Parking Lot Problem

About Problem

To design a parking lot system with ability to find:

Registration numbers of all cars of a particular colour.
Slot number in which a car with a given registration number is parked.
Slot numbers of all slots where a car of a particular colour is parked.

Pre requisites

The source code for this project is written using Node.js. Make sure you have Node.js installed on your computer before running this application, if not please install Node.js from here.

To check if you have Node.js and NPM installed by running simple commands to see what version of each is installed:

Test Node.js: To see if Node is installed, type node -v in Terminal. This should print the version number so you’ll see something like this v10.16.0.
Test NPM. To see if NPM is installed, type npm -v in Terminal. This should print the version number so you’ll see something like this 6.9.0.

Note: Node installer installs both Node.js and npm on your system.

How to run?

This is a console application written in Node.js. This can be run in two modes:

Interactive Mode: An interactive terminal based shell where commands can be typed in to perform different actions.
File Mode: It accepts a filename as a parameter at the terminal and read the commands from that file.

Quick Start

Proceed to the steps below only if you've Node.js installed. If not, please refer pre requisites section.

For Interactive Mode

Open terminal and navigate (cd) to this folder and type the following commands:

1. npm install
2. npm start

For File Mode

Open terminal and type node src/index.js data/input.txt.

node src/index.js <path_to_file.txt>

Note: You can find a few sample input files inside data/ folder.

Explained

STEP 1: npm install or npm i will download all the dependencies defined in package.json file and generate a node_modules/ folder with the installed modules. Learn more here.

STEP 2: npm start or npm run start will start the application. It is equivalent to node src/index.js

Console Application

Navigate to bin/ folder and open parking_lot with double click. It'll open a terminal where different commands can be typed in. You may face permission related issues, please allow opening applications from unauthorized developers as it's blocked due to security reasons. If you're using macOS catalina, you'll be prompted security warning as this binary is not notarized. Learn more about Notarization here.

If you're still facing issues, please build the console application locally. Kindly refer Build Script section to build locally.

List of User Commands

Users can interact with the Parking Lot system via a following simple set of commands which produce a specific output:

create_parking_lot: create_parking_lot 6 will create a parking lot with 6 slots.
park < REGISTRATION NUMBER > < COLOR >: park KA-01-HH-1234 White will allocate the nearest slot from entry gate.
leave: leave 4 will make slot number 4 free.
status: status will display cars and their slot details

Slot No.  Registration No Color
1         KA-01-HH-1234  White
2         KA-01-HH-9999  Red
3         KA-01-BB-0001  White
5         KA-01-HH-2701  Black
6         KA-01-HH-3141  Black

registration_numbers_for_cars_with_colour < COLOR >: registration_numbers_for_cars_with_colour White will display the registration number of the cars of white color e.g. KA-01-HH-1234, KA-01-BB-0001
slot_numbers_for_cars_with_colour < COLOR >: slot_numbers_for_cars_with_colour White will display slot numbers of the cars of white color e.g. 1, 3
slot_number_for_registration_number < REGISTRATION NUMBER >: slot_number_for_registration_number MH-04-AY-1111 will display the slot number for the car with registration number MH-04-AY-1111.
leave_car_by_registration_number: leave_car_by_registration_number JH-01-LT-0008 will free the slot occupied by car with registration number JH-01-LT-0008.
available_slot_numbers: available_slot_numbers will display available slot numbers e.g. 2, 6, 8.
allocated_slot_numbers: allocated_slot_numbers will display occupied slot numbers e.g. 1, 3, 4, 5, 7.
exit: exit will quit the application and return to the console.

NOTE: Any commands which are not mentioned above will throw an error: <INPUT> is an invalid command

To view all the commands in terminal, please run npm run help

Modules - OOPS Approach

There are two classes defined:

ParkingLot(): It is the main class which is used to initialize a parking lot. In each parking lot there is maximum number of slots and an array of slots that will be occupied by the car. It has following methods:

createParkingLot(input) : Creates a parking lot with given input. It throws an error Minimum one slot is required to create parking slot if zero or negative number (n <= 0) is provided as an input.
parkCar(input) : Allocates nearest slot from entry gate to the car. It can throw following errors:
- Minimum one slot is required to create parking slot : When parking lot is not initialized.
- Sorry, parking lot is full : When parking lot has reached its maximum capacity.
- Please provide registration number and color both : When input contains either of two i.e. registration number and color of the car, not both.
leaveCar(input) : Removes car in given slot in parking lot. It throws following errors:
- Sorry, parking lot is empty if parking lot is empty.
- Slot number <SLOT NUMBER> is not found when slot number is absent.
- Slot number <SLOT NUMBER> is already free when slot number is not occupied.
leaveCarByCarNumber (input) : Makes the slot free for car of given registration number.
getParkingStatus() : Returns an array containing slot number, registration number and color. It throws an error Sorry, parking lot is empty if parking lot is empty.
getCarsWithSameColor(input) : Returns a comma separated string containing registration numbers of cars with same color e.g. KA-01-HH-1234, KA-01-HH-9999, KA-01-P-333.
getSlotsWithSameColorCar(input) : Returns a comma separated string containing slot numbers of car with same color e.g. 3, 5, 6.
getSlotByCarNumber(input) : Finds slot number of car for given registration number. It returns Not found when car is not present.
findNearestAvailableSlot() : Finds nearest free slot.
findAllAvailableSlots() : returns a comma separated string of free parking slots e.g. 1, 4, 7. It returns null if parking lot is not created.
findAllAllocatedSlots() : returns a comma separated string of allocated parking slots e.g. 2, 3, 5, 6. It returns null if parking lot is not created.

Car()

new Car(NUMBER, COLOR) : Constructor used to initialize a car object containing two fields, registration number and color.
isCarEqual() : Checks whether two cars are equal or not.

Note: I've made an assumption that the registration number for two cars can never be same.

Test Scripts

Tests are written using Mocha and can be run using npm test

npm run test-unit : Run unit tests only (Tests for functions in Parking Class)
npm run test-system : Run repository tests only (See this section)
npm run test-lint : Run lint tests using ESLint
npm run test : Run all tests (lint tests + unit tests + system tests)

Unit tests

Unit tests are written for the methods of ParkingLot class.

System tests

System tests mainly include repository structure tests. It tests for the following:

Repository must contain:

package.json
README.md
.gitignore
.eslintrc
npm/ folder
src/ folder
tests/ folder

package.json

must have valid name, author and license
must have proper keywords
must have valid version string
must

ParkingLot

Install / Use

README