Notify key observers when needed

Cache.xcodeproj/project.pbxproj

@@ -145,9 +145,6 @@
 		D5A9D1B721134547005DBD3F /* ObservationToken.swift in Sources */ = {isa = PBXBuildFile; fileRef = D5A9D1B621134547005DBD3F /* ObservationToken.swift */; };
 		D5A9D1B821134547005DBD3F /* ObservationToken.swift in Sources */ = {isa = PBXBuildFile; fileRef = D5A9D1B621134547005DBD3F /* ObservationToken.swift */; };
 		D5A9D1B921134547005DBD3F /* ObservationToken.swift in Sources */ = {isa = PBXBuildFile; fileRef = D5A9D1B621134547005DBD3F /* ObservationToken.swift */; };
-		D5A9D1BF21134776005DBD3F /* StoreChange.swift in Sources */ = {isa = PBXBuildFile; fileRef = D5A9D1BE21134776005DBD3F /* StoreChange.swift */; };
-		D5A9D1C021134776005DBD3F /* StoreChange.swift in Sources */ = {isa = PBXBuildFile; fileRef = D5A9D1BE21134776005DBD3F /* StoreChange.swift */; };
-		D5A9D1C121134776005DBD3F /* StoreChange.swift in Sources */ = {isa = PBXBuildFile; fileRef = D5A9D1BE21134776005DBD3F /* StoreChange.swift */; };
 		D5A9D1C321144B65005DBD3F /* StorageObservationRegistry.swift in Sources */ = {isa = PBXBuildFile; fileRef = D5A9D1C221144B65005DBD3F /* StorageObservationRegistry.swift */; };
 		D5A9D1C421144B65005DBD3F /* StorageObservationRegistry.swift in Sources */ = {isa = PBXBuildFile; fileRef = D5A9D1C221144B65005DBD3F /* StorageObservationRegistry.swift */; };
 		D5A9D1C521144B65005DBD3F /* StorageObservationRegistry.swift in Sources */ = {isa = PBXBuildFile; fileRef = D5A9D1C221144B65005DBD3F /* StorageObservationRegistry.swift */; };
@@ -242,7 +239,6 @@
 		D5A138C01EB29BFA00881A20 /* UIImage+Extensions.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "UIImage+Extensions.swift"; sourceTree = "<group>"; };
 		D5A138C31EB29C2100881A20 /* NSImage+Extensions.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "NSImage+Extensions.swift"; sourceTree = "<group>"; };
 		D5A9D1B621134547005DBD3F /* ObservationToken.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ObservationToken.swift; sourceTree = "<group>"; };
-		D5A9D1BE21134776005DBD3F /* StoreChange.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = StoreChange.swift; sourceTree = "<group>"; };
 		D5A9D1C221144B65005DBD3F /* StorageObservationRegistry.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = StorageObservationRegistry.swift; sourceTree = "<group>"; };
 		D5DC59E01C20593E003BD79B /* Cache.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Cache.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		EBAACA991FBC369300FA206E /* SimpleStorage.playground */ = {isa = PBXFileReference; lastKnownFileType = file.playground; path = SimpleStorage.playground; sourceTree = "<group>"; xcLanguageSpecificationIdentifier = xcode.lang.swift; };
@@ -371,7 +367,6 @@
 				D270147F20D10982003B45C7 /* Storage.swift */,
 				D270148320D10E76003B45C7 /* AsyncStorage.swift */,
 				D270148720D11040003B45C7 /* Storage+Transform.swift */,
-				D5A9D1BE21134776005DBD3F /* StoreChange.swift */,
 				D5A9D1C221144B65005DBD3F /* StorageObservationRegistry.swift */,
 				D51146522118337500197DCE /* KeyObservationRegistry.swift */,
 			);
@@ -852,7 +847,6 @@
 				D28897071F8B79B300C61DEE /* JSONDecoder+Extensions.swift in Sources */,
 				D270148220D10982003B45C7 /* Storage.swift in Sources */,
 				D221E5C220D00DCC00BC940E /* Entry.swift in Sources */,
-				D5A9D1C121134776005DBD3F /* StoreChange.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -941,7 +935,6 @@
 				D28897061F8B79B300C61DEE /* JSONDecoder+Extensions.swift in Sources */,
 				D270148120D10982003B45C7 /* Storage.swift in Sources */,
 				D221E5C120D00DCC00BC940E /* Entry.swift in Sources */,
-				D5A9D1C021134776005DBD3F /* StoreChange.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -995,7 +988,6 @@
 				D2CF98611F694FFA00CE8F68 /* MemoryConfig.swift in Sources */,
 				D2CF98661F694FFA00CE8F68 /* ExpirationMode.swift in Sources */,
 				D221E5C020D00DCC00BC940E /* Entry.swift in Sources */,
-				D5A9D1BF21134776005DBD3F /* StoreChange.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

Source/Shared/Storage/DiskStorage.swift

@@ -9,11 +9,14 @@ final public class DiskStorage<T> {
   /// File manager to read/write to the disk
   public let fileManager: FileManager
   /// Configuration
-  fileprivate let config: DiskConfig
+  private let config: DiskConfig
   /// The computed path `directory+name`
   public let path: String
+  /// The closure to be called when single file has been removed
+  var onRemove: ((String) -> Void)?
 
   private let transformer: Transformer<T>
+
 
   // MARK: - Initialization
 
@@ -86,7 +89,9 @@ extension DiskStorage: StorageAware {
   }
 
   public func removeObject(forKey key: String) throws {
-    try fileManager.removeItem(atPath: makeFilePath(for: key))
+    let filePath = makeFilePath(for: key)
+    try fileManager.removeItem(atPath: filePath)
+    onRemove?(filePath)
   }
 
   public func removeAll() throws {
@@ -135,6 +140,7 @@ extension DiskStorage: StorageAware {
     // Remove expired objects
     for url in filesToDelete {
       try fileManager.removeItem(at: url)
+      onRemove?(url.path)
     }
 
     // Remove objects if storage size exceeds max size
@@ -220,9 +226,12 @@ extension DiskStorage {
 
     for file in sortedFiles {
       try fileManager.removeItem(at: file.url)
+      onRemove?(file.url.path)
+
       if let fileSize = file.resourceValues.totalFileAllocatedSize {
         totalSize -= UInt(fileSize)
       }
+
       if totalSize < targetSize {
         break
       }
@@ -238,6 +247,7 @@ extension DiskStorage {
     let attributes = try fileManager.attributesOfItem(atPath: filePath)
     if let expiryDate = attributes[.modificationDate] as? Date, expiryDate.inThePast {
       try fileManager.removeItem(atPath: filePath)
+      onRemove?(filePath)
     }
   }
 }

Source/Shared/Storage/HybridStorage.swift

@@ -5,10 +5,22 @@ public final class HybridStorage<T> {
   public let memoryStorage: MemoryStorage<T>
   public let diskStorage: DiskStorage<T>
   public let storageObservationRegistry = StorageObservationRegistry<HybridStorage>()
+  public let keyObservationRegistry = KeyObservationRegistry<HybridStorage>()
 
   public init(memoryStorage: MemoryStorage<T>, diskStorage: DiskStorage<T>) {
     self.memoryStorage = memoryStorage
     self.diskStorage = diskStorage
+
+    diskStorage.onRemove = { [weak self] path in
+      self?.handleRemovedObject(at: path)
+    }
+  }
+
+  private func handleRemovedObject(at path: String) {
+    keyObservationRegistry.notifyObserver(about: .remove, in: self) { key in
+      let fileName = diskStorage.makeFileName(for: key)
+      return path.contains(fileName)
+    }
   }
 }
 
@@ -27,24 +39,40 @@ extension HybridStorage: StorageAware {
   public func removeObject(forKey key: String) throws {
     memoryStorage.removeObject(forKey: key)
     try diskStorage.removeObject(forKey: key)
+
     storageObservationRegistry.notifyObservers(about: .remove(key: key), in: self)
   }
 
   public func setObject(_ object: T, forKey key: String, expiry: Expiry? = nil) throws {
+    var keyChange: KeyChange<T>?
+
+    if !keyObservationRegistry.isEmpty {
+      keyChange = .edit(before: try? self.object(forKey: key), after: object)
+    }
+
     memoryStorage.setObject(object, forKey: key, expiry: expiry)
     try diskStorage.setObject(object, forKey: key, expiry: expiry)
+
+
+    if let change = keyChange {
+      keyObservationRegistry.notifyObserver(forKey: key, about: change, in: self)
+    }
+
     storageObservationRegistry.notifyObservers(about: .add(key: key), in: self)
   }
 
   public func removeAll() throws {
     memoryStorage.removeAll()
     try diskStorage.removeAll()
+
     storageObservationRegistry.notifyObservers(about: .removeAll, in: self)
+    keyObservationRegistry.notifyAllObservers(about: .remove, in: self)
   }
 
   public func removeExpiredObjects() throws {
     memoryStorage.removeExpiredObjects()
     try diskStorage.removeExpiredObjects()
+
     storageObservationRegistry.notifyObservers(about: .removeExpired, in: self)
   }
 }

Source/Shared/Storage/KeyObservationRegistry.swift

@@ -1,14 +1,13 @@
 import Foundation
 
-public enum KeyChange<T> {
-  case edit(before: T?, after: T?)
-  case remove
-}
-
 public final class KeyObservationRegistry<Storage: StorageAware> {
   public typealias Observation = (Storage, KeyChange<Storage.T>) -> Void
   private(set) var observations = [String: Observation]()
 
+  public var isEmpty: Bool {
+    return observations.isEmpty
+  }
+
   @discardableResult
   public func addObservation(_ observation: @escaping Observation, forKey key: String) -> ObservationToken {
     observations[key] = observation
@@ -30,9 +29,40 @@ public final class KeyObservationRegistry<Storage: StorageAware> {
     observations.removeAll()
   }
 
-  func notifyObservers(about change: KeyChange<Storage.T>, in storage: Storage) {
+  func notifyObserver(forKey key: String, about change: KeyChange<Storage.T>, in storage: Storage) {
+    observations[key]?(storage, change)
+  }
+
+  func notifyObserver(about change: KeyChange<Storage.T>,
+                      in storage: Storage,
+                      where closure: ((String) -> Bool)) {
+    let observation = observations.first { key, value in closure(key) }?.value
+    observation?(storage, change)
+  }
+
+  func notifyAllObservers(about change: KeyChange<Storage.T>, in storage: Storage) {
     observations.values.forEach { closure in
       closure(storage, change)
     }
   }
 }
+
+// MARK: - KeyChange
+
+public enum KeyChange<T> {
+  case edit(before: T?, after: T)
+  case remove
+}
+
+extension KeyChange: Equatable where T: Equatable {
+  public static func == (lhs: KeyChange<T>, rhs: KeyChange<T>) -> Bool {
+    switch (lhs, rhs) {
+    case (.edit(let before1, let after1), .edit(let before2, let after2)):
+      return before1 == before2 && after1 == after2
+    case (.remove, .remove):
+      return true
+    default:
+      return false
+    }
+  }
+}

Source/Shared/Storage/Storage.swift

@@ -9,6 +9,7 @@ public final class Storage<T> {
   let asyncStorage: AsyncStorage<T>
 
   public let storageObservationRegistry = StorageObservationRegistry<Storage>()
+  public let keyObservationRegistry = KeyObservationRegistry<Storage>()
 
   /// Initialize storage with configuration options.
   ///

Source/Shared/Storage/StorageObservationRegistry.swift

@@ -4,6 +4,10 @@ public final class StorageObservationRegistry<Storage: StorageAware> {
   public typealias Observation = (Storage, StorageChange) -> Void
   private(set) var observations = [UUID: Observation]()
 
+  public var isEmpty: Bool {
+    return observations.isEmpty
+  }
+
   @discardableResult
   public func addObservation(_ observation: @escaping Observation) -> ObservationToken {
     let id = UUID()
@@ -28,3 +32,23 @@ public final class StorageObservationRegistry<Storage: StorageAware> {
     }
   }
 }
+
+// MARK: - StorageChange
+
+public enum StorageChange: Equatable {
+  case add(key: String)
+  case remove(key: String)
+  case removeAll
+  case removeExpired
+}
+
+public func == (lhs: StorageChange, rhs: StorageChange) -> Bool {
+  switch (lhs, rhs) {
+  case (.add(let key1), .add(let key2)), (.remove(let key1), .remove(let key2)):
+    return key1 == key2
+  case (.removeAll, .removeAll), (.removeExpired, .removeExpired):
+    return true
+  default:
+    return false
+  }
+}