Pagination

Metatext.xcodeproj/project.pbxproj

@@ -27,6 +27,8 @@
 		D074577A24D29366004758DB /* URLSessionConfiguration+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = D074577924D29366004758DB /* URLSessionConfiguration+Extensions.swift */; };
 		D0A652AD24DE3EB6002EA33F /* PreferencesEndpoint+Stubbing.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0A652AC24DE3EB6002EA33F /* PreferencesEndpoint+Stubbing.swift */; };
 		D0BEB1F324F8EE8C001B0F04 /* AttachmentView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0BEB1F224F8EE8C001B0F04 /* AttachmentView.swift */; };
+		D0BEB1F524F9A216001B0F04 /* Paged.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0BEB1F424F9A216001B0F04 /* Paged.swift */; };
+		D0BEB1F724F9A84B001B0F04 /* LoadingTableFooterView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0BEB1F624F9A84B001B0F04 /* LoadingTableFooterView.swift */; };
 		D0C7D49724F7616A001EBDBB /* IdentitiesView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0C7D42224F76169001EBDBB /* IdentitiesView.swift */; };
 		D0C7D49824F7616A001EBDBB /* CustomEmojiText.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0C7D42324F76169001EBDBB /* CustomEmojiText.swift */; };
 		D0C7D49924F7616A001EBDBB /* AddIdentityView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0C7D42424F76169001EBDBB /* AddIdentityView.swift */; };
@@ -194,6 +196,8 @@
 		D074577924D29366004758DB /* URLSessionConfiguration+Extensions.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "URLSessionConfiguration+Extensions.swift"; sourceTree = "<group>"; };
 		D0A652AC24DE3EB6002EA33F /* PreferencesEndpoint+Stubbing.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "PreferencesEndpoint+Stubbing.swift"; sourceTree = "<group>"; };
 		D0BEB1F224F8EE8C001B0F04 /* AttachmentView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AttachmentView.swift; sourceTree = "<group>"; };
+		D0BEB1F424F9A216001B0F04 /* Paged.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Paged.swift; sourceTree = "<group>"; };
+		D0BEB1F624F9A84B001B0F04 /* LoadingTableFooterView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LoadingTableFooterView.swift; sourceTree = "<group>"; };
 		D0C7D41E24F76169001EBDBB /* Metatext.entitlements */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.entitlements; path = Metatext.entitlements; sourceTree = "<group>"; };
 		D0C7D41F24F76169001EBDBB /* Info.plist */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		D0C7D42224F76169001EBDBB /* IdentitiesView.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = IdentitiesView.swift; sourceTree = "<group>"; };
@@ -416,10 +420,11 @@
 		D0C7D42024F76169001EBDBB /* Views */ = {
 			isa = PBXGroup;
 			children = (
-				D01F41E024F8885900D55A2D /* Attachments */,
 				D0C7D42424F76169001EBDBB /* AddIdentityView.swift */,
+				D01F41E024F8885900D55A2D /* Attachments */,
 				D0C7D42324F76169001EBDBB /* CustomEmojiText.swift */,
 				D0C7D42224F76169001EBDBB /* IdentitiesView.swift */,
+				D0BEB1F624F9A84B001B0F04 /* LoadingTableFooterView.swift */,
 				D0C7D42D24F76169001EBDBB /* NotificationTypesPreferencesView.swift */,
 				D0C7D42824F76169001EBDBB /* PostingReadingPreferencesView.swift */,
 				D0C7D42624F76169001EBDBB /* PreferencesView.swift */,
@@ -577,6 +582,7 @@
 				D0C7D48324F76169001EBDBB /* ContextEndpoint.swift */,
 				D0C7D48224F76169001EBDBB /* DeletionEndpoint.swift */,
 				D0C7D47D24F76169001EBDBB /* InstanceEndpoint.swift */,
+				D0BEB1F424F9A216001B0F04 /* Paged.swift */,
 				D0C7D47C24F76169001EBDBB /* PreferencesEndpoint.swift */,
 				D0C7D47B24F76169001EBDBB /* PushSubscriptionEndpoint.swift */,
 				D0C7D48424F76169001EBDBB /* StatusEndpoint.swift */,
@@ -860,6 +866,7 @@
 				D0C7D4CD24F7616A001EBDBB /* AddIdentityViewModel.swift in Sources */,
 				D03658D124EDD80900AC17EC /* ContextEndpoint+Stubbing.swift in Sources */,
 				D0BEB1F324F8EE8C001B0F04 /* AttachmentView.swift in Sources */,
+				D0BEB1F524F9A216001B0F04 /* Paged.swift in Sources */,
 				D0DC174A24CFF15F00A75C65 /* AppAuthorizationEndpoint+Stubbing.swift in Sources */,
 				D0C7D49A24F7616A001EBDBB /* StatusListView.swift in Sources */,
 				D01F41D924F880C400D55A2D /* TouchFallthroughTextView.swift in Sources */,
@@ -908,6 +915,7 @@
 				D0C7D4A224F7616A001EBDBB /* NotificationTypesPreferencesView.swift in Sources */,
 				D0C7D4CF24F7616A001EBDBB /* StatusViewModel.swift in Sources */,
 				D0C7D4C724F7616A001EBDBB /* PostingReadingPreferencesViewModel.swift in Sources */,
+				D0BEB1F724F9A84B001B0F04 /* LoadingTableFooterView.swift in Sources */,
 				D0DC175224D008E300A75C65 /* MastodonTarget+Stubbing.swift in Sources */,
 				D0C7D4F124F7616A001EBDBB /* IdentityService.swift in Sources */,
 				D04FD74224D4AA34007D572D /* DevelopmentModels.swift in Sources */,

Networking/Mastodon API/Endpoints/Paged.swift

@@ -0,0 +1,46 @@
+// Copyright © 2020 Metabolist. All rights reserved.
+
+import Foundation
+
+struct Paged<T: MastodonEndpoint> {
+    let endpoint: T
+    let maxID: String?
+    let minID: String?
+    let sinceID: String?
+    let limit: Int?
+
+    init(_ endpoint: T, maxID: String? = nil, minID: String? = nil, sinceID: String? = nil, limit: Int? = nil) {
+        self.endpoint = endpoint
+        self.maxID = maxID
+        self.minID = minID
+        self.sinceID = sinceID
+        self.limit = limit
+    }
+}
+
+extension Paged: MastodonEndpoint {
+    typealias ResultType = T.ResultType
+
+    var APIVersion: String { endpoint.APIVersion }
+
+    var context: [String] { endpoint.context }
+
+    var pathComponentsInContext: [String] { endpoint.pathComponentsInContext }
+
+    var method: HTTPMethod { endpoint.method }
+
+    var encoding: ParameterEncoding { endpoint.encoding }
+
+    var parameters: [String: Any]? {
+        var parameters = endpoint.parameters ?? [String: Any]()
+
+        parameters["max_id"] = maxID
+        parameters["min_id"] = minID
+        parameters["since_id"] = sinceID
+        parameters["limit"] = limit
+
+        return parameters
+    }
+
+    var headers: HTTPHeaders? { endpoint.headers }
+}

Services/Status List Services/ContextService.swift

@@ -5,6 +5,7 @@ import Combine
 
 struct ContextService {
     let statusSections: AnyPublisher<[[Status]], Error>
+    let paginates = false
 
     private let status: Status
     private let context = CurrentValueSubject<MastodonContext, Never>(MastodonContext(ancestors: [], descendants: []))

Services/Status List Services/StatusListService.swift

@@ -5,6 +5,7 @@ import Combine
 
 protocol StatusListService {
     var statusSections: AnyPublisher<[[Status]], Error> { get }
+    var paginates: Bool { get }
     var contextParentID: String? { get }
     func isPinned(status: Status) -> Bool
     func isReplyInContext(status: Status) -> Bool
@@ -15,6 +16,8 @@ protocol StatusListService {
 }
 
 extension StatusListService {
+    var paginates: Bool { true }
+
     var contextParentID: String? { nil }
 
     func isPinned(status: Status) -> Bool { false }

Services/Status List Services/TimelineService.swift

@@ -22,7 +22,7 @@ struct TimelineService {
 
 extension TimelineService: StatusListService {
     func request(maxID: String?, minID: String?) -> AnyPublisher<Never, Error> {
-        return networkClient.request(timeline.endpoint)
+        networkClient.request(Paged(timeline.endpoint, maxID: maxID, minID: minID))
             .map { ($0, timeline) }
             .flatMap(contentDatabase.insert(statuses:collection:))
             .eraseToAnyPublisher()

View Controllers/StatusListViewController.swift

@@ -5,6 +5,7 @@ import Combine
 
 class StatusListViewController: UITableViewController {
     private let viewModel: StatusListViewModel
+    private let loadingTableFooterView = LoadingTableFooterView()
     private var cancellables = Set<AnyCancellable>()
     private var cellHeightCaches = [CGFloat: [String: CGFloat]]()
 
@@ -30,6 +31,7 @@ class StatusListViewController: UITableViewController {
         super.init(style: .plain)
     }
 
+    @available(*, unavailable)
     required init?(coder: NSCoder) {
         fatalError("init(coder:) has not been implemented")
     }
@@ -45,8 +47,10 @@ class StatusListViewController: UITableViewController {
         }
 
         tableView.dataSource = dataSource
+        tableView.prefetchDataSource = self
         tableView.cellLayoutMarginsFollowReadableWidth = true
         tableView.separatorInset = .zero
+        tableView.tableFooterView = UIView()
 
         viewModel.$statusIDs
             .sink { [weak self] in
@@ -73,6 +77,16 @@ class StatusListViewController: UITableViewController {
                 }
             }
             .store(in: &cancellables)
+
+        viewModel.$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)
     }
 
     override func viewWillAppear(_ animated: Bool) {
@@ -114,6 +128,26 @@ class StatusListViewController: UITableViewController {
             StatusListViewController(viewModel: contextViewModel),
             animated: true)
     }
+
+    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)
+    }
 }
 
 extension StatusListViewController: StatusTableViewCellDelegate {
@@ -130,6 +164,35 @@ private extension StatusListViewController {
 
         present(activityViewController, animated: true, completion: nil)
     }
+
+    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()
+            }
+        }
+    }
 }
 
 private extension Array where Element: Sequence, Element.Element: Hashable {

View Models/StatusListViewModel.swift

@@ -29,6 +29,8 @@ class StatusListViewModel: ObservableObject {
 }
 
 extension StatusListViewModel {
+    var paginates: Bool { statusListService.paginates }
+
     var contextParentID: String? { statusListService.contextParentID }
 
     func request(maxID: String? = nil, minID: String? = nil) {

Views/LoadingTableFooterView.swift

@@ -0,0 +1,23 @@
+// Copyright © 2020 Metabolist. All rights reserved.
+
+import UIKit
+
+class LoadingTableFooterView: UIView {
+    let activityIndicatorView = UIActivityIndicatorView()
+
+    override init(frame: CGRect) {
+        super.init(frame: frame)
+
+        addSubview(activityIndicatorView)
+        activityIndicatorView.translatesAutoresizingMaskIntoConstraints = false
+        activityIndicatorView.centerXAnchor.constraint(equalTo: centerXAnchor).isActive = true
+        activityIndicatorView.topAnchor.constraint(equalTo: layoutMarginsGuide.topAnchor).isActive = true
+        activityIndicatorView.bottomAnchor.constraint(equalTo: layoutMarginsGuide.bottomAnchor).isActive = true
+        activityIndicatorView.startAnimating()
+    }
+
+    @available(*, unavailable)
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+}