/*

    Copyright (C) 2017 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    A `UICollectionViewController` subclass that is used to show `DataItem` search results for the `UISearchController` shown by `SearchViewController`.

*/

import UIKit

class SearchResultsViewController: UICollectionViewController, UISearchResultsUpdating {

    // MARK: Properties

    static let storyboardIdentifier = "SearchResultsViewController"

    private let cellComposer = DataItemCellComposer()

    private let allDataItems = DataItem.sampleItems

    private var filteredDataItems = DataItem.sampleItems

    var filterString = "" {

        didSet {

            // Return if the filter string hasn't changed.

            guard filterString != oldValue else { return }

            // Apply the filter or show all items if the filter string is empty.

            if filterString.isEmpty {

                filteredDataItems = allDataItems

            }

            else {

                filteredDataItems = allDataItems.filter { $0.title.localizedStandardContains(filterString) }

            }

            // Reload the collection view to reflect the changes.

            collectionView?.reloadData()

        }

    }

    // MARK: UIViewController

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        super.prepare(for: segue, sender: sender)

        // Check if a DataItemViewController is being presented.

        if let dataItemViewController = segue.destination as? DataItemViewController {

            // Pass the selected `DataItem` to the `DataItemViewController`.

            guard let indexPath = collectionView?.indexPathsForSelectedItems?.first else { fatalError("Expected a cell to have been selected") }

            dataItemViewController.configure(with: filteredDataItems[indexPath.row])

        }

    }

    // MARK: UICollectionViewDataSource

    override func numberOfSections(in collectionView: UICollectionView) -> Int {

        return 1

    }

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

        return filteredDataItems.count

    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        // Dequeue a cell from the collection view.

        return collectionView.dequeueReusableCell(withReuseIdentifier: DataItemCollectionViewCell.reuseIdentifier, for: indexPath)

    }

    // MARK: UICollectionViewDelegate

    override func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {

        guard let cell = cell as? DataItemCollectionViewCell else { fatalError("Expected to display a `DataItemCollectionViewCell`.") }

        let item = filteredDataItems[(indexPath as NSIndexPath).row]

        // Configure the cell.

        cellComposer.compose(cell, withDataItem: item)

    }

    // MARK: UISearchResultsUpdating

    func updateSearchResults(for searchController: UISearchController) {

        filterString = searchController.searchBar.text ?? ""

    }

}