move example relay implementations to examples/ folder.

examples/expensive/.gitignore

@@ -0,0 +1 @@
+relayer-expensive

examples/expensive/Makefile

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+relayer-expensive: $(shell find .. -name "*.go")
+	CC=$$(which musl-gcc) go build -ldflags='-s -w -linkmode external -extldflags "-static"' -o ./relayer-expensive

examples/expensive/README.md

@@ -0,0 +1,31 @@
+expensive-relay, a sybil-free corner of nostr
+=============================================
+
+  - a nostr relay implementation based on relayer.
+  - uses postgres, which I think must be over version 12 since it uses generated columns.
+  - requires users to manually register themselves to be able to publish events and pay a fee. this should prevent spam.
+  - aside from that it's basically the same thing as relayer basic.
+
+running
+-------
+
+this requires a recent CLN version with Commando.
+
+grab a binary from the releases page and run it with the following environment variables:
+
+    POSTGRESQL_DATABASE=postgresql://...
+    CLN_NODE_ID=02fed8723...
+    CLN_HOST=127.0.0.1:9735
+    CLN_RUNE=...
+    TICKET_PRICE_SATS=500
+
+adjust the values above accordingly.
+
+compiling
+---------
+
+if you know Go you already know this:
+
+    go install github.com/fiatjaf/relayer/expensive
+
+or something like that.

examples/expensive/handler.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+func handleWebpage(w http.ResponseWriter, rq *http.Request) {
+	w.Header().Set("Content-Type", "text/html")
+	w.Write([]byte(`
+<meta charset=utf-8>
+<title>expensive relay</title>
+<h1>expensive relay</h1>
+<a href="https://github.com/fiatjaf/expensive-relay">https://github.com/fiatjaf/expensive-relay</a>
+<p>this is a nostr relay that only accepts events published from keys that pay a registration fee. this is an antispam measure. you can still be banned if you're spamming or doing something bad.</p>
+<p>to register your nostr public key, type it below and click the button.</p>
+<form>
+  <label>
+    nostr public key:
+    <input name=pubkey />
+  </label>
+  <button>Get Invoice</button>
+</form>
+<p id=message></p>
+<a id=link><canvas id=qr /></a>
+<code id=invoice></code>
+<script src="https://cdnjs.cloudflare.com/ajax/libs/qrious/4.0.2/qrious.min.js"></script>
+<script>
+document.querySelector('form').addEventListener('submit', async ev => {
+  ev.preventDefault()
+  let res = await (await fetch('/invoice?pubkey=' + ev.target.pubkey.value)).text()
+  let { bolt11, error } = JSON.parse(res)
+  if (bolt11) {
+    invoice.innerHTML = bolt11
+    link.href = 'lightning:' + bolt11
+    new QRious({
+      element: qr,
+      value: bolt11.toUpperCase(),
+      size: 300
+    });
+  } else {
+    message.innerHTML = error
+  }
+})
+</script>
+<style>
+body {
+  margin: 10px auto;
+  width: 800px;
+  max-width: 90%;
+}
+</style>
+    `))
+}
+
+func handleInvoice(w http.ResponseWriter, rq *http.Request, r *Relay) {
+	w.Header().Set("Content-Type", "application/json")
+	invoice, err := generateInvoice(r, rq.URL.Query().Get("pubkey"))
+	if err != nil {
+		json.NewEncoder(w).Encode(struct {
+			Error string `json:"error"`
+		}{err.Error()})
+	} else {
+		json.NewEncoder(w).Encode(struct {
+			Invoice string `json:"bolt11"`
+		}{invoice})
+	}
+}

examples/expensive/lightning.go

@@ -0,0 +1,88 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"time"
+
+	lnsocket "github.com/jb55/lnsocket/go"
+	"github.com/tidwall/gjson"
+)
+
+func generateLabel(pubkey string) string { return fmt.Sprintf("relayer-expensive:ticket:%s", pubkey) }
+
+func generateInvoice(r *Relay, pubkey string) (string, error) {
+	label := generateLabel(pubkey)
+	cln := lnsocket.LNSocket{}
+	cln.GenKey()
+
+	err := cln.ConnectAndInit(r.CLNHost, r.CLNNodeId)
+	if err != nil {
+		return "", err
+	}
+	defer cln.Disconnect()
+
+	// check if there is an invoice already
+	jparams, _ := json.Marshal(map[string]any{
+		"label": label,
+	})
+	result, _ := cln.Rpc(r.CLNRune, "listinvoices", string(jparams))
+	if gjson.Get(result, "result.invoices.#").Int() == 1 {
+		timestamp := time.Now().Unix()
+		if (gjson.Get(result, "result.invoices.0.expires_at").Int() > timestamp) {
+			return gjson.Get(result, "result.invoices.0.bolt11").String(), nil
+		}
+		jparams, _ := json.Marshal(map[string]any{
+			"label": label,
+			"status": "expired",
+		})
+		cln.Rpc(r.CLNRune, "delinvoice", string(jparams))
+	}
+
+	// otherwise generate an invoice
+	jparams, _ = json.Marshal(map[string]any{
+		"amount_msat": r.TicketPriceSats * 1000,
+		"label":       label,
+		"description": fmt.Sprintf("%s's ticket for writing to relayer-expensive", pubkey),
+	})
+	result, err = cln.Rpc(r.CLNRune, "invoice", string(jparams))
+	if err != nil {
+		return "", err
+	}
+
+	resErr := gjson.Get(result, "error")
+	if resErr.Type != gjson.Null {
+		if resErr.Type == gjson.JSON {
+			return "", errors.New(resErr.Get("message").String())
+		} else if resErr.Type == gjson.String {
+			return "", errors.New(resErr.String())
+		}
+		return "", fmt.Errorf("Unknown commando error: '%v'", resErr)
+	}
+
+	invoice := gjson.Get(result, "result.bolt11")
+	if invoice.Type != gjson.String {
+		return "", fmt.Errorf("No bolt11 result found in invoice response, got %v", result)
+	}
+
+	return invoice.String(), nil
+}
+
+func checkInvoicePaidOk(pubkey string) bool {
+	cln := lnsocket.LNSocket{}
+	cln.GenKey()
+
+	err := cln.ConnectAndInit(r.CLNHost, r.CLNNodeId)
+	if err != nil {
+		return false
+	}
+	defer cln.Disconnect()
+
+	jparams, _ := json.Marshal(map[string]any{
+		"label": generateLabel(pubkey),
+	})
+	result, _ := cln.Rpc(r.CLNRune, "listinvoices", string(jparams))
+
+	return gjson.Get(result, "result.invoices.0.status").String() == "paid"
+}

examples/expensive/main.go

@@ -0,0 +1,85 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"log"
+	"net/http"
+	"time"
+
+	"github.com/fiatjaf/relayer/v2"
+	"github.com/fiatjaf/relayer/v2/storage/postgresql"
+	"github.com/kelseyhightower/envconfig"
+	_ "github.com/lib/pq"
+	"github.com/nbd-wtf/go-nostr"
+)
+
+type Relay struct {
+	PostgresDatabase string `envconfig:"POSTGRESQL_DATABASE"`
+	CLNNodeId        string `envconfig:"CLN_NODE_ID"`
+	CLNHost          string `envconfig:"CLN_HOST"`
+	CLNRune          string `envconfig:"CLN_RUNE"`
+	TicketPriceSats  int64  `envconfig:"TICKET_PRICE_SATS"`
+
+	storage *postgresql.PostgresBackend
+}
+
+var r = &Relay{}
+
+func (r *Relay) Name() string {
+	return "ExpensiveRelay"
+}
+
+func (r *Relay) Storage(ctx context.Context) relayer.Storage {
+	return r.storage
+}
+
+func (r *Relay) Init() error {
+	// every hour, delete all very old events
+	go func() {
+		db := r.Storage(context.TODO()).(*postgresql.PostgresBackend)
+
+		for {
+			time.Sleep(60 * time.Minute)
+			db.DB.Exec(`DELETE FROM event WHERE created_at < $1`, time.Now().AddDate(0, -3, 0).Unix()) // 6 months
+		}
+	}()
+
+	return nil
+}
+
+func (r *Relay) AcceptEvent(ctx context.Context, evt *nostr.Event) bool {
+	// only accept they have a good preimage for a paid invoice for their public key
+	if !checkInvoicePaidOk(evt.PubKey) {
+		return false
+	}
+
+	// block events that are too large
+	jsonb, _ := json.Marshal(evt)
+	if len(jsonb) > 100000 {
+		return false
+	}
+
+	return true
+}
+
+func main() {
+	r := Relay{}
+	if err := envconfig.Process("", &r); err != nil {
+		log.Fatalf("failed to read from env: %v", err)
+		return
+	}
+	r.storage = &postgresql.PostgresBackend{DatabaseURL: r.PostgresDatabase}
+	server, err := relayer.NewServer(&r)
+	if err != nil {
+		log.Fatalf("failed to create server: %v", err)
+	}
+	// special handlers
+	server.Router().HandleFunc("/", handleWebpage)
+	server.Router().HandleFunc("/invoice", func(w http.ResponseWriter, rq *http.Request) {
+		handleInvoice(w, rq, &r)
+	})
+	if err := server.Start("0.0.0.0", 7447); err != nil {
+		log.Fatalf("server terminated: %v", err)
+	}
+}