NSManagedObjectContext.swift

//
//  NSManagedObjectContext.swift
//  TeamKnect
//
//  Created by Scott Grosch on 8/7/15.
//  Copyright (c) 2015 Gargoyle Software, LLC. All rights reserved.
//

import UIKit
import CoreData

extension NSManagedObjectContext {
    class func errorToMessages(error: NSError) -> String {
        return "\n".join(NSManagedObjectContext.errorToMessageSet(error))
    }
    
    class func errorToMessageSet(error: NSError) -> Set<String> {
        var set = Set<String>()
        
        if error.domain != NSCocoaErrorDomain {
            set.insert("\(error.localizedDescription)\n\(error.localizedFailureReason)")
        }
        
        let userInfo = error.userInfo
        
        var attribute = userInfo[NSValidationKeyErrorKey] as? String
        if attribute == nil {
            attribute = ""
        }
        
        var msg = ""
        
        switch error.code {
        case NSManagedObjectValidationError:
            msg = "Generic validation error"
        case NSValidationDateTooLateError:
            msg = "Date for '\(attribute!)' is newer than allowed."
        case NSValidationDateTooSoonError:
            msg = "Date for '\(attribute!)' is older than allowed."
        case NSValidationInvalidDateError:
            msg = "Date for '\(attribute!)' is invalid."
        case NSValidationMissingMandatoryPropertyError:
            msg = "Required attribute '\(attribute!)' is nil."
        case NSValidationNumberTooLargeError:
            msg = "Number '\(attribute!)' is larger than allowed."
        case NSValidationNumberTooSmallError:
            msg = "Number '\(attribute!)' is smaller than required.'"
        case NSValidationRelationshipDeniedDeleteError:
            msg = "Relationship '\(attribute!)' must be empty before deletion."
        case NSValidationRelationshipExceedsMaximumCountError:
            msg = "Relationship '\(attribute!)' has more than the maximum number of entries allowed."
        case NSValidationRelationshipLacksMinimumCountError:
            msg = "Relationship '\(attribute!)' has fewer than the minimum number of entries allowed."
        case NSValidationStringTooLongError:
            msg = "Text of '\(attribute!)' is longer than allowed."
        case NSValidationStringTooShortError:
            msg = "Text of '\(attribute!)' is shorter than required."
        case NSValidationMultipleErrorsError:
            if let subErrors = userInfo[NSDetailedErrorsKey] as? [NSError] {
                for error in subErrors {
                    set.unionInPlace(NSManagedObjectContext.errorToMessageSet(error))
                }
            } else {
                return set
            }
        default:
            msg = "Unknown reason, error code \(error.code)"
        }
        
        if let managedObject = userInfo[NSValidationObjectErrorKey] as? NSManagedObject {
            if let entity = managedObject.entity.name {
                msg = "\(entity): \(msg)"
            }
        }
        
        set.insert(msg)
        
        return set
    }
    
    /**
    Save the managed object context.  On failure, logs a message to the console and also, if in DEBUG
    mode, pops up an alert with the message to make development easier.
    
    :param: presentingViewController The view controller from which saveFromViewController was called
    
    :returns: true on successful save, false on failure.
    */
    func saveFromViewController(presentingViewController presentingViewController: UIViewController? = nil) -> Bool {
        if hasChanges {
            do {
                try save()
            } catch {
                let errorMessages = NSManagedObjectContext.errorToMessages(error as NSError)
                
                print(errorMessages)
                
                #if DEBUG
                    if let presentingViewController = presentingViewController {
                        dispatch_async(dispatch_get_main_queue()) {
                            let alert = UIAlertController(title: nil, message: errorMessages, preferredStyle: .Alert)
                            alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: nil))
                            presentingViewController.presentViewController(alert, animated: true, completion: nil)
                        }
                    }
                #endif
            }
        }
        
        return true
    }
}