Technical Challenge - Interstellar Route Planner

Brief

Hyperspace Tunneling Corp manages a system-to-system web of hyperspace gates that spans the United Terran Systems. They charge a fee to their users in order to use their network but they want to expand their business.

Recently, they've expanded into transporting people through their network using light transport space-ships that can take up to 5 people to the gate and then use their hyperspace-enabled ships to travel to the destination gate.

We've been asked to develop a system to help calculate the costs of this journey for their clients.

A journey is defined as:

1. Journey to the gate:

   • Personal Transport: £0.30/AU (standard fuel cost) plus £5 per day for ship storage at the gate - (fits up to 4 people)
   • HSTC Transport: £0.45/AU - (fits up to 5 people)

2. An outbound and an inbound hyperspace journey:

   • Spaceflight: £0.10/passenger/hyperplane-unit

• AU (Astronomical Unit) is roughly 149597870.7 Km - the average distance between the Earth and the Sun.
• HU (Hyperplane Unit) is a fictional unit which measures the distance between two gates in the hyperplane - it has no correlation to real-space measurements.

HSTC keeps a table with its gates and their connections:

Gate ID	Gate Name	Connections and Hyperplane units of distance (HU)
SOL	Sol	RAN: 100HU PRX: 90HU SIR: 100HU ARC: 200HU ALD: 250HU
PRX	Proxima	SOL: 90HU SIR: 100HU ALT: 150HU
SIR	Sirius	SOL: 80HU PRX: 10HU CAS: 200HU
CAS	Castor	SIR: 200HU PRO: 120HU
PRO	Procyon	CAS: 80HU
DEN	Denebula	PRO: 5HU ARC: 2HU FOM: 8HU RAN: 100HU ALD: 3HU
RAN	Ran	SOL: 100HU
ARC	Arcturus	SOL: 500HU DEN: 120HU
FOM	Fomalhaut	PRX: 10HU DEN: 20HU ALS: 9HU
ALT	Altair	FOM: 140HU VEG: 220HU
VEG	Vega	ARC: 220HU ALD: 580HU
ALD	Aldermain	SOL: 200HU ALS: 160HU VEG: 320HU
ALS	Alshain	ALT: 1HU ALD: 1HU

graph TD
    SOL[Sol]
    PRX[Proxima]
    SIR[Sirius]
    CAS[Castor]
    PRO[Procyon]
    DEN[Denebula]
    RAN[Ran]
    ARC[Arcturus]
    FOM[Fomalhaut]
    ALT[Altair]
    VEG[Vega]
    ALD[Aldermain]
    ALS[Alshain]

    SOL --100--> RAN
    SOL --90--> PRX
    SOL --100--> SIR
    SOL --200--> ARC
    SOL --250--> ALD
    PRX --90--> SOL
    PRX --100--> SIR
    PRX --150--> ALT
    SIR --80--> SOL
    SIR --10--> PRX
    SIR --200--> CAS
    CAS --200--> SIR
    CAS --80--> PRO
    PRO --80--> CAS
    DEN --5--> PRO
    DEN --2--> ARC
    DEN --8--> FOM
    DEN --100--> RAN
    DEN --3--> ALD
    RAN --100--> SOL
    ARC --500--> SOL
    ARC --120--> DEN
    FOM --10--> PRX
    FOM --20--> DEN
    FOM --9--> ALS
    ALT --140--> FOM
    ALT --220--> VEG
    VEG --220--> ARC
    VEG --580--> ALD
    ALD --200--> SOL
    ALD --160--> ALS
    ALD --320--> VEG
    ALS --1--> ALT
    ALS --1--> ALD

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Gates are typically one-way, so while the route A->B can exist, it doesn't necessarily mean that B->A exists. Additionally, the hyperplane distance varies depending on which way you travel - Our best theories say the hyperplane not only does not match real-space but also has a preferred direction.

Gate Data

Feel free to use any form of storage for the gate and routes information.

You can make use of the SQL script create-local-postgres-db.sql to seed a postgres database.

Your task:

Write a server that exposes an API that allows a user to calculate the cost of their journey:

• From wherever they are to the nearest gate
• From one gate to a destination gate

The API should expose, at least, the following endpoints:

• GET: /transport/{distance}?passengers={number}&parking={days} - returns the cheapest vehicle to use (and the cost of the journey) for the given distance (in AUs), number or passengers and days of parking (i.e. vehicle storage at the gate)
  • Gates typically sit above the star, so if you're on Earth and want to travel to the Sol gate, the distance would be ~1AU.
• GET: /gates - returns a list of gates with their information
• GET: /gates/{gateCode} - returns the details of a single gate
• GET: /gates/{gateCode}/to/{targetGateCode} - returns the cheapest route from gateCode to targetGateCode

These endpoints should be public.

Expectations

• A link to the deployed API
• API documentation - e.g. Swagger, Postman collection
• Any diagrams, plans or notes you made while designing the solution
• A git repository with the solution
  • Application code
    • Use any programming language you like (unless stated otherwise)
  • Infrastructure config/code - e.g. Terraform
  • Tests
  • Any CI/CD configuration - e.g. github actions
  • Any supporting scripts to generate, package, run, etc...
• Instructions on how to run the application locally

Getting help

If you have any questions, please feel free to reach out to me via email (tco@keyholding.com).

This is a genuine offer for help - I want to see you succeed! - and it lets me understand how you work and communicate.