Status contexts

Development Assets/Mastodon API Stubs/ContextEndpoint+Stubbing.swift

@@ -0,0 +1,17 @@
+// Copyright © 2020 Metabolist. All rights reserved.
+
+import Foundation
+
+extension ContextEndpoint: Stubbing {
+    func dataString(url: URL) -> String? {
+        switch self {
+        case .context:
+            return """
+            {
+              "ancestors": [],
+              "descendants": []
+            }
+            """
+        }
+    }
+}

Metatext.xcodeproj/project.pbxproj

@@ -44,6 +44,16 @@
 		D019E6EE24DF7BF300697C7D /* IdentityDatabase.swift in Sources */ = {isa = PBXBuildFile; fileRef = D019E6EC24DF7BF300697C7D /* IdentityDatabase.swift */; };
 		D019E6F024DF7C2F00697C7D /* DatabaseError.swift in Sources */ = {isa = PBXBuildFile; fileRef = D019E6EF24DF7C2F00697C7D /* DatabaseError.swift */; };
 		D019E6F124DF7C2F00697C7D /* DatabaseError.swift in Sources */ = {isa = PBXBuildFile; fileRef = D019E6EF24DF7C2F00697C7D /* DatabaseError.swift */; };
+		D020F50B24EC9F1D005AB084 /* ContextService.swift in Sources */ = {isa = PBXBuildFile; fileRef = D020F50A24EC9F1D005AB084 /* ContextService.swift */; };
+		D020F50C24EC9F1D005AB084 /* ContextService.swift in Sources */ = {isa = PBXBuildFile; fileRef = D020F50A24EC9F1D005AB084 /* ContextService.swift */; };
+		D020F50E24ECA25F005AB084 /* ContextEndpoint.swift in Sources */ = {isa = PBXBuildFile; fileRef = D020F50D24ECA25F005AB084 /* ContextEndpoint.swift */; };
+		D020F50F24ECA25F005AB084 /* ContextEndpoint.swift in Sources */ = {isa = PBXBuildFile; fileRef = D020F50D24ECA25F005AB084 /* ContextEndpoint.swift */; };
+		D020F51124ECA309005AB084 /* MastodonContext.swift in Sources */ = {isa = PBXBuildFile; fileRef = D020F51024ECA309005AB084 /* MastodonContext.swift */; };
+		D020F51224ECA309005AB084 /* MastodonContext.swift in Sources */ = {isa = PBXBuildFile; fileRef = D020F51024ECA309005AB084 /* MastodonContext.swift */; };
+		D020F51424ECBA60005AB084 /* LazyView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D020F51324ECBA60005AB084 /* LazyView.swift */; };
+		D020F51524ECBA60005AB084 /* LazyView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D020F51324ECBA60005AB084 /* LazyView.swift */; };
+		D03658D124EDD80900AC17EC /* ContextEndpoint+Stubbing.swift in Sources */ = {isa = PBXBuildFile; fileRef = D03658D024EDD80900AC17EC /* ContextEndpoint+Stubbing.swift */; };
+		D03658D224EDD80900AC17EC /* ContextEndpoint+Stubbing.swift in Sources */ = {isa = PBXBuildFile; fileRef = D03658D024EDD80900AC17EC /* ContextEndpoint+Stubbing.swift */; };
 		D03DF45B24E62A68007A8CD5 /* DeletionEndpoint.swift in Sources */ = {isa = PBXBuildFile; fileRef = D03DF45A24E62A68007A8CD5 /* DeletionEndpoint.swift */; };
 		D03DF45C24E62A68007A8CD5 /* DeletionEndpoint.swift in Sources */ = {isa = PBXBuildFile; fileRef = D03DF45A24E62A68007A8CD5 /* DeletionEndpoint.swift */; };
 		D047FAAE24C3E21200AF17C5 /* MetatextApp.swift in Sources */ = {isa = PBXBuildFile; fileRef = D047FA8524C3E21000AF17C5 /* MetatextApp.swift */; };
@@ -272,6 +282,11 @@
 		D019E6E024DF72E700697C7D /* InstanceEndpoint.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = InstanceEndpoint.swift; sourceTree = "<group>"; };
 		D019E6EC24DF7BF300697C7D /* IdentityDatabase.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = IdentityDatabase.swift; sourceTree = "<group>"; };
 		D019E6EF24DF7C2F00697C7D /* DatabaseError.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = DatabaseError.swift; sourceTree = "<group>"; };
+		D020F50A24EC9F1D005AB084 /* ContextService.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ContextService.swift; sourceTree = "<group>"; };
+		D020F50D24ECA25F005AB084 /* ContextEndpoint.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ContextEndpoint.swift; sourceTree = "<group>"; };
+		D020F51024ECA309005AB084 /* MastodonContext.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MastodonContext.swift; sourceTree = "<group>"; };
+		D020F51324ECBA60005AB084 /* LazyView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LazyView.swift; sourceTree = "<group>"; };
+		D03658D024EDD80900AC17EC /* ContextEndpoint+Stubbing.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "ContextEndpoint+Stubbing.swift"; sourceTree = "<group>"; };
 		D03DF45A24E62A68007A8CD5 /* DeletionEndpoint.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DeletionEndpoint.swift; sourceTree = "<group>"; };
 		D047FA8524C3E21000AF17C5 /* MetatextApp.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MetatextApp.swift; sourceTree = "<group>"; };
 		D047FA8724C3E21200AF17C5 /* Assets.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; path = Assets.xcassets; sourceTree = "<group>"; };
@@ -447,6 +462,7 @@
 				D019E6DF24DF72E700697C7D /* AccessTokenEndpoint.swift */,
 				D019E6DE24DF72E700697C7D /* AccountEndpoint.swift */,
 				D019E6DC24DF72E700697C7D /* AppAuthorizationEndpoint.swift */,
+				D020F50D24ECA25F005AB084 /* ContextEndpoint.swift */,
 				D03DF45A24E62A68007A8CD5 /* DeletionEndpoint.swift */,
 				D019E6E024DF72E700697C7D /* InstanceEndpoint.swift */,
 				D019E6DD24DF72E700697C7D /* PreferencesEndpoint.swift */,
@@ -548,6 +564,7 @@
 		D054951024EB101F008B00A5 /* Status List Services */ = {
 			isa = PBXGroup;
 			children = (
+				D020F50A24EC9F1D005AB084 /* ContextService.swift */,
 				D054951124EB1041008B00A5 /* StatusListService.swift */,
 				D054951424EB1053008B00A5 /* TimelineService.swift */,
 			);
@@ -575,6 +592,7 @@
 				D0ED1BD624CF94B200B4899C /* Application.swift */,
 				D05494E924EA3F54008B00A5 /* Attachment.swift */,
 				D05494EF24EA3FE5008B00A5 /* Card.swift */,
+				D020F51024ECA309005AB084 /* MastodonContext.swift */,
 				D0666A5324C6C3E500F3F04B /* Emoji.swift */,
 				D0666A4A24C6C37700F3F04B /* Identity.swift */,
 				D0666A4D24C6C39600F3F04B /* Instance.swift */,
@@ -613,6 +631,7 @@
 			isa = PBXGroup;
 			children = (
 				D0DB6EF324C5228A00D965FE /* AddIdentityView.swift */,
+				D020F51324ECBA60005AB084 /* LazyView.swift */,
 				D075817B24E6659A0081F6A3 /* NotificationTypesPreferencesView.swift */,
 				D0091B6724DC10B30040E8D2 /* PostingReadingPreferencesView.swift */,
 				D0091B6D24DD68090040E8D2 /* PreferencesView.swift */,
@@ -666,6 +685,7 @@
 				D0DC175424D00F0A00A75C65 /* AccessTokenEndpoint+Stubbing.swift */,
 				D04FD73824D4A7B4007D572D /* AccountEndpoint+Stubbing.swift */,
 				D0DC174924CFF15F00A75C65 /* AppAuthorizationEndpoint+Stubbing.swift */,
+				D03658D024EDD80900AC17EC /* ContextEndpoint+Stubbing.swift */,
 				D04FD73B24D4A83A007D572D /* InstanceEndpoint+Stubbing.swift */,
 				D0DC175124D008E300A75C65 /* MastodonTarget+Stubbing.swift */,
 				D0A652AC24DE3EB6002EA33F /* PreferencesEndpoint+Stubbing.swift */,
@@ -963,17 +983,20 @@
 				D075817924E6657B0081F6A3 /* NotificationTypesPreferencesViewModel.swift in Sources */,
 				D0ED1BD724CF94B200B4899C /* Application.swift in Sources */,
 				D047FAAE24C3E21200AF17C5 /* MetatextApp.swift in Sources */,
+				D03658D124EDD80900AC17EC /* ContextEndpoint+Stubbing.swift in Sources */,
 				D0BEC94724CA22C400E864C4 /* StatusesViewModel.swift in Sources */,
 				D0666A4E24C6C39600F3F04B /* Instance.swift in Sources */,
 				D057426724E9FE1D00839EBA /* ContentDatabase.swift in Sources */,
 				D054951524EB1053008B00A5 /* TimelineService.swift in Sources */,
 				D019E6E924DF72E700697C7D /* InstanceEndpoint.swift in Sources */,
 				D0ED1BE324CFA84400B4899C /* MastodonError.swift in Sources */,
+				D020F50E24ECA25F005AB084 /* ContextEndpoint.swift in Sources */,
 				D0EC8DE824E21FEC00A08489 /* Data+Extensions.swift in Sources */,
 				D0666A6324C6DC6C00F3F04B /* AppAuthorization.swift in Sources */,
 				D05494F024EA3FE5008B00A5 /* Card.swift in Sources */,
 				D019E6E524DF72E700697C7D /* AccountEndpoint.swift in Sources */,
 				D075817C24E6659A0081F6A3 /* NotificationTypesPreferencesView.swift in Sources */,
+				D020F51424ECBA60005AB084 /* LazyView.swift in Sources */,
 				D065F53B24D3B33A00741304 /* View+Extensions.swift in Sources */,
 				D0DC174A24CFF15F00A75C65 /* AppAuthorizationEndpoint+Stubbing.swift in Sources */,
 				D05494E424EA3EF7008B00A5 /* Tag.swift in Sources */,
@@ -1004,6 +1027,7 @@
 				D0BEC93B24C96FD500E864C4 /* RootView.swift in Sources */,
 				D04FD74224D4AA34007D572D /* DevelopmentModels.swift in Sources */,
 				D0EC8DC524DF842700A08489 /* KeychainService.swift in Sources */,
+				D020F50B24EC9F1D005AB084 /* ContextService.swift in Sources */,
 				D0DC175824D0130800A75C65 /* HTTPStubs.swift in Sources */,
 				D0DC177724D0CF2600A75C65 /* MockKeychainService.swift in Sources */,
 				D0EC8DC224DF7D9C00A08489 /* IdentityService.swift in Sources */,
@@ -1042,6 +1066,7 @@
 				D0EC8DCE24DFB64200A08489 /* AuthenticationService.swift in Sources */,
 				D04FD73C24D4A83A007D572D /* InstanceEndpoint+Stubbing.swift in Sources */,
 				D0DC175B24D0154F00A75C65 /* MastodonAPI.swift in Sources */,
+				D020F51124ECA309005AB084 /* MastodonContext.swift in Sources */,
 				D0ED1BD124CF779B00B4899C /* MastodonTarget.swift in Sources */,
 				D0CD847C24DBEA9F00CF380C /* Unknowable.swift in Sources */,
 				D0666A6F24C6DFB300F3F04B /* AccessToken.swift in Sources */,
@@ -1108,6 +1133,7 @@
 				D054951624EB1053008B00A5 /* TimelineService.swift in Sources */,
 				D019E6D824DF728400697C7D /* MastodonEncoder.swift in Sources */,
 				D054951C24EB2825008B00A5 /* TransientStatusCollection.swift in Sources */,
+				D03658D224EDD80900AC17EC /* ContextEndpoint+Stubbing.swift in Sources */,
 				D0DC174E24CFF1F100A75C65 /* Stubbing.swift in Sources */,
 				D0091B6C24DC10CE0040E8D2 /* PostingReadingPreferencesViewModel.swift in Sources */,
 				D0091B6F24DD68090040E8D2 /* PreferencesView.swift in Sources */,
@@ -1121,6 +1147,7 @@
 				D019E6F124DF7C2F00697C7D /* DatabaseError.swift in Sources */,
 				D074577824D29006004758DB /* MockWebAuthSession.swift in Sources */,
 				D057426E24EA339300839EBA /* ListTimeline.swift in Sources */,
+				D020F51224ECA309005AB084 /* MastodonContext.swift in Sources */,
 				D0ED1BCF24CF768200B4899C /* MastodonEndpoint.swift in Sources */,
 				D074577B24D29366004758DB /* URLSessionConfiguration+Extensions.swift in Sources */,
 				D0ED1BB824CE47F400B4899C /* WebAuthSession.swift in Sources */,
@@ -1133,8 +1160,11 @@
 				D019E6E824DF72E700697C7D /* AccessTokenEndpoint.swift in Sources */,
 				D04FD73D24D4A83A007D572D /* InstanceEndpoint+Stubbing.swift in Sources */,
 				D0DC175C24D0154F00A75C65 /* MastodonAPI.swift in Sources */,
+				D020F51524ECBA60005AB084 /* LazyView.swift in Sources */,
 				D0ED1BD224CF779B00B4899C /* MastodonTarget.swift in Sources */,
 				D0EC8DC624DF842700A08489 /* KeychainService.swift in Sources */,
+				D020F50C24EC9F1D005AB084 /* ContextService.swift in Sources */,
+				D020F50F24ECA25F005AB084 /* ContextEndpoint.swift in Sources */,
 				D0CD847D24DBEA9F00CF380C /* Unknowable.swift in Sources */,
 				D0666A7024C6DFB300F3F04B /* AccessToken.swift in Sources */,
 				D0ED1BCC24CF744200B4899C /* MastodonClient.swift in Sources */,

Shared/Databases/ContentDatabase.swift

@@ -56,6 +56,26 @@ extension ContentDatabase {
             .map { $0.map(Status.init(statusResult:)) }
             .eraseToAnyPublisher()
     }
+
+    func statusesObservation(collection: TransientStatusCollection) -> AnyPublisher<[Status], Error> {
+        ValueObservation.tracking {
+            try StatusResult.fetchAll(
+                $0,
+                StoredStatus.filter(
+                    try collection
+                        .elements
+                        .fetchAll($0)
+                        .map(\.statusId)
+                        .contains(Column("id")))
+                    .including(required: StoredStatus.account)
+                    .including(optional: StoredStatus.reblogAccount)
+                    .including(optional: StoredStatus.reblog))
+        }
+        .removeDuplicates()
+        .publisher(in: databaseQueue)
+        .map { $0.map(Status.init(statusResult:)) }
+        .eraseToAnyPublisher()
+    }
 }
 
 private extension ContentDatabase {

Shared/Model/MastodonContext.swift

@@ -0,0 +1,8 @@
+// Copyright © 2020 Metabolist. All rights reserved.
+
+import Foundation
+
+struct MastodonContext: Codable, Hashable {
+    let ancestors: [Status]
+    let descendants: [Status]
+}

Shared/Model/Status.swift

@@ -105,3 +105,69 @@ class Status: Codable, Identifiable {
         self.pinned = pinned
     }
 }
+
+extension Status: Hashable {
+    static func == (lhs: Status, rhs: Status) -> Bool {
+        lhs.id == rhs.id
+            && lhs.uri == rhs.uri
+            && lhs.createdAt == rhs.createdAt
+            && lhs.account == rhs.account
+            && lhs.content == rhs.content
+            && lhs.visibility == rhs.visibility
+            && lhs.sensitive == rhs.sensitive
+            && lhs.spoilerText == rhs.spoilerText
+            && lhs.mediaAttachments == rhs.mediaAttachments
+            && lhs.mentions == rhs.mentions
+            && lhs.tags == rhs.tags
+            && lhs.emojis == rhs.emojis
+            && lhs.reblogsCount == rhs.reblogsCount
+            && lhs.favouritesCount == rhs.favouritesCount
+            && lhs.repliesCount == rhs.repliesCount
+            && lhs.application == rhs.application
+            && lhs.url == rhs.url
+            && lhs.inReplyToId == rhs.inReplyToId
+            && lhs.inReplyToAccountId == rhs.inReplyToAccountId
+            && lhs.reblog == rhs.reblog
+            && lhs.poll == rhs.poll
+            && lhs.card == rhs.card
+            && lhs.language == rhs.language
+            && lhs.text == rhs.text
+            && lhs.favourited == rhs.favourited
+            && lhs.reblogged == rhs.reblogged
+            && lhs.muted == rhs.muted
+            && lhs.bookmarked == rhs.bookmarked
+            && lhs.pinned == rhs.pinned
+    }
+
+    func hash(into hasher: inout Hasher) {
+        hasher.combine(id)
+        hasher.combine(uri)
+        hasher.combine(createdAt)
+        hasher.combine(account)
+        hasher.combine(content)
+        hasher.combine(visibility)
+        hasher.combine(sensitive)
+        hasher.combine(spoilerText)
+        hasher.combine(mediaAttachments)
+        hasher.combine(mentions)
+        hasher.combine(tags)
+        hasher.combine(emojis)
+        hasher.combine(reblogsCount)
+        hasher.combine(favouritesCount)
+        hasher.combine(repliesCount)
+        hasher.combine(application)
+        hasher.combine(url)
+        hasher.combine(inReplyToId)
+        hasher.combine(inReplyToAccountId)
+        hasher.combine(reblog)
+        hasher.combine(poll)
+        hasher.combine(card)
+        hasher.combine(language)
+        hasher.combine(text)
+        hasher.combine(favourited)
+        hasher.combine(reblogged)
+        hasher.combine(muted)
+        hasher.combine(bookmarked)
+        hasher.combine(pinned)
+    }
+}

Shared/Networking/Mastodon API/Endpoints/ContextEndpoint.swift

@@ -0,0 +1,24 @@
+// Copyright © 2020 Metabolist. All rights reserved.
+
+import Foundation
+
+enum ContextEndpoint {
+    case context(id: String)
+}
+
+extension ContextEndpoint: MastodonEndpoint {
+    typealias ResultType = MastodonContext
+
+    var context: [String] {
+        defaultContext + ["statuses"]
+    }
+
+    var pathComponentsInContext: [String] {
+        switch self {
+        case let .context(id):
+            return [id, "context"]
+        }
+    }
+
+    var method: HTTPMethod { .get }
+}

Shared/Services/Status List Services/ContextService.swift

@@ -0,0 +1,48 @@
+// Copyright © 2020 Metabolist. All rights reserved.
+
+import Foundation
+import Combine
+
+struct ContextService {
+    let statusSections: AnyPublisher<[[Status]], Error>
+
+    private var status: Status
+    private let context = CurrentValueSubject<MastodonContext, Never>(MastodonContext(ancestors: [], descendants: []))
+    private let networkClient: MastodonClient
+    private let contentDatabase: ContentDatabase
+    private let collection: TransientStatusCollection
+
+    init(status: Status, networkClient: MastodonClient, contentDatabase: ContentDatabase) {
+        self.status = status
+        self.networkClient = networkClient
+        self.contentDatabase = contentDatabase
+        collection = TransientStatusCollection(id: "context-\(status.id)")
+        statusSections = contentDatabase.statusesObservation(collection: collection)
+            .combineLatest(context.setFailureType(to: Error.self))
+            .map { statuses, context in
+                [
+                    context.ancestors.map { a in statuses.first { $0.id == a.id } ?? a },
+                    [statuses.first { $0.id == status.id } ?? status],
+                    context.descendants.map { d in statuses.first { $0.id == d.id } ?? d }
+                ]
+            }
+            .removeDuplicates()
+            .eraseToAnyPublisher()
+    }
+}
+
+extension ContextService: StatusListService {
+    var contextParent: Status? { status }
+
+    func request(maxID: String?, minID: String?) -> AnyPublisher<Void, Error> {
+        networkClient.request(ContextEndpoint.context(id: status.id))
+            .handleEvents(receiveOutput: context.send)
+            .map { ($0.ancestors + $0.descendants, collection) }
+            .flatMap(contentDatabase.insert(statuses:collection:))
+            .eraseToAnyPublisher()
+    }
+
+    func contextService(status: Status) -> ContextService {
+        ContextService(status: status, networkClient: networkClient, contentDatabase: contentDatabase)
+    }
+}

Shared/Services/Status List Services/StatusListService.swift

@@ -5,5 +5,11 @@ import Combine
 
 protocol StatusListService {
     var statusSections: AnyPublisher<[[Status]], Error> { get }
+    var contextParent: Status? { get }
     func request(maxID: String?, minID: String?) -> AnyPublisher<Void, Error>
+    func contextService(status: Status) -> ContextService
+}
+
+extension StatusListService {
+    var contextParent: Status? { nil }
 }

Shared/Services/Status List Services/TimelineService.swift

@@ -3,7 +3,7 @@
 import Foundation
 import Combine
 
-struct TimelineService: StatusListService {
+struct TimelineService {
     let statusSections: AnyPublisher<[[Status]], Error>
 
     private let timeline: Timeline
@@ -18,11 +18,17 @@ struct TimelineService: StatusListService {
             .map { [$0] }
             .eraseToAnyPublisher()
     }
+}
 
+extension TimelineService: StatusListService {
     func request(maxID: String?, minID: String?) -> AnyPublisher<Void, Error> {
         return networkClient.request(timeline.endpoint)
             .map { ($0, timeline) }
             .flatMap(contentDatabase.insert(statuses:collection:))
             .eraseToAnyPublisher()
     }
+
+    func contextService(status: Status) -> ContextService {
+        ContextService(status: status, networkClient: networkClient, contentDatabase: contentDatabase)
+    }
 }

Shared/View Models/StatusesViewModel.swift

@@ -4,25 +4,53 @@ import Foundation
 import Combine
 
 class StatusesViewModel: ObservableObject {
-    @Published var statusSections = [[Status]]()
+    @Published private(set) var statusSections = [[Status]]()
     @Published var alertItem: AlertItem?
+    @Published private(set) var loading = false
+    let scrollToStatusID: AnyPublisher<String, Never>
     private let statusListService: StatusListService
+    private let scrollToStatusIDInput = PassthroughSubject<String, Never>()
+    private var hasScrolledToParentAfterContextLoad = false
     private var cancellables = Set<AnyCancellable>()
 
     init(statusListService: StatusListService) {
         self.statusListService = statusListService
+        scrollToStatusID = scrollToStatusIDInput.eraseToAnyPublisher()
 
         statusListService.statusSections
             .assignErrorsToAlertItem(to: \.alertItem, on: self)
             .assign(to: &$statusSections)
+
+        $statusSections
+            .sink { [weak self] in
+            guard let self = self else { return }
+
+            if
+                let contextParent = self.contextParent,
+                !($0.first ?? []).isEmpty || !(($0.last ?? []).isEmpty),
+                !self.hasScrolledToParentAfterContextLoad {
+                self.hasScrolledToParentAfterContextLoad = true
+                self.scrollToStatusIDInput.send(contextParent.id)
+            }
+        }
+        .store(in: &cancellables)
     }
 }
 
 extension StatusesViewModel {
+    var contextParent: Status? { statusListService.contextParent }
+
     func request(maxID: String? = nil, minID: String? = nil) {
         statusListService.request(maxID: maxID, minID: minID)
             .assignErrorsToAlertItem(to: \.alertItem, on: self)
+            .handleEvents(
+                receiveSubscription: { [weak self] _ in self?.loading = true },
+                receiveCompletion: { [weak self] _ in self?.loading = false })
             .sink {}
             .store(in: &cancellables)
     }
+
+    func contextViewModel(status: Status) -> StatusesViewModel {
+        StatusesViewModel(statusListService: statusListService.contextService(status: status))
+    }
 }

Shared/Views/LazyView.swift

@@ -0,0 +1,17 @@
+// Copyright © 2020 Metabolist. All rights reserved.
+
+import SwiftUI
+
+struct LazyView<V: View>: View {
+    typealias RenderClosure = () -> V
+
+    let render: RenderClosure
+
+    init(_ render: @autoclosure @escaping RenderClosure) {
+        self.render = render
+    }
+
+    var body: V {
+        render()
+    }
+}

Shared/Views/StatusesView.swift

@@ -6,15 +6,34 @@ struct StatusesView: View {
     @StateObject var viewModel: StatusesViewModel
 
     var body: some View {
+        ScrollViewReader { scrollViewProxy in
             ScrollView {
                 LazyVStack {
                     ForEach(Array(zip(viewModel.statusSections.indices, viewModel.statusSections)),
                             id: \.0) { _, statuses in
                         ForEach(statuses) { status in
-                        Text(status.content)
+                            if status == viewModel.contextParent {
+                                statusView(status: status)
+                            } else {
+                                NavigationLink(destination:
+                                                LazyView(StatusesView(viewModel:
+                                                                        viewModel.contextViewModel(status: status)))) {
+                                    statusView(status: status)
+                                }
+                                .buttonStyle(PlainButtonStyle())
+                            }
                             Divider()
                         }
                     }
+                    if viewModel.loading {
+                        ProgressView()
+                    }
+                }
+            }
+            .onReceive(viewModel.scrollToStatusID.receive(on: DispatchQueue.main)) { id in
+                withAnimation {
+                    scrollViewProxy.scrollTo(id)
+                }
             }
         }
         .onAppear { viewModel.request() }
@@ -22,6 +41,12 @@ struct StatusesView: View {
     }
 }
 
+private extension StatusesView {
+    func statusView(status: Status) -> some View {
+        Text(status.content)
+    }
+}
+
 #if DEBUG
 struct StatusesView_Previews: PreviewProvider {
     static var previews: some View {