/*

    Copyright (C) 2016 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    Defines the `FavoriteCreatureListViewController` which displays a list

                of creatures. The user can pick their favorite creature from this

                view controller. This view controller is displayed when the favorite

                creature cell is tapped from the `DreamListViewController`.

*/

import UIKit

/**

    A view controller that displays a list of creatures to select as a user's

    favorite creature.

*/

class FavoriteCreatureListViewController: UITableViewController {

    // MARK: Properties

    var favoriteCreatureDidChange: ((Dream.Creature) -> Void)?

    /*

        We only have one state property for this view controller so we won't create

        a wrapper struct for it.

    */

    private var favoriteCreature: Dream.Creature!

    /**

        Setter accessible to  other view controllers. Only set this before the

        view controller's view has appeared.

    */

    func setFavoriteCreature(_ favoriteCreature: Dream.Creature) {

        self.favoriteCreature = favoriteCreature

    }

    /**

        This method takes in a closure that can modify the view controller's

        `favoriteCreature` property.

        Look at the call sites that use this method to get a better understanding

        of how the model is changed.

        The crux of this design is that after we mutate the favorite creature we

        perform a diff of the previous values and new value. Based on that diff

        we update our UI with the appropriate changes.

        This is a very nice aspect of this design approach because it centralizes

        our UI update code, preserving "Locality of Reasoning" for our UI (this

        is described in the WWDC session).

    */

    func withFavoriteCreature(_ mutateFavoriteCreature: (inout Dream.Creature) -> Void) {

        let old = favoriteCreature

        mutateFavoriteCreature(&favoriteCreature!)

        guard favoriteCreature != old else {

            // If the new and old are the same we just need to deselect the row.

            if let indexPathForSelectedRow = tableView.indexPathForSelectedRow {

                tableView.deselectRow(at: indexPathForSelectedRow, animated: true)

            }

            return

        }

        /*

            Perform the diff. Deselect the previously selected cell and select

            the recently tapped one.

        */

        tableView.beginUpdates()

        if let old = old {

            let indexOfPreviousFavoriteCreature = Dream.Creature.all.index(of: old)!

            let indexPathOfPreviousFavoriteCreature = IndexPath(row: indexOfPreviousFavoriteCreature, section: 0)

            tableView.deselectRow(at: indexPathOfPreviousFavoriteCreature, animated: true)

            let previousFavoriteCreatureCell = tableView.cellForRow(at: indexPathOfPreviousFavoriteCreature)

            previousFavoriteCreatureCell?.accessoryType = .none

        }

        let indexOfNewFavoriteCreature = Dream.Creature.all.index(of: favoriteCreature!)!

        let indexPathofNewFavoriteCreature = IndexPath(row: indexOfNewFavoriteCreature, section: 0)

        tableView.deselectRow(at: indexPathofNewFavoriteCreature, animated: true)

        let newFavoriteCreatureCell = tableView.cellForRow(at: indexPathofNewFavoriteCreature)

        newFavoriteCreatureCell?.accessoryType = .checkmark

        tableView.endUpdates()

    }

    // MARK: UITableViewDelegate & UITableViewDataSource

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

        return Dream.Creature.all.count

    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)

        let creature = Dream.Creature.all[indexPath.row]

        if creature == favoriteCreature {

            cell.accessoryType = .checkmark

        } else {

            cell.accessoryType = .none

        }

        cell.imageView!.image = creature.image

        cell.textLabel!.text = creature.name

        return cell

    }

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        withFavoriteCreature { newFavoriteCreature in

            newFavoriteCreature = Dream.Creature.all[indexPath.row]

        }

    }

    // MARK: IBActions

    @IBAction func cancelTapped() {

        dismiss(animated: true, completion: nil)

    }

    @IBAction func doneTapped() {

        favoriteCreatureDidChange?(favoriteCreature)

        dismiss(animated: true, completion: nil)

    }

}