  {
    "id": "food",
    "name": "food",
    "description": "food and other eatable things",
    "valueAddedTax": 0.0,
    "customs": 0.05
  }
]

Post on /types with

{
  "id": "wood",
  "name": "Wood",
  "description": "Wood can burn",
  "valueAddedTax": 0.10,
  "customs": 0.05
}

creates the corresponding type. Post on /types/initialization initializes standard types.

Authentication

Writing actions require authentication. In development mode user and password is admin. HTTP basic auth is used.

Bill creation

POST on /bill with

[
  {
    "price": 2799,
    "name": "bottle of perfume",
    "quantity": 1,
    "imported": true
  },
  {
    "price": 1899,
    "name": "bottle of perfume",
    "quantity": 1,
    "imported": false
  },
  {
    "price": 975,
    "name": "packet of headache pills",
    "quantity": 1,
    "typeId": "meds"
  },
  {
    "price": 1125,
    "name": "chocolates",
    "quantity": 1,
    "typeId": "food",
    "imported": true
  }
]

results in

{
  "items": [
    {
      "name": "bottle of perfume",
      "quantity": 1,
      "price": 2799,
      "imported": true,
      "typeId": null,
      "sumRawPrice": 2799,
      "sumTaxes": 420,
      "sumAfterTaxesPrice": 3219
    },
    {
      "name": "bottle of perfume",
      "quantity": 1,
      "price": 1899,
      "imported": false,
      "typeId": null,
      "sumRawPrice": 1899,
      "sumTaxes": 190,
      "sumAfterTaxesPrice": 2089
    },
    {
      "name": "packet of headache pills",
      "quantity": 1,
      "price": 975,
      "imported": false,
      "typeId": "meds",
      "sumRawPrice": 975,
      "sumTaxes": 0,
      "sumAfterTaxesPrice": 975
    },
    {
      "name": "chocolates",
      "quantity": 1,
      "price": 1125,
      "imported": true,
      "typeId": "food",
      "sumRawPrice": 1125,
      "sumTaxes": 55,
      "sumAfterTaxesPrice": 1180
    }
  ],
  "sumRawPrice": 6798,
  "sumTaxes": 665,
  "sumAfterTaxesPrice": 7463
}

Alternatively you can request this in a pdf table. For this set Accept header to application/pdf.

Could be improved / one day

More generic taxation system with a special entity that hold customs and VAT Taxes specific to a point in time
OPEN API specs
Maybe GRAPHQL over JSON
Testing PDF content
PDF generation in Front End might be preferable
Upload Docker image to registry

1-alex98/billing