cache: Add method to update or initialize items

src/cache.rs

@@ -13,6 +13,14 @@ where
     fn key(&self) -> K;
 }
 
+pub trait Initable<T, K>
+where
+    T: Cachable<K>,
+    K: core::cmp::PartialEq,
+{
+    fn init(key: K) -> T;
+}
+
 struct CacheItem<K, T>
 where
     T: Cachable<K>,
@@ -105,7 +113,7 @@ where
     K: core::cmp::PartialEq + core::fmt::Display,
 {
     /// Creates a new cache with a certain item lifetime
-    pub fn new(lifetime: chrono::Duration) -> Self {
+    pub const fn new(lifetime: chrono::Duration) -> Self {
         Self {
             lifetime,
             items: alloc::vec![],
@@ -120,6 +128,13 @@ where
             .is_some()
     }
 
+    /// Determines the index of a certain key
+    fn find(&mut self, key: &K) -> Option<usize> {
+        self.items
+            .iter()
+            .position(|i| i.data.borrow().key() == *key)
+    }
+
     /// Retrieves all known keys
     pub fn keys(&self) -> Vec<K> {
         self.items.iter().map(|i| i.data.borrow().key()).collect()
@@ -194,7 +209,7 @@ where
         K: core::fmt::Display,
     {
         // find item
-        let Some(pos) = self.items.iter().position(|i| i.data.borrow().key() == key) else {
+        let Some(pos) = self.find(&key) else {
             return Err(CacheError::KeyNotFound(key));
         };
 
@@ -209,6 +224,28 @@ where
         Ok(())
     }
 
+    /// Updates an item in the cache using the provided function or create a new item with default values
+    pub fn update_or_init<F>(&mut self, time_now: chrono::NaiveDateTime, key: K, mut func: F)
+    where
+        F: FnMut(&mut T),
+        K: core::fmt::Display,
+        T: Initable<T, K>,
+    {
+        if let Some(pos) = self.find(&key) {
+            // update existsting item
+            // unwrap is fine since we fetched the position before
+            let item = self.items.get_mut(pos).unwrap();
+
+            let mut data = item.data.borrow_mut();
+            func(&mut data);
+
+            item.timestamp = time_now;
+        } else {
+            // insert new item
+            self.items.push(CacheItem::new(time_now, T::init(key)));
+        }
+    }
+
     /// Cleans items which timed out from the cache
     ///
     /// Call this regularly to prune old items.