enostr: introduce PubkeyRef

This will be used for typesafe and copy-free pubkey references

Signed-off-by: William Casarin <jb55@jb55.com>

crates/enostr/src/pubkey.rs

@@ -1,6 +1,7 @@
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
 
 use crate::Error;
+use std::borrow::Borrow;
 use std::fmt;
 use std::ops::Deref;
 use tracing::debug;
@@ -8,8 +9,35 @@ use tracing::debug;
 #[derive(Eq, PartialEq, Clone, Copy, Hash, Ord, PartialOrd)]
 pub struct Pubkey([u8; 32]);
 
+#[derive(Eq, PartialEq, Clone, Copy, Hash, Ord, PartialOrd)]
+pub struct PubkeyRef<'a>(&'a [u8; 32]);
+
 static HRP_NPUB: bech32::Hrp = bech32::Hrp::parse_unchecked("npub");
 
+impl<'a> Borrow<[u8; 32]> for PubkeyRef<'a> {
+    fn borrow(&self) -> &[u8; 32] {
+        self.0
+    }
+}
+
+impl<'a> PubkeyRef<'a> {
+    pub fn new(bytes: &'a [u8; 32]) -> Self {
+        Self(bytes)
+    }
+
+    pub fn bytes(&self) -> &[u8; 32] {
+        self.0
+    }
+
+    pub fn to_owned(&self) -> Pubkey {
+        Pubkey::new(*self.bytes())
+    }
+
+    pub fn hex(&self) -> String {
+        hex::encode(self.bytes())
+    }
+}
+
 impl Deref for Pubkey {
     type Target = [u8; 32];
 
@@ -18,6 +46,12 @@ impl Deref for Pubkey {
     }
 }
 
+impl Borrow<[u8; 32]> for Pubkey {
+    fn borrow(&self) -> &[u8; 32] {
+        &self.0
+    }
+}
+
 impl Pubkey {
     pub fn new(data: [u8; 32]) -> Self {
         Self(data)
@@ -31,6 +65,10 @@ impl Pubkey {
         &self.0
     }
 
+    pub fn as_ref(&self) -> PubkeyRef<'_> {
+        PubkeyRef(self.bytes())
+    }
+
     pub fn parse(s: &str) -> Result<Self, Error> {
         match Pubkey::from_hex(s) {
             Ok(pk) => Ok(pk),
@@ -88,6 +126,12 @@ impl fmt::Display for Pubkey {
     }
 }
 
+impl fmt::Debug for PubkeyRef<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.hex())
+    }
+}
+
 impl fmt::Debug for Pubkey {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}", self.hex())