# Fenceless Grazing System API Server

This is the repository for the API server component of the Fenceless
Grazing System. This server is written in Python using the Flask
microframework, and uses the SQLAlchemy ORM to interact with the SQLite
database.

## Getting the Dependencies

The API server depends on several packages to operate properly, which
will likely not be installed by default on your system. There are two
ways to get the required dependencies: using Python's
`virtualenv` (standard in the Python ecosystem), or using Nix (only if you are into that kind of thing).

### Getting the Dependencies with `virtualenv`

First, create a virtual environment (this only has to be done once):

```Bash
virtualenv venv
```

Once the virtual environment has been created, activate it using the
following command:

```Bash
source venv/bin/activate
```

This effectively creates an independent Python environment, into
which you can install packages without affecting your entire
system. You can now install the packages from the `requirements.txt` file:

```Bash
pip install -r requirements.txt
```

With this, you should have all the necessary dependencies.

### Getting the Dependencies with Nix

Below is the Nix expression I use daily to work on
this application:

```Nix
with import <nixpkgs> {};

mkShell {
    buildInputs = [ (python3.withPackages (ps: with ps; [ flask flask_sqlalchemy pyjwt bcrypt geopy pip ])) ];
}
```

Note that some packages (`geopy` in particular) are currently unstable; the expressions from stable Nixpkgs
may not provide a working derivation. When using the `nixpkgs-unstable`, I have no such issues.

## Setting Up
The application requires the `DB_LOC` environment variable to be set to indicate the location
of the database that the server should use:

```Bash
export DB_LOC=database.sqlite
```

Additionally, Flask uses the `FLASK_APP` environment variable to determine the entry point
of a web application

```Bash
# Here, fgs represents the fgs/ directory in the repository's root.
export FLASK_APP=fgs
```

Finally, on first run, you need to create the tables in the application's database.
This can be done as follows:

```Python
flask shell
# Imports, among other things, the db variable, which is the handle for the SQLAlchemy ORM.
from fgs import *

# SQLAlchemy needs to be aware of the various tables in our database
from fgs.model import *

# Creates all tables
db.create_all()

# It also helps to set up a user and a couple of collars:
user = User(username='user', password='password')
collar1 = Collar(name='Sample Collar', active=True)
collar2 = Collar(name='Another Collar', active=True)

# To add the newly created objects to the database, use
# db.session.add and db.session.commit
db.session.add(user)
db.session.add(collar1)
db.session.add(collar2)
db.session.commit()

# You can now press Ctrl-D to exit the Flask shell. 
```

Once the database has been created, you can start the server
with:

```Bash
flask run
```

## Next Steps
Once the server is up and running, consider setting up the
[app](https://dev.danilafe.com/CS-46X/app), which is able
interact with this API server. Additionally, check out the
[cow description language](https://dev.danilafe.com/CS-46X/cdl)
if you want to generate mock data for the API server's database.