khatru: add policies to validate event tags by kind and replace reactions.

khatru/policies/reactions.go

@@ -0,0 +1,33 @@
+package policies
+
+import (
+	"fiatjaf.com/nostr"
+	"fiatjaf.com/nostr/eventstore"
+)
+
+// UniqueReactionsWrapper ensures that only the latest reaction or poll response from an author to an event is kept.
+// When a new reaction (kind 7) or poll response (kind 1018) is received, it deletes any previous ones from the same author to the same event.
+type UniqueReactionsWrapper struct {
+	eventstore.Store
+}
+
+func (w *UniqueReactionsWrapper) SaveEvent(event nostr.Event) error {
+	// check if it's a reaction or poll response
+	if event.Kind == 7 || event.Kind == 1018 {
+		// find the referenced event ID
+		ref := event.Tags.Find("e")
+		if ref != nil {
+			// query for existing events of same kind from same author referencing the same event and delete them
+			for old := range w.Store.QueryEvents(nostr.Filter{
+				Authors: []nostr.PubKey{event.PubKey},
+				Kinds:   []nostr.Kind{event.Kind},
+				Tags:    nostr.TagMap{"e": []string{ref[1]}},
+			}, 1_000) {
+				w.Store.DeleteEvent(old.ID)
+			}
+		}
+	}
+
+	// Save the new event
+	return w.Store.SaveEvent(event)
+}

khatru/policies/schema_validation.go

@@ -0,0 +1,18 @@
+package policies
+
+import (
+	"context"
+
+	"fiatjaf.com/nostr"
+	"fiatjaf.com/nostr/schema"
+)
+
+func ValidateAgainstSchema(ctx context.Context, evt nostr.Event) (bool, string) {
+	v := schema.NewDefaultValidator()
+	v.FailOnUnknown = true
+	err := v.ValidateEvent(evt)
+	if err != nil {
+		return true, err.Error()
+	}
+	return false, ""
+}