utils: Make pubkey shortening panic-free

crates/utils/src/pubkey.rs

@@ -2,13 +2,48 @@ use nostr::prelude::*;
 
 /// Shorten a [`PublicKey`] to `npub1abc...wxyz` form.
 pub fn shorten_pubkey(public_key: PublicKey) -> String {
+    let encoded = public_key
+        .to_bech32()
+        .unwrap_or_else(|_| public_key.to_hex());
+
+    truncate_middle(&encoded)
+}
+
+fn truncate_middle(value: &str) -> String {
     const HEAD_CHARS: usize = 9;
     const TAIL_CHARS: usize = 4;
 
-    let npub = public_key.to_bech32().unwrap();
-    format!(
-        "{}...{}",
-        &npub[..HEAD_CHARS],
-        &npub[npub.len() - TAIL_CHARS..]
-    )
+    let length = value.chars().count();
+    if length <= HEAD_CHARS + TAIL_CHARS + 3 {
+        return value.to_owned();
+    }
+
+    let head: String = value.chars().take(HEAD_CHARS).collect();
+    let tail: String = value.chars().skip(length - TAIL_CHARS).collect();
+
+    format!("{head}...{tail}")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const PUBLIC_KEY_HEX: &str = "68d81165918100b7da43fc28f7d1fc12554466e1115886b9e7bb326f65ec4272";
+
+    #[test]
+    fn shortens_a_valid_pubkey() {
+        let public_key = PublicKey::from_hex(PUBLIC_KEY_HEX).expect("valid pubkey");
+        let npub = public_key.to_bech32().expect("valid pubkey encodes");
+
+        assert_eq!(
+            shorten_pubkey(public_key),
+            format!("{}...{}", &npub[..9], &npub[npub.len() - 4..])
+        );
+    }
+
+    #[test]
+    fn leaves_short_values_intact() {
+        assert_eq!(truncate_middle("npub1short"), "npub1short");
+        assert_eq!(truncate_middle("thirteenchars"), "thirteenchars");
+    }
 }