Update front storage with back storage when cache only found in back storage

Cache.xcodeproj/project.pbxproj

@@ -7,6 +7,9 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		57506FAE1EC29437009B71E9 /* CacheEntry.swift in Sources */ = {isa = PBXBuildFile; fileRef = 57506FAD1EC29437009B71E9 /* CacheEntry.swift */; };
+		57506FBF1EC2E1B7009B71E9 /* CacheEntry.swift in Sources */ = {isa = PBXBuildFile; fileRef = 57506FAD1EC29437009B71E9 /* CacheEntry.swift */; };
+		57506FC01EC2E1BA009B71E9 /* CacheEntry.swift in Sources */ = {isa = PBXBuildFile; fileRef = 57506FAD1EC29437009B71E9 /* CacheEntry.swift */; };
 		BDEDD3601DBCE5CE007416A6 /* BasicHybridCache.swift in Sources */ = {isa = PBXBuildFile; fileRef = D5291C6A1C2827FB00B702C9 /* BasicHybridCache.swift */; };
 		BDEDD3611DBCE5CE007416A6 /* Cache.swift in Sources */ = {isa = PBXBuildFile; fileRef = D5ACACDD1CD0272600567809 /* Cache.swift */; };
 		BDEDD3621DBCE5CE007416A6 /* Config.swift in Sources */ = {isa = PBXBuildFile; fileRef = D5291C151C28220B00B702C9 /* Config.swift */; };
@@ -143,6 +146,7 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
+		57506FAD1EC29437009B71E9 /* CacheEntry.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = CacheEntry.swift; sourceTree = "<group>"; };
 		BDEDD3561DBCE5B1007416A6 /* Cache.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Cache.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		BDEDD3781DBCEB8A007416A6 /* Cache-tvOS-Tests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = "Cache-tvOS-Tests.xctest"; sourceTree = BUILT_PRODUCTS_DIR; };
 		D5291C151C28220B00B702C9 /* Config.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Config.swift; sourceTree = "<group>"; };
@@ -196,7 +200,7 @@
 		D5ACACCB1CD0207300567809 /* SyncHybridCache.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = SyncHybridCache.swift; sourceTree = "<group>"; };
 		D5ACACCE1CD0227200567809 /* SyncCacheSpec.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = SyncCacheSpec.swift; sourceTree = "<group>"; };
 		D5ACACD21CD0254300567809 /* SyncHybridCacheSpec.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = SyncHybridCacheSpec.swift; sourceTree = "<group>"; };
-		D5ACACDD1CD0272600567809 /* Cache.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Cache.swift; sourceTree = "<group>"; };
+		D5ACACDD1CD0272600567809 /* Cache.swift */ = {isa = PBXFileReference; fileEncoding = 4; indentWidth = 2; lastKnownFileType = sourcecode.swift; path = Cache.swift; sourceTree = "<group>"; tabWidth = 2; };
 		D5DC59E01C20593E003BD79B /* Cache.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Cache.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 /* End PBXFileReference section */
 
@@ -322,6 +326,7 @@
 				D5291C251C28220B00B702C9 /* MemoryStorage.swift */,
 				D5291C261C28220B00B702C9 /* StorageAware.swift */,
 				D5291C271C28220B00B702C9 /* StorageFactory.swift */,
+				57506FAD1EC29437009B71E9 /* CacheEntry.swift */,
 			);
 			path = Storage;
 			sourceTree = "<group>";
@@ -840,6 +845,7 @@
 				BDEDD36D1DBCE5D8007416A6 /* SyncCache.swift in Sources */,
 				BDEDD36A1DBCE5D8007416A6 /* NSDate+Cache.swift in Sources */,
 				BDEDD36F1DBCE5D8007416A6 /* DiskStorage.swift in Sources */,
+				57506FC01EC2E1BA009B71E9 /* CacheEntry.swift in Sources */,
 				D5A138C21EB29BFA00881A20 /* UIImage+Cache.swift in Sources */,
 				BDEDD3601DBCE5CE007416A6 /* BasicHybridCache.swift in Sources */,
 				BDEDD3701DBCE5D8007416A6 /* MemoryStorage.swift in Sources */,
@@ -922,6 +928,7 @@
 				D5291D911C283CFB00B702C9 /* String+Cache.swift in Sources */,
 				D5291D901C283CFB00B702C9 /* NSDate+Cache.swift in Sources */,
 				D5A138C41EB29C2100881A20 /* NSImage+Cache.swift in Sources */,
+				57506FBF1EC2E1B7009B71E9 /* CacheEntry.swift in Sources */,
 				D5291D931C283CFB00B702C9 /* DiskStorage.swift in Sources */,
 				D5291D861C283CFB00B702C9 /* BasicHybridCache.swift in Sources */,
 				D5ACACCD1CD0207300567809 /* SyncHybridCache.swift in Sources */,
@@ -960,6 +967,7 @@
 				D5291C321C28220B00B702C9 /* StorageKind.swift in Sources */,
 				D5291C301C28220B00B702C9 /* Expiry.swift in Sources */,
 				D5291C331C28220B00B702C9 /* JSON+Cache.swift in Sources */,
+				57506FAE1EC29437009B71E9 /* CacheEntry.swift in Sources */,
 				D5A138C11EB29BFA00881A20 /* UIImage+Cache.swift in Sources */,
 				D5291C2F1C28220B00B702C9 /* Capsule.swift in Sources */,
 				D5291C2D1C28220B00B702C9 /* Config.swift in Sources */,

Source/Shared/BasicHybridCache.swift

@@ -32,16 +32,22 @@ public class BasicHybridCache: NSObject {
    - Parameter name: A name of the cache
    - Parameter config: Cache configuration
    */
-  public init(name: String, config: Config = Config.defaultConfig) {
+  public convenience init(name: String, config: Config = Config.defaultConfig) {
+    let frontStorage = StorageFactory.resolve(name, kind: config.frontKind, maxSize: UInt(config.maxObjects))
+    let backStorage = StorageFactory.resolve(name, kind: config.backKind, maxSize: config.maxSize)
+    self.init(name: name, frontStorage: frontStorage, backStorage: backStorage, config: config)
+
+  }
+  internal init(name: String, frontStorage: StorageAware, backStorage: StorageAware, config: Config) {
     self.name = name
+    self.frontStorage = frontStorage
+    self.backStorage = backStorage
     self.config = config
 
-    frontStorage = StorageFactory.resolve(name, kind: config.frontKind, maxSize: UInt(config.maxObjects))
-    backStorage = StorageFactory.resolve(name, kind: config.backKind, maxSize: config.maxSize)
     super.init()
-
+    
     let notificationCenter = NotificationCenter.default
-
+    
     #if os(macOS)
       notificationCenter.addObserver(self, selector: #selector(clearExpiredDataInBackStorage),
                                      name: NSNotification.Name.NSApplicationWillTerminate, object: nil)
@@ -56,7 +62,7 @@ public class BasicHybridCache: NSObject {
                                      name: .UIApplicationDidEnterBackground, object: nil)
     #endif
   }
-
+  
   /**
    Removes notification center observer.
    */
@@ -96,20 +102,39 @@ public class BasicHybridCache: NSObject {
    - Parameter key: Unique key to identify the object in the cache
    - Parameter completion: Completion closure returns object or nil
    */
-  func object<T: Cachable>(forKey key: String, completion: @escaping (_ object: T?) -> Void) {
-    frontStorage.object(key) { [weak self] (object: T?) in
-      if let object = object {
-        completion(object)
+  func object<T: Cachable>(forKey key: String, completion: @escaping (_ object: T?) -> Void){
+    cacheEntry(forKey: key) { (entry: CacheEntry<T>?) in
+      completion(entry?.object)
+    }
+  }
+
+  /**
+   Tries to retrieve the cache entry from to the front and back cache storages.
+
+   - Parameter key: Unique key to identify the cache entry in the cache
+   - Parameter completion: Completion closure returns cache entry or nil
+   */
+  func cacheEntry<T: Cachable>(forKey key: String, completion: @escaping (_ object: CacheEntry<T>?) -> Void) {
+    frontStorage.cacheEntry(key) { [weak self] (entry: CacheEntry<T>?) in
+      if let entry = entry {
+        completion(entry)
         return
       }
-
+      
       guard let weakSelf = self else {
-        completion(object)
+        completion(entry)
         return
       }
-
-      weakSelf.backStorage.object(key) { (object: T?) in
-        completion(object)
+
+      weakSelf.backStorage.cacheEntry(key) { (entry: CacheEntry<T>?) in
+        guard let entry = entry else {
+          completion(nil)
+          return
+        }
+
+        weakSelf.frontStorage.add(key, object: entry.object, expiry: entry.expiry) { _ in
+          completion(entry)
+        }
       }
     }
   }

Source/Shared/Cache.swift

@@ -27,8 +27,17 @@ public final class Cache<T: Cachable>: BasicHybridCache {
    - Parameter key: Unique key to identify the object in the cache
    - Parameter completion: Completion closure returns object or nil
    */
-
   public func object(_ key: String, completion: @escaping (_ object: T?) -> Void) {
     super.object(forKey: key, completion: completion)
   }
+
+  /**
+   Tries to retrieve the cache entry from to the front and back cache storages.
+   
+   - Parameter key: Unique key to identify the cache entry in the cache
+   - Parameter completion: Completion closure returns cache entry or nil
+   */
+  public func cacheEntry(_ key: String, completion: @escaping (_ object: CacheEntry<T>?) -> Void) {
+    super.cacheEntry(forKey: key, completion: completion)
+  }
 }

Source/Shared/HybridCache.swift

@@ -26,4 +26,14 @@ public class HybridCache: BasicHybridCache {
   public func object<T: Cachable>(_ key: String, completion: @escaping (_ object: T?) -> Void) {
     super.object(forKey: key, completion: completion)
   }
+
+  /**
+   Tries to retrieve the cache entry from to the front and back cache storages.
+   
+   - Parameter key: Unique key to identify the cache entry in the cache
+   - Parameter completion: Completion closure returns cache entry or nil
+   */
+  public func cacheEntry<T: Cachable>(_ key: String, completion: @escaping (_ object: CacheEntry<T>?) -> Void) {
+    super.cacheEntry(forKey: key, completion: completion)
+  }
 }

Source/Shared/Storage/CacheEntry.swift

@@ -0,0 +1,4 @@
+public struct CacheEntry<T> {
+  public let object: T
+  public let expiry: Expiry
+}

Source/Shared/Storage/DiskStorage.swift

@@ -81,30 +81,62 @@ public final class DiskStorage: StorageAware {
       completion?()
     }
   }
-
+  
   /**
-   Tries to retrieve the object from the disk storage.
-
+   Gets information about the cached object.
+   
    - Parameter key: Unique key to identify the object in the cache
    - Parameter completion: Completion closure returns object or nil
    */
   public func object<T: Cachable>(_ key: String, completion: @escaping (_ object: T?) -> Void) {
+    cacheEntry(key) { (entry: CacheEntry<T>?) in
+      completion(entry?.object)
+    }
+  }
+
+  /**
+   Get cache entry which includes object with metadata.
+
+   - Parameter key: Unique key to identify the object in the cache
+   - Parameter completion: Completion closure returns object wrapper with metadata or nil
+   */
+  public func cacheEntry<T: Cachable>(_ key: String, completion: @escaping (_ object: CacheEntry<T>?) -> Void) {
     readQueue.async { [weak self] in
       guard let weakSelf = self else {
         completion(nil)
         return
       }
-
+      
       let filePath = weakSelf.filePath(key)
       var cachedObject: T?
-
+      
       if let data = try? Data(contentsOf: URL(fileURLWithPath: filePath)) {
         cachedObject = T.decode(data) as? T
       }
-
-      completion(cachedObject)
+
+      if let cachedObject = cachedObject,
+        let expiry = weakSelf.cachedObjectExpiry(path: filePath) {
+
+        completion(CacheEntry(object: cachedObject, expiry: expiry))
+        return
+      }
+
+      completion(nil)
     }
   }
+
+  private func cachedObjectExpiry(path: String) -> Expiry? {
+    do {
+      let attributes = try fileManager.attributesOfItem(atPath: path)
+
+      guard let modificationDate = attributes[FileAttributeKey.modificationDate] as? Date else {
+        return nil
+      }
+      return Expiry.date(modificationDate)
+    } catch {}
+
+    return nil
+  }
 
   /**
    Removes the object from the cache by the given key.

Source/Shared/Storage/MemoryStorage.swift

@@ -64,26 +64,47 @@ public final class MemoryStorage: StorageAware {
       completion?()
     }
   }
-
+  
   /**
    Tries to retrieve the object from the memory storage.
-
+   
    - Parameter key: Unique key to identify the object in the cache
    - Parameter completion: Completion closure returns object or nil
    */
+
   public func object<T: Cachable>(_ key: String, completion: @escaping (_ object: T?) -> Void) {
+    cacheEntry(key) { (entry: CacheEntry<T>?) in
+      completion(entry?.object)
+    }
+  }
+
+  /**
+   Get cache entry which includes object with metadata.
+
+   - Parameter key: Unique key to identify the object in the cache
+   - Parameter completion: Completion closure returns object wrapper with metadata or nil
+   */
+  public func cacheEntry<T: Cachable>(_ key: String, completion: @escaping (_ object: CacheEntry<T>?) -> Void) {
     readQueue.async { [weak self] in
       guard let weakSelf = self else {
         completion(nil)
         return
       }
-
-      let capsule = weakSelf.cache.object(forKey: key as AnyObject) as? Capsule
-      completion(capsule?.object as? T)
-
-      if let capsule = capsule {
-        weakSelf.removeIfExpired(key, capsule: capsule)
+
+      guard let capsule = weakSelf.cache.object(forKey: key as AnyObject) as? Capsule else {
+        completion(nil)
+        return
+      }
+
+      var entry: CacheEntry<T>?
+
+      if let object = capsule.object as? T {
+        entry = CacheEntry(object: object, expiry: Expiry.date(capsule.expiryDate))
       }
+
+      completion(entry)
+
+      weakSelf.removeIfExpired(key, capsule: capsule)
     }
   }
 

Source/Shared/Storage/StorageAware.swift

@@ -15,6 +15,14 @@ public protocol CacheAware {
    */
   func add<T: Cachable>(_ key: String, object: T, expiry: Expiry, completion: (() -> Void)?)
 
+  /**
+   Get cache entry which includes object with metadata.
+
+   - Parameter key: Unique key to identify the object in the cache
+   - Parameter completion: Completion closure returns object wrapper with metadata or nil
+   */
+  func cacheEntry<T: Cachable>(_ key: String, completion: @escaping (_ object: CacheEntry<T>?) -> Void)
+
   /**
    Tries to retrieve the object from the cache.
 

Tests/iOS/Specs/CacheSpec.swift

@@ -65,21 +65,67 @@ class CacheSpec: QuickSpec {
           self.waitForExpectations(timeout: 8.0, handler:nil)
         }
       }
-
+
+      describe("#cacheEntry") {
+        it("resolves cache entry") {
+          waitUntil(timeout: 4.0) { done in
+            let expiryDate = Date()
+
+            cache.add(key, object: object, expiry: .date(expiryDate)) {
+              cache.cacheEntry(key) { (entry: CacheEntry<User>?) in
+                expect(entry?.object.firstName).to(equal(object.firstName))
+                expect(entry?.object.lastName).to(equal(object.lastName))
+                expect(entry?.expiry.date).to(equal(expiryDate))
+
+                done()
+              }
+            }
+          }
+        }
+      }
+
       describe("#object") {
         it("resolves cached object") {
           let expectation = self.expectation(description: "Object Expectation")
-
+          
           cache.add(key, object: object) {
             cache.object(key) { (receivedObject: User?) in
               expect(receivedObject?.firstName).to(equal(object.firstName))
               expect(receivedObject?.lastName).to(equal(object.lastName))
               expectation.fulfill()
             }
           }
-
+          
           self.waitForExpectations(timeout: 4.0, handler:nil)
         }
+
+        it("should resolve from disk and set in-memory cache if object not in-memory") {
+          let frontStorage = MemoryStorage(name: "MemoryStorage")
+          let backStorage = DiskStorage(name: "DiskStorage")
+          let config = Config.defaultConfig
+          let key = "myusernamedjohn"
+          let object = SpecHelper.user
+
+          let cache = Cache<User>(name: "MyCache", frontStorage: frontStorage, backStorage: backStorage, config: config)
+
+          waitUntil(timeout: 4.0) { done in
+
+            backStorage.add(key, object: object) {
+
+              cache.object(key) { (receivedObject: User?) in
+
+                expect(receivedObject?.firstName).to(equal(object.firstName))
+                expect(receivedObject?.lastName).to(equal(object.lastName))
+
+                frontStorage.object(key) { (inmemoryCachedUser: User?) in
+                  expect(inmemoryCachedUser?.firstName).to(equal(object.firstName))
+                  expect(inmemoryCachedUser?.lastName).to(equal(object.lastName))
+                  done()
+                }
+              }
+            }
+          }
+        }
       }
 
       describe("#remove") {