PARKING LOT PROBLEM

Rules

The main programming langauge is Ruby
We expect that you will not use any big frameworks like Rails, because we want to understand how you will structure your code
You can use any library you want to avoid overengineering (for tests, database connection and mapping, etc)
Please ensure that you follow the syntax and formatting of both the input and output samples.
We are really, really interested in your object orientated development skills, so please solve the problem keeping this in mind.
Unit tests are mandatory, so please ensure that all your code has tests/specs. Additionally, it's a huge plus if you test drive your code.
When implementing this solution, please use a version control system of your choice that works on Linux and OSX. We expect you to send us a zip/tarball or a git bundle of your source code when you're done that includes the VCS metadata so we can look at your commit logs and understand how your solution evolved.
Please do not make either your solution or this problem statement publicly available by, for example, using github or bitbucket or by posting this problem to a blog or forum.

How to submit the task ?

Please create a public Github repository.
Upload your task in to the repository.
Commit the code in atomic chunks of commits with meaningful description for each commit.
Send us an email at tech@getgrover.com (and cc andreaboada@getgrover.com) with subject "Submit - Backend Coding Challenge" Include the repository link to your submission in the email.
For queries, shoot us an email at tech@getgrover.com

Our Judgement Guidelines

Attention to detail.
Architectural choices.
Is the code clean and robust.
We expect high test coverage

Problem Statement

I own a multi-storey parking lot that can hold up to 'n' cars at any given point in time. Each slot is given a number starting at 1 increasing with increasing distance from the entry point in steps of one. I want to create an automated ticketing system that allows my customers to use my parking lot without human intervention.

When a car enters my parking lot, I want to have a ticket issued to the driver. The ticket issuing process includes us documenting the registration number (number plate) and the colour of the car and allocating an available parking slot to the car before actually handing over a ticket to the driver (we assume that our customers are nice enough to always park in the slots allocated to them). The customer should be allocated a parking slot which is nearest to the entry. At the exit the customer returns the ticket which then marks the slot they were using as being available.

Due to government regulation, the system should provide me with the ability to find out: a) Registration numbers of all cars of a particular colour. b) Slot number in which a car with a given registration number is parked. c) Slot numbers of all slots where a car of a particular colour is parked.

We interact with the system via a simple set of commands which produce a specific output. Please take a look at the example below, which includes all the commands you need to support - they're self explanatory. The system should allow input in two ways. Just to clarify, the same codebase should support both modes of input - we don't want two distinct submissions.

It should provide us with an interactive command prompt based shell where commands can be typed in.
It should accept a filename as a parameter at the command prompt and read the commands from that file.

Example: File

To run the program:

$ my_program file_inputs.txt > output.txt

Input (file):

create_parking_lot 6
park KA-01-HH-1234 White
park KA-01-HH-9999 White
park KA-01-BB-0001 Black
park KA-01-HH-7777 Red
park KA-01-HH-2701 Blue
park KA-01-HH-3141 Black
leave 4
status
park KA-01-P-333 White
park DL-12-AA-9999 White
registration_numbers_for_cars_with_colour White
slot_numbers_for_cars_with_colour White
slot_number_for_registration_number KA-01-HH-3141
slot_number_for_registration_number MH-04-AY-1111

Output (could be a console or a file):

Created a parking lot with 6 slots
Allocated slot number: 1
Allocated slot number: 2
Allocated slot number: 3
Allocated slot number: 4
Allocated slot number: 5
Allocated slot number: 6
Slot number 4 is free
Slot No.    Registration No    Colour
1    KA-01-HH-1234    White
2    KA-01-HH-9999    White
3    KA-01-BB-0001    Black
5    KA-01-HH-2701    Blue
6    KA-01-HH-3141    Black
Allocated slot number: 4
Sorry, parking lot is full
KA-01-HH-1234, KA-01-HH-9999, KA-01-P-333
1, 2, 4
6
Not found

Example: Interactive

To run the program and launch the shell:

$ my_program

Assuming a parking lot with 6 slots, the following commands should be run in sequence by typing them in at a prompt and should produce output as described below the command:

Input: create_parking_lot 6

Output: Created a parking lot with 6 slots

Input: park KA-01-HH-1234 White

Output: Allocated slot number: 1

Input: park KA-01-HH-9999 White

Output: Allocated slot number: 2

Input: park KA-01-BB-0001 Black

Output: Allocated slot number: 3

Input: park KA-01-HH-7777 Red

Output: Allocated slot number: 4

Input: park KA-01-HH-2701 Blue

Output: Allocated slot number: 5

Input: park KA-01-HH-3141 Black

Output: Allocated slot number: 6

Input: leave 4

Output: Slot number 4 is free

Input: status

Output (we've used a table to make our lives easier, but tab delimited output is fine):

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

Input: park KA-01-P-333 White

Output: Allocated slot number: 4

Input: park DL-12-AA-9999 White

Output: Sorry, parking lot is full

Input: registration_numbers_for_cars_with_colour White

Output: KA-01-HH-1234, KA-01-HH-9999, KA-01-P-333

Input: slot_numbers_for_cars_with_colour White

Output: 1, 2, 4

Input: slot_number_for_registration_number KA-01-HH-3141

Output: 6

Input: slot_number_for_registration_number MH-04-AY-1111

Output: Not found