metatext-app-ios-iphone-ipad/View Controllers/CollectionViewController.swift

240 lines
9.1 KiB
Swift
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// Copyright © 2020 Metabolist. All rights reserved.
import Combine
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import SafariServices
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import SwiftUI
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import ViewModels
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class CollectionViewController: UITableViewController {
private let viewModel: CollectionViewModel
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private let loadingTableFooterView = LoadingTableFooterView()
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private var cancellables = Set<AnyCancellable>()
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private var cellHeightCaches = [CGFloat: [CollectionItem: CGFloat]]()
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private let dataSourceQueue =
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DispatchQueue(label: "com.metabolist.metatext.collection.data-source-queue")
private lazy var dataSource: UITableViewDiffableDataSource<Int, CollectionItem> = {
UITableViewDiffableDataSource(tableView: tableView) { [weak self] tableView, indexPath, item in
guard let self = self, let cellViewModel = self.viewModel.viewModel(item: item) else { return nil }
let cell = tableView.dequeueReusableCell(
withIdentifier: String(describing: item.kind.cellClass),
for: indexPath)
switch (cell, cellViewModel) {
case (let statusListCell as StatusListCell, let statusViewModel as StatusViewModel):
statusListCell.viewModel = statusViewModel
case (let accountListCell as AccountListCell, let accountViewModel as AccountViewModel):
accountListCell.viewModel = accountViewModel
default:
return nil
}
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return cell
}
}()
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init(viewModel: CollectionViewModel) {
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self.viewModel = viewModel
super.init(style: .plain)
}
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@available(*, unavailable)
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required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
override func viewDidLoad() {
super.viewDidLoad()
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for kind in CollectionItem.Kind.allCases {
tableView.register(kind.cellClass, forCellReuseIdentifier: String(describing: kind.cellClass))
}
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tableView.dataSource = dataSource
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tableView.prefetchDataSource = self
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tableView.cellLayoutMarginsFollowReadableWidth = true
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tableView.tableFooterView = UIView()
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viewModel.title.sink { [weak self] in self?.navigationItem.title = $0 }.store(in: &cancellables)
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viewModel.collectionItems
.sink { [weak self] in self?.update(items: $0) }
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.store(in: &cancellables)
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viewModel.navigationEvents.sink { [weak self] in
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guard let self = self else { return }
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switch $0 {
case let .share(url):
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self.share(url: url)
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case let .collectionNavigation(collectionViewModel):
self.show(CollectionViewController(viewModel: collectionViewModel), sender: self)
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case let .urlNavigation(url):
self.present(SFSafariViewController(url: url), animated: true)
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}
}
.store(in: &cancellables)
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viewModel.loading
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.receive(on: RunLoop.main)
.sink { [weak self] in
guard let self = self else { return }
self.tableView.tableFooterView = $0 ? self.loadingTableFooterView : UIView()
self.sizeTableHeaderFooterViews()
}
.store(in: &cancellables)
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if let accountsStatusesViewModel = viewModel as? AccountStatusesViewModel {
// Initial size is to avoid unsatisfiable constraint warning
let accountHeaderView = AccountHeaderView(
frame: .init(
origin: .zero,
size: .init(width: 100, height: 100)))
accountHeaderView.viewModel = accountsStatusesViewModel
accountsStatusesViewModel.$account.dropFirst().receive(on: DispatchQueue.main).sink { [weak self] _ in
accountHeaderView.viewModel = accountsStatusesViewModel
self?.sizeTableHeaderFooterViews()
}
.store(in: &cancellables)
tableView.tableHeaderView = accountHeaderView
}
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}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
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viewModel.request(maxID: nil, minID: nil)
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}
override func tableView(_ tableView: UITableView,
willDisplay cell: UITableViewCell,
forRowAt indexPath: IndexPath) {
guard let item = dataSource.itemIdentifier(for: indexPath) else { return }
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var heightCache = cellHeightCaches[tableView.frame.width] ?? [CollectionItem: CGFloat]()
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heightCache[item] = cell.frame.height
cellHeightCaches[tableView.frame.width] = heightCache
}
override func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
guard let item = dataSource.itemIdentifier(for: indexPath) else { return UITableView.automaticDimension }
return cellHeightCaches[tableView.frame.width]?[item] ?? UITableView.automaticDimension
}
override func tableView(_ tableView: UITableView, shouldHighlightRowAt indexPath: IndexPath) -> Bool {
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guard let item = dataSource.itemIdentifier(for: indexPath) else { return true }
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return viewModel.canSelect(item: item)
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}
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
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guard let item = dataSource.itemIdentifier(for: indexPath) else { return }
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viewModel.itemSelected(item)
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}
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override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
sizeTableHeaderFooterViews()
}
}
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extension CollectionViewController: UITableViewDataSourcePrefetching {
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func tableView(_ tableView: UITableView, prefetchRowsAt indexPaths: [IndexPath]) {
guard
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let maxID = viewModel.nextPageMaxID,
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let indexPath = indexPaths.last,
indexPath.section == dataSource.numberOfSections(in: tableView) - 1,
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indexPath.row == dataSource.tableView(tableView, numberOfRowsInSection: indexPath.section) - 1
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else { return }
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viewModel.request(maxID: maxID, minID: nil)
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}
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}
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private extension CollectionViewController {
func update(items: [[CollectionItem]]) {
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var offsetFromNavigationBar: CGFloat?
if
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let item = viewModel.maintainScrollPositionOfItem,
let indexPath = dataSource.indexPath(for: item),
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let navigationBar = navigationController?.navigationBar {
let navigationBarMaxY = tableView.convert(navigationBar.bounds, from: navigationBar).maxY
offsetFromNavigationBar = tableView.rectForRow(at: indexPath).origin.y - navigationBarMaxY
}
dataSourceQueue.async { [weak self] in
guard let self = self else { return }
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self.dataSource.apply(items.snapshot(), animatingDifferences: false) {
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if
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let item = self.viewModel.maintainScrollPositionOfItem,
let indexPath = self.dataSource.indexPath(for: item) {
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self.tableView.scrollToRow(at: indexPath, at: .top, animated: false)
if let offsetFromNavigationBar = offsetFromNavigationBar {
self.tableView.contentOffset.y -= offsetFromNavigationBar
}
}
}
}
}
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func share(url: URL) {
let activityViewController = UIActivityViewController(activityItems: [url], applicationActivities: nil)
present(activityViewController, animated: true, completion: nil)
}
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func sizeTableHeaderFooterViews() {
// https://useyourloaf.com/blog/variable-height-table-view-header/
if let headerView = tableView.tableHeaderView {
let size = headerView.systemLayoutSizeFitting(
CGSize(width: tableView.frame.width, height: .greatestFiniteMagnitude),
withHorizontalFittingPriority: .required,
verticalFittingPriority: .fittingSizeLevel)
if headerView.frame.size.height != size.height {
headerView.frame.size.height = size.height
tableView.tableHeaderView = headerView
tableView.layoutIfNeeded()
}
}
if let footerView = tableView.tableFooterView {
let size = footerView.systemLayoutSizeFitting(
CGSize(width: tableView.frame.width, height: .greatestFiniteMagnitude),
withHorizontalFittingPriority: .required,
verticalFittingPriority: .fittingSizeLevel)
if footerView.frame.size.height != size.height {
footerView.frame.size.height = size.height
tableView.tableFooterView = footerView
tableView.layoutIfNeeded()
}
}
}
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}
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private extension Array where Element: Sequence, Element.Element: Hashable {
func snapshot() -> NSDiffableDataSourceSnapshot<Int, Element.Element> {
var snapshot = NSDiffableDataSourceSnapshot<Int, Element.Element>()
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let sections = [Int](0..<count)
snapshot.appendSections(sections)
for section in sections {
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snapshot.appendItems(self[section].map { $0 }, toSection: section)
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}
return snapshot
}
}