1 files changed, 158 insertions, 0 deletions
diff --git a/src/protocol.rs b/src/protocol.rs
new file mode 100644
index 0000000..60d2fa9
--- /dev/null
+++ b/src/protocol.rs
@@ -0,0 +1,158 @@
+//! Unix socket protocol for daemon ↔ CLI.
+//!
+//! Simple line-oriented text protocol:
+//!   SHORTEN <ttl_secs> <slug|auto> <url>\n
+//!   RESOLVE <slug>\n
+//!   DEL <slug>\n
+//!   LIST\n
+//!   STATUS\n
+//!   SHUTDOWN\n
+//!
+//! Responses:
+//!   OK <data>\n
+//!   ERR <message>\n
+
+/// A parsed request received from the CLI over the Unix socket.
+pub enum Request {
+    Shorten {
+        ttl_secs: u64,
+        slug: String,
+        target_url: String,
+    },
+    Resolve {
+        slug: String,
+    },
+    Del {
+        slug: String,
+    },
+    List,
+    Status,
+    Shutdown,
+}
+
+/// A response sent back to the CLI over the Unix socket.
+pub enum Response {
+    Ok(String),
+    Err(String),
+}
+
+/// Parse a single protocol line into a [`Request`].
+pub fn parse_request(line: &str) -> Result<Request, String> {
+    let line = line.trim();
+    if line.is_empty() {
+        return Err("empty request".into());
+    }
+
+    let mut parts = line.splitn(4, ' ');
+    let cmd = parts.next().unwrap();
+
+    match cmd {
+        "SHORTEN" => {
+            let ttl_str = parts
+                .next()
+                .ok_or("SHORTEN requires: SHORTEN <ttl> <slug> <url>")?;
+            let slug = parts
+                .next()
+                .ok_or("SHORTEN requires: SHORTEN <ttl> <slug> <url>")?;
+            let target_url = parts
+                .next()
+                .ok_or("SHORTEN requires: SHORTEN <ttl> <slug> <url>")?;
+            let ttl_secs: u64 =
+                ttl_str.parse().map_err(|_| "invalid TTL number")?;
+            Ok(Request::Shorten {
+                ttl_secs,
+                slug: slug.to_string(),
+                target_url: target_url.to_string(),
+            })
+        }
+        "RESOLVE" => {
+            let slug = parts.next().ok_or("RESOLVE requires: RESOLVE <slug>")?;
+            Ok(Request::Resolve {
+                slug: slug.to_string(),
+            })
+        }
+        "DEL" => {
+            let slug = parts.next().ok_or("DEL requires: DEL <slug>")?;
+            Ok(Request::Del {
+                slug: slug.to_string(),
+            })
+        }
+        "LIST" => Ok(Request::List),
+        "STATUS" => Ok(Request::Status),
+        "SHUTDOWN" => Ok(Request::Shutdown),
+        _ => Err(format!("unknown command: {cmd}")),
+    }
+}
+
+/// Serialize a [`Response`] into a protocol line.
+pub fn format_response(r: &Response) -> String {
+    match r {
+        Response::Ok(data) => format!("OK {data}\n"),
+        Response::Err(msg) => format!("ERR {msg}\n"),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_shorten() {
+        let r =
+            parse_request("SHORTEN 0 auto https://example.com").unwrap();
+        match r {
+            Request::Shorten {
+                ttl_secs,
+                slug,
+                target_url,
+            } => {
+                assert_eq!(ttl_secs, 0);
+                assert_eq!(slug, "auto");
+                assert_eq!(target_url, "https://example.com");
+            }
+            _ => panic!("expected Shorten"),
+        }
+    }
+
+    #[test]
+    fn parse_shorten_custom_slug() {
+        let r =
+            parse_request("SHORTEN 3600 myslug https://example.com").unwrap();
+        match r {
+            Request::Shorten { slug, .. } => assert_eq!(slug, "myslug"),
+            _ => panic!("expected Shorten"),
+        }
+    }
+
+    #[test]
+    fn parse_resolve() {
+        let r = parse_request("RESOLVE abc123").unwrap();
+        match r {
+            Request::Resolve { slug } => assert_eq!(slug, "abc123"),
+            _ => panic!("expected Resolve"),
+        }
+    }
+
+    #[test]
+    fn parse_status() {
+        assert!(matches!(
+            parse_request("STATUS").unwrap(),
+            Request::Status
+        ));
+    }
+
+    #[test]
+    fn parse_list() {
+        assert!(matches!(parse_request("LIST").unwrap(), Request::List));
+    }
+
+    #[test]
+    fn parse_empty_fails() {
+        assert!(parse_request("").is_err());
+    }
+
+    #[test]
+    fn parse_unknown_fails() {
+        assert!(parse_request("FOOBAR").is_err());
+    }
+}