darciopacifico / traffic-lights-safetyculture

prompted coding test

Traffic Lights Simulation

Disclaimer:

This little app outputs the result of simulating a set of traffic lights within a time frame and with preset configurations. This was my first contact with Node.js and I leaned it on-the-fly, so some misapplication of concepts or non-conformity for standards are to be expected.

Design choices

The exercise prompt called for a simulation of a set of traffic lights (NS) and (EW) in a cross road where each direction should be Red for 5 minutes, while the opposing set remained 4:30 secs in Green and 30 secs in Yellow, before going Red while the previous Red lights went green, and the cycle repeats. It was necessary to output the result of this running for 30 minutes.

• EventEmitter: the problem looks like a good candidate for the application of an Observer Pattern, so the traffic lights were modelled to be controlled via events.

• The main application: I designed the logic of the traffic lights to be expansible and include multiple sets of traffic lights, but in the spirit of remaining within the bounds of the proposed problem the main executable of the application acts more like a template that solves the proposed problem, but the real meat lies within the code inside the lib/ package. All manner of crossroads configurations could possibly be achieved by multiple instances of LinkedLightsManager coordinating via events.

• Output format: as it was not specified, I went with simplicity, so when ran the application simply outputs to terminal console the resulting state changes along with its simulated times. Again, this can be easily adapted to a more useful format and the variables controlling the simulation start and running time are the top of crossroad-lights.js in the root folder. Cycle and Yellow time configurations are found in /config/time-configs.js

Running

Requirements

This application was developed with Node.js version 5.9.0. Earlier versions were not tested, but it uses some features of ECMA Script 6, so be advised it might not work in earlier versions of Node.js

Instalation

Clone this repository:

git clone https://github.com/vantroy/traffic-lights-safetyculture.git
cd traffic-lights-safetyculture

Install

npm install

Run

npm start

Tests & Coverage

Running tests

npm test

Generating Coverage

Install the Istanbul coverage tool

npm install istanbul -g

Then run:

istanbul cover node_modules/mocha/bin/_mocha      

Open in a browser:

open ./coverage/lcov-report/index.html

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Have a good day :)