filter: add protected_events filter

This adds support for protected events

Link: https://github.com/nostr-protocol/nips/pull/1030
Signed-off-by: William Casarin <jb55@jb55.com>

src/filters/mod.rs

@@ -1,5 +1,7 @@
+mod protected_events;
 mod ratelimit;
 mod whitelist;
 
+pub use protected_events::ProtectedEvents;
 pub use ratelimit::RateLimit;
 pub use whitelist::Whitelist;

src/filters/protected_events.rs

@@ -0,0 +1,29 @@
+use crate::{Action, InputMessage, NoteFilter, OutputMessage};
+use serde::Deserialize;
+
+#[derive(Deserialize, Default)]
+pub struct ProtectedEvents {}
+
+impl NoteFilter for ProtectedEvents {
+    fn filter_note(&mut self, input: &InputMessage) -> OutputMessage {
+        for tag in &input.event.tags {
+            for entry in tag {
+                if entry == "-" {
+                    return OutputMessage::new(
+                        input.event.id.clone(),
+                        Action::Reject,
+                        Some("blocked: event marked as protected".to_string()),
+                    );
+                }
+                break;
+            }
+            break;
+        }
+
+        OutputMessage::new(input.event.id.clone(), Action::Accept, None)
+    }
+
+    fn name(&self) -> &'static str {
+        "protected_events"
+    }
+}

src/main.rs

@@ -1,4 +1,4 @@
-use noteguard::filters::{RateLimit, Whitelist};
+use noteguard::filters::{ProtectedEvents, RateLimit, Whitelist};
 use noteguard::{Action, InputMessage, NoteFilter, OutputMessage};
 use serde::de::DeserializeOwned;
 use serde::Deserialize;
@@ -42,6 +42,7 @@ impl Noteguard {
     fn register_builtin_filters(&mut self) {
         self.register_filter::<RateLimit>();
         self.register_filter::<Whitelist>();
+        self.register_filter::<ProtectedEvents>();
     }
 
     /// Run the loaded filters. You must call `load_config` before calling this, otherwise