//
//  ManagedObjectObserver.swift
//  CoreStore
//
//  Copyright (c) 2015 John Rommel Estropia
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in all
//  copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
//  SOFTWARE.
//

import Foundation
import CoreData


// MARK: - ManagedObjectObserver

/**
Implement the `ManagedObjectObserver` protocol to observe changes to a single `NSManagedObject` instance. `ManagedObjectObserver`'s may register themselves to a `ManagedObjectController`'s `addObserver(_:)` method:

    let objectController = CoreStore.observeObject(object)
    objectController.addObserver(self)
*/
public protocol ManagedObjectObserver: class {
    
    /**
    The `NSManagedObject` type for the observed object
    */
    typealias EntityType: NSManagedObject
    
    /**
    Handles processing just before a change to the observed `object` occurs
    
    :param: objectController the `ManagedObjectController` monitoring the object being observed
    :param: object the `NSManagedObject` instance being observed
    */
    func managedObjectWillUpdate(objectController: ManagedObjectController<EntityType>, object: EntityType)
    
    /**
    Handles processing right after a change to the observed `object` occurs
    
    :param: objectController the `ManagedObjectController` monitoring the object being observed
    :param: object the `NSManagedObject` instance being observed
    :param: changedPersistentKeys a `Set` of key paths for the attributes that were changed. Note that `changedPersistentKeys` only contains keys for attributes/relationships present in the persistent store, thus transient properties will not be reported.
    */
    func managedObjectWasUpdated(objectController: ManagedObjectController<EntityType>, object: EntityType, changedPersistentKeys: Set<KeyPath>)
    
    /**
    Handles processing right after `object` is deleted
    
    :param: objectController the `ManagedObjectController` monitoring the object being observed
    :param: object the `NSManagedObject` instance being observed
    */
    func managedObjectWasDeleted(objectController: ManagedObjectController<EntityType>, object: EntityType)
}