Echo-LSAT

A middleware for Echo framework that uses LSAT (a protocol standard for authentication and paid APIs) and provides handler functions to accept microtransactions before serving ad-free content or any paid APIs.

Installation

Assuming you've installed Go and Echo

1. Run this:

go get github.com/getAlby/echo-lsat

2. Create .env file (refer .env_example) and configure LND_ADDRESS and MACAROON_HEX for LND client or LNURL_ADDRESS for LNURL client, LN_CLIENT_TYPE (out of LND, LNURL) and ROOT_KEY (for minting macaroons).

Usage

This example shows how to use Echo-LSAT for serving simple JSON response:-

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"strconv"

	"github.com/getAlby/echo-lsat/echolsat"
	"github.com/getAlby/echo-lsat/ln"

	"github.com/joho/godotenv"
	"github.com/labstack/echo/v4"
)

const SATS_PER_BTC = 100000000

const MIN_SATS_TO_BE_PAID = 1

type FiatRateConfig struct {
	Currency string
	Amount   float64
}

func (fr *FiatRateConfig) FiatToBTCAmountFunc(req *http.Request) (amount int64) {
	if req == nil {
		return MIN_SATS_TO_BE_PAID
	}
	res, err := http.Get(fmt.Sprintf("https://blockchain.info/tobtc?currency=%s&value=%f", fr.Currency, fr.Amount))
	if err != nil {
		return MIN_SATS_TO_BE_PAID
	}
	defer res.Body.Close()

	amountBits, err := ioutil.ReadAll(res.Body)
	if err != nil {
		return MIN_SATS_TO_BE_PAID
	}
	amountInBTC, err := strconv.ParseFloat(string(amountBits), 32)
	if err != nil {
		return MIN_SATS_TO_BE_PAID
	}
	amountInSats := SATS_PER_BTC * amountInBTC
	return int64(amountInSats)
}

func main() {
	router := echo.New()

	router.GET("/", func(c echo.Context) error {
		return c.JSON(http.StatusAccepted, map[string]interface{}{
			"code":    http.StatusAccepted,
			"message": "Free content",
		})
	})

	err := godotenv.Load(".env")
	if err != nil {
		log.Fatal("Failed to load .env file")
	}
	lnClientConfig := &ln.LNClientConfig{
		LNClientType: os.Getenv("LN_CLIENT_TYPE"),
		LNDConfig: ln.LNDoptions{
			Address:     os.Getenv("LND_ADDRESS"),
			MacaroonHex: os.Getenv("MACAROON_HEX"),
		},
		LNURLConfig: ln.LNURLoptions{
			Address: os.Getenv("LNURL_ADDRESS"),
		},
	}
	fr := &FiatRateConfig{
		Currency: "USD",
		Amount:   0.01,
	}
	lsatmiddleware, err := echolsat.NewLsatMiddleware(lnClientConfig, fr.FiatToBTCAmountFunc)
	if err != nil {
		log.Fatal(err)
	}

	router.Use(lsatmiddleware.Handler)

	router.GET("/protected", func(c echo.Context) error {
		lsatInfo := c.Get("LSAT").(*echolsat.LsatInfo)
		if lsatInfo.Type == echolsat.LSAT_TYPE_FREE {
			return c.JSON(http.StatusAccepted, map[string]interface{}{
				"code":    http.StatusAccepted,
				"message": "Free content",
			})
		} else if lsatInfo.Type == echolsat.LSAT_TYPE_PAID {
			return c.JSON(http.StatusAccepted, map[string]interface{}{
				"code":    http.StatusAccepted,
				"message": "Protected content",
			})
		} else {
			return c.JSON(http.StatusAccepted, map[string]interface{}{
				"code":    http.StatusInternalServerError,
				"message": fmt.Sprint(lsatInfo.Error),
			})
		}
	})

	router.Start("localhost:8080")
}

Testing

Run go test to run tests.