mastodon-ios/Mastodon/Scene/Onboarding/PickServer/MastodonPickServerViewModel+Diffable.swift at f1aee92fa277cdbe736161a9500b8e9464ced753 · mastodon/mastodon-ios · GitHub

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//
//  MastodonPickServerViewController+Diffable.swift
//  Mastodon
//
//  Created by Cirno MainasuK on 2021/3/5.
//

import UIKit
import Combine
import MastodonSDK

extension MastodonPickServerViewModel {

    func setupDiffableDataSource(
        for tableView: UITableView,
        dependency: NeedsDependency,
        pickServerServerSectionTableHeaderViewDelegate: PickServerServerSectionTableHeaderViewDelegate
    ) {
        // set section header
        serverSectionHeaderView.diffableDataSource = CategoryPickerSection.collectionViewDiffableDataSource(
            for: serverSectionHeaderView.collectionView,
            dependency: dependency,
            viewModel: self
        )
        var sectionHeaderSnapshot = NSDiffableDataSourceSnapshot<CategoryPickerSection, CategoryPickerItem>()
        sectionHeaderSnapshot.appendSections([.main])
        sectionHeaderSnapshot.appendItems(categoryPickerItems, toSection: .main)
        serverSectionHeaderView.delegate = pickServerServerSectionTableHeaderViewDelegate
        serverSectionHeaderView.diffableDataSource?.apply(sectionHeaderSnapshot, animatingDifferences: false) { [weak self] in
            guard let self = self else { return }
            guard let indexPath = self.serverSectionHeaderView.diffableDataSource?.indexPath(for: .category(category: .init(category: Mastodon.Entity.Category.Kind.general.rawValue, serversCount: 0))) else { return }

            self.serverSectionHeaderView.collectionView.selectItem(at: indexPath, animated: false, scrollPosition: .right)

            let firstIndex = IndexPath(item: 0, section: 0)
            self.serverSectionHeaderView.collectionView.scrollToItem(at: firstIndex, at: .left, animated: false)
        }

        // set tableView
        diffableDataSource = PickServerSection.tableViewDiffableDataSource(
            for: tableView,
            dependency: dependency
        )

        var snapshot = NSDiffableDataSourceSnapshot<PickServerSection, PickServerItem>()
        snapshot.appendSections([.header, .servers])
        diffableDataSource?.apply(snapshot, animatingDifferences: false, completion: nil)

        loadIndexedServerStateMachine.enter(LoadIndexedServerState.Loading.self)

        Publishers.CombineLatest3(
            filteredIndexedServers,
            selectCategoryItem,
            unindexedServers
        )
        .receive(on: DispatchQueue.main)
        .sink(receiveValue: { [weak self] indexedServers, selectCategoryItem, unindexedServers in
            guard let self = self else { return }
            guard let diffableDataSource = self.diffableDataSource else { return }

            let oldSnapshot = diffableDataSource.snapshot()
            var oldSnapshotServerItemAttributeDict: [String : PickServerItem.ServerItemAttribute] = [:]
            for item in oldSnapshot.itemIdentifiers {
                guard case let .server(server, attribute) = item else { continue }
                oldSnapshotServerItemAttributeDict[server.domain] = attribute
            }

            var snapshot = NSDiffableDataSourceSnapshot<PickServerSection, PickServerItem>()
            snapshot.appendSections([.header, .servers])

            // TODO: handle filter
            var serverItems: [PickServerItem] = []
            if let indexedServers {
                if indexedServers.didIgnoreCategory,
                   indexedServers.servers.isNotEmpty,
                   case .category(let category) = selectCategoryItem {
                    serverItems.append(.message(attribute: .categoryIgnored(category: category.category)))
                }
                for server in indexedServers.servers {
                    let attribute = oldSnapshotServerItemAttributeDict[server.domain] ?? PickServerItem.ServerItemAttribute(isLast: false, isExpand: false)
                    attribute.isLast.value = false
                    let item = PickServerItem.server(server: server, attribute: attribute)
                    guard !serverItems.contains(item) else { continue }
                    serverItems.append(item)
                }
            }

            if let unindexedServers = unindexedServers {
                if !unindexedServers.isEmpty {
                    for server in unindexedServers {
                        let attribute = oldSnapshotServerItemAttributeDict[server.domain] ?? PickServerItem.ServerItemAttribute(isLast: false, isExpand: false)
                        attribute.isLast.value = false
                        let item = PickServerItem.server(server: server, attribute: attribute)
                        guard !serverItems.contains(item) else { continue }
                        serverItems.append(item)
                    }
                } else {
                    if (indexedServers?.servers.isEmpty ?? true),
                       !self.isLoadingIndexedServers.value {
                        serverItems.append(.loader(attribute: PickServerItem.LoaderItemAttribute(isLast: false, isEmptyResult: true)))
                    }
                }
            } else {
                serverItems.append(.loader(attribute: PickServerItem.LoaderItemAttribute(isLast: false, isEmptyResult: false)))
            }

            if case let .server(_, attribute) = serverItems.last {
                attribute.isLast.value = true
            }
            if case let .loader(attribute) = serverItems.last {
                attribute.isLast = true
            }
            snapshot.appendItems(serverItems, toSection: .servers)

            diffableDataSource.defaultRowAnimation = .fade
            diffableDataSource.apply(snapshot, animatingDifferences: true, completion: nil)
        })
        .store(in: &disposeBag)
    }

}