capsul-flask/README.md

# capsulflask

Python Flask web application for capsul.org


## how to run locally

Ensure you have the pre-requisites for the psycopg2 Postgres database adapter package

```
sudo apt install python3-dev libpq-dev
pg_config --version
```

Ensure you have the wonderful `pipenv` python package management and virtual environment cli

```
sudo apt install pipenv
```

Create python virtual environment and install packages

```
# install deps
pipenv install
```

Run an instance of Postgres (I used docker for this, you can use whatever you want, point is its listening on localhost:5432)

```
docker run --rm -it -e POSTGRES_PASSWORD=dev -p 5432:5432 postgres
```

Create a `.env` file to set up the application configuration:

```
nano .env
```

Enter your SMTP credentials like this:
```
MAIL_USERNAME=forest@nullhex.com
MAIL_DEFAULT_SENDER=forest@nullhex.com
MAIL_PASSWORD=**************
```

Run the app 

```
pipenv run flask run
```

Run the app in gunicorn:

```
pipenv run gunicorn --bind 127.0.0.1:5000 app:app
```

-----

## cli 

You can manually mess around with the database like this:

```
pipenv run flask cli sql -f test.sql
```

```
pipenv run flask cli sql -c 'SELECT * FROM vms'
```

This one selects the vms table with the column name header:

```
pipenv run flask cli sql -c "SELECT string_agg(column_name::text, ', ') from information_schema.columns WHERE table_name='vms'; SELECT * from vms"
```

How to modify a payment manually, like if you get a chargeback or to fix customer payment issues:

```
$ pipenv run flask cli sql -c "SELECT id, created, email, dollars, invalidated from payments"
1, 2020-05-05T00:00:00, forest.n.johnson@gmail.com, 20.00, FALSE

$ pipenv run flask cli sql -c "UPDATE payments SET invalidated = True WHERE id = 1"
1 rows affected.

$ pipenv run flask cli sql -c "SELECT id, created, email, dollars, invalidated from payments"
1, 2020-05-05T00:00:00, forest.n.johnson@gmail.com, 20.00, TRUE
```


How you would kick off the scheduled task:

```
pipenv run flask cli cron-task
```

-----

## postgres database schema management

capsulflask has a concept of a schema version. When the application starts, it will query the database for a table named
`schemaversion` that has one row and one column (`version`). If the `version` it finds is not equal to the `desiredSchemaVersion` variable set in `db.py`, it will run  migration scripts from the `schema_migrations` folder one by one until the `schemaversion` table shows the correct version.

For example, the script named `02_up_xyz.sql` should contain code that migrates the database from schema version 1 to schema version 2. Likewise, the script `02_down_xyz.sql` should contain code that migrates from schema version 2 back to schema version 1.

**IMPORTANT: if you need to make changes to the schema, make a NEW schema version. DO NOT EDIT the existing schema versions.**

In general, for safety, schema version upgrades should not delete data. Schema version downgrades will simply throw an error and exit for now. 

-----

## how to setup btcpay server

Generate a private key and the accompanying bitpay SIN for the btcpay API client. 

  I used this code as an example: https://github.com/bitpay/bitpay-python/blob/master/bitpay/key_utils.py#L6

```
$ pipenv run python ./readme/generate_btcpay_keys.py
```

It should output something looking like this:

```
-----BEGIN EC PRIVATE KEY-----
EXAMPLEIArx/EXAMPLEKH23EXAMPLEsYXEXAMPLE5qdEXAMPLEcFHoAcEXAMPLEK
oUQDQgAEnWs47PT8+ihhzyvXX6/yYMAWWODluRTR2Ix6ZY7Z+MV7v0W1maJzqeqq
NQ+cpBvPDbyrDk9+Uf/sEaRCma094g==
-----END EC PRIVATE KEY-----


EXAMPLEwzAEXAMPLEEXAMPLEURD7EXAMPLE
```

In order to register the key with the btcpay server, you have to first generate a pairing token using the btcpay server interface.
This requires your btcpay server account to have access to the capsul store. Ask Cass about this.

Navigate to `Manage store: Access Tokens` at: `https://btcpay.cyberia.club/stores/<store-id>/Tokens`

![](readme/btcpay_sin_pairing.jpg)


Finally, send an http request to the btcpay server to complete the pairing:

```
curl -H "Content-Type: application/json" https://btcpay.cyberia.club/tokens -d "{'id': 'EXAMPLEwzAEXAMPLEEXAMPLEURD7EXAMPLE', 'pairingCode': 'XXXXXXX'}"
```

It should respond with a token: 

```
{"data":[{"policies":[],"pairingCode":"XXXXXXX","pairingExpiration":1589473817597,"dateCreated":1589472917597,"facade":"merchant","token":"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx","label":"capsulflask"}]}
```

And you should see the token in the btcpay server UI:

![](readme/paired.jpg)

Now simply set your `BTCPAY_PRIVATE_KEY` variable in `.env`

NOTE: make sure to use single quotes and replace the new lines with \n.

```
BTCPAY_PRIVATE_KEY='-----BEGIN EC PRIVATE KEY-----\nEXAMPLEIArx/EXAMPLEKH23EXAMPLEsYXEXAMPLE5qdEXAMPLEcFHoAcEXAMPLEK\noUQDQgAEnWs47PT8+ihhzyvXX6/yYMAWWODluRTR2Ix6ZY7Z+MV7v0W1maJzqeqq\nNQ+cpBvPDbyrDk9+Uf/sEaRCma094g==\n-----END EC PRIVATE KEY-----'
```


-----

## testing cryptocurrency payments

I used litecoin to test cryptocurrency payments, because its the simplest & lowest fee cryptocurrency that BTCPay server supports. You can download the easy-to-use litecoin SPV wallet `electrum-ltc` from [github.com/pooler/electrum-ltc](https://github.com/pooler/electrum-ltc) or [electrum-ltc.org](https://electrum-ltc.org/), set up a wallet, and then either purchase some litecoin from an exchange, or ask Forest for some litecoin to use for testing.


## sequence diagram explaining how BTC payment process works

![btcpayment_process](readme/btcpayment_process.png)

This diagram was created with https://app.diagrams.net/.
To edit it, download the <a download href="readme/btcpayment_process.drawio">diagram file</a> and edit it with the https://app.diagrams.net/ web application, or you may run the application from [source](https://github.com/jgraph/drawio) if you wish.