import Foundation

/// A protocol used for saving and loading from storage
public protocol StorageAware {
  associatedtype T
  /**
   Tries to retrieve the object from the storage.
   - Parameter key: Unique key to identify the object in the cache
   - Returns: Cached object or nil if not found
   */
  func object(forKey key: String) throws -> T

  /**
   Get cache entry which includes object with metadata.
   - Parameter key: Unique key to identify the object in the cache
   - Returns: Object wrapper with metadata or nil if not found
   */
  func entry(forKey key: String) throws -> Entry<T>

  /**
   Removes the object by the given key.
   - Parameter key: Unique key to identify the object.
   */
  func removeObject(forKey key: String) throws

  /**
   Saves passed object.
   - Parameter key: Unique key to identify the object in the cache.
   - Parameter object: Object that needs to be cached.
   - Parameter expiry: Overwrite expiry for this object only.
   */
  func setObject(_ object: T, forKey key: String, expiry: Expiry?) throws

  /**
   Check if an object exist by the given key.
   - Parameter key: Unique key to identify the object.
   */
  func existsObject(forKey key: String) throws -> Bool

  /**
   Removes all objects from the cache storage.
   */
  func removeAll() throws

  /**
   Clears all expired objects.
   */
  func removeExpiredObjects() throws

  /**
   Check if an expired object by the given key.
   - Parameter key: Unique key to identify the object.
   */
  func isExpiredObject(forKey key: String) throws -> Bool
}

public extension StorageAware {
  func object(forKey key: String) throws -> T {
    return try entry(forKey: key).object
  }

  func existsObject(forKey key: String) throws -> Bool {
    do {
      let _: T = try object(forKey: key)
      return true
    } catch {
      return false
    }
  }

  func isExpiredObject(forKey key: String) throws -> Bool {
    do {
      let entry = try self.entry(forKey: key)
      return entry.expiry.isExpired
    } catch {
      return true
    }
  }
}