yevdyko / airport-challenge

An air traffic control simulation at an airport

Airport Challenge

We have a request from a client to write the software to control the flow of planes at an airport. The planes can land and take off provided that the weather is sunny. Occasionally it may be stormy, in which case no planes can land or take off. Here are the user stories that we worked out in collaboration with the client:

User Stories

As an air traffic controller
So planes can land safely at my airport
I would like to instruct a plane to land

As an air traffic controller
So planes can take off safely from my airport
I would like to instruct a plane to take off

As an air traffic controller
So that I can avoid collisions
I want to prevent airplanes landing when my airport if full

As an air traffic controller
So that I can avoid accidents
I want to prevent airplanes landing or taking off when the weather is stormy

As an air traffic controller
So that I can ensure safe take off procedures
I want planes only to take off from the airport they are at

As the system designer
So that the software can be used for many different airports
I would like a default airport capacity that can be overridden as appropriate

As an air traffic controller
So the system is consistent and correctly reports plane status and location
I want to ensure a flying plane cannot take off and cannot be in an airport

As an air traffic controller
So the system is consistent and correctly reports plane status and location
I want to ensure a plane that is not flying cannot land and must be in an airport

As an air traffic controller
So the system is consistent and correctly reports plane status and location
I want to ensure a plane that has taken off from an airport is no longer in that airport

Here are the user stories converted into a Domain Model:

Object	Messages	Object	Messages	Object	Messages
airport	land	plane	land	weather	stormy?
	take_off		take_off
			airport

Approach

My approach to solving this challenge was to start with an Airport class, build it as much as I could until I needed to start understanding how one class object would interact with another one. At some point I found it's better to extract the weather behaviour into a separate class, with this class containing a single method #stormy? which returned true with a probability of 5%. It has been implemented with the Kernel method rand.

Installation

Clone the repository:

$ git clone [email protected]:yevdyko/airport-challenge.git

Change into the directory:

$ cd airport-challenge

If you don't have bundle already, run the command:

$ gem install bundle

Install all dependencies with:

$ bundle

Testing

To run the tests:

$ rspec

How to use

To see the code in action, open IRB and require the files:

2.3.0 :001 > require './lib/weather'
 => true
2.3.0 :002 > require './lib/plane'
 => true
2.3.0 :003 > require './lib/airport'
 => true

Create a weather object:

2.3.0 :004 > weather = Weather.new
 => #<Weather:0x007f94420bb430>

Create a new airport:

2.3.0 :005 > airport = Airport.new(weather)
 => #<Airport:0x007f94420b22b8 @weather=#<Weather:0x007f94420bb430>,
 @capacity=25, @planes=[]>

Create some planes:

2.3.0 :006 > plane1 = Plane.new
 => #<Plane:0x007f94420aa1d0 @flying=true>
2.3.0 :007 > plane2 = Plane.new
 => #<Plane:0x007f94420a02c0 @flying=true>

Land planes:

2.3.0 :008 > airport.land(plane1)
 => [#<Plane:0x007f94420aa1d0 @flying=false, @airport=#<Airport:0x007f94420b22b8
 @weather=#<Weather:0x007f94420bb430>, @capacity=25, @planes=[...]>>]
2.3.0 :009 > airport.land(plane2)
 => [#<Plane:0x007f94420aa1d0 @flying=false, @airport=#<Airport:0x007f94420b22b8
 @weather=#<Weather:0x007f94420bb430>, @capacity=25, @planes=[...]>>,
 #<Plane:0x007f94420a02c0 @flying=false, @airport=#<Airport:0x007f94420b22b8
 @weather=#<Weather:0x007f94420bb430>, @capacity=25, @planes=[...]>>]

If the weather is stormy, you may need to try landing the plane a few times.

Send a plane to take off:

2.3.0 :010 > airport.take_off(plane2)
 => #<Plane:0x007f94420a02c0 @flying=false, @airport=#<Airport:0x007f94420b22b8
 @weather=#<Weather:0x007f94420bb430>, @capacity=25,
 @planes=[#<Plane:0x007f94420aa1d0 @flying=false, @airport=#<Airport:0x007f94420b22b8 ...>>,
 #<Plane:0x007f9442098890 @flying=false, @airport=#<Airport:0x007f94420b22b8 ...>>]>>

Check the planes in the airport:

2.3.0 :011 > airport.planes
 => [#<Plane:0x007f94420aa1d0 @flying=false, @airport=#<Airport:0x007f94420b22b8
 @weather=#<Weather:0x007f94420bb430>, @capacity=25, @planes=[...]>>]