From c5c17029ba0e02baab2bf7f81bc0b7148ef8de93 Mon Sep 17 00:00:00 2001
From: fiatjaf <fiatjaf@gmail.com>
Date: Wed, 13 Mar 2024 12:40:54 -0300
Subject: [PATCH] basic kind validation policy.

---
 README.md                    |  9 +++++++++
 examples/readme-demo/main.go | 10 ++++++++++
 policies/kind_validation.go  | 29 +++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+)
 create mode 100644 policies/kind_validation.go

diff --git a/README.md b/README.md
index 8974535..9cd3f8b 100644
--- a/README.md
+++ b/README.md
@@ -69,6 +69,11 @@ func main() {
 
 	// there are many other configurable things you can set
 	relay.RejectEvent = append(relay.RejectEvent,
+		// built-in policies
+		policies.ValidateKind,
+
+		// define your own policies
+		policies.PreventLargeTags(80),
 		func(ctx context.Context, event *nostr.Event) (reject bool, msg string) {
 			if event.PubKey == "fa984bd7dbb282f07e16e7ae87b26a2a7b9b90b7246a44771f0cf5ae58018f52" {
 				return true, "we don't allow this person to write here"
@@ -79,6 +84,10 @@ func main() {
 
 	// you can request auth by rejecting an event or a request with the prefix "auth-required: "
 	relay.RejectFilter = append(relay.RejectFilter,
+		// built-in policies
+		policies.NoComplexFilters,
+
+		// define your own policies
 		func(ctx context.Context, filter nostr.Filter) (reject bool, msg string) {
 			if pubkey := khatru.GetAuthed(ctx); pubkey != "" {
 				log.Printf("request from %s\n", pubkey)
diff --git a/examples/readme-demo/main.go b/examples/readme-demo/main.go
index c5ec340..1561956 100644
--- a/examples/readme-demo/main.go
+++ b/examples/readme-demo/main.go
@@ -7,6 +7,7 @@ import (
 	"net/http"
 
 	"github.com/fiatjaf/khatru"
+	"github.com/fiatjaf/khatru/policies"
 	"github.com/nbd-wtf/go-nostr"
 )
 
@@ -53,6 +54,11 @@ func main() {
 
 	// there are many other configurable things you can set
 	relay.RejectEvent = append(relay.RejectEvent,
+		// built-in policies
+		policies.ValidateKind,
+
+		// define your own policies
+		policies.PreventLargeTags(80),
 		func(ctx context.Context, event *nostr.Event) (reject bool, msg string) {
 			if event.PubKey == "fa984bd7dbb282f07e16e7ae87b26a2a7b9b90b7246a44771f0cf5ae58018f52" {
 				return true, "we don't allow this person to write here"
@@ -63,6 +69,10 @@ func main() {
 
 	// you can request auth by rejecting an event or a request with the prefix "auth-required: "
 	relay.RejectFilter = append(relay.RejectFilter,
+		// built-in policies
+		policies.NoComplexFilters,
+
+		// define your own policies
 		func(ctx context.Context, filter nostr.Filter) (reject bool, msg string) {
 			if pubkey := khatru.GetAuthed(ctx); pubkey != "" {
 				log.Printf("request from %s\n", pubkey)
diff --git a/policies/kind_validation.go b/policies/kind_validation.go
new file mode 100644
index 0000000..e3506ce
--- /dev/null
+++ b/policies/kind_validation.go
@@ -0,0 +1,29 @@
+package policies
+
+import (
+	"context"
+	"encoding/json"
+
+	"github.com/nbd-wtf/go-nostr"
+)
+
+func ValidateKind(ctx context.Context, evt *nostr.Event) (bool, string) {
+	switch evt.Kind {
+	case 0:
+		var m struct {
+			Name string `json:"name"`
+		}
+		json.Unmarshal([]byte(evt.Content), &m)
+		if m.Name == "" {
+			return true, "missing json name in kind 0"
+		}
+	case 1:
+		return false, ""
+	case 2:
+		return true, "this kind has been deprecated"
+	}
+
+	// TODO: all other kinds
+
+	return false, ""
+}