frenzy-ios/Reader/Screens/Items/ItemsViewController.swift

//
//  ItemsViewController.swift
//  Reader
//
//  Created by Shadowfacts on 1/9/22.
//

import UIKit
import CoreData
import SafariServices

class ItemsViewController: UIViewController {
    
    let fervorController: FervorController
    let fetchRequest: NSFetchRequest<Item>
    
    private var collectionView: UICollectionView!
    private var dataSource: UICollectionViewDiffableDataSource<Section, Item>!
    private var resultsController: NSFetchedResultsController<Item>!
    
    init(fetchRequest: NSFetchRequest<Item>, fervorController: FervorController) {
        self.fervorController = fervorController
        self.fetchRequest = fetchRequest
        
        super.init(nibName: nil, bundle: nil)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        var configuration = UICollectionLayoutListConfiguration(appearance: .plain)
        configuration.backgroundColor = .appBackground
        let layout = UICollectionViewCompositionalLayout.list(using: configuration)
        collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout)
        collectionView.delegate = self
        collectionView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        collectionView.register(ItemCollectionViewCell.self, forCellWithReuseIdentifier: "itemCell")
        view.addSubview(collectionView)
        
        dataSource = createDataSource()
        
        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
        snapshot.appendSections([.items])
        dataSource.apply(snapshot, animatingDifferences: false)
        
        fetchRequest.sortDescriptors = [NSSortDescriptor(key: "published", ascending: false)]
        resultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: fervorController.persistentContainer.viewContext, sectionNameKeyPath: nil, cacheName: nil)
        resultsController.delegate = self
        try! resultsController.performFetch()
    }
    
    private func createDataSource() -> UICollectionViewDiffableDataSource<Section, Item> {
        let itemCell = UICollectionView.CellRegistration<ItemCollectionViewCell, Item> { [unowned self] cell, indexPath, item in
            cell.updateUI(item: item)
            cell.delegate = self
        }
        let dataSource = UICollectionViewDiffableDataSource<Section, Item>(collectionView: collectionView) { collectionView, indexPath, item in
            return collectionView.dequeueConfiguredReusableCell(using: itemCell, for: indexPath, item: item)
        }
        return dataSource
    }

}

extension ItemsViewController {
    enum Section: Hashable {
        case items
    }
}

extension ItemsViewController: NSFetchedResultsControllerDelegate {
    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: NSDiffableDataSourceSnapshotReference) {
        var snapshot = self.dataSource.snapshot()
        snapshot.deleteItems(snapshot.itemIdentifiers(inSection: .items))
        // use resultsController here instead of controller so we don't have to cast
        snapshot.appendItems(resultsController.fetchedObjects!, toSection: .items)
        self.dataSource.apply(snapshot, animatingDifferences: false)
    }
}

extension ItemsViewController: UICollectionViewDelegate {
    func collectionView(_ collectionView: UICollectionView, contextMenuConfigurationForItemAt indexPath: IndexPath, point: CGPoint) -> UIContextMenuConfiguration? {
        guard let item = dataSource.itemIdentifier(for: indexPath) else {
            return nil
        }
        return UIContextMenuConfiguration(identifier: nil, previewProvider: {
            ReadViewController(item: item, fervorController: self.fervorController)
        }, actionProvider: { _ in
            var children: [UIAction] = []
            if let url = item.url {
                children.append(UIAction(title: "Open in Safari", image: UIImage(systemName: "safari"), handler: { [weak self] _ in
                    let vc = SFSafariViewController(url: url)
                    vc.preferredControlTintColor = .appTintColor
                    self?.present(vc, animated: true)
                }))
                children.append(UIAction(title: "Share", image: UIImage(systemName: "square.and.arrow.up"), handler: { [weak self] _ in
                    self?.present(UIActivityViewController(activityItems: [url], applicationActivities: nil), animated: true)
                }))
            }
            if item.read {
                children.append(UIAction(title: "Mark as Unread", image: UIImage(systemName: "checkmark.circle"), handler: { _ in
                    item.read = false
                }))
            } else {
                children.append(UIAction(title: "Mark as Read", image: UIImage(systemName: "checkmark.circle.fill"), handler: { _ in
                    item.read = true
                }))
            }
            return UIMenu(children: children)
        })
    }
    
    func collectionView(_ collectionView: UICollectionView, willPerformPreviewActionForMenuWith configuration: UIContextMenuConfiguration, animator: UIContextMenuInteractionCommitAnimating) {
        guard let vc = animator.previewViewController else {
            return
        }
        animator.preferredCommitStyle = .pop
        animator.addCompletion {
            self.show(vc, sender: nil)
        }
    }
}

extension ItemsViewController: ItemCollectionViewCellDelegate {
    func itemCellSelected(cell: ItemCollectionViewCell, item: Item) {
        cell.setRead(true, animated: true)
        show(ReadViewController(item: item, fervorController: fervorController), sender: nil)
    }
}