metatext/View Controllers/StatusListViewController.swift

218 lines
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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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final class StatusListViewController: UITableViewController {
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private let viewModel: StatusListViewModel
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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: [String: CGFloat]]()
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private let dataSourceQueue =
DispatchQueue(label: "com.metabolist.metatext.status-list.data-source-queue")
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private lazy var dataSource: UITableViewDiffableDataSource<Int, String> = {
UITableViewDiffableDataSource(tableView: tableView) { [weak self] tableView, indexPath, statusID in
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guard
let self = self,
let cell = tableView.dequeueReusableCell(
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withIdentifier: String(describing: StatusListCell.self),
for: indexPath) as? StatusListCell
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else { return nil }
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cell.viewModel = self.viewModel.statusViewModel(id: statusID)
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return cell
}
}()
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init(viewModel: StatusListViewModel) {
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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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tableView.register(StatusListCell.self, forCellReuseIdentifier: String(describing: StatusListCell.self))
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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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navigationItem.title = viewModel.title
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viewModel.$statusIDs
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.sink { [weak self] in self?.update(statusIDs: $0) }
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.store(in: &cancellables)
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viewModel.events.sink { [weak self] in
guard let self = self else { return }
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switch $0 {
case let .share(url):
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self.share(url: url)
case let .statusListNavigation(statusListViewModel):
self.show(StatusListViewController(viewModel: statusListViewModel), sender: self)
case let .urlNavigation(url):
self.present(SFSafariViewController(url: url), animated: true)
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}
}
.store(in: &cancellables)
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viewModel.$loading
.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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}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
viewModel.request()
}
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] ?? [String: 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 id = dataSource.itemIdentifier(for: indexPath) else { return true }
return id != viewModel.contextParentID
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}
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
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guard let id = dataSource.itemIdentifier(for: indexPath) else { return }
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show(StatusListViewController(viewModel: viewModel.contextViewModel(id: id)), sender: self)
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}
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override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
sizeTableHeaderFooterViews()
}
}
extension StatusListViewController: UITableViewDataSourcePrefetching {
func tableView(_ tableView: UITableView, prefetchRowsAt indexPaths: [IndexPath]) {
guard
viewModel.paginates,
let indexPath = indexPaths.last,
indexPath.section == dataSource.numberOfSections(in: tableView) - 1,
indexPath.row == dataSource.tableView(tableView, numberOfRowsInSection: indexPath.section) - 1,
let maxID = dataSource.itemIdentifier(for: indexPath)
else { return }
viewModel.request(maxID: maxID)
}
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}
private extension StatusListViewController {
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func update(statusIDs: [[String]]) {
var offsetFromNavigationBar: CGFloat?
if
let id = viewModel.maintainScrollPositionOfStatusID,
let indexPath = dataSource.indexPath(for: id),
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 }
self.dataSource.apply(statusIDs.snapshot(), animatingDifferences: false) {
if
let id = self.viewModel.maintainScrollPositionOfStatusID,
let indexPath = self.dataSource.indexPath(for: id) {
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
}
}