Mid-market Currency Converter

This repository contains the code for the API that converts mid-market currencies for given source and target currencies. It scrapes the exchange rates from wise.com and calculates the converted amount to provide a response.

Project Setup

The project is containerized using docker to ensure consistent dev environment across developers and create a "good-enough" replica of the production environment. The project uses requirement.txt for packaging and dependency management. It is also used to create a virtual environment from the dependencies listed in the file.

The developer is expected to install the following tools before starting work on this project:

• Docker
• git
• python 3.11.0a3
• make**

*Why is make a pre-requisite? Makefile is used to help with some commands that are frequently used in the development worflow like:

• Setting up virtual environment
• Building docker images
• Installing requirements

Setup virtual environment

In order to maintain a consistent development environment across all developers, it is advised that they install Pyenv which is a Python Version Management tool. This allows to download and switch between multiple versions of python easily. This project uses Python 3.11.0a3 as specified in the .python-version file.

Build Docker Images

First build the backend docker image using the following make command:

make docker/build

Collect Environment file

Refer to the "dev.env" file and collect all the required environment variables to run the containers.

Run the containers

Use the following make command to run the docker container:

make docker/run

The api docs should be accessible at localhost:5000/api/docs.

Running DB Migrations

I am using PostgreSQL as the database of choice to store/fetch data in the pipeline. So, naturally, you will need to create and run migrations to change the table schemas in database. alembic is used to handle migrations in this project which under the hood uses SQLAlchemy engine to connect to the database.

Following is the common sequence of actions you would perform to create & run migrations in the database during local development.

• Add/Remove or Make changes to the table schemas in src/db/models folder. Use SQLAlchemy ORM to define the models.

• Attach a shell to the docker container

  docker exec -it <container-id> sh
  

• Once inside the container, cd src/db to get into the directory that contains the alembic.ini file

• Here, you can run alembic commands to auto-generate the migration

  alembic revision --autogenerate -m "<migration name>"
  

• This will create a migration file that has upgrade and downgrade commands. Check it thoroughly.

• Run migrations

  alembic upgrade head
  

  Pending migrations are automatically applied when you spin up the container next time after closing/exiting.

Pre-commit checks

To ensure strict linting in the future commits, I encourage using a pre-commit hook:

1. Setup the pre-commit hook

• Setup virtualenv

make venv/build

• Install precommit in the venv

pre-commit install

• Now the pre-commit hook should run before each commit. Or, you can check by using:

pre-commit run --all-files