Split device registration out of the update path

Add dedicated db::devices::register/unregister methods so registration
state (is_registered, owner) is owned by the API endpoints, and make
update sighting-only. This stops scanner re-sightings from wiping a
device's registration. Also preserve an existing mDNS hostname instead
of overwriting it on re-sighting.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/src/db/devices.rs

@@ -183,18 +183,18 @@ pub fn get_summary() -> Result<DeviceSummary, DbError> {
     })
 }
 
+// Records a sighting of an existing device. Registration fields (is_registered, owner) are
+// owned by register/unregister and are intentionally never touched here.
 pub fn update(device: Device) -> Result<(), DbError> {
     let conn = db::get_db_connection();
 
-    let mut sql = "UPDATE devices SET ipv4_address=?, last_seen=?, is_registered=?, owner=?".to_string();
+    let mut sql = "UPDATE devices SET ipv4_address=?, last_seen=?".to_string();
     let mut params: Vec<rusqlite::types::Value> = vec![
         device.ipv4_address.clone().into(),
         device
             .last_seen
             .to_rfc3339_opts(chrono::SecondsFormat::Nanos, false)
             .into(),
-        device.is_registered.into(),
-        device.owner.clone().into(),
     ];
 
     // Only write the vendor (and its derived device_type) when deduced, so a sighting that
@@ -227,6 +227,42 @@ pub fn update(device: Device) -> Result<(), DbError> {
     }
 }
 
+pub fn register(mac_address: String, owner: String, device_type: String) -> Result<(), DbError> {
+    let conn = db::get_db_connection();
+
+    match conn.execute(
+        "UPDATE devices SET is_registered=1, owner=?1, device_type=?2 WHERE mac_address=?3",
+        params![owner, device_type, mac_address],
+    ) {
+        Ok(_) => {
+            debug!("Device registered in database: {mac_address}");
+            Ok(())
+        }
+        Err(error) => {
+            error!("Error registering device ({mac_address}) in database: {error}");
+            Err(DbError::from(error))
+        }
+    }
+}
+
+pub fn unregister(mac_address: String) -> Result<(), DbError> {
+    let conn = db::get_db_connection();
+
+    match conn.execute(
+        "UPDATE devices SET is_registered=0, owner='' WHERE mac_address=?1",
+        params![mac_address],
+    ) {
+        Ok(_) => {
+            debug!("Device unregistered in database: {mac_address}");
+            Ok(())
+        }
+        Err(error) => {
+            error!("Error unregistering device ({mac_address}) in database: {error}");
+            Err(DbError::from(error))
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use chrono::{DateTime, TimeZone, Utc};
@@ -392,10 +428,22 @@ mod tests {
         ))
         .unwrap();
 
+        // Register the device, then update it with a Device carrying the scanner defaults
+        // (is_registered=false, owner=""). The update must NOT clobber the registration while
+        // still refreshing sighting fields like ipv4_address and last_seen.
+        register(
+            "uu:tt:tt:tt:tt:aa".to_string(),
+            "Grace".to_string(),
+            "Phone".to_string(),
+        )
+        .unwrap();
+
+        let new_last_seen = Utc::now();
         let mut device = read("uu:tt:tt:tt:tt:aa".to_string()).unwrap();
-        device.is_registered = true;
-        device.owner = "Grace".to_string();
-        device.device_type = "Phone".to_string();
+        device.is_registered = false;
+        device.owner = "".to_string();
+        device.ipv4_address = "192.168.200.50".to_string();
+        device.last_seen = new_last_seen;
 
         update(device).unwrap();
 
@@ -405,9 +453,9 @@ mod tests {
             device,
             "uu:tt:tt:tt:tt:aa".to_string(),
             "Phone".to_string(),
-            "192.168.200.1".to_string(),
+            "192.168.200.50".to_string(),
             true,
-            last_seen,
+            new_last_seen,
             "Grace".to_string(),
             "Test vendor".to_string(),
         );
@@ -521,6 +569,63 @@ mod tests {
         assert_eq!(device.device_type, "tablet".to_string());
     }
 
+    #[tokio::test]
+    async fn test_register() {
+        tests_common::setup().await;
+
+        // A device with no deduced vendor must still persist the device_type chosen at registration.
+        let last_seen = Utc::now();
+        insert(Device::new(
+            "rr:rr:rr:rr:rr:01".to_string(),
+            "192.168.230.1".to_string(),
+            "".to_string(),
+            last_seen,
+        ))
+        .unwrap();
+
+        register(
+            "rr:rr:rr:rr:rr:01".to_string(),
+            "Grace".to_string(),
+            "Phone".to_string(),
+        )
+        .unwrap();
+
+        let device = read("rr:rr:rr:rr:rr:01".to_string()).unwrap();
+        assert!(device.is_registered, "Device should be registered");
+        assert_eq!(device.owner, "Grace".to_string());
+        assert_eq!(device.device_type, "Phone".to_string());
+        assert_eq!(device.vendor, "".to_string());
+    }
+
+    #[tokio::test]
+    async fn test_unregister() {
+        tests_common::setup().await;
+
+        let last_seen = Utc::now();
+        insert(Device::new(
+            "rr:rr:rr:rr:rr:02".to_string(),
+            "192.168.230.2".to_string(),
+            "Test vendor".to_string(),
+            last_seen,
+        ))
+        .unwrap();
+
+        register(
+            "rr:rr:rr:rr:rr:02".to_string(),
+            "Grace".to_string(),
+            "Phone".to_string(),
+        )
+        .unwrap();
+
+        unregister("rr:rr:rr:rr:rr:02".to_string()).unwrap();
+
+        let device = read("rr:rr:rr:rr:rr:02".to_string()).unwrap();
+        assert!(!device.is_registered, "Device should not be registered");
+        assert_eq!(device.owner, "".to_string());
+        // device_type is left untouched by unregister
+        assert_eq!(device.device_type, "Phone".to_string());
+    }
+
     #[tokio::test]
     async fn test_insert() {
         tests_common::setup().await;

backend/src/mdns_scanner.rs

@@ -88,6 +88,11 @@ async fn process_announcement(
     match db::devices::read(mac.clone()) {
         Some(recorded) => {
             debug!("mDNS sighting of known device {mac}; updating");
+            // Keep the previously stored hostname rather than overwriting it with this
+            // announcement's hostname.
+            if recorded.name.is_some() {
+                device.name = recorded.name.clone();
+            }
             if let Err(err) = db::devices::update(device.clone()) {
                 error!("Failed to update mDNS device {mac}: {err}");
                 return;

backend/src/web_server/devices.rs

@@ -105,7 +105,7 @@ pub async fn register(Json(payload): Json<RegisterDevicePayload>) -> impl IntoRe
         payload.mac_address, payload.owner, payload.device_type
     );
 
-    let mut device = match db::devices::read(payload.mac_address) {
+    let device = match db::devices::read(payload.mac_address.clone()) {
         Some(value) => value,
         None => {
             return (
@@ -122,11 +122,7 @@ pub async fn register(Json(payload): Json<RegisterDevicePayload>) -> impl IntoRe
         );
     }
 
-    device.is_registered = true;
-    device.owner = payload.owner;
-    device.device_type = payload.device_type;
-
-    match db::devices::update(device) {
+    match db::devices::register(payload.mac_address, payload.owner, payload.device_type) {
         Ok(_) => (axum::http::StatusCode::CREATED, "Device registered"),
         Err(err) => {
             error!("Error registering device in the database: {}", err);
@@ -154,7 +150,7 @@ pub async fn register(Json(payload): Json<RegisterDevicePayload>) -> impl IntoRe
     security(("bearer_auth" = []))
 )]
 pub async fn unregister(Path(mac_address): Path<String>) -> impl IntoResponse {
-    let mut device = match db::devices::read(mac_address) {
+    let device = match db::devices::read(mac_address.clone()) {
         Some(value) => value,
         None => {
             return (
@@ -171,10 +167,7 @@ pub async fn unregister(Path(mac_address): Path<String>) -> impl IntoResponse {
         );
     }
 
-    device.is_registered = false;
-    device.owner = "".to_string();
-
-    match db::devices::update(device) {
+    match db::devices::unregister(mac_address) {
         Ok(_) => (axum::http::StatusCode::OK, "Device un-registered"),
         Err(err) => {
             error!("Error updating device in the database: {}", err);