feat: implement a basic backend (#1)

Reviewed-on: https://git.reya.su/reya/signed/pulls/1

crates/signed_core/src/clone_url.rs

@@ -0,0 +1,119 @@
+use nostr::prelude::*;
+
+use crate::RepoAddr;
+
+/// Target of a `nostr://` clone URL (NIP-34 "Nostr Clone URL format").
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum CloneTarget {
+    /// `nostr://<naddr1...>` — direct repository address.
+    Addr(RepoAddr),
+    /// `nostr://<npub|nip05>/[relay-hint/]<identifier>`
+    UserRepo {
+        /// `npub1...` or a NIP-05 identifier.
+        user: String,
+        relay_hint: Option<RelayUrl>,
+        /// `d` tag identifier of the repository.
+        identifier: String,
+    },
+}
+
+/// Parse a `nostr://` clone URL. Returns `None` for other URL schemes.
+pub fn parse_clone_url(url: &str) -> Option<CloneTarget> {
+    let rest = url.strip_prefix("nostr://")?;
+    let mut parts = rest.split('/');
+
+    let first = parts.next()?;
+    let second = parts.next()?;
+    let third = parts.next();
+
+    if first.starts_with("naddr1") {
+        let coordinate = Nip19Coordinate::from_bech32(first).ok()?;
+        return Some(CloneTarget::Addr(RepoAddr::new(
+            coordinate.coordinate.public_key,
+            coordinate.coordinate.identifier,
+        )));
+    }
+
+    let (relay_hint, identifier) = match third {
+        Some(id) => (
+            RelayUrl::parse(&percent_decode(second)).ok(),
+            percent_decode(id),
+        ),
+        None => (None, percent_decode(second)),
+    };
+
+    Some(CloneTarget::UserRepo {
+        user: first.to_owned(),
+        relay_hint,
+        identifier,
+    })
+}
+
+fn percent_decode(input: &str) -> String {
+    let bytes = input.as_bytes();
+    let mut out = Vec::with_capacity(bytes.len());
+    let mut i = 0;
+    while i < bytes.len() {
+        if bytes[i] == b'%' && i + 2 < bytes.len() {
+            let hex = &input[i + 1..i + 3];
+            if let Ok(v) = u8::from_str_radix(hex, 16) {
+                out.push(v);
+                i += 3;
+                continue;
+            }
+        }
+        out.push(bytes[i]);
+        i += 1;
+    }
+    String::from_utf8_lossy(&out).into_owned()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_user_repo_without_relay() {
+        let target = parse_clone_url(
+            "nostr://npub15qydau2hjma6ngxkl2cyar74wzyjshvl65za5k5rl69264ar2exs5cyejr/ngit",
+        )
+        .unwrap();
+        assert_eq!(
+            target,
+            CloneTarget::UserRepo {
+                user: "npub15qydau2hjma6ngxkl2cyar74wzyjshvl65za5k5rl69264ar2exs5cyejr".to_owned(),
+                relay_hint: None,
+                identifier: "ngit".to_owned(),
+            }
+        );
+    }
+
+    #[test]
+    fn parses_user_repo_with_relay_hint() {
+        let target = parse_clone_url("nostr://danconwaydev.com/relay.ngit.dev/ngit").unwrap();
+        assert_eq!(
+            target,
+            CloneTarget::UserRepo {
+                user: "danconwaydev.com".to_owned(),
+                relay_hint: RelayUrl::parse("relay.ngit.dev").ok(),
+                identifier: "ngit".to_owned(),
+            }
+        );
+    }
+
+    #[test]
+    fn decodes_percent_encoded_parts() {
+        let target = parse_clone_url(
+            "nostr://danconwaydev.com/ws%3A%2F%2Flocalhost%3A7334/my-local-only-repo",
+        )
+        .unwrap();
+        assert_eq!(
+            target,
+            CloneTarget::UserRepo {
+                user: "danconwaydev.com".to_owned(),
+                relay_hint: RelayUrl::parse("ws://localhost:7334").ok(),
+                identifier: "my-local-only-repo".to_owned(),
+            }
+        );
+    }
+}