check if shipmaster is already on the water

src/model/logbook.rs

@@ -62,6 +62,7 @@ pub enum LogbookCreateError {
     BoatLocked,
     BoatNotFound,
     TooManyRowers(usize, usize),
+    ShipmasterAlreadyOnWater,
 }
 
 impl Logbook {
@@ -144,6 +145,10 @@ impl Logbook {
         if boat.on_water(db).await {
             return Err(LogbookCreateError::BoatAlreadyOnWater);
         }
+        if (User::find_by_id(db, log.shipmaster as i32).await.unwrap()).on_water(db).await {
+            return Err(LogbookCreateError::BoatAlreadyOnWater);
+        }
+        
 
         if log.rower.len() > boat.amount_seats as usize - 1 {
             return Err(LogbookCreateError::TooManyRowers(

src/model/user.rs

@@ -93,6 +93,17 @@ WHERE name like ?
         .ok()
     }
 
+    pub async fn on_water(&self, db: &SqlitePool) -> bool {
+        sqlx::query!(
+            "SELECT * FROM logbook WHERE shipmaster=? AND arrival is null",
+            self.id
+        )
+        .fetch_optional(db)
+        .await
+        .unwrap()
+        .is_some()
+    }
+
     pub async fn all(db: &SqlitePool) -> Vec<Self> {
         sqlx::query_as!(
             User,