/shopeetax

Primary LanguageGo

Tax Calculator

Simple tax calculator for test assignment.

How To run:

  1. Install docker in your machine
  2. Run docker-compose up --build

Make sure your machine is connected to internet. On first build, the Dockerfile will download go-dep and its dependencies

Troubleshoot:

  1. docker-compose down -v
  2. docker-compose up --build once more

Live Demo: http://167.99.64.23:9091/shopee/tax/index

A. Database Design

table shopee_tax

This table contains the tax definition for each tax category

Field Type Desc
id INT PRIMARY KEY, NOT NULL
code VARCHAR NOT NULL
description VARCHAR NULL
expression VARCHAR NOT NULL
min_price FLOAT NOT NULL DEFAULT 0.0 
INSERT INTO shopee_tax (code, description, expression, min_price) VALUES 
    ('Food', 'tax for tobacco', '0.1 * ${price}', -1),
    ('Tobaco', 'tax for food items', '10 + (0.02 * ${price})', -1),
    ('Entertainment', 'tax for entertainment', '0.1 * (${price} - 100)', 99);

expression field contains tax calculation ruleset expression. It is possible to add developer assigned variable such as ${price} , etc.

table shopee_taxable_product

This table contains calculated tax product snapshot

Field Type Desc
id INT PRIMARY KEY, NOT NULL
product_name VARCHAR NOT NULL
tax_category_id INT FK
price FLOAT NOT NULL DEFAULT 0.0
tax_price FLOAT NOT NULL DEFAULT 0.0
total_price FLOAT NOT NULL DEFAULT 0.0

B. Code Structure

I uses the N-Layer design pattern with observer pattern support. To sustain Golang idiomaticity, I uses a lot of Go closure or anonymous function to replace the interface, or factory definition. This is the code structure of project module:

app
    +db
        +tax
            -db.go
            -query.go
    +domain
        +tax
            -helper.go
            -struct.go
            -
    +infra
        +lib1
        +lib2
    +model
        +tax
            -struct.go
    resource
        +uires
            -resource.go
        +repores
            -resource.go
        +usecaseres
            -resource.go
    usecase
        +tax
            -usecase_1.go
            -usecase_2.go
    server
        +http.go
        +server.go
    service
        +api
            -tax.go

Description:

  1. db: db package has a single reponsibility as a database repository. It holds database accessor object, and has an ability to perform a query directly by using its connection string. This package has separated module folder based on its database accessor. i.e: tax, user, etc.
  2. model: model package contains definition of business entity. Usually it is described as database table definition. model should not be accessible by other layer, except repository (i.e: database, and domain).
  3. domain: domain contains of helper functions (internal logic) for a module business, structure builder, and connector between business logic (called usecase) and its model. Since business logic is unable to import model, it needs domain to access it.
  4. usecase: usecase is the main business logic or knitting zone for the business logic. Use case has access to domain and repository directly, but not to model. This to ensure model is remain untouched, and refactor should be in domain only.
  5. resource: this package is used to holds all dependencies to each usecase, repository db, and server / presenter ui. By using dependency injection, we can make sure, the code is mockable and testable.
  6. service: contains handler (similar to controller in MVC)
  7. server: server definition and initialization, including routing handling.

C. Unit Test

Not added, (template only). Real implementation can be seen on domain/tax/helper_test.go