//
//  coreDataStorage.swift
//  testSCD
//
//  Created by Kai Gothe on 19.10.18.
//  Copyright © 2018 Kai Gothe. All rights reserved.
//

import Foundation
import CoreData

open class coreDataStorage {

    // MARK: - Project Settings

    let productName = "Appname"
    let AppGroup    = "APPGroup"

    // MARK: - Shared Instance

    public static let sharedInstance = coreDataStorage()

    // MARK: - Initialization

    init() {
        NotificationCenter.default.addObserver(self, selector: #selector(contextDidSavePrivateQueueContext(_:)), name: NSNotification.Name.NSManagedObjectContextDidSave, object: self.privateQueueCtxt)
        NotificationCenter.default.addObserver(self, selector: #selector(contextDidSaveMainQueueContext(_:)), name: NSNotification.Name.NSManagedObjectContextDidSave, object: self.mainQueueCtxt)
    }

    deinit {
        NotificationCenter.default.removeObserver(self)
    }

    // MARK: - Notifications

    @objc func contextDidSavePrivateQueueContext(_ notification: Notification) {
        if let context = self.mainQueueCtxt {
            self.synced(self, closure: { () -> () in
                context.perform({() -> Void in
                    context.mergeChanges(fromContextDidSave: notification)
                })
            })
        }
    }

    @objc func contextDidSaveMainQueueContext(_ notification: Notification) {
        if let context = self.privateQueueCtxt {
            self.synced(self, closure: { () -> () in
                context.perform({() -> Void in
                    context.mergeChanges(fromContextDidSave: notification)
                })
            })
        }
    }

    func synced(_ lock: AnyObject, closure: () -> ()) {
        objc_sync_enter(lock)
        closure()
        objc_sync_exit(lock)
    }

    // MARK: - Core Data stack

    lazy var applicationDocumentsDirectory: URL = {
        // The directory the application uses to store the Core Data store file. This code uses a directory named 'Bundle identifier' in the application's documents Application Support directory.
        let urls = Foundation.FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
        return urls[urls.count-1]
    }()

    lazy var managedObjectModel: NSManagedObjectModel = {
        // The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
        let modelURL = Bundle.main.url(forResource: productName, withExtension: "momd")!
        return NSManagedObjectModel(contentsOf: modelURL)!
    }()

    lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {
        // The persistent store coordinator for the application. This implementation creates and return a coordinator, having added 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.
        // Create the coordinator and store
        var coordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
        let options = [
            NSMigratePersistentStoresAutomaticallyOption: true,
            NSInferMappingModelAutomaticallyOption: true
        ]
        let directory = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: AppGroup)!
        let url = directory.appendingPathComponent("\(productName).sqlite")
        do {
            try coordinator!.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: options)
        } catch var error as NSError {
            coordinator = nil
            NSLog("Unresolved error \(error), \(error.userInfo)")
            abort()
        } catch {
            fatalError()
        }
        return coordinator
    }()

    // MARK: - NSManagedObject Contexts

    open class func mainQueueContext() -> NSManagedObjectContext {
        return self.sharedInstance.mainQueueCtxt!
    }

    open class func privateQueueContext() -> NSManagedObjectContext {
        return self.sharedInstance.privateQueueCtxt!
    }

    lazy var mainQueueCtxt: NSManagedObjectContext? = {
        // Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
        var managedObjectContext = NSManagedObjectContext(concurrencyType:.mainQueueConcurrencyType)
        managedObjectContext.persistentStoreCoordinator = self.persistentStoreCoordinator
        return managedObjectContext
    }()

    lazy var privateQueueCtxt: NSManagedObjectContext? = {
        // Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
        var managedObjectContext = NSManagedObjectContext(concurrencyType:.privateQueueConcurrencyType)
        managedObjectContext.persistentStoreCoordinator = self.persistentStoreCoordinator
        return managedObjectContext
    }()

    // MARK: - Core Data Saving support

    open class func saveContext(_ context: NSManagedObjectContext?) {
        if let moc = context {
            if moc.hasChanges {
                do {
                    try moc.save()
                } catch {
                    print(error.localizedDescription)
                }
            }
        }
    }

}
extension NSManagedObject {

    public class func findAllForEntity(_ entityName: String, context: NSManagedObjectContext) -> [AnyObject]? {
        let request = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
        let result: [AnyObject]?
        do {
            result = try context.fetch(request)
        } catch let error as NSError {
            print(error)
            result = nil
        }
        return result
    }
}