class ProjectsViewController: UIViewController {
    //MARK: - Types
    enum Section: CaseIterable {
        case normal
    }
    
    //MARK: - Properties
    let projectsController = ProjectsController()
    
    var collectionView: UICollectionView!
    var dataSource: UICollectionViewDiffableDataSource<Section, Project>!
    
    var lastScrollPosition: CGFloat = 0
    var isSearching = false
    
    let searchController = UISearchController()
    
    //MARK: - ViewController Methods
    override func viewDidLoad() {
        super.viewDidLoad()
        
        configureViewController()
        configureSearchController()
        configureCollectionView()
        createDataSource()
        updateData(on: projectsController.filteredProjects())        
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        if isSearching {
            isSearching.toggle()
            searchController.searchBar.text = ""
            searchController.resignFirstResponder()
        }
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        searchController.searchBar.searchTextField.attributedPlaceholder = NSAttributedString(string: "Title or details text ...",
                                                                                              attributes: [NSAttributedString.Key.foregroundColor: UIColor.secondaryLabel])
    }
        
    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
        super.traitCollectionDidChange(previousTraitCollection)
        
        collectionView.collectionViewLayout = UICollectionView.createFlexibleFlowLayout(in: view)
    }
    
    
    //MARK: - DataSource
    func createDataSource() {
        dataSource = UICollectionViewDiffableDataSource<Section, Project>(collectionView: collectionView) { (collectionView, indexPath, project) in
                return self.configure(NormalProjectCell.self, with: project, for: indexPath)
        }
    }
    
    func updateData(on projects: [Project]) {
        var snapshot = NSDiffableDataSourceSnapshot<Section, Project>()
        snapshot.appendSections([Section.normal])
        snapshot.appendItems(projects)

        //apply() is safe to call from a background queue!
        self.dataSource.apply(snapshot, animatingDifferences: true)
    }
    
    ///Configure any type of cell that conforms to selfConfiguringProjectCell!
    func configure<T: SelfConfiguringProjectCell>(_ cellType: T.Type, with project: Project, for indexPath: IndexPath) -> T {
        guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellType.reuseIdentifier, for: indexPath) as? T else {
            fatalError("Unable to dequeue \(cellType)")
        }
        
        cell.configure(with: project)
        return cell
    }
    
    //MARK: - Actions
    @objc func addButtonTapped() {
        let project = Project()
        let viewController = ProjectDetailsViewController(withProject: project)
        viewController.delegate = self
        navigationController?.pushViewController(viewController, animated: true)
    }
    
    @objc private func tapAndHoldCell(recognizer: UILongPressGestureRecognizer) {
        if recognizer.state == .ended {
            guard let indexPath = collectionView.indexPathForItem(at: recognizer.location(in: self.collectionView)),
                let project = dataSource?.itemIdentifier(for: indexPath) else {
                    return
            }
            
            let viewController = ProjectDetailsViewController(withProject: project)
            viewController.delegate = self
            navigationController?.pushViewController(viewController, animated: true)
        }
    }
    
    @objc private func swipeFromRightOnCell(recognizer: UISwipeGestureRecognizer) {
        if recognizer.state == .ended {
            guard let indexPath = collectionView.indexPathForItem(at: recognizer.location(in: self.collectionView)),
                let cell = collectionView.cellForItem(at: indexPath),
                let project = dataSource?.itemIdentifier(for: indexPath) else {
                    return
            }
            
            let overlay = ProjectCellDeletionOverlay(frame: CGRect(x: cell.bounds.width, y: 0, width: 0, height: cell.bounds.height))
            cell.addSubview(overlay)
            
            UIView.animate(withDuration: 0.70, animations: {
                overlay.backgroundColor = UIColor.red.withAlphaComponent(0.60)
                overlay.frame = CGRect(x: cell.bounds.width / 2, y: 0, width: cell.bounds.width / 2, height: cell.bounds.height)
            }) { _ in
                self.presentProjectAlertOnMainThread(withTitle: "Delete this Project?",
                                                     andMessage: "Are you sure?\nThis cannot be undone!\nAll associated notes will also be deleted!",
                                                     andDismissButtonTitle: "Cancel",
                                                     andConfirmButtonTitle: "Delete!",
                                                     completion: { success in
                                                        if success {
                                                            UIView.animate(withDuration: 1.40, animations: {
                                                                overlay.frame = CGRect(x: 0, y: 0, width: cell.bounds.width, height: cell.bounds.height)
                                                                cell.alpha = 0
                                                            }) { _ in
                                                                self.delete(project)
                                                                overlay.removeFromSuperview()
                                                            }
                                                        } else {
                                                            UIView.animate(withDuration: 1.5, animations: {
                                                                overlay.frame = CGRect(x: cell.bounds.width, y: 0, width: 0, height: cell.bounds.height)
                                                                overlay.alpha = 0
                                                            }) { _ in
                                                                overlay.removeFromSuperview()
                                                            }
                                                        }
                })
            }
        }
    }
    
    ///Will show an overlay view with help text on the app
    @objc private func showHelpView() {
        let helpViewController = AppHelpViewController(with: HelpViewDisplayTextFor.projects)
        helpViewController.modalTransitionStyle = .flipHorizontal
        helpViewController.modalPresentationStyle = .fullScreen
        present(helpViewController, animated: true)
    }
    
    ///Will show a menu with several options
    @objc private func showMenu() {
        
    }

    //MARK: - UI & Layout
    private func configureViewController() {
        view.backgroundColor = .systemPurple
        title = "Projects"
        
        navigationController?.navigationBar.prefersLargeTitles = false
        
        let menu =  UIBarButtonItem(image: ProjectImages.BarButton.menu, style: .plain, target: self, action: #selector(showMenu))
        let add =  UIBarButtonItem(barButtonSystemItem: .add, target: self, action: #selector(addButtonTapped))
        navigationItem.leftBarButtonItems = [menu, add]
        let questionMark = UIBarButtonItem(image: ProjectImages.BarButton.questionmark, style: .plain, target: self, action: #selector(showHelpView))
        navigationItem.rightBarButtonItem = questionMark
    }

    private func configureCollectionView() {
        collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: UICollectionView.createFlexibleFlowLayout(in: view))
        collectionView.delegate = self
        collectionView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        collectionView.backgroundColor = .clear
        view.addSubview(collectionView)
        
        collectionView.register(NormalProjectCell.self, forCellWithReuseIdentifier: NormalProjectCell.reuseIdentifier)
        
        let tapAndHold = UILongPressGestureRecognizer(target: self, action: #selector(tapAndHoldCell))
        tapAndHold.minimumPressDuration = 0.3
        collectionView.addGestureRecognizer(tapAndHold)
        
        let swipeFromRight = UISwipeGestureRecognizer(target: self, action: #selector(swipeFromRightOnCell) )
        swipeFromRight.direction = UISwipeGestureRecognizer.Direction.left
        collectionView.addGestureRecognizer(swipeFromRight)
    }
    
    private func configureSearchController() {
        searchController.searchResultsUpdater = self
        searchController.obscuresBackgroundDuringPresentation = false
        navigationItem.searchController = searchController
        
        //CollectionView under searchbar fix ???
        searchController.extendedLayoutIncludesOpaqueBars = true
//        searchController.edgesForExtendedLayout = .top
    }
    
}

//MARK: - Ext CollectionView Delegate
extension ProjectsViewController: UICollectionViewDelegate  {
    
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        guard let project = dataSource?.itemIdentifier(for: indexPath) else { return }
        ProjectsController.activeProject = project
        
        let loadingView = showLoadingView(for: project)

        let viewController = SplitOrFlipContainerController()
        UIView.animate(withDuration: 1.5, animations: {
            loadingView.alpha = 1
        }) { (complete) in
            self.dismiss(animated: false) {
                self.present(viewController, animated: false)
            }
        }
    }
}

//MARK: - Ext Search Results & Bar
extension ProjectsViewController: UISearchResultsUpdating {
    func updateSearchResults(for searchController: UISearchController) {
        guard let filter = searchController.searchBar.text, filter.isNotEmpty else {
            isSearching = false
            updateData(on: projectsController.filteredProjects())
            return
        }

        isSearching = true
        updateData(on: projectsController.filteredProjects(with: filter.lowercased()))
    }
    
    func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
        lastScrollPosition = scrollView.contentOffset.y
    }

    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        if lastScrollPosition < scrollView.contentOffset.y {
            navigationItem.hidesSearchBarWhenScrolling = true
        } else if lastScrollPosition > scrollView.contentOffset.y {
            navigationItem.hidesSearchBarWhenScrolling = false
        }
    }
}

//MARK: - ProjectHandler
extension ProjectsViewController: ProjectHandler {
    internal func save(_ project: Project, withImage image: UIImage?) {
        //call save and update the snapshot
        projectsController.save(project, withImage: image)
        updateData(on: projectsController.filteredProjects())
        collectionView.reloadData()
    }
    
    internal func delete(_ project: Project) {
        //call delete and update the snapshot
        projectsController.delete(project)
        updateData(on: projectsController.filteredProjects())
    }
}