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309 lines
12 KiB
Swift
309 lines
12 KiB
Swift
// Copyright © 2020 Metabolist. All rights reserved.
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import Combine
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import Foundation
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import Mastodon
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import ServiceLayer
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final public class CollectionItemsViewModel: ObservableObject {
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@Published public var alertItem: AlertItem?
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public private(set) var nextPageMaxId: String?
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private let items = CurrentValueSubject<[[CollectionItem]], Never>([])
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private let collectionService: CollectionService
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private let identification: Identification
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private var viewModelCache = [CollectionItem: (viewModel: CollectionItemViewModel, events: AnyCancellable)]()
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private let eventsSubject = PassthroughSubject<CollectionItemEvent, Never>()
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private let loadingSubject = PassthroughSubject<Bool, Never>()
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private let expandAllSubject: CurrentValueSubject<ExpandAllState, Never>
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private var maintainScrollPosition: CollectionItem?
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private var topVisibleIndexPath = IndexPath(item: 0, section: 0)
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private let lastReadId = CurrentValueSubject<String?, Never>(nil)
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private var lastSelectedLoadMore: LoadMore?
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private var hasRequestedUsingMarker = false
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private var hasRememberedPosition = false
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private var cancellables = Set<AnyCancellable>()
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public init(collectionService: CollectionService, identification: Identification) {
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self.collectionService = collectionService
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self.identification = identification
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expandAllSubject = CurrentValueSubject(
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collectionService is ContextService && !identification.identity.preferences.readingExpandSpoilers
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? .expand : .hidden)
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collectionService.sections
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.handleEvents(receiveOutput: { [weak self] in self?.process(items: $0) })
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.receive(on: DispatchQueue.main)
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.assignErrorsToAlertItem(to: \.alertItem, on: self)
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.sink { _ in }
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.store(in: &cancellables)
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collectionService.nextPageMaxId
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.sink { [weak self] in self?.nextPageMaxId = $0 }
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.store(in: &cancellables)
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if let markerTimeline = collectionService.markerTimeline {
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lastReadId.compactMap { $0 }
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.removeDuplicates()
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.debounce(for: 0.5, scheduler: DispatchQueue.global())
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.flatMap { identification.service.setLastReadId($0, forMarker: markerTimeline) }
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.sink { _ in } receiveValue: { _ in }
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.store(in: &cancellables)
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}
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}
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}
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extension CollectionItemsViewModel: CollectionViewModel {
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public var updates: AnyPublisher<CollectionUpdate, Never> {
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items.map { [weak self] in
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CollectionUpdate(items: $0,
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maintainScrollPosition: self?.maintainScrollPosition)
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}
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.eraseToAnyPublisher()
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}
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public var title: AnyPublisher<String, Never> { collectionService.title }
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public var expandAll: AnyPublisher<ExpandAllState, Never> {
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expandAllSubject.eraseToAnyPublisher()
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}
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public var alertItems: AnyPublisher<AlertItem, Never> { $alertItem.compactMap { $0 }.eraseToAnyPublisher() }
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public var loading: AnyPublisher<Bool, Never> { loadingSubject.eraseToAnyPublisher() }
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public var events: AnyPublisher<CollectionItemEvent, Never> { eventsSubject.eraseToAnyPublisher() }
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public var shouldAdjustContentInset: Bool { collectionService is ContextService }
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public func request(maxId: String? = nil, minId: String? = nil) {
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let publisher: AnyPublisher<Never, Error>
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if let markerTimeline = collectionService.markerTimeline,
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identification.appPreferences.positionBehavior(markerTimeline: markerTimeline) == .syncPosition,
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!hasRequestedUsingMarker {
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publisher = identification.service.getMarker(markerTimeline)
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.flatMap { [weak self] in
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self?.collectionService.request(maxId: $0.lastReadId, minId: nil) ?? Empty().eraseToAnyPublisher()
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}
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.catch { [weak self] _ in
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self?.collectionService.request(maxId: nil, minId: nil) ?? Empty().eraseToAnyPublisher()
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}
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.collect()
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.flatMap { [weak self] _ in
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self?.collectionService.request(maxId: nil, minId: nil) ?? Empty().eraseToAnyPublisher()
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}
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.eraseToAnyPublisher()
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self.hasRequestedUsingMarker = true
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} else {
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publisher = collectionService.request(maxId: maxId, minId: minId)
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}
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publisher
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.receive(on: DispatchQueue.main)
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.assignErrorsToAlertItem(to: \.alertItem, on: self)
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.handleEvents(
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receiveSubscription: { [weak self] _ in self?.loadingSubject.send(true) },
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receiveCompletion: { [weak self] _ in self?.loadingSubject.send(false) })
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.sink { _ in }
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.store(in: &cancellables)
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}
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public func select(indexPath: IndexPath) {
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let item = items.value[indexPath.section][indexPath.item]
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switch item {
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case let .status(status, _):
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eventsSubject.send(
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.navigation(.collection(collectionService
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.navigationService
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.contextService(id: status.displayStatus.id))))
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case let .loadMore(loadMore):
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lastSelectedLoadMore = loadMore
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(viewModel(indexPath: indexPath) as? LoadMoreViewModel)?.loadMore()
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case let .account(account):
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eventsSubject.send(
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.navigation(.profile(collectionService
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.navigationService
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.profileService(account: account))))
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}
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}
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public func viewedAtTop(indexPath: IndexPath) {
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topVisibleIndexPath = indexPath
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if items.value.count > indexPath.section, items.value[indexPath.section].count > indexPath.item {
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switch items.value[indexPath.section][indexPath.item] {
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case let .status(status, _):
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lastReadId.send(status.id)
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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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public func canSelect(indexPath: IndexPath) -> Bool {
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switch items.value[indexPath.section][indexPath.item] {
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case let .status(_, configuration):
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return !configuration.isContextParent
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case .loadMore:
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return !((viewModel(indexPath: indexPath) as? LoadMoreViewModel)?.loading ?? false)
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default:
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return true
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}
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}
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public func viewModel(indexPath: IndexPath) -> CollectionItemViewModel {
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let item = items.value[indexPath.section][indexPath.item]
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let cachedViewModel = viewModelCache[item]?.viewModel
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switch item {
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case let .status(status, configuration):
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let viewModel: StatusViewModel
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if let cachedViewModel = cachedViewModel as? StatusViewModel {
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viewModel = cachedViewModel
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} else {
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viewModel = .init(
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statusService: collectionService.navigationService.statusService(status: status),
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identification: identification)
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cache(viewModel: viewModel, forItem: item)
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}
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viewModel.configuration = configuration
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return viewModel
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case let .loadMore(loadMore):
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if let cachedViewModel = cachedViewModel {
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return cachedViewModel
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}
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let viewModel = LoadMoreViewModel(
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loadMoreService: collectionService.navigationService.loadMoreService(loadMore: loadMore))
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cache(viewModel: viewModel, forItem: item)
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return viewModel
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case let .account(account):
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if let cachedViewModel = cachedViewModel {
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return cachedViewModel
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}
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let viewModel = AccountViewModel(
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accountService: collectionService.navigationService.accountService(account: account),
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identification: identification)
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cache(viewModel: viewModel, forItem: item)
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return viewModel
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}
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}
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public func toggleExpandAll() {
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let statusIds = Set(items.value.reduce([], +).compactMap { item -> Status.Id? in
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guard case let .status(status, _) = item else { return nil }
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return status.id
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})
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switch expandAllSubject.value {
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case .hidden:
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break
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case .expand:
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(collectionService as? ContextService)?.expand(ids: statusIds)
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.assignErrorsToAlertItem(to: \.alertItem, on: self)
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.collect()
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.sink { [weak self] _ in self?.expandAllSubject.send(.collapse) }
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.store(in: &cancellables)
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case .collapse:
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(collectionService as? ContextService)?.collapse(ids: statusIds)
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.assignErrorsToAlertItem(to: \.alertItem, on: self)
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.collect()
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.sink { [weak self] _ in self?.expandAllSubject.send(.expand) }
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.store(in: &cancellables)
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}
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}
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}
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private extension CollectionItemsViewModel {
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func cache(viewModel: CollectionItemViewModel, forItem item: CollectionItem) {
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viewModelCache[item] = (viewModel, viewModel.events.flatMap { $0 }
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.assignErrorsToAlertItem(to: \.alertItem, on: self)
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.sink { [weak self] in self?.eventsSubject.send($0) })
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}
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func process(items: [[CollectionItem]]) {
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maintainScrollPosition = itemForScrollPositionMaintenance(newItems: items)
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self.items.send(items)
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let itemsSet = Set(items.reduce([], +))
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viewModelCache = viewModelCache.filter { itemsSet.contains($0.key) }
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}
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// swiftlint:disable:next cyclomatic_complexity function_body_length
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func itemForScrollPositionMaintenance(newItems: [[CollectionItem]]) -> CollectionItem? {
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let flatNewItems = newItems.reduce([], +)
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if let markerTimeline = collectionService.markerTimeline,
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identification.appPreferences.positionBehavior(markerTimeline: markerTimeline) == .rememberPosition,
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let localLastReadId = identification.service.getLocalLastReadId(markerTimeline),
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!hasRememberedPosition,
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let lastReadItem = flatNewItems.first(where: {
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switch $0 {
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case let .status(status, _):
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return status.id == localLastReadId
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default:
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return false
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}
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}) {
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hasRememberedPosition = true
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return lastReadItem
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}
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if collectionService is ContextService,
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items.value.isEmpty || items.value.map(\.count) == [0, 1, 0],
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let contextParent = flatNewItems.first(where: {
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guard case let .status(_, configuration) = $0 else { return false }
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return configuration.isContextParent // Maintain scroll position of parent after initial load of context
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}) {
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return contextParent
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} else if collectionService is TimelineService {
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let flatItems = items.value.reduce([], +)
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let difference = flatNewItems.difference(from: flatItems)
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if let lastSelectedLoadMore = lastSelectedLoadMore {
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for removal in difference.removals {
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if case let .remove(_, item, _) = removal,
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case let .loadMore(loadMore) = item,
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loadMore == lastSelectedLoadMore,
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let direction = (viewModelCache[item]?.viewModel as? LoadMoreViewModel)?.direction,
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direction == .up,
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let statusAfterLoadMore = flatItems.first(where: {
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guard case let .status(status, _) = $0 else { return false }
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return status.id == loadMore.beforeStatusId
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}) {
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return statusAfterLoadMore
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}
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}
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}
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if items.value.count > topVisibleIndexPath.section,
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items.value[topVisibleIndexPath.section].count > topVisibleIndexPath.item {
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let topVisibleItem = items.value[topVisibleIndexPath.section][topVisibleIndexPath.item]
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if newItems.count > topVisibleIndexPath.section,
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let newIndex = newItems[topVisibleIndexPath.section].firstIndex(of: topVisibleItem),
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newIndex > topVisibleIndexPath.item {
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return topVisibleItem
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}
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}
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}
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return nil
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}
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}
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