Startup and syncing

DB/Sources/DB/Content/ContentDatabase+Migration.swift

@@ -105,6 +105,11 @@ extension ContentDatabase {
                 t.column("wholeWord", .boolean).notNull()
             }
 
+            try db.create(table: "lastReadIdRecord") { t in
+                t.column("markerTimeline", .text).primaryKey(onConflict: .replace)
+                t.column("id", .text).notNull()
+            }
+
             try db.create(table: "statusAncestorJoin") { t in
                 t.column("parentId", .text).indexed().notNull()
                     .references("statusRecord", onDelete: .cascade)

DB/Sources/DB/Content/ContentDatabase.swift

@@ -7,12 +7,17 @@ import Keychain
 import Mastodon
 import Secrets
 
+// swiftlint:disable file_length
 public struct ContentDatabase {
     public let activeFiltersPublisher: AnyPublisher<[Filter], Error>
 
     private let databaseWriter: DatabaseWriter
 
-    public init(id: Identity.Id, inMemory: Bool, keychain: Keychain.Type) throws {
+    public init(id: Identity.Id,
+                useHomeTimelineLastReadId: Bool,
+                useNotificationsLastReadId: Bool,
+                inMemory: Bool,
+                keychain: Keychain.Type) throws {
         if inMemory {
             databaseWriter = DatabaseQueue()
         } else {
@@ -27,7 +32,10 @@ public struct ContentDatabase {
         }
 
         try Self.migrator.migrate(databaseWriter)
-        try Self.clean(databaseWriter)
+        try Self.clean(
+            databaseWriter,
+            useHomeTimelineLastReadId: useHomeTimelineLastReadId,
+            useNotificationsLastReadId: useNotificationsLastReadId)
 
         activeFiltersPublisher = ValueObservation.tracking {
             try Filter.filter(Filter.Columns.expiresAt == nil || Filter.Columns.expiresAt > Date()).fetchAll($0)
@@ -278,6 +286,12 @@ public extension ContentDatabase {
             .eraseToAnyPublisher()
     }
 
+    func setLastReadId(_ id: String, markerTimeline: Marker.Timeline) -> AnyPublisher<Never, Error> {
+        databaseWriter.writePublisher(updates: LastReadIdRecord(markerTimeline: markerTimeline, id: id).save)
+            .ignoreOutput()
+            .eraseToAnyPublisher()
+    }
+
     func timelinePublisher(_ timeline: Timeline) -> AnyPublisher<[[CollectionItem]], Error> {
         ValueObservation.tracking(
             TimelineItemsInfo.request(TimelineRecord.filter(TimelineRecord.Columns.id == timeline.id)).fetchOne)
@@ -331,19 +345,64 @@ public extension ContentDatabase {
             .publisher(in: databaseWriter)
             .eraseToAnyPublisher()
     }
+
+    func lastReadId(_ markerTimeline: Marker.Timeline) -> String? {
+        try? databaseWriter.read {
+            try String.fetchOne(
+                $0,
+                LastReadIdRecord.filter(LastReadIdRecord.Columns.markerTimeline == markerTimeline.rawValue)
+                    .select(LastReadIdRecord.Columns.id))
+        }
+    }
 }
 
 private extension ContentDatabase {
+    static let cleanAfterLastReadIdCount = 40
     static func fileURL(id: Identity.Id) throws -> URL {
         try FileManager.default.databaseDirectoryURL(name: id.uuidString)
     }
 
-    static func clean(_ databaseWriter: DatabaseWriter) throws {
+    static func clean(_ databaseWriter: DatabaseWriter,
+                      useHomeTimelineLastReadId: Bool,
+                      useNotificationsLastReadId: Bool) throws {
         try databaseWriter.write {
-            try TimelineRecord.deleteAll($0)
-            try StatusRecord.deleteAll($0)
-            try AccountRecord.deleteAll($0)
+            if useHomeTimelineLastReadId {
+                try TimelineRecord.filter(TimelineRecord.Columns.id != Timeline.home.id).deleteAll($0)
+                var statusIds = try Status.Id.fetchAll(
+                    $0,
+                    TimelineStatusJoin.select(TimelineStatusJoin.Columns.statusId)
+                        .order(TimelineStatusJoin.Columns.statusId.desc))
+
+                if let lastReadId = try Status.Id.fetchOne(
+                    $0,
+                    LastReadIdRecord.filter(LastReadIdRecord.Columns.markerTimeline == Marker.Timeline.home.rawValue)
+                        .select(LastReadIdRecord.Columns.id))
+                    ?? statusIds.first,
+                   let index = statusIds.firstIndex(of: lastReadId) {
+                    statusIds = Array(statusIds.prefix(index + Self.cleanAfterLastReadIdCount))
+                }
+
+                statusIds += try Status.Id.fetchAll(
+                    $0,
+                    StatusRecord.filter(statusIds.contains(StatusRecord.Columns.id)
+                                            && StatusRecord.Columns.reblogId != nil)
+                        .select(StatusRecord.Columns.reblogId))
+                try StatusRecord.filter(!statusIds.contains(StatusRecord.Columns.id) ).deleteAll($0)
+                var accountIds = try Account.Id.fetchAll($0, StatusRecord.select(StatusRecord.Columns.accountId))
+                accountIds += try Account.Id.fetchAll(
+                    $0,
+                    AccountRecord.filter(accountIds.contains(AccountRecord.Columns.id)
+                                            && AccountRecord.Columns.movedId != nil)
+                        .select(AccountRecord.Columns.movedId))
+                try AccountRecord.filter(!accountIds.contains(AccountRecord.Columns.id)).deleteAll($0)
+            } else {
+                try TimelineRecord.deleteAll($0)
+                try StatusRecord.deleteAll($0)
+                try AccountRecord.deleteAll($0)
+            }
+
             try AccountList.deleteAll($0)
         }
     }
 }
+// swiftlint:enable file_length

DB/Sources/DB/Content/LastReadIdRecord.swift

@@ -0,0 +1,17 @@
+// Copyright © 2020 Metabolist. All rights reserved.
+
+import Foundation
+import GRDB
+import Mastodon
+
+struct LastReadIdRecord: ContentDatabaseRecord, Hashable {
+    let markerTimeline: Marker.Timeline
+    let id: String
+}
+
+extension LastReadIdRecord {
+    enum Columns {
+        static let markerTimeline = Column(LastReadIdRecord.CodingKeys.markerTimeline)
+        static let id = Column(LastReadIdRecord.CodingKeys.id)
+    }
+}

HTTP/Sources/HTTP/Target.swift

@@ -6,7 +6,7 @@ public protocol Target {
     var baseURL: URL { get }
     var pathComponents: [String] { get }
     var method: HTTPMethod { get }
-    var queryParameters: [String: String]? { get }
+    var queryParameters: [URLQueryItem] { get }
     var jsonBody: [String: Any]? { get }
     var headers: [String: String]? { get }
 }
@@ -19,9 +19,8 @@ public extension Target {
             url.appendPathComponent(pathComponent)
         }
 
-        if var components = URLComponents(url: url, resolvingAgainstBaseURL: true),
-           let queryItems = queryParameters?.map(URLQueryItem.init(name:value:)) {
-            components.queryItems = queryItems
+        if var components = URLComponents(url: url, resolvingAgainstBaseURL: true), !queryParameters.isEmpty {
+            components.queryItems = queryParameters
 
             if let queryComponentURL = components.url {
                 url = queryComponentURL

Localizations/Localizable.strings

@@ -67,6 +67,13 @@
 "preferences.notification-types.reblog" = "Reblog";
 "preferences.notification-types.mention" = "Mention";
 "preferences.notification-types.poll" = "Poll";
+"preferences.startup-and-syncing" = "Startup and Syncing";
+"preferences.startup-and-syncing.home-timeline" = "Home timeline";
+"preferences.startup-and-syncing.notifications-tab" = "Notifications tab";
+"preferences.startup-and-syncing.position-on-startup" = "Position on startup";
+"preferences.startup-and-syncing.remember-position" = "Remember position";
+"preferences.startup-and-syncing.sync-position" = "Sync position with web and other devices";
+"preferences.startup-and-syncing.newest" = "Load newest";
 "filters.active" = "Active";
 "filters.expired" = "Expired";
 "filter.add-new" = "Add New Filter";

Mastodon/Sources/Mastodon/Entities/Marker.swift

@@ -0,0 +1,16 @@
+// Copyright © 2020 Metabolist. All rights reserved.
+
+import Foundation
+
+public struct Marker: Codable, Hashable {
+    public let lastReadId: String
+    public let updatedAt: Date
+    public let version: Int
+}
+
+public extension Marker {
+    enum Timeline: String, Codable {
+        case home
+        case notifications
+    }
+}

MastodonAPI/Sources/MastodonAPI/Endpoint.swift

@@ -9,7 +9,7 @@ public protocol Endpoint {
     var context: [String] { get }
     var pathComponentsInContext: [String] { get }
     var method: HTTPMethod { get }
-    var queryParameters: [String: String]? { get }
+    var queryParameters: [URLQueryItem] { get }
     var jsonBody: [String: Any]? { get }
     var headers: [String: String]? { get }
 }
@@ -29,7 +29,7 @@ public extension Endpoint {
         context + pathComponentsInContext
     }
 
-    var queryParameters: [String: String]? { nil }
+    var queryParameters: [URLQueryItem] { [] }
 
     var jsonBody: [String: Any]? { nil }
 

MastodonAPI/Sources/MastodonAPI/Endpoints/MarkersEndpoint.swift

@@ -0,0 +1,45 @@
+// Copyright © 2020 Metabolist. All rights reserved.
+
+import Foundation
+import HTTP
+import Mastodon
+
+public enum MarkersEndpoint {
+    case get(Set<Marker.Timeline>)
+    case post([Marker.Timeline: String])
+}
+
+extension MarkersEndpoint: Endpoint {
+    public typealias ResultType = [String: Marker]
+
+    public var pathComponentsInContext: [String] {
+        ["markers"]
+    }
+
+    public var queryParameters: [URLQueryItem] {
+        switch self {
+        case let .get(timelines):
+            return Array(timelines).map { URLQueryItem(name: "timeline[]", value: $0.rawValue) }
+        case .post:
+            return []
+        }
+    }
+
+    public var jsonBody: [String: Any]? {
+        switch self {
+        case .get:
+            return nil
+        case let .post(lastReadIds):
+            return Dictionary(uniqueKeysWithValues: lastReadIds.map { ($0.rawValue, ["last_read_id": $1]) })
+        }
+    }
+
+    public var method: HTTPMethod {
+        switch self {
+        case .get:
+            return .get
+        case .post:
+            return .post
+        }
+    }
+}

MastodonAPI/Sources/MastodonAPI/Endpoints/Paged.swift

@@ -31,15 +31,23 @@ extension Paged: Endpoint {
 
     public var method: HTTPMethod { endpoint.method }
 
-    public var queryParameters: [String: String]? {
-        var queryParameters = endpoint.queryParameters ?? [String: String]()
+    public var queryParameters: [URLQueryItem] {
+        var queryParameters = endpoint.queryParameters
 
-        queryParameters["max_id"] = maxId
-        queryParameters["min_id"] = minId
-        queryParameters["since_id"] = sinceId
+        if let maxId = maxId {
+            queryParameters.append(.init(name: "max_id", value: maxId))
+        }
+
+        if let minId = minId {
+            queryParameters.append(.init(name: "min_id", value: minId))
+        }
+
+        if let sinceId = sinceId {
+            queryParameters.append(.init(name: "since_id", value: sinceId))
+        }
 
         if let limit = limit {
-            queryParameters["limit"] = String(limit)
+            queryParameters.append(.init(name: "limit", value: String(limit)))
         }
 
         return queryParameters

MastodonAPI/Sources/MastodonAPI/Endpoints/ResultsEndpoint.swift

@@ -32,13 +32,13 @@ extension ResultsEndpoint: Endpoint {
         }
     }
 
-    public var queryParameters: [String: String]? {
+    public var queryParameters: [URLQueryItem] {
         switch self {
         case let .search(query, resolve):
-            var params = ["q": query]
+            var params = [URLQueryItem(name: "q", value: query)]
 
             if resolve {
-                params["resolve"] = String(true)
+                params.append(.init(name: "resolve", value: "true"))
             }
 
             return params

MastodonAPI/Sources/MastodonAPI/Endpoints/StatusesEndpoint.swift

@@ -39,16 +39,16 @@ extension StatusesEndpoint: Endpoint {
         }
     }
 
-    public var queryParameters: [String: String]? {
+    public var queryParameters: [URLQueryItem] {
         switch self {
         case let .timelinesPublic(local):
-            return ["local": String(local)]
+            return [URLQueryItem(name: "local", value: String(local))]
         case let .accountsStatuses(_, excludeReplies, onlyMedia, pinned):
-            return ["exclude_replies": String(excludeReplies),
-                    "only_media": String(onlyMedia),
-                    "pinned": String(pinned)]
+            return [URLQueryItem(name: "exclude_replies", value: String(excludeReplies)),
+                    URLQueryItem(name: "only_media", value: String(onlyMedia)),
+                    URLQueryItem(name: "pinned", value: String(pinned))]
         default:
-            return nil
+            return []
         }
     }
 

MastodonAPI/Sources/MastodonAPI/MastodonAPITarget.swift

@@ -22,7 +22,7 @@ extension MastodonAPITarget: DecodableTarget {
 
     public var method: HTTPMethod { endpoint.method }
 
-    public var queryParameters: [String: String]? { endpoint.queryParameters }
+    public var queryParameters: [URLQueryItem] { endpoint.queryParameters }
 
     public var jsonBody: [String: Any]? { endpoint.jsonBody }
 

Metatext.xcodeproj/project.pbxproj

@@ -15,6 +15,7 @@
 		D01F41E424F8889700D55A2D /* StatusAttachmentsView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D01F41E224F8889700D55A2D /* StatusAttachmentsView.swift */; };
 		D02E1F95250B13210071AD56 /* SafariView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D02E1F94250B13210071AD56 /* SafariView.swift */; };
 		D03B1B2A253818F3008F964B /* MediaPreferencesView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D03B1B29253818F3008F964B /* MediaPreferencesView.swift */; };
+		D04226FD2546AC0B000980A3 /* StartupAndSyncingPreferencesView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D04226FC2546AC0B000980A3 /* StartupAndSyncingPreferencesView.swift */; };
 		D0625E59250F092900502611 /* StatusListCell.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0625E58250F092900502611 /* StatusListCell.swift */; };
 		D0625E5D250F0B5C00502611 /* StatusContentConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0625E5C250F0B5C00502611 /* StatusContentConfiguration.swift */; };
 		D06B492324D4611300642749 /* KingfisherSwiftUI in Frameworks */ = {isa = PBXBuildFile; productRef = D06B492224D4611300642749 /* KingfisherSwiftUI */; };
@@ -118,6 +119,7 @@
 		D01F41E224F8889700D55A2D /* StatusAttachmentsView.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = StatusAttachmentsView.swift; sourceTree = "<group>"; };
 		D02E1F94250B13210071AD56 /* SafariView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SafariView.swift; sourceTree = "<group>"; };
 		D03B1B29253818F3008F964B /* MediaPreferencesView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MediaPreferencesView.swift; sourceTree = "<group>"; };
+		D04226FC2546AC0B000980A3 /* StartupAndSyncingPreferencesView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = StartupAndSyncingPreferencesView.swift; sourceTree = "<group>"; };
 		D047FA8C24C3E21200AF17C5 /* Metatext.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = Metatext.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		D0625E58250F092900502611 /* StatusListCell.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = StatusListCell.swift; sourceTree = "<group>"; };
 		D0625E5C250F0B5C00502611 /* StatusContentConfiguration.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = StatusContentConfiguration.swift; sourceTree = "<group>"; };
@@ -348,6 +350,7 @@
 				D0C7D42724F76169001EBDBB /* RootView.swift */,
 				D02E1F94250B13210071AD56 /* SafariView.swift */,
 				D0C7D42924F76169001EBDBB /* SecondaryNavigationView.swift */,
+				D04226FC2546AC0B000980A3 /* StartupAndSyncingPreferencesView.swift */,
 				D0625E55250F086B00502611 /* Status */,
 				D0C7D42524F76169001EBDBB /* TableView.swift */,
 				D0C7D42E24F76169001EBDBB /* TabNavigationView.swift */,
@@ -632,6 +635,7 @@
 				D0C7D49724F7616A001EBDBB /* IdentitiesView.swift in Sources */,
 				D01EF22425182B1F00650C6B /* AccountHeaderView.swift in Sources */,
 				D0EA59482522B8B600804347 /* ViewConstants.swift in Sources */,
+				D04226FD2546AC0B000980A3 /* StartupAndSyncingPreferencesView.swift in Sources */,
 				D0C7D49824F7616A001EBDBB /* CustomEmojiText.swift in Sources */,
 				D08B8D3D253F929E00B1EBEF /* ImageViewController.swift in Sources */,
 				D0B8510C25259E56004E0744 /* LoadMoreCell.swift in Sources */,

ServiceLayer/Sources/ServiceLayer/Services/CollectionService.swift

@@ -8,6 +8,7 @@ public protocol CollectionService {
     var nextPageMaxId: AnyPublisher<String, Never> { get }
     var title: AnyPublisher<String, Never> { get }
     var navigationService: NavigationService { get }
+    var markerTimeline: Marker.Timeline? { get }
     func request(maxId: String?, minId: String?) -> AnyPublisher<Never, Error>
 }
 
@@ -15,4 +16,6 @@ extension CollectionService {
     public var nextPageMaxId: AnyPublisher<String, Never> { Empty().eraseToAnyPublisher() }
 
     public var title: AnyPublisher<String, Never> { Empty().eraseToAnyPublisher() }
+
+    public var markerTimeline: Marker.Timeline? { nil }
 }

ServiceLayer/Sources/ServiceLayer/Services/IdentityService.swift

@@ -27,9 +27,14 @@ public struct IdentityService {
                                               instanceURL: try secrets.getInstanceURL())
         mastodonAPIClient.accessToken = try? secrets.getAccessToken()
 
-        contentDatabase = try ContentDatabase(id: id,
-                                              inMemory: environment.inMemoryContent,
-                                              keychain: environment.keychain)
+        let appPreferences = AppPreferences(environment: environment)
+
+        contentDatabase = try ContentDatabase(
+            id: id,
+            useHomeTimelineLastReadId: appPreferences.homeTimelineBehavior == .rememberPosition,
+            useNotificationsLastReadId: appPreferences.notificationsTabBehavior == .rememberPosition,
+            inMemory: environment.inMemoryContent,
+            keychain: environment.keychain)
     }
 }
 
@@ -87,6 +92,29 @@ public extension IdentityService {
             .eraseToAnyPublisher()
     }
 
+    func getMarker(_ markerTimeline: Marker.Timeline) -> AnyPublisher<Marker, Error> {
+        mastodonAPIClient.request(MarkersEndpoint.get([markerTimeline]))
+            .compactMap { $0[markerTimeline.rawValue] }
+            .eraseToAnyPublisher()
+    }
+
+    func getLocalLastReadId(_ markerTimeline: Marker.Timeline) -> String? {
+        contentDatabase.lastReadId(markerTimeline)
+    }
+
+    func setLastReadId(_ id: String, forMarker markerTimeline: Marker.Timeline) -> AnyPublisher<Never, Error> {
+        switch AppPreferences(environment: environment).positionBehavior(markerTimeline: markerTimeline) {
+        case .rememberPosition:
+            return contentDatabase.setLastReadId(id, markerTimeline: markerTimeline)
+        case .syncPosition:
+            return mastodonAPIClient.request(MarkersEndpoint.post([markerTimeline: id]))
+                .ignoreOutput()
+                .eraseToAnyPublisher()
+        case .newest:
+            return Empty().eraseToAnyPublisher()
+        }
+    }
+
     func identityPublisher(immediate: Bool) -> AnyPublisher<Identity, Error> {
         identityDatabase.identityPublisher(id: id, immediate: immediate)
     }

ServiceLayer/Sources/ServiceLayer/Services/InstanceURLService.swift

@@ -73,7 +73,7 @@ private struct UpdatedFilterTarget: DecodableTarget {
     let baseURL = URL(string: "https://filter.metabolist.com")!
     let pathComponents = ["filter"]
     let method = HTTPMethod.get
-    let queryParameters: [String: String]? = nil
+    let queryParameters: [URLQueryItem] = []
     let jsonBody: [String: Any]? = nil
     let headers: [String: String]? = nil
 }

ServiceLayer/Sources/ServiceLayer/Services/TimelineService.swift

@@ -15,15 +15,27 @@ public struct TimelineService {
     private let timeline: Timeline
     private let mastodonAPIClient: MastodonAPIClient
     private let contentDatabase: ContentDatabase
-    private let nextPageMaxIdSubject = PassthroughSubject<String, Never>()
+    private let nextPageMaxIdSubject: CurrentValueSubject<String, Never>
 
     init(timeline: Timeline, mastodonAPIClient: MastodonAPIClient, contentDatabase: ContentDatabase) {
         self.timeline = timeline
         self.mastodonAPIClient = mastodonAPIClient
         self.contentDatabase = contentDatabase
+
+        let nextPageMaxIdSubject = CurrentValueSubject<String, Never>(String(Int.max))
+
+        self.nextPageMaxIdSubject = nextPageMaxIdSubject
         sections = contentDatabase.timelinePublisher(timeline)
+            .handleEvents(receiveOutput: {
+                guard case let .status(status, _) = $0.last?.last,
+                      status.id < nextPageMaxIdSubject.value
+                else { return }
+
+                nextPageMaxIdSubject.send(status.id)
+            })
+            .eraseToAnyPublisher()
         navigationService = NavigationService(mastodonAPIClient: mastodonAPIClient, contentDatabase: contentDatabase)
-        nextPageMaxId = nextPageMaxIdSubject.eraseToAnyPublisher()
+        nextPageMaxId = nextPageMaxIdSubject.dropFirst().eraseToAnyPublisher()
 
         if case let .tag(tag) = timeline {
             title = Just("#".appending(tag)).eraseToAnyPublisher()
@@ -34,10 +46,19 @@ public struct TimelineService {
 }
 
 extension TimelineService: CollectionService {
+    public var markerTimeline: Marker.Timeline? {
+        switch timeline {
+        case .home:
+            return .home
+        default:
+            return nil
+        }
+    }
+
     public func request(maxId: String?, minId: String?) -> AnyPublisher<Never, Error> {
         mastodonAPIClient.pagedRequest(timeline.endpoint, maxId: maxId, minId: minId)
             .handleEvents(receiveOutput: {
-                guard let maxId = $0.info.maxId else { return }
+                guard let maxId = $0.info.maxId, maxId < nextPageMaxIdSubject.value else { return }
 
                 nextPageMaxIdSubject.send(maxId)
             })

ServiceLayer/Sources/ServiceLayer/Utilities/AppPreferences.swift

@@ -2,6 +2,7 @@
 
 import CodableBloomFilter
 import Foundation
+import Mastodon
 
 public struct AppPreferences {
     private let userDefaults: UserDefaults
@@ -30,6 +31,14 @@ public extension AppPreferences {
         public var id: String { rawValue }
     }
 
+    enum PositionBehavior: String, CaseIterable, Identifiable {
+        case rememberPosition
+        case syncPosition
+        case newest
+
+        public var id: String { rawValue }
+    }
+
     var useSystemReduceMotionForMedia: Bool {
         get { self[.useSystemReduceMotionForMedia] ?? true }
         set { self[.useSystemReduceMotionForMedia] = newValue }
@@ -76,9 +85,42 @@ public extension AppPreferences {
         set { self[.autoplayVideos] = newValue.rawValue }
     }
 
+    var homeTimelineBehavior: PositionBehavior {
+        get {
+            if let rawValue = self[.homeTimelineBehavior] as String?,
+               let value = PositionBehavior(rawValue: rawValue) {
+                return value
+            }
+
+            return .rememberPosition
+        }
+        set { self[.homeTimelineBehavior] = newValue.rawValue }
+    }
+
+    var notificationsTabBehavior: PositionBehavior {
+        get {
+            if let rawValue = self[.notificationsTabBehavior] as String?,
+               let value = PositionBehavior(rawValue: rawValue) {
+                return value
+            }
+
+            return .newest
+        }
+        set { self[.notificationsTabBehavior] = newValue.rawValue }
+    }
+
     var shouldReduceMotion: Bool {
         systemReduceMotion() && useSystemReduceMotionForMedia
     }
+
+    func positionBehavior(markerTimeline: Marker.Timeline) -> PositionBehavior {
+        switch markerTimeline {
+        case .home:
+            return homeTimelineBehavior
+        case .notifications:
+            return notificationsTabBehavior
+        }
+    }
 }
 
 extension AppPreferences {
@@ -103,6 +145,8 @@ private extension AppPreferences {
         case animateHeaders
         case autoplayGIFs
         case autoplayVideos
+        case homeTimelineBehavior
+        case notificationsTabBehavior
     }
 
     subscript<T>(index: Item) -> T? {

View Controllers/TableViewController.swift

@@ -6,6 +6,7 @@ import SafariServices
 import SwiftUI
 import ViewModels
 
+// swiftlint:disable file_length
 class TableViewController: UITableViewController {
     var transitionViewTag = -1
 
@@ -272,13 +273,16 @@ private extension TableViewController {
             if
                 let item = update.maintainScrollPosition,
                 let indexPath = self.dataSource.indexPath(for: item) {
-                self.tableView.contentInset.bottom = max(
-                    0,
-                    self.tableView.frame.height
-                        - self.tableView.contentSize.height
-                        - self.tableView.safeAreaInsets.top
-                        - self.tableView.safeAreaInsets.bottom)
-                    + self.tableView.rectForRow(at: indexPath).minY
+                if self.viewModel.shouldAdjustContentInset {
+                    self.tableView.contentInset.bottom = max(
+                        0,
+                        self.tableView.frame.height
+                            - self.tableView.contentSize.height
+                            - self.tableView.safeAreaInsets.top
+                            - self.tableView.safeAreaInsets.bottom)
+                        + self.tableView.rectForRow(at: indexPath).minY
+                }
+
                 self.tableView.scrollToRow(at: indexPath, at: .top, animated: false)
 
                 if let offsetFromNavigationBar = offsetFromNavigationBar {
@@ -399,3 +403,4 @@ private extension TableViewController {
         }
     }
 }
+// swiftlint:enable file_length

ViewModels/Sources/ViewModels/CollectionItemsViewModel.swift

@@ -18,7 +18,10 @@ final public class CollectionItemsViewModel: ObservableObject {
     private let expandAllSubject: CurrentValueSubject<ExpandAllState, Never>
     private var maintainScrollPosition: CollectionItem?
     private var topVisibleIndexPath = IndexPath(item: 0, section: 0)
+    private let lastReadId = CurrentValueSubject<String?, Never>(nil)
     private var lastSelectedLoadMore: LoadMore?
+    private var hasRequestedUsingMarker = false
+    private var hasRememberedPosition = false
     private var cancellables = Set<AnyCancellable>()
 
     public init(collectionService: CollectionService, identification: Identification) {
@@ -38,6 +41,15 @@ final public class CollectionItemsViewModel: ObservableObject {
         collectionService.nextPageMaxId
             .sink { [weak self] in self?.nextPageMaxId = $0 }
             .store(in: &cancellables)
+
+        if let markerTimeline = collectionService.markerTimeline {
+            lastReadId.compactMap { $0 }
+                .removeDuplicates()
+                .debounce(for: 0.5, scheduler: DispatchQueue.global())
+                .flatMap { identification.service.setLastReadId($0, forMarker: markerTimeline) }
+                .sink { _ in } receiveValue: { _ in }
+                .store(in: &cancellables)
+        }
     }
 }
 
@@ -62,8 +74,32 @@ extension CollectionItemsViewModel: CollectionViewModel {
 
     public var events: AnyPublisher<CollectionItemEvent, Never> { eventsSubject.eraseToAnyPublisher() }
 
+    public var shouldAdjustContentInset: Bool { collectionService is ContextService }
+
     public func request(maxId: String? = nil, minId: String? = nil) {
-        collectionService.request(maxId: maxId, minId: minId)
+        let publisher: AnyPublisher<Never, Error>
+
+        if let markerTimeline = collectionService.markerTimeline,
+           identification.appPreferences.positionBehavior(markerTimeline: markerTimeline) == .syncPosition,
+           !hasRequestedUsingMarker {
+            publisher = identification.service.getMarker(markerTimeline)
+                .flatMap { [weak self] in
+                    self?.collectionService.request(maxId: $0.lastReadId, minId: nil) ?? Empty().eraseToAnyPublisher()
+                }
+                .catch { [weak self] _ in
+                    self?.collectionService.request(maxId: nil, minId: nil) ?? Empty().eraseToAnyPublisher()
+                }
+                .collect()
+                .flatMap { [weak self] _ in
+                    self?.collectionService.request(maxId: nil, minId: nil) ?? Empty().eraseToAnyPublisher()
+                }
+                .eraseToAnyPublisher()
+            self.hasRequestedUsingMarker = true
+        } else {
+            publisher = collectionService.request(maxId: maxId, minId: minId)
+        }
+
+        publisher
             .receive(on: DispatchQueue.main)
             .assignErrorsToAlertItem(to: \.alertItem, on: self)
             .handleEvents(
@@ -95,6 +131,15 @@ extension CollectionItemsViewModel: CollectionViewModel {
 
     public func viewedAtTop(indexPath: IndexPath) {
         topVisibleIndexPath = indexPath
+
+        if items.value.count > indexPath.section, items.value[indexPath.section].count > indexPath.item {
+            switch items.value[indexPath.section][indexPath.item] {
+            case let .status(status, _):
+                lastReadId.send(status.id)
+            default:
+                break
+            }
+        }
     }
 
     public func canSelect(indexPath: IndexPath) -> Bool {
@@ -196,9 +241,27 @@ private extension CollectionItemsViewModel {
         viewModelCache = viewModelCache.filter { itemsSet.contains($0.key) }
     }
 
+    // swiftlint:disable:next cyclomatic_complexity function_body_length
     func itemForScrollPositionMaintenance(newItems: [[CollectionItem]]) -> CollectionItem? {
         let flatNewItems = newItems.reduce([], +)
 
+        if let markerTimeline = collectionService.markerTimeline,
+           identification.appPreferences.positionBehavior(markerTimeline: markerTimeline) == .rememberPosition,
+           let localLastReadId = identification.service.getLocalLastReadId(markerTimeline),
+           !hasRememberedPosition,
+           let lastReadItem = flatNewItems.first(where: {
+            switch $0 {
+            case let .status(status, _):
+                return status.id == localLastReadId
+            default:
+                return false
+            }
+           }) {
+            hasRememberedPosition = true
+
+            return lastReadItem
+        }
+
         if collectionService is ContextService,
            items.value.isEmpty || items.value.map(\.count) == [0, 1, 0],
            let contextParent = flatNewItems.first(where: {

ViewModels/Sources/ViewModels/CollectionViewModel.swift

@@ -10,6 +10,7 @@ public protocol CollectionViewModel {
     var alertItems: AnyPublisher<AlertItem, Never> { get }
     var loading: AnyPublisher<Bool, Never> { get }
     var events: AnyPublisher<CollectionItemEvent, Never> { get }
+    var shouldAdjustContentInset: Bool { get }
     var nextPageMaxId: String? { get }
     func request(maxId: String?, minId: String?)
     func viewedAtTop(indexPath: IndexPath)

ViewModels/Sources/ViewModels/ProfileViewModel.swift

@@ -81,6 +81,10 @@ extension ProfileViewModel: CollectionViewModel {
             .eraseToAnyPublisher()
     }
 
+    public var shouldAdjustContentInset: Bool {
+        collectionViewModel.value.shouldAdjustContentInset
+    }
+
     public var nextPageMaxId: String? {
         collectionViewModel.value.nextPageMaxId
     }

Views/PreferencesView.swift

@@ -26,6 +26,8 @@ struct PreferencesView: View {
                 NavigationLink("preferences.media",
                                destination: MediaPreferencesView(
                                 viewModel: .init(identification: identification)))
+                NavigationLink("preferences.startup-and-syncing",
+                               destination: StartupAndSyncingPreferencesView())
             }
         }
         .navigationTitle("preferences")

Views/StartupAndSyncingPreferencesView.swift

@@ -0,0 +1,53 @@
+// Copyright © 2020 Metabolist. All rights reserved.
+
+import SwiftUI
+import ViewModels
+
+struct StartupAndSyncingPreferencesView: View {
+    @EnvironmentObject var identification: Identification
+
+    var body: some View {
+        Form {
+            Section(header: Text("preferences.startup-and-syncing.home-timeline")) {
+                Picker("preferences.startup-and-syncing.position-on-startup",
+                       selection: $identification.appPreferences.homeTimelineBehavior) {
+                    ForEach(AppPreferences.PositionBehavior.allCases) { option in
+                        Text(option.localizedStringKey).tag(option)
+                    }
+                }
+            }
+            Section(header: Text("preferences.startup-and-syncing.notifications-tab")) {
+                Picker("preferences.startup-and-syncing.position-on-startup",
+                       selection: $identification.appPreferences.notificationsTabBehavior) {
+                    ForEach(AppPreferences.PositionBehavior.allCases) { option in
+                        Text(option.localizedStringKey).tag(option)
+                    }
+                }
+            }
+        }
+    }
+}
+
+extension AppPreferences.PositionBehavior {
+    var localizedStringKey: LocalizedStringKey {
+        switch self {
+        case .rememberPosition:
+            return "preferences.startup-and-syncing.remember-position"
+        case .syncPosition:
+            return "preferences.startup-and-syncing.sync-position"
+        case .newest:
+            return "preferences.startup-and-syncing.newest"
+        }
+    }
+}
+
+#if DEBUG
+import PreviewViewModels
+
+struct StartupAndSyncingPreferencesView_Previews: PreviewProvider {
+    static var previews: some View {
+        StartupAndSyncingPreferencesView()
+            .environmentObject(Identification.preview)
+    }
+}
+#endif