add cache system

LeStorage/StoredCollection.swift

@@ -212,7 +212,7 @@ public class StoredCollection<T: Storable>: SomeCollection {
     
     /// Sets a collection of items and indexes them
     func setItems(_ items: [T]) {
-        self.items.removeAll()
+        self.clear()
         for item in items {
             self._addItem(instance: item)
         }
@@ -277,7 +277,7 @@ public class StoredCollection<T: Storable>: SomeCollection {
         defer {
             self.requestWriteIfNecessary()
         }
-        self.items.removeAll()
+        self.clear()
         self._addItem(instance: instance)
     }
 
@@ -333,7 +333,8 @@ public class StoredCollection<T: Storable>: SomeCollection {
             self.addPendingOperation(method: .add, instance: instance, actionOption: actionOption)
             return false
         }
-        
+        self.invalidateCache()
+
         self._affectStoreIdIfNecessary(instance: instance)
         self.items.append(instance)
         instance.store = self.store
@@ -359,6 +360,7 @@ public class StoredCollection<T: Storable>: SomeCollection {
             self.addPendingOperation(method: .update, instance: instance, actionOption: actionOption)
             return false
         }
+        self.invalidateCache()
 
         let item = self.items[index]
         if item !== instance {
@@ -408,6 +410,7 @@ public class StoredCollection<T: Storable>: SomeCollection {
     }
     
     func localDeleteOnly(instance: T) {
+        self.invalidateCache()
         self.items.removeAll { $0.id == instance.id }
         self._indexes?.removeValue(forKey: instance.id)
     }
@@ -437,12 +440,12 @@ public class StoredCollection<T: Storable>: SomeCollection {
         return self.items.first(where: { $0.id == id })
     }
 
-    /// Proceeds to "hard" delete the items without synchronizing them
-    /// Also removes related API calls
+    /// Deletes a list of items
     public func deleteDependencies(_ items: any Sequence<T>) {
         defer {
             self.requestWriteIfNecessary()
         }
+        self.invalidateCache()
         let itemsArray = Array(items) // fix error if items is self.items
         for item in itemsArray {
             if let index = self.items.firstIndex(where: { $0.id == item.id }) {
@@ -534,12 +537,13 @@ public class StoredCollection<T: Storable>: SomeCollection {
 
     /// Simply clears the items of the collection
     public func clear() {
+        self.invalidateCache()
         self.items.removeAll()
     }
 
     /// Removes the items of the collection and deletes the corresponding file
     public func reset() {
-        self.items.removeAll()
+        self.clear()
         self.store.removeFile(type: T.self)
     }
 
@@ -572,6 +576,31 @@ public class StoredCollection<T: Storable>: SomeCollection {
         }
     }
     
+    // MARK: - Cached queries
+    
+    fileprivate var _cacheVersion = 0
+    fileprivate var _queryCache: [AnyHashable: (version: Int, result: Any)] = [:]
+    
+    // Generic query method with caching
+    public func cached<Result>(
+        key: AnyHashable,
+        compute: ([T]) -> Result
+    ) -> Result {
+        if let cached = self._queryCache[key],
+           cached.version == self._cacheVersion,
+           let result = cached.result as? Result {
+            return result
+        }
+        
+        let result = compute(items)
+        self._queryCache[key] = (self._cacheVersion, result)
+        return result
+    }
+    
+    private func invalidateCache() {
+        self._cacheVersion += 1
+    }
+    
 }
 
 extension StoredCollection: RandomAccessCollection {

LeStorage/SyncedCollection.swift

@@ -417,6 +417,15 @@ public class SyncedCollection<T : SyncedStorable>: SomeSyncedCollection, Collect
         self.collection.requestWriteIfNecessary()
     }
     
+    // MARK: - Cached queries
+    
+    public func cached<Result>(
+        key: AnyHashable,
+        compute: ([T]) -> Result
+    ) -> Result {
+        return self.collection.cached(key: key, compute: compute)
+    }
+    
 }
 
 class OperationBatch<T> {