added example/example.go with subscription and publication code example

example/example.go

@@ -0,0 +1,132 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/nbd-wtf/go-nostr"
+	"github.com/nbd-wtf/go-nostr/nip19"
+)
+
+func main() {
+	ctx := context.Background()
+
+	// connect to relay
+	url := "wss://nostr.zebedee.cloud"
+	relay, err := nostr.RelayConnect(ctx, url)
+	if err != nil {
+		panic(err)
+	}
+
+	reader := os.Stdin
+	var npub string
+	var b [64]byte
+	fmt.Fprintf(os.Stderr, "using %s\n----\nexample subscription for three most recent notes mentioning user\npaste npub key: ", url)
+	if n, err := reader.Read(b[:]); err == nil {
+		npub = strings.TrimSpace(fmt.Sprintf("%s", b[:n]))
+	} else {
+		panic(err)
+	}
+
+	// create filters
+	var filters nostr.Filters
+	if _, v, err := nip19.Decode(npub); err == nil {
+		t := make(map[string][]string)
+		// making a "p" tag for the above public key.
+		// this filters for messages tagged with the user "npub1sg6plz..." (mainly replies to this user).
+		t["p"] = []string{v.(string)}
+		filters = []nostr.Filter{{
+			Kinds: []int{1},
+			Tags:  t,
+			// limit = 3, get the three most recent notes
+			Limit: 3,
+		}}
+	} else {
+		panic("not a valid npub!")
+	}
+
+	// create a subscription and submit to relay
+	// results will be returned on the sub.Events channel
+	sub := relay.Subscribe(ctx, filters)
+
+	// we will append the returned events to this slice
+	evs := make([]nostr.Event, 0)
+
+	go func() {
+		<-sub.EndOfStoredEvents
+		sub.Unsub()
+	}()
+	for ev := range sub.Events {
+		evs = append(evs, ev)
+	}
+
+	filename := "example_output.json"
+	if f, err := os.Create(filename); err == nil {
+		fmt.Fprintf(os.Stderr, "returned events saved to %s\n", filename)
+		// encode the returned events in a file
+		enc := json.NewEncoder(f)
+		enc.SetIndent("", " ")
+		enc.Encode(evs)
+		f.Close()
+	} else {
+		panic(err)
+	}
+
+	fmt.Fprintf(os.Stderr, "----\nexample publication of note.\npaste nsec key (leave empty to autogenerate): ")
+	var nsec string
+	if n, err := reader.Read(b[:]); err == nil {
+		nsec = strings.TrimSpace(fmt.Sprintf("%s", b[:n]))
+	} else {
+		panic(err)
+	}
+
+	var sk string
+	ev := nostr.Event{}
+	if _, s, e := nip19.Decode(nsec); e == nil {
+		sk = s.(string)
+	} else {
+		sk = nostr.GeneratePrivateKey()
+	}
+	if pub, e := nostr.GetPublicKey(sk); e == nil {
+		ev.PubKey = pub
+		if npub, e := nip19.EncodePublicKey(pub); e == nil {
+			fmt.Fprintln(os.Stderr, "using:", npub)
+		}
+	} else {
+		panic(e)
+	}
+
+	ev.CreatedAt = time.Now()
+	ev.Kind = 1
+	var content string
+	fmt.Fprintln(os.Stderr, "enter content of note, ending with an empty newline:")
+	for {
+		if n, err := reader.Read(b[:]); err == nil {
+			new_line := strings.TrimSpace(fmt.Sprintf("%s", b[:n]))
+			if new_line == "" {
+				break
+			} else if content == "" {
+				content = new_line
+			} else {
+				content = fmt.Sprintf("%s\n%s", content, new_line)
+			}
+		} else {
+			panic(err)
+		}
+	}
+	ev.Content = content
+	ev.Sign(sk)
+	for _, url := range []string{"wss://nostr.zebedee.cloud"} {
+		ctx := context.WithValue(context.Background(), "url", url)
+		relay, e := nostr.RelayConnect(ctx, url)
+		if e != nil {
+			fmt.Println(e)
+			continue
+		}
+		fmt.Println("posting to: ", url, relay.Publish(ctx, ev))
+	}
+}