Validations Station

You've been tasked with designing a system that will automate some operations for a railway system. For each station in the system, your app will be able to assign incoming trains to a vacant platform, as well as publish the arrival and departure schedules for individual stations.

You'll be adding validations to the provided models as specified below using Flask validations and constraints. There is also some seed data provided in server/seed.py to give you some data so you can test your models.

Setup

cd into server and run the following in Terminal:

• export FLASK_APP=app.py (if you'll run from the Flask shell)
• export FLASK_RUN_PORT=5555 (if you'll run from the Flask shell)
• flask db init
• flask db migrate -m'Create tables'
• flask db upgrade
• python seed.py

Model Associations

The models are already done for you, and associations should be as follows:

Station --< Platform --< Assignment >--Train

The relationship between platforms and trains is many-to-many through assignments because the same train could be assigned to different platforms in the same station on different days depending on the other traffic through the station.

Instructions

• Add the appropriate code to each model to meet the requirements below
• Some models may need relationships as well as validations
• You do not need to create api routes or a server appliation for this challenge
• There are no tests, so you'll need to test your code with an API client (Postman, etc.) or using ipdb and debug.py
• Test your validations by trying to create model objects which deliberately violate them.
• When creating Assignment objects, enter arrival and departure strings in the format "HH:MM"

Deliverables

Station

• must have a name
• name must be at least 3 characters long
• name must be unique

Platform

• platform_num must be an integer
• platform_num must be in the range 1-20 (inclusive)
• BONUS: platform_num must be unique to each station

Train

• must have an origin and a destination
• origin and destination strings must be between 3 and 24 characters long, inclusive
• service_type must be either "express" or "local"

Assignment

• must have arrival and departure times

BONUS (see the docs on the @validates decorator to help with these):

• must arrive before it departs
• must not stay at platform for more than 20 minutes
• must only be assigned to a vacant platform