//
//  Persistence.swift
//  Simoleon
//
//  Created by Dennis Concepción Martín on 08/07/2021.
//

import CoreData

struct PersistenceController {
    static let shared = PersistenceController()
    
    static var preview: PersistenceController = {
        let result = PersistenceController(inMemory: true)
        let viewContext = result.container.viewContext
        
        for _ in 0..<10 {
            let favoritePair = FavoritePair(context: viewContext)
            favoritePair.baseSymbol = "USD"
            favoritePair.quoteSymbol = "EUR"
        }
        
        do {
            try viewContext.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)")
        }
        return result
    }()
    
    let container: NSPersistentCloudKitContainer
    
    init(inMemory: Bool = false) {
        container = NSPersistentCloudKitContainer(name: "Simoleon")
        container.viewContext.automaticallyMergesChangesFromParent = true
        container.viewContext.mergePolicy = NSMergeByPropertyStoreTrumpMergePolicy
        if inMemory {
            container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
        }
        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)")
            }
        })
    }
}