From 751462990665087e7cedbe7f74ad5ff7f6cc873c Mon Sep 17 00:00:00 2001
From: fiatjaf <fiatjaf@gmail.com>
Date: Tue, 10 Sep 2024 15:28:30 -0300
Subject: [PATCH] nip17 and nip59.

---
 nip17/nip17.go | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++
 nip59/nip59.go | 91 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 190 insertions(+)
 create mode 100644 nip17/nip17.go
 create mode 100644 nip59/nip59.go

diff --git a/nip17/nip17.go b/nip17/nip17.go
new file mode 100644
index 0000000..cd7d9b8
--- /dev/null
+++ b/nip17/nip17.go
@@ -0,0 +1,99 @@
+package nip17
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/nbd-wtf/go-nostr"
+	"github.com/nbd-wtf/go-nostr/nip59"
+)
+
+func GetDMRelays(ctx context.Context, pubkey string, pool *nostr.SimplePool, relaysToQuery []string) []string {
+	ie := pool.QuerySingle(ctx, relaysToQuery, nostr.Filter{
+		Authors: []string{pubkey},
+		Kinds:   []int{10050},
+	})
+	if ie == nil {
+		return nil
+	}
+
+	res := make([]string, 0, 3)
+	for _, tag := range ie.Tags {
+		if len(tag) >= 2 && tag[0] == "relay" {
+			res = append(res, tag[1])
+			if len(res) == 3 {
+				return res
+			}
+		}
+	}
+
+	return res
+}
+
+func PrepareMessage(
+	content string,
+	tags nostr.Tags,
+	ourPubkey string,
+	encrypt func(string) (string, error),
+	finalizeAndSign func(*nostr.Event) error,
+	recipientPubKey string,
+	modify func(*nostr.Event),
+) (nostr.Event, error) {
+	rumor := nostr.Event{
+		Kind:      14,
+		Content:   content,
+		Tags:      tags,
+		CreatedAt: nostr.Now(),
+		PubKey:    ourPubkey,
+	}
+	rumor.ID = rumor.GetID()
+
+	seal, err := nip59.Seal(rumor, encrypt)
+	if err != nil {
+		return nostr.Event{}, fmt.Errorf("failed to seal: %w", err)
+	}
+
+	if err := finalizeAndSign(&seal); err != nil {
+		return nostr.Event{}, fmt.Errorf("finalizeAndSign failed: %w", err)
+	}
+
+	return nip59.GiftWrap(seal, recipientPubKey, modify)
+}
+
+// ListenForMessages returns a channel with the rumors already decrypted and checked
+func ListenForMessages(
+	ctx context.Context,
+	pool *nostr.SimplePool,
+	relays []string,
+	ourPubkey string,
+	since nostr.Timestamp,
+	decrypt func(string) (string, error),
+) chan nostr.Event {
+	ch := make(chan nostr.Event)
+
+	go func() {
+		for ie := range pool.SubMany(ctx, relays, nostr.Filters{
+			{
+				Kinds: []int{1059},
+				Tags:  nostr.TagMap{"p": []string{ourPubkey}},
+				Since: &since,
+			},
+		}) {
+			seal, err := nip59.GiftUnwrap(*ie.Event, decrypt)
+			if err != nil {
+				nostr.InfoLogger.Printf("[nip17] failed to unwrap received message: %s\n", err)
+				continue
+			}
+
+			rumor, err := nip59.Unseal(seal, decrypt)
+			if err != nil {
+				nostr.InfoLogger.Printf("[nip17] failed to unseal received message: %s\n", err)
+				continue
+			}
+
+			ch <- rumor
+		}
+	}()
+
+	return ch
+}
diff --git a/nip59/nip59.go b/nip59/nip59.go
new file mode 100644
index 0000000..935a023
--- /dev/null
+++ b/nip59/nip59.go
@@ -0,0 +1,91 @@
+package nip59
+
+import (
+	"fmt"
+	"math/rand"
+
+	"github.com/mailru/easyjson"
+	"github.com/nbd-wtf/go-nostr"
+	"github.com/nbd-wtf/go-nostr/nip44"
+)
+
+// Seal takes a rumor, encrypts it and returns an unsigned 'seal' event, the 'seal' must be signed
+// afterwards.
+func Seal(rumor nostr.Event, encrypt func(string) (string, error)) (nostr.Event, error) {
+	rumor.Sig = ""
+	ciphertext, err := encrypt(rumor.String())
+
+	return nostr.Event{
+		Kind:      13,
+		Content:   ciphertext,
+		CreatedAt: nostr.Now() - nostr.Timestamp(60*rand.Int63n(600) /* up to 6 hours in the past */),
+		Tags:      make(nostr.Tags, 0),
+	}, err
+}
+
+// Takes a signed 'seal' and gift-wraps it using a random key, returns it signed.
+//
+// modify is a function that takes the gift-wrap before signing, can be used to apply
+// NIP-13 PoW or other things, otherwise can be nil.
+func GiftWrap(seal nostr.Event, recipientPublicKey string, modify func(*nostr.Event)) (nostr.Event, error) {
+	nonceKey := nostr.GeneratePrivateKey()
+	temporaryConversationKey, err := nip44.GenerateConversationKey(recipientPublicKey, nonceKey)
+	if err != nil {
+		return nostr.Event{}, err
+	}
+
+	ciphertext, err := nip44.Encrypt(seal.String(), temporaryConversationKey, nil)
+	if err != nil {
+		return nostr.Event{}, err
+	}
+
+	gw := nostr.Event{
+		Kind:      1059,
+		Content:   ciphertext,
+		CreatedAt: nostr.Now() - nostr.Timestamp(60*rand.Int63n(600) /* up to 6 hours in the past */),
+		Tags: nostr.Tags{
+			nostr.Tag{"p", recipientPublicKey},
+		},
+	}
+
+	// apply POW if necessary
+	if modify != nil {
+		modify(&gw)
+	}
+
+	err = gw.Sign(nonceKey)
+	return gw, nil
+}
+
+func GiftUnwrap(gw nostr.Event, decrypt func(string) (string, error)) (seal nostr.Event, err error) {
+	jevt, err := decrypt(gw.Content)
+	if err != nil {
+		return seal, err
+	}
+
+	err = easyjson.Unmarshal([]byte(jevt), &seal)
+	if err != nil {
+		return seal, err
+	}
+
+	if ok, _ := seal.CheckSignature(); !ok {
+		return seal, fmt.Errorf("seal signature is invalid")
+	}
+
+	return seal, nil
+}
+
+func Unseal(seal nostr.Event, decrypt func(string) (string, error)) (rumor nostr.Event, err error) {
+	jevt, err := decrypt(seal.Content)
+	if err != nil {
+		return rumor, err
+	}
+
+	err = easyjson.Unmarshal([]byte(jevt), &rumor)
+	if err != nil {
+		return rumor, err
+	}
+
+	rumor.PubKey = seal.PubKey
+	return rumor, nil
+}