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 /* ObjectMetadata.swift in Sources */ = {isa = PBXBuildFile; fileRef = 57506FAD1EC29437009B71E9 /* ObjectMetadata.swift */; };
+		57506FBF1EC2E1B7009B71E9 /* ObjectMetadata.swift in Sources */ = {isa = PBXBuildFile; fileRef = 57506FAD1EC29437009B71E9 /* ObjectMetadata.swift */; };
+		57506FC01EC2E1BA009B71E9 /* ObjectMetadata.swift in Sources */ = {isa = PBXBuildFile; fileRef = 57506FAD1EC29437009B71E9 /* ObjectMetadata.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 /* ObjectMetadata.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ObjectMetadata.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>"; };
@@ -322,6 +326,7 @@
 				D5291C251C28220B00B702C9 /* MemoryStorage.swift */,
 				D5291C261C28220B00B702C9 /* StorageAware.swift */,
 				D5291C271C28220B00B702C9 /* StorageFactory.swift */,
+				57506FAD1EC29437009B71E9 /* ObjectMetadata.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 /* ObjectMetadata.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 /* ObjectMetadata.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 /* ObjectMetadata.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.
    */
@@ -109,10 +115,26 @@ public class BasicHybridCache: NSObject {
       }
 
       weakSelf.backStorage.object(key) { (object: T?) in
-        completion(object)
+        guard let object = object else {
+            completion(nil)
+            return
+        }
+        weakSelf.copyToFrontStorage(key, object: object, completion: completion)
       }
     }
   }
+
+  private func copyToFrontStorage<T: Cachable>(_ key: String, object: T, completion: @escaping (_ object: T?) -> Void) {
+
+    guard let metadata = self.backStorage.objectMetadata(key) else {
+        completion(nil)
+        return
+    }
+
+    self.frontStorage.add(key, object: object, expiry: metadata.expiry, completion: { _ in
+        completion(object)
+    })
+  }
 
   /**
    Removes the object from to the front and back cache storages.

Source/Shared/Storage/DiskStorage.swift

@@ -81,6 +81,23 @@ public final class DiskStorage: StorageAware {
       completion?()
     }
   }
+
+  /**
+   Gets information about the cached object.
+
+   - Parameter key: Unique key to identify the object in the cache
+   */
+  public func objectMetadata(_ key: String) -> ObjectMetadata? {
+
+    do {
+      let attributes = try fileManager.attributesOfItem(atPath: filePath(key))
+      let fileModifiedDate = Expiry.date(attributes[FileAttributeKey.modificationDate] as! Date)
+      return ObjectMetadata(expiry: fileModifiedDate)
+
+    } catch {}
+
+    return nil
+  }
 
   /**
    Tries to retrieve the object from the disk storage.

Source/Shared/Storage/MemoryStorage.swift

@@ -65,6 +65,20 @@ public final class MemoryStorage: StorageAware {
     }
   }
 
+  /**
+   Gets information about the cached object.
+
+   - Parameter key: Unique key to identify the object in the cache
+   */
+  public func objectMetadata(_ key: String) -> ObjectMetadata? {
+
+    guard let capsule = cache.object(forKey: key as AnyObject) as? Capsule else {
+      return nil
+    }
+
+    return ObjectMetadata(expiry: Expiry.date(capsule.expiryDate))
+  }
+
   /**
    Tries to retrieve the object from the memory storage.
 

Source/Shared/Storage/ObjectMetadata.swift

@@ -0,0 +1,9 @@
+public struct ObjectMetadata {
+    let expiry: Expiry
+}
+
+extension ObjectMetadata: Equatable {}
+
+public func ==(lhs: ObjectMetadata, rhs: ObjectMetadata) -> Bool {
+    return lhs.expiry.date == rhs.expiry.date
+}

Source/Shared/Storage/StorageAware.swift

@@ -15,6 +15,13 @@ public protocol CacheAware {
    */
   func add<T: Cachable>(_ key: String, object: T, expiry: Expiry, completion: (() -> Void)?)
 
+  /**
+   Gets information about the cached object.
+
+   - Parameter key: Unique key to identify the object in the cache
+   */
+  func objectMetadata(_ key: String) -> ObjectMetadata?
+
   /**
    Tries to retrieve the object from the cache.
 

Tests/iOS/Specs/CacheSpec.swift

@@ -80,6 +80,34 @@ class CacheSpec: QuickSpec {
 
           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") {

Tests/iOS/Specs/Storage/DiskStorageSpec.swift

@@ -65,6 +65,33 @@ class DiskStorageSpec: QuickSpec {
         }
       }
 
+      describe("#objectMetadata") {
+        it("returns nil if object doesn't exist") {
+          let storage = DiskStorage(name: name)
+
+          let metadata = storage.objectMetadata(key)
+
+          expect(metadata).to(beNil())
+        }
+
+        it("returns object metadata if object exists") {
+          let storage = DiskStorage(name: name)
+
+          waitUntil(timeout: 2.0) { done in
+
+            storage.add(key, object: object) {
+              let metadata = storage.objectMetadata(key)
+              let attributes = try! fileManager.attributesOfItem(atPath: storage.filePath(key))
+              let fileModifiedDate = Expiry.date(attributes[FileAttributeKey.modificationDate] as! Date)
+              let expectedMetadata = ObjectMetadata(expiry: fileModifiedDate)
+
+              expect(metadata).to(equal(expectedMetadata))
+              done()
+            }
+          }
+        }
+      }
+
       describe("#object") {
         it("resolves cached object") {
           let expectation = self.expectation(description: "Object Expectation")

Tests/iOS/Specs/Storage/MemoryStorageSpec.swift

@@ -47,7 +47,32 @@ class MemoryStorageSpec: QuickSpec {
           self.waitForExpectations(timeout: 2.0, handler:nil)
         }
       }
-
+
+      describe("#objectMetadata") {
+        it("returns nil if object doesn't exist") {
+          let storage = MemoryStorage(name: name)
+
+          let metadata = storage.objectMetadata(key)
+
+          expect(metadata).to(beNil())
+        }
+
+        it("returns object metadata if object exists") {
+          let storage = MemoryStorage(name: name)
+          let expiry = Expiry.date(Date())
+
+          waitUntil(timeout: 2.0) { done in
+
+            storage.add(key, object: object, expiry: expiry) {
+              let metadata = storage.objectMetadata(key)
+              let expectedMetadata = ObjectMetadata(expiry: expiry)
+              expect(metadata).to(equal(expectedMetadata))
+              done()
+            }
+          }
+        }
+      }
+
       describe("#object") {
         it("resolves cached object") {
           let expectation = self.expectation(description: "Object Expectation")