Car Cutter - Backend Challenge

Task

As a backend developer you get the task to implement an API route using Python

... which accepts json data from our customers and store certain parts of it to the filesystem.
Since this is a pretty simple task, we want you to think of best practices, edge cases and good software engineering.

Please fork our repo and implement the challenge in src/core/challenge_api.py.

Customers will post some json data to this api route, and we want to store each Vehicle in the Vehicle-List to a single file. This file should be stored to a folder named like the user_id and the filename should be the id with a ".json" extension.

Once you are done, just create a pull request to base:develop. Please leave a comment what you think about the task and how long it took you to finish.

Run It

Serve the API route with:

$ python src/cli.py api-server vehicle-features

By default, the API is now reachable at http://127.0.0.1:8080/backend/
Our customers will post json files to the route /challenge. We provide a json schema and an example.

Expect our customers to post their data with different approaches like:

curl --location --request POST 'http://localhost:8080/backend/challenge' \
  --header "Content-Type: application/json" \
  --data @json/vehicle-features.v1.example.json

or

curl --request POST 'http://localhost:8080/backend/challenge' \
  --header "Content-Type: application/json" \
  --form data=@json/vehicle-features.v1.example.json

Setup

We use Python 3.7 with Flask to run the http server.

Virtual Environment (API and CLI)

You can use pyenv to manage different versions of Python on your local PC.

To complete the setup run the following command inside the repository directory. Whenever you enter the repository folder then, pyenv will automatically use Python 3.7:

pyenv install 3.7.13
pyenv local 3.7.13
python3 --version  # verify whether we're indeed using Python 3.7

We need a virtual environment for local development. Inside the repository directory run:

python3 -m venv venv
source venv/bin/activate
pip install -r requirements.txt

Formatting

To format your code before committing run make format or integrate black into your IDE.

Caveat: Black either puts all function arguments into a single line or one argument per line. To split a long line of arguments into several lines, you must add a trailing comma after the last argument. For example, transform(argument1, argument2,) will be converted to multiple lines by Black. The following example on the other hand will be collapsed into a single line, because it lacks a trailing comma:

transform(
    argument1,
    argument2
)

PyCharm

If you're using PyCharm and you want your files to be auto-formatted on save follow these steps:

• Setup the virtualenv environment venv as outlined above. Black should automatically be installed, because it's listed in requirements.txt. As a short-cut (without local development possibility) you can run: python3 -m venv venv && venv/bin/python install black==22.3.0
• Install the File Watchers plugin
• In the File Watchers plugin, setup black with the following settings:
  • File Type: Python
  • Program: $PyInterpreterDirectory$/black
  • Arguments: --line-length=140 $FilePath$
  • Output paths to refresh: $FilePath$
  • Working Directory: $ProjectFileDir$
  • Uncheck "Auto-save edited files to trigger the watcher"
  • Uncheck "Trigger the watcher on external changes"

VSCode

The repository already contains the required settings for VSCode in .vscode. If you want to automatically format when you save a file, you can additionally enable the setting Format on Save in your VSCode.

Unit Tests

Unit tests require the following dependencies: pytest, coverage

pip install coverage pytest
make unit-test
make coverage