Multiple identities

Development Assets/DevelopmentModels.swift

@@ -123,11 +123,15 @@ extension RootViewModel {
 }
 
 extension MainNavigationViewModel {
-    static let development = RootViewModel.development.mainNavigationViewModel(identityID: devIdentityID)!
+    static let development = try! MainNavigationViewModel(identityID: devIdentityID, environment: .development)
 }
 
 extension SettingsViewModel {
     static let development = MainNavigationViewModel.development.settingsViewModel()
 }
 
+extension IdentitiesViewModel {
+    static let development = SettingsViewModel.development.identitiesViewModel()
+}
+
 // swiftlint:enable force_try

Metatext.xcodeproj/project.pbxproj

@@ -30,8 +30,6 @@
 		D052BBD224D750CB00A80A7A /* AppEnvironment.swift in Sources */ = {isa = PBXBuildFile; fileRef = D052BBCC24D750A100A80A7A /* AppEnvironment.swift */; };
 		D052BBE024D805E300A80A7A /* MainNavigationViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = D052BBDF24D805E300A80A7A /* MainNavigationViewModel.swift */; };
 		D052BBE124D805E300A80A7A /* MainNavigationViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = D052BBDF24D805E300A80A7A /* MainNavigationViewModel.swift */; };
-		D052BBE424D81C4700A80A7A /* CurrentValuePublisher.swift in Sources */ = {isa = PBXBuildFile; fileRef = D052BBE324D81C4700A80A7A /* CurrentValuePublisher.swift */; };
-		D052BBE524D81C4700A80A7A /* CurrentValuePublisher.swift in Sources */ = {isa = PBXBuildFile; fileRef = D052BBE324D81C4700A80A7A /* CurrentValuePublisher.swift */; };
 		D065F53924D37E5100741304 /* CombineExpectations in Frameworks */ = {isa = PBXBuildFile; productRef = D065F53824D37E5100741304 /* CombineExpectations */; };
 		D065F53B24D3B33A00741304 /* View+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = D065F53A24D3B33A00741304 /* View+Extensions.swift */; };
 		D065F53C24D3B33A00741304 /* View+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = D065F53A24D3B33A00741304 /* View+Extensions.swift */; };
@@ -65,6 +63,10 @@
 		D06B492024D3FB8000642749 /* Localizable.strings in Resources */ = {isa = PBXBuildFile; fileRef = D06B491E24D3F7FE00642749 /* Localizable.strings */; };
 		D06B492324D4611300642749 /* KingfisherSwiftUI in Frameworks */ = {isa = PBXBuildFile; productRef = D06B492224D4611300642749 /* KingfisherSwiftUI */; };
 		D06B492524D4612400642749 /* KingfisherSwiftUI in Frameworks */ = {isa = PBXBuildFile; productRef = D06B492424D4612400642749 /* KingfisherSwiftUI */; };
+		D06BAB4E24D942BD0081B8FD /* IdentitiesViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = D06BAB4D24D942BC0081B8FD /* IdentitiesViewModel.swift */; };
+		D06BAB4F24D942BD0081B8FD /* IdentitiesViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = D06BAB4D24D942BC0081B8FD /* IdentitiesViewModel.swift */; };
+		D06BAB5124D942CF0081B8FD /* IdentitiesView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D06BAB5024D942CF0081B8FD /* IdentitiesView.swift */; };
+		D06BAB5224D942CF0081B8FD /* IdentitiesView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D06BAB5024D942CF0081B8FD /* IdentitiesView.swift */; };
 		D074577724D29006004758DB /* StubbingWebAuthSession.swift in Sources */ = {isa = PBXBuildFile; fileRef = D074577624D29006004758DB /* StubbingWebAuthSession.swift */; };
 		D074577824D29006004758DB /* StubbingWebAuthSession.swift in Sources */ = {isa = PBXBuildFile; fileRef = D074577624D29006004758DB /* StubbingWebAuthSession.swift */; };
 		D074577A24D29366004758DB /* URLSessionConfiguration+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = D074577924D29366004758DB /* URLSessionConfiguration+Extensions.swift */; };
@@ -73,8 +75,6 @@
 		D081A40624D0F1A8001B016E /* String+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = D081A40424D0F1A8001B016E /* String+Extensions.swift */; };
 		D0B23F0D24D210E90066F411 /* NSError+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0B23F0C24D210E90066F411 /* NSError+Extensions.swift */; };
 		D0B23F0E24D210E90066F411 /* NSError+Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0B23F0C24D210E90066F411 /* NSError+Extensions.swift */; };
-		D0B93B3024D55098007AF646 /* Screen.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0B93B2F24D55098007AF646 /* Screen.swift */; };
-		D0B93B3124D55098007AF646 /* Screen.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0B93B2F24D55098007AF646 /* Screen.swift */; };
 		D0BEC93824C9632800E864C4 /* RootViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0BEC93724C9632800E864C4 /* RootViewModel.swift */; };
 		D0BEC93924C9632800E864C4 /* RootViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0BEC93724C9632800E864C4 /* RootViewModel.swift */; };
 		D0BEC93B24C96FD500E864C4 /* RootView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0BEC93A24C96FD500E864C4 /* RootView.swift */; };
@@ -166,7 +166,6 @@
 		D052BBCC24D750A100A80A7A /* AppEnvironment.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppEnvironment.swift; sourceTree = "<group>"; };
 		D052BBCE24D750C000A80A7A /* Preferences.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Preferences.swift; sourceTree = "<group>"; };
 		D052BBDF24D805E300A80A7A /* MainNavigationViewModel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MainNavigationViewModel.swift; sourceTree = "<group>"; };
-		D052BBE324D81C4700A80A7A /* CurrentValuePublisher.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CurrentValuePublisher.swift; sourceTree = "<group>"; };
 		D065F53A24D3B33A00741304 /* View+Extensions.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "View+Extensions.swift"; sourceTree = "<group>"; };
 		D065F53D24D3D20300741304 /* InstanceEndpoint.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = InstanceEndpoint.swift; sourceTree = "<group>"; };
 		D0666A2124C677B400F3F04B /* Tests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = Tests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -183,11 +182,12 @@
 		D0666A6E24C6DFB300F3F04B /* AccessToken.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AccessToken.swift; sourceTree = "<group>"; };
 		D0666A7124C6E0D300F3F04B /* Secrets.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Secrets.swift; sourceTree = "<group>"; };
 		D06B491E24D3F7FE00642749 /* Localizable.strings */ = {isa = PBXFileReference; lastKnownFileType = text.plist.strings; path = Localizable.strings; sourceTree = "<group>"; };
+		D06BAB4D24D942BC0081B8FD /* IdentitiesViewModel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = IdentitiesViewModel.swift; sourceTree = "<group>"; };
+		D06BAB5024D942CF0081B8FD /* IdentitiesView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = IdentitiesView.swift; sourceTree = "<group>"; };
 		D074577624D29006004758DB /* StubbingWebAuthSession.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = StubbingWebAuthSession.swift; sourceTree = "<group>"; };
 		D074577924D29366004758DB /* URLSessionConfiguration+Extensions.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "URLSessionConfiguration+Extensions.swift"; sourceTree = "<group>"; };
 		D081A40424D0F1A8001B016E /* String+Extensions.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "String+Extensions.swift"; sourceTree = "<group>"; };
 		D0B23F0C24D210E90066F411 /* NSError+Extensions.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "NSError+Extensions.swift"; sourceTree = "<group>"; };
-		D0B93B2F24D55098007AF646 /* Screen.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Screen.swift; sourceTree = "<group>"; };
 		D0BEC93724C9632800E864C4 /* RootViewModel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RootViewModel.swift; sourceTree = "<group>"; };
 		D0BEC93A24C96FD500E864C4 /* RootView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RootView.swift; sourceTree = "<group>"; };
 		D0BEC94624CA22C400E864C4 /* TimelineViewModel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TimelineViewModel.swift; sourceTree = "<group>"; };
@@ -275,7 +275,6 @@
 				D047FA8524C3E21000AF17C5 /* MetatextApp.swift */,
 				D0666A3A24C6B56200F3F04B /* Model */,
 				D0DB6EFA24C5730600D965FE /* Networking */,
-				D052BBE224D81C2300A80A7A /* Publishers */,
 				D0DB6EFB24C658E400D965FE /* View Models */,
 				D0DB6EF024C5224F00D965FE /* Views */,
 			);
@@ -311,14 +310,6 @@
 			path = macOS;
 			sourceTree = "<group>";
 		};
-		D052BBE224D81C2300A80A7A /* Publishers */ = {
-			isa = PBXGroup;
-			children = (
-				D052BBE324D81C4700A80A7A /* CurrentValuePublisher.swift */,
-			);
-			path = Publishers;
-			sourceTree = "<group>";
-		};
 		D0666A2224C677B400F3F04B /* Tests */ = {
 			isa = PBXGroup;
 			children = (
@@ -369,8 +360,8 @@
 			isa = PBXGroup;
 			children = (
 				D0DB6EF324C5228A00D965FE /* AddIdentityView.swift */,
+				D06BAB5024D942CF0081B8FD /* IdentitiesView.swift */,
 				D0BEC93A24C96FD500E864C4 /* RootView.swift */,
-				D0B93B2F24D55098007AF646 /* Screen.swift */,
 				D04FD73224D48F37007D572D /* SettingsView.swift */,
 				D0BEC94924CA231200E864C4 /* TimelineView.swift */,
 			);
@@ -394,6 +385,7 @@
 			isa = PBXGroup;
 			children = (
 				D0DB6F0824C65AC000D965FE /* AddIdentityViewModel.swift */,
+				D06BAB4D24D942BC0081B8FD /* IdentitiesViewModel.swift */,
 				D052BBDF24D805E300A80A7A /* MainNavigationViewModel.swift */,
 				D0BEC93724C9632800E864C4 /* RootViewModel.swift */,
 				D04FD73524D49506007D572D /* SettingsViewModel.swift */,
@@ -670,9 +662,7 @@
 				D0666A5A24C6C64100F3F04B /* MastodonEncoder.swift in Sources */,
 				D0666A5124C6C3BC00F3F04B /* Account.swift in Sources */,
 				D0ED1BE024CF98FB00B4899C /* AccountEndpoint.swift in Sources */,
-				D0B93B3024D55098007AF646 /* Screen.swift in Sources */,
 				D052BBD224D750CB00A80A7A /* AppEnvironment.swift in Sources */,
-				D052BBE424D81C4700A80A7A /* CurrentValuePublisher.swift in Sources */,
 				D081A40524D0F1A8001B016E /* String+Extensions.swift in Sources */,
 				D0BEC93824C9632800E864C4 /* RootViewModel.swift in Sources */,
 				D0ED1BC124CED48800B4899C /* HTTPClient.swift in Sources */,
@@ -683,6 +673,7 @@
 				D0DC175524D00F0A00A75C65 /* AccessTokenEndpoint+Stubbing.swift in Sources */,
 				D0B23F0D24D210E90066F411 /* NSError+Extensions.swift in Sources */,
 				D052BBCA24D74C9200A80A7A /* FakeUserDefaults.swift in Sources */,
+				D06BAB4E24D942BD0081B8FD /* IdentitiesViewModel.swift in Sources */,
 				D0DC175224D008E300A75C65 /* MastodonTarget+Stubbing.swift in Sources */,
 				D0666A4224C6BB7B00F3F04B /* IdentityDatabase.swift in Sources */,
 				D0BEC94A24CA231200E864C4 /* TimelineView.swift in Sources */,
@@ -697,6 +688,7 @@
 				D0666A5724C6C63400F3F04B /* MastodonDecoder.swift in Sources */,
 				D0DB6EF424C5228A00D965FE /* AddIdentityView.swift in Sources */,
 				D0DC177424D0B58800A75C65 /* Keychain.swift in Sources */,
+				D06BAB5124D942CF0081B8FD /* IdentitiesView.swift in Sources */,
 				D074577724D29006004758DB /* StubbingWebAuthSession.swift in Sources */,
 				D0ED1BCE24CF768200B4899C /* MastodonEndpoint.swift in Sources */,
 				D074577A24D29366004758DB /* URLSessionConfiguration+Extensions.swift in Sources */,
@@ -735,9 +727,7 @@
 				D0666A5B24C6C64100F3F04B /* MastodonEncoder.swift in Sources */,
 				D0666A5224C6C3BC00F3F04B /* Account.swift in Sources */,
 				D0ED1BE124CF98FB00B4899C /* AccountEndpoint.swift in Sources */,
-				D0B93B3124D55098007AF646 /* Screen.swift in Sources */,
 				D052BBD124D750CA00A80A7A /* AppEnvironment.swift in Sources */,
-				D052BBE524D81C4700A80A7A /* CurrentValuePublisher.swift in Sources */,
 				D081A40624D0F1A8001B016E /* String+Extensions.swift in Sources */,
 				D0BEC93924C9632800E864C4 /* RootViewModel.swift in Sources */,
 				D0ED1BC224CED48800B4899C /* HTTPClient.swift in Sources */,
@@ -748,6 +738,7 @@
 				D0DC175624D00F0A00A75C65 /* AccessTokenEndpoint+Stubbing.swift in Sources */,
 				D0B23F0E24D210E90066F411 /* NSError+Extensions.swift in Sources */,
 				D052BBCB24D74C9300A80A7A /* FakeUserDefaults.swift in Sources */,
+				D06BAB4F24D942BD0081B8FD /* IdentitiesViewModel.swift in Sources */,
 				D0DC175324D008E300A75C65 /* MastodonTarget+Stubbing.swift in Sources */,
 				D0666A4324C6BB7B00F3F04B /* IdentityDatabase.swift in Sources */,
 				D0BEC94B24CA231200E864C4 /* TimelineView.swift in Sources */,
@@ -762,6 +753,7 @@
 				D0666A5824C6C63400F3F04B /* MastodonDecoder.swift in Sources */,
 				D0DB6EF524C5233E00D965FE /* AddIdentityView.swift in Sources */,
 				D0DC177524D0B58800A75C65 /* Keychain.swift in Sources */,
+				D06BAB5224D942CF0081B8FD /* IdentitiesView.swift in Sources */,
 				D074577824D29006004758DB /* StubbingWebAuthSession.swift in Sources */,
 				D0ED1BCF24CF768200B4899C /* MastodonEndpoint.swift in Sources */,
 				D074577B24D29366004758DB /* URLSessionConfiguration+Extensions.swift in Sources */,

Shared/Model/Identity.swift

@@ -2,9 +2,10 @@
 
 import Foundation
 
-struct Identity: Codable, Hashable {
+struct Identity: Codable, Hashable, Identifiable {
     let id: String
     let url: URL
+    let lastUsedAt: Date
     let instance: Identity.Instance?
     let account: Identity.Account?
 }

Shared/Model/IdentityDatabase.swift

@@ -31,10 +31,24 @@ struct IdentityDatabase {
 
 extension IdentityDatabase {
     func createIdentity(id: String, url: URL) -> AnyPublisher<Void, Error> {
-        databaseQueue.writePublisher(updates: StoredIdentity(id: id, url: url, instanceURI: nil).save)
+        databaseQueue.writePublisher(
+            updates: StoredIdentity(
+                id: id,
+                url: url,
+                lastUsedAt: Date(),
+                instanceURI: nil).save)
             .eraseToAnyPublisher()
     }
 
+    func updateLastUsedAt(identityID: String) -> AnyPublisher<Void, Error> {
+        databaseQueue.writePublisher {
+            try StoredIdentity
+                .filter(Column("id") == identityID)
+                .updateAll($0, Column("lastUsedAt").set(to: Date()))
+        }
+        .eraseToAnyPublisher()
+    }
+
     func updateInstance(_ instance: Instance, forIdentityID identityID: String) -> AnyPublisher<Void, Error> {
         databaseQueue.writePublisher {
             try Identity.Instance(
@@ -82,6 +96,29 @@ extension IdentityDatabase {
             }
             .eraseToAnyPublisher()
     }
+
+    func identitiesObservation() -> AnyPublisher<[Identity], Error> {
+        ValueObservation.tracking(
+            StoredIdentity
+                .including(optional: StoredIdentity.instance)
+                .including(optional: StoredIdentity.account)
+                .asRequest(of: IdentityResult.self).fetchAll)
+            .removeDuplicates()
+            .publisher(in: databaseQueue, scheduling: .immediate)
+            .map { $0.map(Identity.init(result:)) }
+            .eraseToAnyPublisher()
+    }
+
+    func identityCountObservation() -> AnyPublisher<Int, Error> {
+        ValueObservation.tracking(StoredIdentity.fetchCount)
+            .removeDuplicates()
+            .publisher(in: databaseQueue, scheduling: .immediate)
+            .eraseToAnyPublisher()
+    }
+
+    var mostRecentlyUsedIdentityID: String? {
+        try? databaseQueue.read(StoredIdentity.select(Column("id")).order(Column("lastUsedAt").desc).fetchOne)
+    }
 }
 
 private extension IdentityDatabase {
@@ -99,6 +136,7 @@ private extension IdentityDatabase {
             try db.create(table: "storedIdentity", ifNotExists: true) { t in
                 t.column("id", .text).notNull().primaryKey(onConflict: .replace)
                 t.column("url", .text).notNull()
+                t.column("lastUsedAt", .datetime).notNull()
                 t.column("instanceURI", .text)
                     .indexed()
                     .references("instance", column: "uri")
@@ -126,6 +164,7 @@ private extension IdentityDatabase {
 private struct StoredIdentity: Codable, Hashable, TableRecord, FetchableRecord, PersistableRecord {
     let id: String
     let url: URL
+    let lastUsedAt: Date
     let instanceURI: String?
 }
 
@@ -150,7 +189,12 @@ private struct IdentityResult: Codable, Hashable, FetchableRecord {
 
 private extension Identity {
     init(result: IdentityResult) {
-        self.init(id: result.identity.id, url: result.identity.url, instance: result.instance, account: result.account)
+        self.init(
+            id: result.identity.id,
+            url: result.identity.url,
+            lastUsedAt: result.identity.lastUsedAt,
+            instance: result.instance,
+            account: result.account)
     }
 }
 

Shared/Publishers/CurrentValuePublisher.swift

@@ -1,24 +0,0 @@
-// Copyright © 2020 Metabolist. All rights reserved.
-
-import Combine
-
-class CurrentValuePublisher<Output> {
-    @Published private var wrappedValue: Output
-
-    init<P>(initial: Output, then: P) where P: Publisher, P.Output == Output, P.Failure == Never {
-        wrappedValue = initial
-        then.assign(to: &$wrappedValue)
-    }
-}
-
-extension CurrentValuePublisher {
-    var value: Output { wrappedValue }
-}
-
-extension CurrentValuePublisher: Publisher {
-    typealias Failure = Never
-
-    func receive<S>(subscriber: S) where S: Subscriber, S.Input == Output, S.Failure == Never {
-        $wrappedValue.receive(subscriber: subscriber)
-    }
-}

Shared/View Models/AddIdentityViewModel.swift

@@ -179,11 +179,7 @@ private extension Publisher where Output == AccessToken {
             return (id, instanceURL)
         }
         .flatMap(environment.identityDatabase.createIdentity)
-        .map {
+        .map { id }
-            environment.preferences[.recentIdentityID] = id
-
-            return id
-        }
         .eraseToAnyPublisher()
     }
 }

Shared/View Models/IdentitiesViewModel.swift

@@ -0,0 +1,31 @@
+// Copyright © 2020 Metabolist. All rights reserved.
+
+import Combine
+import Foundation
+
+class IdentitiesViewModel: ObservableObject {
+    @Published private(set) var identity: Identity
+    @Published var identities = [Identity]()
+    @Published var alertItem: AlertItem?
+
+    private let environment: AppEnvironment
+    private var cancellables = Set<AnyCancellable>()
+
+    init(identity: Published<Identity>, environment: AppEnvironment) {
+        _identity = identity
+        self.environment = environment
+
+        environment.identityDatabase.identitiesObservation()
+            .assignErrorsToAlertItem(to: \.alertItem, on: self)
+            .assign(to: &$identities)
+    }
+}
+
+extension IdentitiesViewModel {
+    func identitySelected(id: String) {
+        environment.identityDatabase.updateLastUsedAt(identityID: id)
+            .assignErrorsToAlertItem(to: \.alertItem, on: self)
+            .sink(receiveValue: {})
+            .store(in: &cancellables)
+    }
+}

Shared/View Models/MainNavigationViewModel.swift

@@ -4,41 +4,50 @@ import Foundation
 import Combine
 
 class MainNavigationViewModel: ObservableObject {
-    var selectedTab: Tab? = .timelines
+    @Published private(set) var identity: Identity
     @Published var presentingSettings = false
-    @Published private(set) var alertItem: AlertItem?
+    @Published var alertItem: AlertItem?
-    @Published private(set) var handle: String
+    var selectedTab: Tab? = .timelines
-    @Published private(set) var image: URL?
 
     private let environment: AppEnvironment
-    private let identity: CurrentValuePublisher<Identity>
     private let networkClient: MastodonClient
     private var cancellables = Set<AnyCancellable>()
 
-    init(identity: CurrentValuePublisher<Identity>, environment: AppEnvironment) {
+    init(identityID: String, environment: AppEnvironment) throws {
-        self.identity = identity
         self.environment = environment
         networkClient = MastodonClient(configuration: environment.URLSessionConfiguration)
 
-        networkClient.instanceURL = identity.value.url
+        let observation = environment.identityDatabase.identityObservation(id: identityID).share()
+        var initialIdentity: Identity?
+
+        observation.first().sink(
+            receiveCompletion: { _ in },
+            receiveValue: { initialIdentity = $0 })
+            .store(in: &cancellables)
+
+        guard let identity = initialIdentity else { throw IdentityDatabaseError.identityNotFound }
+
+        self.identity = identity
+        networkClient.instanceURL = identity.url
 
         do {
-            networkClient.accessToken = try environment.secrets.item(.accessToken, forIdentityID: identity.value.id)
+            networkClient.accessToken = try environment.secrets.item(.accessToken, forIdentityID: identity.id)
         } catch {
             alertItem = AlertItem(error: error)
         }
 
-        handle = identity.value.handle
+        observation.assignErrorsToAlertItem(to: \.alertItem, on: self).assign(to: &$identity)
-        identity.map(\.handle).assign(to: &$handle)
 
-        image = identity.value.image
+        environment.identityDatabase.updateLastUsedAt(identityID: identityID)
-        identity.map(\.image).assign(to: &$image)
+            .assignErrorsToAlertItem(to: \.alertItem, on: self)
+            .sink(receiveValue: {})
+            .store(in: &cancellables)
     }
 }
 
 extension MainNavigationViewModel {
     func refreshIdentity() {
-        let id = identity.value.id
+        let id = identity.id
 
         if networkClient.accessToken != nil {
             networkClient.request(AccountEndpoint.verifyCredentials)
@@ -58,7 +67,7 @@ extension MainNavigationViewModel {
     }
 
     func settingsViewModel() -> SettingsViewModel {
-        SettingsViewModel(identity: identity, environment: environment)
+        SettingsViewModel(identity: _identity, environment: environment)
     }
 }
 

Shared/View Models/RootViewModel.swift

@@ -4,49 +4,39 @@ import Foundation
 import Combine
 
 class RootViewModel: ObservableObject {
-    @Published private(set) var identityID: String?
+    @Published private(set) var mainNavigationViewModel: MainNavigationViewModel?
-    @Published var alertItem: AlertItem?
 
+    @Published private var identityID: String?
     private let environment: AppEnvironment
     private var cancellables = Set<AnyCancellable>()
 
     init(environment: AppEnvironment) {
         self.environment = environment
-        identityID = environment.preferences[.recentIdentityID]
+        identityID = environment.identityDatabase.mostRecentlyUsedIdentityID
+
+        $identityID
+            .tryMap {
+                guard let id = $0 else { return nil }
+
+                return try MainNavigationViewModel(identityID: id, environment: environment)
+            }
+            .replaceError(with: nil)
+            .assign(to: &$mainNavigationViewModel)
     }
 }
 
 extension RootViewModel {
+    func newIdentitySelected(id: String) {
+        identityID = id
+    }
+
     func addIdentityViewModel() -> AddIdentityViewModel {
         let addAccountViewModel = AddIdentityViewModel(environment: environment)
 
-        addAccountViewModel.addedIdentityID.map { $0 as String? }.assign(to: &$identityID)
+        addAccountViewModel.addedIdentityID
+            .sink(receiveValue: newIdentitySelected(id:))
+            .store(in: &cancellables)
 
         return addAccountViewModel
     }
-
-    func mainNavigationViewModel(identityID: String) -> MainNavigationViewModel? {
-        environment.preferences[.recentIdentityID] = identityID
-
-        let identityObservation = environment.identityDatabase.identityObservation(id: identityID)
-            .share()
-        var initialIdentity: Identity?
-
-        // setting `initialIdentity` works because of immediate scheduling
-        identityObservation.sink(receiveCompletion: { _ in }, receiveValue: { initialIdentity = $0 })
-            .store(in: &cancellables)
-        identityObservation.map { $0.id }
-            .catch { [weak self] _ -> AnyPublisher<String?, Never> in
-                Just(self?.environment.preferences[.recentIdentityID]).eraseToAnyPublisher()
-            }
-            .assign(to: &$identityID)
-
-        guard let presentIdentity = initialIdentity else { return nil }
-
-        return MainNavigationViewModel(
-            identity: CurrentValuePublisher(
-                initial: presentIdentity,
-                then: identityObservation.assignErrorsToAlertItem(to: \.alertItem, on: self)),
-            environment: environment)
-    }
 }

Shared/View Models/SettingsViewModel.swift

@@ -3,11 +3,17 @@
 import Foundation
 
 class SettingsViewModel: ObservableObject {
-    private let identity: CurrentValuePublisher<Identity>
+    @Published private(set) var identity: Identity
     private let environment: AppEnvironment
 
-    init(identity: CurrentValuePublisher<Identity>, environment: AppEnvironment) {
+    init(identity: Published<Identity>, environment: AppEnvironment) {
-        self.identity = identity
+        _identity = identity
         self.environment = environment
     }
 }
+
+extension SettingsViewModel {
+    func identitiesViewModel() -> IdentitiesViewModel {
+        IdentitiesViewModel(identity: _identity, environment: environment)
+    }
+}

Shared/Views/IdentitiesView.swift

@@ -0,0 +1,33 @@
+// Copyright © 2020 Metabolist. All rights reserved.
+
+import SwiftUI
+
+struct IdentitiesView: View {
+    @StateObject var viewModel: IdentitiesViewModel
+    @EnvironmentObject var rootViewModel: RootViewModel
+
+    var body: some View {
+        Form {
+            Section {
+                NavigationLink(
+                    destination: AddIdentityView(viewModel: rootViewModel.addIdentityViewModel()),
+                    label: {
+                        Label("add new account", systemImage: "plus")
+                    })
+            }
+            Section {
+                List(viewModel.identities) { identity in
+                    Button(identity.handle) {
+                        rootViewModel.newIdentitySelected(id: identity.id)
+                    }
+                }
+            }
+        }
+    }
+}
+
+struct IdentitiesView_Previews: PreviewProvider {
+    static var previews: some View {
+        IdentitiesView(viewModel: .development)
+    }
+}

Shared/Views/RootView.swift

@@ -6,29 +6,27 @@ struct RootView: View {
     @StateObject var viewModel: RootViewModel
 
     var body: some View {
-        if
+        ZStack {
-            let identityID = viewModel.identityID,
+            if let mainNavigationViewModel = viewModel.mainNavigationViewModel {
-            let mainNavigationViewModel = viewModel.mainNavigationViewModel(identityID: identityID) {
+                Self.mainNavigation(mainNavigationViewModel: mainNavigationViewModel)
-            Self.mainNavigation(viewModel: mainNavigationViewModel)
+                    .environmentObject(viewModel)
-        } else {
+            } else {
-            addIdentity
+                AddIdentityView(viewModel: viewModel.addIdentityViewModel())
+            }
         }
     }
 }
 
 private extension RootView {
-    private static func mainNavigation(viewModel: MainNavigationViewModel) -> some View {
+    @ViewBuilder
+    private static func mainNavigation(mainNavigationViewModel: MainNavigationViewModel) -> some View {
         #if os(macOS)
-        return SidebarNavigation(viewModel: viewModel)
+        SidebarNavigation(viewModel: mainNavigationViewModel)
             .frame(minWidth: 900, maxWidth: .infinity, minHeight: 500, maxHeight: .infinity)
         #else
-        return TabNavigation(viewModel: viewModel)
+        TabNavigation(viewModel: mainNavigationViewModel)
         #endif
     }
-
-    private var addIdentity: some View {
-        AddIdentityView(viewModel: viewModel.addIdentityViewModel())
-    }
 }
 
 #if DEBUG

Shared/Views/Screen.swift

@@ -1,13 +0,0 @@
-// Copyright © 2020 Metabolist. All rights reserved.
-
-import SwiftUI
-
-struct Screen {
-    static var scale: CGFloat {
-        #if os(macOS)
-        return NSScreen.main?.backingScaleFactor ?? 1
-        #else
-        return UIScreen.main.scale
-        #endif
-    }
-}

Shared/Views/SettingsView.swift

@@ -6,34 +6,41 @@ import struct Kingfisher.DownsamplingImageProcessor
 
 struct SettingsView: View {
     @StateObject var viewModel: SettingsViewModel
-    @EnvironmentObject var mainNavigationViewModel: MainNavigationViewModel
+    @EnvironmentObject var rootViewModel: RootViewModel
+    @Environment(\.presentationMode) var presentationMode
+    @Environment(\.displayScale) var displayScale: CGFloat
 
     var body: some View {
         VStack(spacing: 0) {
             NavigationView {
                 Form {
                     HStack {
-                        KFImage(mainNavigationViewModel.image,
+                        KFImage(viewModel.identity.image,
                                 options: [
                                     .processor(
                                         DownsamplingImageProcessor(size: CGSize(width: 50, height: 50))
                                     ),
-                                    .scaleFactor(Screen.scale),
+                                    .scaleFactor(displayScale),
                                     .cacheOriginalImage
                                 ])
                             .clipShape(Circle())
-                        Text(mainNavigationViewModel.handle)
+                        Text(viewModel.identity.handle)
                             .font(.subheadline)
                     }
+                    NavigationLink(
+                        "accounts",
+                        destination: IdentitiesView(
+                            viewModel: viewModel.identitiesViewModel())
+                            .environmentObject(rootViewModel))
                 }
-                .navigationBarTitleAndItems(mainNavigationViewModel: mainNavigationViewModel)
+                .navigationBarTitleAndItems(presentationMode: presentationMode)
             }
             .navigationViewStyle
             #if os(macOS)
             Divider()
             HStack {
                 Spacer()
-                Button(action: { mainNavigationViewModel.presentingSettings.toggle() }) {
+                Button(action: { presentationMode.wrappedValue.dismiss() }) {
                     Text("Done")
                 }
                 .keyboardShortcut(.defaultAction)
@@ -47,12 +54,12 @@ struct SettingsView: View {
 }
 
 private extension View {
-    func navigationBarTitleAndItems(mainNavigationViewModel: MainNavigationViewModel) -> some View {
+    func navigationBarTitleAndItems(presentationMode: Binding<PresentationMode>) -> some View {
         #if os(iOS)
         return navigationBarTitle(Text("settings"), displayMode: .inline)
         .navigationBarItems(
             leading: Button {
-                mainNavigationViewModel.presentingSettings.toggle()
+                presentationMode.wrappedValue.dismiss()
             } label: {
                 Image(systemName: "xmark.circle.fill").imageScale(.large)
             })
@@ -83,6 +90,7 @@ struct SettingsView_Previews: PreviewProvider {
     static var previews: some View {
         SettingsView(viewModel: .development)
             .environmentObject(MainNavigationViewModel.development)
+            .environmentObject(RootViewModel.development)
     }
 }
 #endif

Tests/View Models/AddIdentityViewModelTests.swift

@@ -20,7 +20,6 @@ class AddIdentityViewModelTests: XCTestCase {
 
         XCTAssertEqual(addedIdentity.id, addedIdentityID)
         XCTAssertEqual(addedIdentity.url, URL(string: "https://mastodon.social")!)
-        XCTAssertEqual(environment.preferences[.recentIdentityID], addedIdentity.id)
         XCTAssertEqual(
             try environment.secrets.item(.clientID, forIdentityID: addedIdentityID) as String?,
             "AUTHORIZATION_CLIENT_ID_STUB_VALUE")

Tests/View Models/RootViewModelTests.swift

@@ -8,17 +8,17 @@ import CombineExpectations
 class RootViewModelTests: XCTestCase {
     func testAddIdentity() throws {
         let sut = RootViewModel(environment: .fresh())
-        let identityIDRecorder = sut.$identityID.record()
+        let recorder = sut.$mainNavigationViewModel.record()
 
-        XCTAssertNil(try wait(for: identityIDRecorder.next(), timeout: 1))
+        XCTAssertNil(try wait(for: recorder.next(), timeout: 1))
 
         let addIdentityViewModel = sut.addIdentityViewModel()
 
         addIdentityViewModel.urlFieldText = "https://mastodon.social"
         addIdentityViewModel.goTapped()
 
-        let identityID = try wait(for: identityIDRecorder.next(), timeout: 1)!
+        let mainNavigationViewModel = try wait(for: recorder.next(), timeout: 1)!
 
-        XCTAssertNotNil(identityID)
+        XCTAssertNotNil(mainNavigationViewModel)
     }
 }

iOS/TabNavigation.swift

@@ -5,7 +5,9 @@ import KingfisherSwiftUI
 import struct Kingfisher.DownsamplingImageProcessor
 
 struct TabNavigation: View {
-    @StateObject var viewModel: MainNavigationViewModel
+    @ObservedObject var viewModel: MainNavigationViewModel
+    @EnvironmentObject var rootViewModel: RootViewModel
+    @Environment(\.displayScale) var displayScale: CGFloat
 
     var body: some View {
         TabView(selection: $viewModel.selectedTab) {
@@ -23,9 +25,10 @@ struct TabNavigation: View {
         }
         .sheet(isPresented: $viewModel.presentingSettings) {
             SettingsView(viewModel: viewModel.settingsViewModel())
-                .environmentObject(viewModel)
+                .environmentObject(rootViewModel)
         }
-        .onAppear(perform: viewModel.refreshIdentity)
+        .onReceive(rootViewModel.$mainNavigationViewModel.map { _ in ()},
+                   perform: viewModel.refreshIdentity)
         .onReceive(NotificationCenter.default
                     .publisher(for: UIScene.willEnterForegroundNotification)
                     .map { _ in () },
@@ -39,17 +42,17 @@ private extension TabNavigation {
             switch tab {
             case .timelines:
                 TimelineView()
-                    .navigationBarTitle(viewModel.handle, displayMode: .inline)
+                    .navigationBarTitle(viewModel.identity.handle, displayMode: .inline)
                     .navigationBarItems(
                         leading: Button {
                             viewModel.presentingSettings.toggle()
                         } label: {
-                            KFImage(viewModel.image,
+                            KFImage(viewModel.identity.image,
                                     options: [
                                         .processor(
                                             DownsamplingImageProcessor(size: CGSize(width: 28, height: 28))
                                         ),
-                                        .scaleFactor(Screen.scale),
+                                        .scaleFactor(displayScale),
                                         .cacheOriginalImage
                                     ])
                                 .placeholder { Image(systemName: "gear") }

macOS/SidebarNavigation.swift

@@ -7,6 +7,8 @@ import struct Kingfisher.RoundCornerImageProcessor
 
 struct SidebarNavigation: View {
     @StateObject var viewModel: MainNavigationViewModel
+    @EnvironmentObject var rootViewModel: RootViewModel
+    @Environment(\.displayScale) var displayScale: CGFloat
 
     var sidebar: some View {
         List(selection: $viewModel.selectedTab) {
@@ -18,7 +20,10 @@ struct SidebarNavigation: View {
                 .tag(tab)
             }
         }
-        .overlay(Pocket().environmentObject(viewModel), alignment: .bottom)
+        .overlay(Pocket()
+                    .environmentObject(viewModel)
+                    .environmentObject(rootViewModel),
+                 alignment: .bottom)
         .listStyle(SidebarListStyle())
         .onAppear(perform: viewModel.refreshIdentity)
         .onReceive(NotificationCenter.default
@@ -51,18 +56,19 @@ private extension SidebarNavigation {
 
     struct Pocket: View {
         @EnvironmentObject var viewModel: MainNavigationViewModel
+        @EnvironmentObject var rootViewModel: RootViewModel
 
         var body: some View {
             VStack(alignment: .leading, spacing: 0) {
                 Divider()
                 Button(action: { viewModel.presentingSettings.toggle() }) {
-                    KFImage(viewModel.image,
+                    KFImage(viewModel.identity.image,
                             options: [
                                 .processor(
                                     DownsamplingImageProcessor(size: CGSize(width: 50, height: 50))
                                         .append(another: RoundCornerImageProcessor(radius: .widthFraction(0.5)))
                                 ),
-                                .scaleFactor(Screen.scale),
+                                .scaleFactor(displayScale),
                                 .cacheOriginalImage
                             ])
                         .placeholder { Image(systemName: "gear") }
@@ -80,6 +86,7 @@ private extension SidebarNavigation {
             .sheet(isPresented: $viewModel.presentingSettings) {
                 SettingsView(viewModel: viewModel.settingsViewModel())
                     .environmentObject(viewModel)
+                    .environmentObject(rootViewModel)
             }
         }
     }
@@ -89,6 +96,7 @@ private extension SidebarNavigation {
 struct SidebarNavigation_Previews: PreviewProvider {
     static var previews: some View {
         SidebarNavigation(viewModel: .development)
+            .environmentObject(RootViewModel.development)
     }
 }
 #endif