339 lines
12 KiB
Swift
339 lines
12 KiB
Swift
//
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// DiffableTimelineLikeTableViewController.swift
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// Tusker
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//
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// Created by Shadowfacts on 6/18/21.
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// Copyright © 2021 Shadowfacts. All rights reserved.
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//
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import UIKit
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import Pachyderm
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class DiffableTimelineLikeTableViewController<Section: Hashable & CaseIterable, Item: Hashable>: EnhancedTableViewController, RefreshableViewController {
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typealias Snapshot = NSDiffableDataSourceSnapshot<Section, Item>
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typealias LoadResult = Result<Snapshot, LoadError>
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private let pageSize = 20
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private(set) var state = State.unloaded
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private var lastLastVisibleRow: IndexPath?
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private(set) var dataSource: UITableViewDiffableDataSource<Section, Item>!
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init() {
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super.init(style: .plain)
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addKeyCommand(MenuController.refreshCommand(discoverabilityTitle: Self.refreshCommandTitle()))
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}
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required init?(coder: NSCoder) {
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fatalError("init(coder:) has not been implemented")
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}
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override func viewDidLoad() {
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super.viewDidLoad()
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dataSource = UITableViewDiffableDataSource(tableView: tableView, cellProvider: self.cellProvider)
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tableView.rowHeight = UITableView.automaticDimension
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tableView.estimatedRowHeight = 140
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#if !targetEnvironment(macCatalyst)
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self.refreshControl = UIRefreshControl()
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self.refreshControl!.addTarget(self, action: #selector(refresh), for: .valueChanged)
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#endif
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if let prefetchSource = self as? UITableViewDataSourcePrefetching {
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tableView.prefetchDataSource = prefetchSource
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}
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}
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override func viewWillAppear(_ animated: Bool) {
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super.viewWillAppear(animated)
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loadInitial()
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}
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override func viewDidDisappear(_ animated: Bool) {
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super.viewDidDisappear(animated)
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pruneOffscreenRows()
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currentToast?.dismissToast(animated: false)
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}
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class func refreshCommandTitle() -> String {
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return "Refresh"
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}
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private func pruneOffscreenRows() {
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guard let lastVisibleRow = lastLastVisibleRow else {
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return
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}
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var snapshot = dataSource.snapshot()
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let lastVisibleRowSection = snapshot.sectionIdentifiers[lastVisibleRow.section]
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let contentSections = snapshot.sectionIdentifiers.filter { timelineContentSections().contains($0) }
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guard let lastVisibleContentSectionIndex = contentSections.lastIndex(of: lastVisibleRowSection) else {
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return
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}
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if lastVisibleContentSectionIndex < contentSections.count - 1 {
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// there are more content sections below the current last visible one
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let sectionsToRemove = contentSections[lastVisibleContentSectionIndex...]
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snapshot.deleteSections(Array(sectionsToRemove))
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willRemoveItems(sectionsToRemove.flatMap(snapshot.itemIdentifiers(inSection:)))
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} else if lastVisibleContentSectionIndex == contentSections.count - 1 {
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let items = snapshot.itemIdentifiers(inSection: lastVisibleRowSection)
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if lastVisibleRow.row < items.count - pageSize {
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let itemsToRemove = Array(items.suffix(pageSize))
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snapshot.deleteItems(itemsToRemove)
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willRemoveItems(itemsToRemove)
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} else {
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return
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}
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} else {
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return
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}
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dataSource.apply(snapshot, animatingDifferences: false)
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}
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private func loadInitial() {
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guard state == .unloaded else { return }
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// set loaded immediately so we don't trigger another request while the current one is running
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state = .loadingInitial
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loadInitialItems() { result in
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DispatchQueue.main.async {
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switch result {
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case let .success(snapshot):
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self.dataSource.apply(snapshot, animatingDifferences: false)
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self.state = .loaded
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case let .failure(.client(error)):
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self.state = .unloaded
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var config = ToastConfiguration(title: "Error Loading")
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config.subtitle = error.localizedDescription
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config.systemImageName = error.systemImageName
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config.actionTitle = "Retry"
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config.action = { [weak self] (toast) in
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toast.dismissToast(animated: true)
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self?.loadInitial()
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}
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self.showToast(configuration: config, animated: true)
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default:
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self.state = .unloaded
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}
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}
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}
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}
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func reloadInitial() {
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state = .unloaded
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loadInitial()
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}
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func loadOlder() {
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guard state != .loadingOlder else { return }
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state = .loadingOlder
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loadOlderItems(currentSnapshot: dataSource.snapshot) { result in
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DispatchQueue.main.async {
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self.state = .loaded
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switch result {
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case let .success(snapshot):
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self.dataSource.apply(snapshot, animatingDifferences: false)
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case let .failure(.client(error)):
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var config = ToastConfiguration(title: "Error Loading Older")
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config.subtitle = error.localizedDescription
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config.systemImageName = error.systemImageName
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config.actionTitle = "Retry"
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config.action = { [weak self] (toast) in
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toast.dismissToast(animated: true)
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self?.loadOlder()
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}
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self.showToast(configuration: config, animated: true)
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default:
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break
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}
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}
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}
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}
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func cellHeightChanged() {
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// causes the table view to recalculate the cell heights
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tableView.beginUpdates()
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tableView.endUpdates()
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}
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// MARK: - UITableViewDelegate
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override func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
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// this assumes that indexPathsForVisibleRows is always in order
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lastLastVisibleRow = tableView.indexPathsForVisibleRows?.last
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let orderedContentSections = dataSource.snapshot().sectionIdentifiers.enumerated().filter { timelineContentSections().contains($0.element) }
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if let lastContentSection = orderedContentSections.last,
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indexPath.section == lastContentSection.offset,
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indexPath.row == tableView.numberOfRows(inSection: indexPath.section) - 1 {
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loadOlder()
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}
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}
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override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
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return true
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}
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override func tableView(_ tableView: UITableView, leadingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration? {
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return (tableView.cellForRow(at: indexPath) as? TableViewSwipeActionProvider)?.leadingSwipeActionsConfiguration()
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}
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override func tableView(_ tableView: UITableView, trailingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration? {
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return (tableView.cellForRow(at: indexPath) as? TableViewSwipeActionProvider)?.trailingSwipeActionsConfiguration()
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}
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// MARK: - RefreshableViewController
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func refresh() {
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guard state != .loadingNewer else { return }
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state = .loadingNewer
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var firstItem: Item? = nil
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let currentSnapshot: () -> Snapshot = {
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let snapshot = self.dataSource.snapshot()
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for section in self.timelineContentSections() {
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if snapshot.indexOfSection(section) != nil,
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let first = snapshot.itemIdentifiers(inSection: section).first {
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firstItem = first
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break
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}
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}
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return snapshot
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}
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loadNewerItems(currentSnapshot: currentSnapshot) { result in
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DispatchQueue.main.async {
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self.refreshControl?.endRefreshing()
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self.state = .loaded
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switch result {
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case let .success(snapshot):
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self.dataSource.apply(snapshot, animatingDifferences: false)
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if let firstItem = firstItem,
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let indexPath = self.dataSource.indexPath(for: firstItem) {
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// maintain the current position in the list (don't scroll to top)
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self.tableView.scrollToRow(at: indexPath, at: .top, animated: false)
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}
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case let .failure(.client(error)):
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var config = ToastConfiguration(title: "Error Loading Newer")
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config.subtitle = error.localizedDescription
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config.systemImageName = error.systemImageName
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config.actionTitle = "Retry"
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config.action = { [weak self] (toast) in
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toast.dismissToast(animated: true)
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self?.refresh()
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}
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self.showToast(configuration: config, animated: true)
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case .failure(.allCaughtUp):
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var config = ToastConfiguration(title: "You're all caught up")
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config.edge = .top
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config.dismissAutomaticallyAfter = 2
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config.action = { (toast) in
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toast.dismissToast(animated: true)
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}
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self.showToast(configuration: config, animated: true)
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default:
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break
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}
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}
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}
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}
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// MARK: - Subclass Methods
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func cellProvider(_ tableView: UITableView, _ indexPath: IndexPath, _ item: Item) -> UITableViewCell? {
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fatalError("cellProvider(_:_:_:) must be implemented by subclasses")
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}
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func loadInitialItems(completion: @escaping (LoadResult) -> Void) {
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fatalError("loadInitialItems(completion:) must be implemented by subclasses")
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}
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func loadOlderItems(currentSnapshot: @escaping () -> Snapshot, completion: @escaping (LoadResult) -> Void) {
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fatalError("loadOlderItesm(completion:) must be implemented by subclasses")
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}
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func loadNewerItems(currentSnapshot: @escaping () -> Snapshot, completion: @escaping (LoadResult) -> Void) {
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fatalError("loadNewerItems(completion:) must be implemented by subclasses")
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}
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func timelineContentSections() -> Section.AllCases {
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return Section.allCases
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}
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func willRemoveItems(_ items: [Item]) {
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}
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}
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extension DiffableTimelineLikeTableViewController {
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enum State: Equatable {
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case unloaded
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case loadingInitial
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case loaded
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case loadingNewer
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case loadingOlder
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}
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}
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extension DiffableTimelineLikeTableViewController {
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enum LoadError: LocalizedError {
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case noClient
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case noOlder
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case noNewer
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case allCaughtUp
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case client(Client.Error)
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}
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}
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extension DiffableTimelineLikeTableViewController: BackgroundableViewController {
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func sceneDidEnterBackground() {
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pruneOffscreenRows()
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currentToast?.dismissToast(animated: false)
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}
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}
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extension DiffableTimelineLikeTableViewController: ToastableViewController {
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}
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fileprivate extension Client.Error {
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var systemImageName: String {
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switch self {
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case .networkError(_):
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return "wifi.exclamationmark"
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default:
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return "exclamationmark.triangle"
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}
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}
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}
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