database: impl FlatBufferDecodeBorrowed for EventBorrow

Signed-off-by: Yuki Kishimoto <[email protected]>

CHANGELOG.md

@@ -44,6 +44,7 @@
 * nostr: add `CowTag` ([Yuki Kishimoto])
 * nostr: add `EventBorrow` ([Yuki Kishimoto])
 * database: add `Events::first_owned` and `Events::last_owned` ([Yuki Kishimoto])
+* database: impl `FlatBufferDecodeBorrowed` for `EventBorrow` ([Yuki Kishimoto])
 * pool: add `Relay::try_connect` ([Yuki Kishimoto])
 * pool: add `Relay::wait_for_connection` ([Yuki Kishimoto])
 * pool: add `RelayPool::try_connect` ([Yuki Kishimoto])

crates/nostr-database/src/flatbuffers/mod.rs

@@ -4,6 +4,7 @@
 
 //! Nostr Database Flatbuffers
 
+use std::borrow::Cow;
 use std::collections::HashSet;
 use std::fmt;
 
@@ -145,6 +146,29 @@ impl FlatBufferDecode for Event {
     }
 }
 
+impl<'a> FlatBufferDecodeBorrowed<'a> for EventBorrow<'a> {
+    fn decode(buf: &'a [u8]) -> Result<Self, Error> {
+        let ev = event_fbs::root_as_event(buf)?;
+
+        let fb_tags = ev.tags().ok_or(Error::NotFound)?;
+        let mut tags = Vec::with_capacity(fb_tags.len());
+
+        for tag in fb_tags.iter().filter_map(|t| t.data()) {
+            tags.push(CowTag::parse(tag.into_iter().map(Cow::Borrowed).collect())?);
+        }
+
+        Ok(Self {
+            id: &ev.id().ok_or(Error::NotFound)?.0,
+            pubkey: &ev.pubkey().ok_or(Error::NotFound)?.0,
+            created_at: Timestamp::from_secs(ev.created_at()),
+            kind: ev.kind() as u16, // TODO: should use try_into
+            tags,
+            content: ev.content().ok_or(Error::NotFound)?,
+            sig: &ev.sig().ok_or(Error::NotFound)?.0,
+        })
+    }
+}
+
 impl FlatBufferEncode for HashSet<RelayUrl> {
     fn encode<'a>(&self, fbb: &'a mut FlatBufferBuilder) -> &'a [u8] {
         fbb.reset();