From 8fb5cd112dd7c8afb1f577f2de19ba1d622baa69 Mon Sep 17 00:00:00 2001
From: fiatjaf <fiatjaf@gmail.com>
Date: Sun, 12 Jan 2025 21:29:20 -0300
Subject: [PATCH] add nip40 helper.

---
 nip40/nip40.go | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 nip40/nip40.go

diff --git a/nip40/nip40.go b/nip40/nip40.go
new file mode 100644
index 0000000..f1cadfd
--- /dev/null
+++ b/nip40/nip40.go
@@ -0,0 +1,22 @@
+package nip40
+
+import (
+	"strconv"
+
+	"github.com/nbd-wtf/go-nostr"
+)
+
+// GetExpiration returns the expiration timestamp for this event, or -1 if no "expiration" tag exists or
+// if it is invalid.
+func GetExpiration(tags nostr.Tags) nostr.Timestamp {
+	for _, tag := range tags {
+		if len(tag) >= 2 && tag[0] == "expiration" {
+			if ts, err := strconv.ParseInt(tag[1], 10, 64); err == nil {
+				return nostr.Timestamp(ts)
+			} else {
+				return -1
+			}
+		}
+	}
+	return -1
+}