remove "display name" from adding new friends

src-tauri/src/user/mod.rs

@@ -1,3 +1,6 @@
+use base64::Engine;
+use base64::engine::general_purpose::URL_SAFE_NO_PAD;
+use ed25519_dalek::VerifyingKey;
 use serde::{Deserialize, Serialize};
 use specta::Type;
 
@@ -9,3 +12,29 @@ pub struct User {
     pub id: String,
     pub display_name: String,
 }
+
+pub(crate) fn validate_id(id: &str) -> Result<(), String> {
+    let bytes = URL_SAFE_NO_PAD
+        .decode(id)
+        .map_err(|_| "Identification key is not valid base64url.".to_owned())?;
+    let bytes: [u8; 32] = bytes
+        .try_into()
+        .map_err(|_| "Identification key must encode a 32-byte public key.".to_owned())?;
+    VerifyingKey::from_bytes(&bytes)
+        .map(|_| ())
+        .map_err(|_| "Identification key is not a valid Ed25519 public key.".to_owned())
+}
+
+#[cfg(test)]
+mod tests {
+    use ed25519_dalek::SigningKey;
+
+    use super::*;
+
+    #[test]
+    fn id_must_be_an_ed25519_public_key() {
+        let valid = URL_SAFE_NO_PAD.encode(SigningKey::from_bytes(&[7; 32]).verifying_key());
+        assert!(validate_id(&valid).is_ok());
+        assert!(validate_id("not a public key").is_err());
+    }
+}