DB: Implementation of iterators returning references

src/rust/liblektor-rs/lektor_db/src/connexion.rs

@@ -161,7 +161,7 @@ impl LktDatabaseConnection {
 
     /// Peek the next kara to play
     pub fn peek_next_kara_in_queue(&self) -> Option<u64> {
-        self.queue.peek_next()
+        self.queue.peek_next().copied()
     }
 
     /// Pop the next kara to play

src/rust/liblektor-rs/lektor_db/src/lib.rs

@@ -8,12 +8,7 @@ pub mod schema;
 
 pub(self) use diesel::prelude::*;
 pub(self) use error::*;
-pub(self) use std::{
-    collections::VecDeque,
-    ops::{Index, Range},
-    path::Path,
-    slice::SliceIndex,
-};
+pub(self) use std::{collections::VecDeque, ops::Range, path::Path};
 
 /// All the information needed to add a kara recieved from a repo!
 pub type NewKaraRequest<'a> = (

src/rust/liblektor-rs/lektor_db/src/queue.rs

@@ -23,6 +23,16 @@ macro_rules! impl_from_for_proprity {
     };
 }
 
+macro_rules! impl_into_for_priority {
+    ($ty: ty) => {
+        impl From<LktDatabasePriority> for $ty {
+            fn from(val: LktDatabasePriority) -> Self {
+                val.value as $ty
+            }
+        }
+    };
+}
+
 impl_from_for_proprity!(u8);
 impl_from_for_proprity!(u16);
 impl_from_for_proprity!(u32);
@@ -33,33 +43,28 @@ impl_from_for_proprity!(i16);
 impl_from_for_proprity!(i32);
 impl_from_for_proprity!(i64);
 
-impl From<LktDatabasePriority> for i32 {
-    fn from(val: LktDatabasePriority) -> Self {
-        val.value as i32
-    }
-}
-
-impl From<LktDatabasePriority> for usize {
-    fn from(val: LktDatabasePriority) -> Self {
-        val.value as usize
-    }
-}
+impl_into_for_priority!(i32);
+impl_into_for_priority!(usize);
 
-/// The iterator for the database queue.
+/// The iterator for the database queue. The iterator returns references to
+/// karas' id to protect modifications while a reference to some karas are
+/// present...
 pub struct LktDatabaseQueueIter<'a> {
     queue: &'a LktDatabaseQueue,
     priority: Option<usize>,
     index: usize,
 }
 
-/// The iterator for a range of karas from the database queue.
+/// The iterator for a range of karas from the database queue. The iterator
+/// returns references to karas' id to protect modifications while a reference
+/// to some karas are present...
 pub struct LktDatabaseQueueRangeIter<'a> {
     iterator: LktDatabaseQueueIter<'a>,
     remaining: usize,
 }
 
 impl<'a> Iterator for LktDatabaseQueueIter<'a> {
-    type Item = u64;
+    type Item = &'a u64;
 
     fn next(&mut self) -> Option<Self::Item> {
         let priority = self.priority?.clamp(0, LKT_DATABASE_QUEUES_COUNT - 1);
@@ -67,7 +72,7 @@ impl<'a> Iterator for LktDatabaseQueueIter<'a> {
         match level.get(self.index) {
             Some(ret) => {
                 self.index += 1;
-                Some(*ret)
+                Some(ret)
             }
             None if priority == 0 => None,
             None => {
@@ -78,6 +83,20 @@ impl<'a> Iterator for LktDatabaseQueueIter<'a> {
     }
 }
 
+impl<'a> Iterator for LktDatabaseQueueRangeIter<'a> {
+    type Item = &'a u64;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let new_remaining = self.remaining.saturating_sub(1);
+        if new_remaining != self.remaining {
+            self.remaining = new_remaining;
+            self.iterator.next()
+        } else {
+            None
+        }
+    }
+}
+
 /// The queue datastructure used for storing karas in the queue.
 #[derive(Debug, Default)]
 pub struct LktDatabaseQueue {
@@ -117,7 +136,7 @@ impl LktDatabaseQueue {
         }
     }
 
-    pub fn peek_next(&self) -> Option<u64> {
+    pub fn peek_next(&self) -> Option<&u64> {
         self.iter().next()
     }