Version number: 5b8d0fd276b6d288905ed2f63a934e057e8feca2

Product Analyzes

Business requirements

Product requirements

• Calculator should be attractive
  • ASCI Art in JSON
  • Web calculator
• Equal Expert Branding
  • Branding in JSON
  • Image
• Feature expected from the simple pocket calculator:
  • sum, subtract, divide, multiplication
  • order of operations execution
  • easy way to input an equation
  • integer and floating
  • 10? chars of precision(is there a limitation for number?)
  • clear input

Technical Requirements

• coding exercise no more than 90 minutes, code like for the paying client - what compromises I would take.

  I've spent some time before starting the coding on analyzes, in the meantime before starting coding exercise. It was hard to find 2h of efficient time to do it. So I had a lot of thoughts before starting. Then did the coding. I decided to split time into 15 minutes sessions maximum. To keep on track of what progress I made and do I need to change a plan o execution.

• Required: Test Coverage, Simplicity, Self-explanatory code

• Include Readme with task version number

• Include the Version number

Additional major requirements that I would suggest to the client

• deployment
• product analytics/metrics

How to deliver business value quickly

• Backend endpoint-based calc as the first stage
• 3rd party calc - https://mathjs.org/ https://nerdamer.com/ , https://www.npmjs.com/package/static-eval
• eval could be used to calc equation from a string, but executing JavaScript from a string can lead to an enormous security risk.
• ASCI Art -> Equal Expert Branding
• Server rendered calc webpage
• express.js as a minimalist framework for the app - easy and quick to use, embedded server rendering

Risks

• Small amount of time -> 15 minutes coding sessions

Story Mapping

ID	Input Equation	Calculate	Display Result	Memorize Equation	Clear
1	Endpoint to send equation	Basic operations(+,-)	Add branding - JSON
2	Validate input string + trim		Add branding - ASCI art
3		Basic operations(*,/)
3.1		Order of operations
3.2		Divide by 0
4			HTML page + branding image
5	Home page with equation input

Technology stack

CI

Simple and quick to build, helps with test coverage, code like for the paying client:

• eslint
• husky
• jest
• supertest
• Create app artifacts using Github Releases
• If MVP is created, think about adding Github action for CI
• If MVP is created, think about the creation of an artifact as a Docker image in GitHub Container Registry

CD

Simple and quick to deploy:

• Manual releases to AWS Lightsail
• If MVP is created, add deployment via AWS Pipeline
• If MVP is created, add IaC

App

Simple and quick to build:

• express
• template engine - ejs

Product Monitoring

• If MVP is created, add Mixpanel

Session Notes

Initialize (14 minutes)

• Maybe I could omit using eslint, as a configuration of it is sometimes time-consuming. If you have only 90 minutes, I think you need to trust yourself, or add it later and analyze the project.
• I thought to use Typescript, but the configuration of it and all tools would be even more time-consuming.

Add Express + home endpoint (16 minutes)

• I feel that I could use some nodejs framework, which would generate an application scaffold. Like NestJs
• I think that in 30 minutes I didn't deliver a lot of value to the client.
• I decided to give up this try and use nestjs.