paypercall

Charge for HTTP APIs on a pay-per-call basis with Bitcoin and Lightning. Available as an express middleware and as a reverse proxy.

Powered by ⚡️ Lightning Charge.

Install

$ npm install paypercall

Server Setup

As a middleware

paypercall can be used as an express middleware to charge payments directly in your node.js apps. Below is an example app that charges 0.1 USD to send out tweets:

app.js

const pay = require('paypercall')({ chargeUrl: ..., chargeToken: ... })
    , twt = require('twitter')({ consumer_key: ..., consumer_secret: ..., ... })
    , app = require('express')()
 
app.use(require('body-parser').urlencoded())
 
app.post('/tweet', pay(0.1, 'USD'), (req, res, next) =>
  twt.post('statuses/update', { status: req.body.message })
    .then(tweet => res.send(tweet))
    .catch(next))
 
app.listen(4000, _ => console.log('HTTP server running on localhost:4000'))

See ifpaytt for a more full-fledged application using paypercall as a middleware.

As a reverse proxy

Alternatively, you can develop your HTTP server with no payments awareness and use paypercall as a reverse proxy to handle payments. An example with a python app:

app.py

from flask import Flask, request
import twitter
 
app = Flask(__name__)
twt = twitter.Api(consumer_key=..., consumer_secret=..., ...)
 
@app.route("/tweet", methods=['POST'])
def tweet():
    return twt.PostUpdate(request.form['message'])
 
@app.run(Port=4001)

Run the python app and the paypercall proxy:

$ FLASK_APP=app.py flask run
* Running on http://localhost:4001/
 
$ paypercall --charge-token mySecretToken --upstream-url http://localhost:4001 \
             --port 4000 --rates-yaml '{ POST /tweet: 0.1 USD }'
HTTP reverse proxy running on http://localhost:4000, proxying to http://localhost:4001

You will now have the python app running on port 4001 (providing API calls free of charge) and the paypercall reverse proxy running on port 4000 (charging on a per-call basis).

Paying for API calls

1. Send an empty request (no body) to the resource to get the BOLT11 payment request and the X-Token header:

   $ curl -i -X POST http://localhost:4000/tweet
    
   HTTP/1.1 402 Payment Required
   Content-Type: application/vnd.lightning.bolt11
   X-Token: lmbdmJeoSQ0ZCB5egtnph.af1eupleFBVuhN2vrbRuDLTlsnnUPYRzDWdL5HtWykY
    
   lnbcrt8925560p1pdfh7n2pp54g5avyupe70l988h30u0hy8agpj2z7qsveu7ejhys97j98rgez0...

2. Make the payment:

   $ lightning-cli pay lnbcrt8925560p1pdfh7n2pp54g5avyupe70l988h30u0hy8agpj2z7qsveu7ejhys97j98rgez0...

3. Send the request again, this time with the request body and with the X-Token header echoed back:

   $ curl -i -X POST http://localhost:4000/tweet \
     -H 'X-Token: lmbdmJeoSQ0ZCB5egtnph.af1eupleFBVuhN2vrbRuDLTlsnnUPYRzDWdL5HtWykY' \
     -d message='I got lightning working and all I got was this tweet'
    
   HTTP/1.1 200 OK
   Content-Type: application/json
    
   {"id_str":"123123123","text":"I got lightning working...",...}

Documentation

Middleware

const pay = require('paypercall')(options)

Returns a new payment middleware factory. options can contain the following fields:

• chargeUrl: Lightning Charge server URL (optional, defaults to http://localhost:9112)
• chargeToken: Lightning Charge access token (required)
• dbPath: Path to sqlite database (optional, defaults to ./paypercall.db)
• currency: Default currency if none is specified (optional, defaults to BTC)
• secret: Secret key used for HMAC tokens (optional, generated based on chargeToken by default)
• invoiceExp: How long should invoices be payable for (optional, defaults to 1 hour)
• accessExp: How long should paid access tokens remain valid for (optional, defaults to 1 hour)

const payware = pay(amount[, currency])

Returns an express middleware that requires a payment of amount units of currency (or the default currency if none provided) before letting requests pass through.

Can be used as following:

const pay = require('paypercall')({ chargeToken: 'myToken', currency: 'EUR' })
    , app = require('express')
 
// charge requests to a specific route
app.post('/sms', pay(0.15), (req, res) => { /* send SMS */ })
 
// charge all requests to /paid-apis/*
app.use('/paid-apis', pay(0.25))
 
// dynamic pricing (should only be based on the method and path)
app.post('/ocr/:type', (req, res, next) => {
  pay(getPriceForType(req.params.type))(req, res, (err) => {
    if (err) return next(err)
    // payment succesfull, run OCR
    // (the paid invoice is accessible at `req.invoice`)
  })
})

Reverse proxy

$ paypercall --help
 
  Charge for HTTP APIs on a pay-per-call basis with Bitcoin and Lightning
 
  Usage
    $ paypercall [options]
 
  Options
    -c, --charge-url <url>      lightning charge server url [default: http://localhost:9112]
    -t, --charge-token <token>  lightning charge access token [required]
 
    -u, --upstream-url <url>    the upstream server to reverse proxy [required]
    -r, --rates-path <path>     path to YAML file mapping from endpoints to rates [default: ./rates.yaml]
    -y, --rates-yaml <yaml>     YAML string to use instead of reading from {rates-path}
    -x, --currency <name>       default rate currency if none is specified [default: BTC]
    -d, --db-path <path>        path to store sqlite database [default: ./payperclick.db]
 
    --invoice-expiry <sec>      how long should invoices be payable for [default: 1 hour]
    --access-expiry <sec>       how long should paid access tokens remain valid for [default: 1 hour]
    --token-secret <secret>     secret key used for HMAC tokens [default: generated based on {charge-token}]
 
    -p, --port <port>           http server port [default: 4000]
    -i, --host <host>           http server listen address [default: 127.0.0.1]
    -e, --node-env <env>        nodejs environment mode [default: production]
    -h, --help                  output usage information
    -v, --version               output version number
 
  Example
    $ payperclick -t myAccessToken -u http://upstream-server.com/ \
                  -y '{ POST /tweet: 0.0001 BTC, PUT /page/:id: 0.0002 BTC }'

License

MIT