import UIKit
import CoreData

public protocol FetchedResultsDelegate {
	func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath, object: AnyObject) -> UITableViewCell
}

public class FetchedResultsDataSource: NSObject, UITableViewDataSource, NSFetchedResultsControllerDelegate {

	public weak var tableView: UITableView?
	public var frc: NSFetchedResultsController
	public var delegate: FetchedResultsDelegate?

	public init(fetchRequest: NSFetchRequest, context: NSManagedObjectContext = DataController.dataStack.mainContext, sectionNameKeyPath: String?) {
		frc = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: context, sectionNameKeyPath: sectionNameKeyPath, cacheName: nil)

		super.init()

		frc.delegate = self
	}

	/// Set `tableView.datasource` to `self`, perform fetch and reload table data
	public func performFetchAndConfigureTableView(tableView: UITableView) {
		self.tableView = tableView

		tableView.dataSource = self

		do {
			try frc.performFetch()
			dispatch_async(dispatch_get_main_queue()) { tableView.reloadData() }
		} catch {
			assertionFailure("\(#function): \(error)")
		}
	}

	public func objectAtIndexPath(indexPath: NSIndexPath) -> AnyObject {
		return frc.objectAtIndexPath(indexPath)
	}

	public func titleForHeaderInSection(section: Int) -> String? {
		return self.frc.sections?[section].name
	}

	// MARK: - UITableViewDataSource

	public func numberOfSectionsInTableView(tableView: UITableView) -> Int {
		return self.frc.sections?.count ?? 0
	}

	public func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
		guard let sections = frc.sections else { return 0 }

		return sections[section].numberOfObjects
	}

	public func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
		if let delegate = delegate {
			return delegate.tableView(tableView, cellForRowAtIndexPath: indexPath, object: self.objectAtIndexPath(indexPath))
		} else {
			assertionFailure("Delegate is not set, can't return cell")
			return UITableViewCell()
		}
	}

	//	func tableView(tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
	//		return self.frc.sections?[section].name
	//	}



	// MARK: - Right section titles

	//	func tableView(tableView: UITableView, sectionForSectionIndexTitle title: String, atIndex index: Int) -> Int {
	//		return self.frc.sectionForSectionIndexTitle(title, atIndex: index) ?? 0
	//	}
	//
	//	func sectionIndexTitlesForTableView(tableView: UITableView) -> [String]? {
	//		return self.frc.sectionIndexTitles
	//	}

	// MARK: - NSFetchedResultsControllerDelegate

	public func controllerWillChangeContent(controller: NSFetchedResultsController) {
		tableView?.beginUpdates()
	}

	public func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {

		let sectionIndexSet = NSIndexSet(index: sectionIndex)

		switch type {
		case NSFetchedResultsChangeType.Insert:
			tableView?.insertSections(sectionIndexSet, withRowAnimation: .Automatic)
		case NSFetchedResultsChangeType.Delete:
			tableView?.deleteSections(sectionIndexSet, withRowAnimation: .Automatic)
		case .Update:
			tableView?.reloadSections(sectionIndexSet, withRowAnimation: .Automatic)
		case .Move:
			// TODO: maybe we have better solution instead of reload, possible bugs
			tableView?.reloadSections(sectionIndexSet, withRowAnimation: .Automatic)
		}
	}

	public func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {
		switch type {
		case .Insert:
			guard let newIndexPath = newIndexPath else { return }
			tableView?.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Automatic)
		case .Delete:
			guard let indexPath = indexPath else { return }
			tableView?.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Automatic)
		case .Update:
			guard let indexPath = indexPath else { return }
			tableView?.reloadRowsAtIndexPaths([indexPath], withRowAnimation: .Automatic)
		case .Move:
			guard let indexPath = indexPath, let newIndexPath = newIndexPath else { return }
			tableView?.deleteRowsAtIndexPaths([indexPath], withRowAnimation: UITableViewRowAnimation.Fade)
			tableView?.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: UITableViewRowAnimation.Fade)
		}
	}

	public func controllerDidChangeContent(controller: NSFetchedResultsController) {
		tableView?.endUpdates()
	}

}