import Foundation
import CoreData

protocol CoreDataStackType {
    var persistentContainer: NSPersistentContainer { get }
    func saveContext()
}

class CoreDataStack: CoreDataStackType {

    static let sharedInstance = CoreDataStack()

    // MARK: - Core Data stack

    lazy var persistentContainer: NSPersistentContainer = {
        /*
        The persistent container for the application. This implementation
        creates and returns a container, having loaded the store for the
        application to it. This property is optional since there are legitimate
        error conditions that could cause the creation of the store to fail.
        */
        let container = NSPersistentContainer(name: "JSONFeedParser")
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {
                // Replace this implementation with code to handle the error appropriately.
                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

                /*
                Typical reasons for an error here include:
                * The parent directory does not exist, cannot be created, or disallows writing.
                * The persistent store is not accessible, due to permissions or data protection when the device is locked.
                * The device is out of space.
                * The store could not be migrated to the current model version.
                Check the error message to determine what the actual problem was.
                */
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
        })
        return container
    }()

    // MARK: - Core Data Saving support

    func saveContext () {
        let context = persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.save()
            } catch {
                // Replace this implementation with code to handle the error appropriately.
                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
                let nserror = error as NSError
                fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
            }
        }
    }
}
