lnurl.go

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"net"
	"net/http"
	"strconv"
	"time"

	"github.com/fiatjaf/go-lnurl"
	"github.com/gorilla/mux"
	"github.com/tidwall/sjson"
)

func handleLNURL(w http.ResponseWriter, r *http.Request) {
	username := mux.Vars(r)["username"]
	domain := r.Host

	log.Info().Str("username", username).Str("domain", domain).
		Msg("got lnurl request")

	if amount := r.URL.Query().Get("amount"); amount == "" {
		// check if the receiver accepts comments
		var commentLength int64 = 0
		if v, err := net.LookupTXT("_webhook." + domain); err == nil && len(v) > 0 {
			commentLength = 500
		}

		json.NewEncoder(w).Encode(lnurl.LNURLPayResponse1{
			LNURLResponse:   lnurl.LNURLResponse{Status: "OK"},
			Callback:        fmt.Sprintf("https://%s/.well-known/lnurlp/%s", domain, username),
			MinSendable:     1000,
			MaxSendable:     100000000,
			EncodedMetadata: makeMetadata(username, domain),
			CommentAllowed:  commentLength,
			Tag:             "payRequest",
		})

	} else {
		msat, err := strconv.Atoi(amount)
		if err != nil {
			json.NewEncoder(w).Encode(lnurl.ErrorResponse("amount is not integer"))
			return
		}

		bolt11, err := makeInvoice(username, domain, msat)
		if err != nil {
			json.NewEncoder(w).Encode(
				lnurl.ErrorResponse("failed to create invoice: " + err.Error()))
			return
		}

		json.NewEncoder(w).Encode(lnurl.LNURLPayResponse2{
			LNURLResponse: lnurl.LNURLResponse{Status: "OK"},
			PR:            bolt11,
			Routes:        make([][]lnurl.RouteInfo, 0),
			Disposable:    lnurl.FALSE,
			SuccessAction: lnurl.Action("Payment received!", ""),
		})

		// send webhook
		go func() {
			if v, err := net.LookupTXT("_webhook." + domain); err == nil && len(v) > 0 {
				body, _ := sjson.Set("{}", "pr", bolt11)
				body, _ = sjson.Set(body, "amount", msat)
				if comment := r.URL.Query().Get("comment"); comment != "" {
					body, _ = sjson.Set(body, "comment", comment)
				}

				(&http.Client{Timeout: 5 * time.Second}).
					Post(v[0], "application/json", bytes.NewBufferString(body))
			}
		}()
	}
}