nip57 and nip61: parse amount.

nip57/nip57.go

@@ -0,0 +1,33 @@
+package nip57
+
+import (
+	"encoding/json"
+	"strconv"
+
+	"fiatjaf.com/nostr"
+)
+
+// GetAmountFromZap takes a zap receipt event (kind 9735) and returns the amount in millisats.
+// It first checks the event's "amount" tag, and if not present, checks the embedded zap request's "amount" tag.
+func GetAmountFromZap(event nostr.Event) uint64 {
+	// Check for "amount" tag in the zap receipt
+	if tag := event.Tags.Find("amount"); tag != nil {
+		if amt, err := strconv.ParseUint(tag[1], 10, 64); err == nil {
+			return amt
+		}
+	}
+
+	// if not found, get from the embedded zap request in "description" tag
+	if descTag := event.Tags.Find("description"); descTag != nil {
+		var embeddedEvent nostr.Event
+		if err := json.Unmarshal([]byte(descTag[1]), &embeddedEvent); err == nil {
+			if tag := embeddedEvent.Tags.Find("amount"); tag != nil {
+				if amt, err := strconv.ParseUint(tag[1], 10, 64); err == nil {
+					return amt
+				}
+			}
+		}
+	}
+
+	return 0
+}

nip61/nip61.go

@@ -12,6 +12,7 @@ import (
 	"fiatjaf.com/nostr"
 	"fiatjaf.com/nostr/nip60"
 	"github.com/btcsuite/btcd/btcec/v2"
+	"github.com/elnosh/gonuts/cashu"
 )
 
 var NutzapsNotAccepted = errors.New("user doesn't accept nutzaps")
@@ -161,3 +162,17 @@ func getEligibleTokensWeHave(
 		}
 	}
 }
+
+func GetAmountFromNutzap(evt nostr.Event) uint64 {
+	var total uint64
+	for _, tag := range evt.Tags {
+		if len(tag) >= 2 && tag[0] == "proof" {
+			var proof cashu.Proof
+			if err := json.Unmarshal([]byte(tag[1]), &proof); err != nil {
+				continue
+			}
+			total += proof.Amount
+		}
+	}
+	return total
+}