add support deletion

crates/signed_core/src/deletions.rs

@@ -0,0 +1,79 @@
+use std::collections::HashSet;
+
+use nostr::prelude::*;
+
+/// NIP-09 deletion requests and NIP-62 vanish requests, used to hide
+/// deleted events before they reach the UI.
+///
+/// Built from the kind-5 / kind-62 events stored in the local database;
+/// pass any event through [`Deletions::is_deleted`] before displaying it.
+pub struct Deletions {
+    /// `(deleted event id, expected author)` from `e` tags of kind-5 events.
+    ids: HashSet<(EventId, PublicKey)>,
+    /// `(coordinate, expected author, cutoff)` from `a` tags of kind-5 events.
+    /// All versions of the addressable event up to `cutoff` are deleted.
+    coords: Vec<(Coordinate, PublicKey, Timestamp)>,
+    /// `(author, cutoff)` from kind-62 vanish requests.
+    vanished: Vec<(PublicKey, Timestamp)>,
+}
+
+impl Deletions {
+    /// Build the deletion index from raw kind-5 and kind-62 events.
+    pub fn from_events(events: impl IntoIterator<Item = Event>) -> Self {
+        let mut ids = HashSet::new();
+        let mut coords = Vec::new();
+        let mut vanished = Vec::new();
+
+        for event in events {
+            if event.kind == Kind::EventDeletion {
+                ids.extend(event.tags.event_ids().map(|id| (id, event.pubkey)));
+                coords.extend(
+                    event
+                        .tags
+                        .coordinates()
+                        .map(|c| (c, event.pubkey, event.created_at)),
+                );
+            } else if event.kind == Kind::RequestToVanish {
+                // Client-side we can't verify which relay the request targeted,
+                // so any vanish request is honored for the author's events.
+                vanished.push((event.pubkey, event.created_at));
+            }
+        }
+
+        Self {
+            ids,
+            coords,
+            vanished,
+        }
+    }
+
+    /// Whether the event is covered by a valid deletion or vanish request.
+    ///
+    /// A request is only valid when its author matches the deleted event's
+    /// author (NIP-09); addressable events are deleted up to the request's
+    /// `created_at`.
+    pub fn is_deleted(&self, event: &Event) -> bool {
+        if self
+            .vanished
+            .iter()
+            .any(|(pk, cutoff)| *pk == event.pubkey && event.created_at <= *cutoff)
+        {
+            return true;
+        }
+
+        if self.ids.contains(&(event.id, event.pubkey)) {
+            return true;
+        }
+
+        if event.kind.is_addressable()
+            && let Some(identifier) = event.tags.identifier()
+        {
+            let coordinate = Coordinate::new(event.kind, event.pubkey).identifier(identifier);
+            return self.coords.iter().any(|(c, pk, cutoff)| {
+                *c == coordinate && *pk == event.pubkey && event.created_at <= *cutoff
+            });
+        }
+
+        false
+    }
+}