Ps/introduce single user state (#7053)

* Specify state provider for currently active user

* Split active and single user States

UserStateProvider is still the mechanism to build each State object.
The SingleUserState is basically a repeat of GlobalState, but with
additional scoping.

* Fixup global state cache

* fix fakers to new interface

* Make userId available in single user state

* Split providers by dependency requirements

This allows usage of the single state provider in contexts that would
otherwise form circular dependencies.

* Offer convenience wrapper classes for common use

* Import for docs

* Bind wrapped methods

libs/angular/src/services/jslib-services.module.ts

@@ -107,9 +107,18 @@ import { NoopNotificationsService } from "@bitwarden/common/platform/services/no
 import { StateService } from "@bitwarden/common/platform/services/state.service";
 import { ValidationService } from "@bitwarden/common/platform/services/validation.service";
 import { WebCryptoFunctionService } from "@bitwarden/common/platform/services/web-crypto-function.service";
-import { GlobalStateProvider } from "@bitwarden/common/platform/state";
-// eslint-disable-next-line import/no-restricted-paths -- We need the implementation to inject, but generally this should not be accessed
+import {
+  ActiveUserStateProvider,
+  GlobalStateProvider,
+  SingleUserStateProvider,
+  StateProvider,
+} from "@bitwarden/common/platform/state";
+/* eslint-disable import/no-restricted-paths -- We need the implementations to inject, but generally these should not be accessed */
+import { DefaultActiveUserStateProvider } from "@bitwarden/common/platform/state/implementations/default-active-user-state.provider";
 import { DefaultGlobalStateProvider } from "@bitwarden/common/platform/state/implementations/default-global-state.provider";
+import { DefaultSingleUserStateProvider } from "@bitwarden/common/platform/state/implementations/default-single-user-state.provider";
+import { DefaultStateProvider } from "@bitwarden/common/platform/state/implementations/default-state.provider";
+/* eslint-enable import/no-restricted-paths */
 import { AvatarUpdateService } from "@bitwarden/common/services/account/avatar-update.service";
 import { ApiService } from "@bitwarden/common/services/api.service";
 import { AuditService } from "@bitwarden/common/services/audit.service";
@@ -785,6 +794,26 @@ import { ModalService } from "./modal.service";
       useClass: DefaultGlobalStateProvider,
       deps: [OBSERVABLE_MEMORY_STORAGE, OBSERVABLE_DISK_STORAGE],
     },
+    {
+      provide: ActiveUserStateProvider,
+      useClass: DefaultActiveUserStateProvider,
+      deps: [
+        AccountServiceAbstraction,
+        EncryptService,
+        OBSERVABLE_MEMORY_STORAGE,
+        OBSERVABLE_DISK_STORAGE,
+      ],
+    },
+    {
+      provide: SingleUserStateProvider,
+      useClass: DefaultSingleUserStateProvider,
+      deps: [EncryptService, OBSERVABLE_MEMORY_STORAGE, OBSERVABLE_DISK_STORAGE],
+    },
+    {
+      provide: StateProvider,
+      useClass: DefaultStateProvider,
+      deps: [ActiveUserStateProvider, SingleUserStateProvider, GlobalStateProvider],
+    },
   ],
 })
 export class JslibServicesModule {}

libs/common/spec/fake-state-provider.ts

@@ -2,48 +2,62 @@ import {
   GlobalState,
   GlobalStateProvider,
   KeyDefinition,
-  UserState,
-  UserStateProvider,
+  ActiveUserState,
+  SingleUserState,
 } from "../src/platform/state";
+import { UserId } from "../src/types/guid";
 
-import { FakeGlobalState, FakeUserState } from "./fake-state";
+import { FakeActiveUserState, FakeGlobalState, FakeSingleUserState } from "./fake-state";
 
 export class FakeGlobalStateProvider implements GlobalStateProvider {
-  states: Map<KeyDefinition<unknown>, GlobalState<unknown>> = new Map();
+  states: Map<string, GlobalState<unknown>> = new Map();
   get<T>(keyDefinition: KeyDefinition<T>): GlobalState<T> {
-    let result = this.states.get(keyDefinition) as GlobalState<T>;
+    let result = this.states.get(keyDefinition.buildCacheKey("global")) as GlobalState<T>;
 
     if (result == null) {
       result = new FakeGlobalState<T>();
-      this.states.set(keyDefinition, result);
+      this.states.set(keyDefinition.buildCacheKey("global"), result);
     }
     return result;
   }
 
   getFake<T>(keyDefinition: KeyDefinition<T>): FakeGlobalState<T> {
-    const key = Array.from(this.states.keys()).find(
-      (k) => k.stateDefinition === keyDefinition.stateDefinition && k.key === keyDefinition.key,
-    );
-    return this.get(key) as FakeGlobalState<T>;
+    return this.get(keyDefinition) as FakeGlobalState<T>;
   }
 }
 
-export class FakeUserStateProvider implements UserStateProvider {
-  states: Map<KeyDefinition<unknown>, UserState<unknown>> = new Map();
-  get<T>(keyDefinition: KeyDefinition<T>): UserState<T> {
-    let result = this.states.get(keyDefinition) as UserState<T>;
+export class FakeSingleUserStateProvider {
+  states: Map<string, SingleUserState<unknown>> = new Map();
+  get<T>(userId: UserId, keyDefinition: KeyDefinition<T>): SingleUserState<T> {
+    let result = this.states.get(keyDefinition.buildCacheKey("user", userId)) as SingleUserState<T>;
 
     if (result == null) {
-      result = new FakeUserState<T>();
-      this.states.set(keyDefinition, result);
+      result = new FakeSingleUserState<T>(userId);
+      this.states.set(keyDefinition.buildCacheKey("user", userId), result);
     }
     return result;
   }
 
-  getFake<T>(keyDefinition: KeyDefinition<T>): FakeUserState<T> {
-    const key = Array.from(this.states.keys()).find(
-      (k) => k.stateDefinition === keyDefinition.stateDefinition && k.key === keyDefinition.key,
-    );
-    return this.get(key) as FakeUserState<T>;
+  getFake<T>(userId: UserId, keyDefinition: KeyDefinition<T>): FakeSingleUserState<T> {
+    return this.get(userId, keyDefinition) as FakeSingleUserState<T>;
+  }
+}
+
+export class FakeActiveUserStateProvider {
+  states: Map<string, ActiveUserState<unknown>> = new Map();
+  get<T>(keyDefinition: KeyDefinition<T>): ActiveUserState<T> {
+    let result = this.states.get(
+      keyDefinition.buildCacheKey("user", "active"),
+    ) as ActiveUserState<T>;
+
+    if (result == null) {
+      result = new FakeActiveUserState<T>();
+      this.states.set(keyDefinition.buildCacheKey("user", "active"), result);
+    }
+    return result;
+  }
+
+  getFake<T>(keyDefinition: KeyDefinition<T>): FakeActiveUserState<T> {
+    return this.get(keyDefinition) as FakeActiveUserState<T>;
   }
 }

libs/common/spec/fake-state.ts

@@ -1,8 +1,15 @@
 import { ReplaySubject, firstValueFrom, timeout } from "rxjs";
 
-import { DerivedUserState, GlobalState, UserState } from "../src/platform/state";
+import {
+  DerivedUserState,
+  GlobalState,
+  SingleUserState,
+  ActiveUserState,
+} from "../src/platform/state";
 // eslint-disable-next-line import/no-restricted-paths -- using unexposed options for clean typing in test class
 import { StateUpdateOptions } from "../src/platform/state/state-update-options";
+// eslint-disable-next-line import/no-restricted-paths -- using unexposed options for clean typing in test class
+import { UserState, activeMarker } from "../src/platform/state/user-state";
 import { UserId } from "../src/types/guid";
 
 const DEFAULT_TEST_OPTIONS: StateUpdateOptions<any, any> = {
@@ -97,3 +104,12 @@ export class FakeUserState<T> implements UserState<T> {
     return this.stateSubject.asObservable();
   }
 }
+
+export class FakeSingleUserState<T> extends FakeUserState<T> implements SingleUserState<T> {
+  constructor(readonly userId: UserId) {
+    super();
+  }
+}
+export class FakeActiveUserState<T> extends FakeUserState<T> implements ActiveUserState<T> {
+  [activeMarker]: true;
+}

libs/common/src/platform/state/implementations/default-active-user-state.provider.ts

@@ -7,13 +7,13 @@ import {
 } from "../../abstractions/storage.service";
 import { KeyDefinition } from "../key-definition";
 import { StorageLocation } from "../state-definition";
-import { UserState } from "../user-state";
-import { UserStateProvider } from "../user-state.provider";
+import { ActiveUserState } from "../user-state";
+import { ActiveUserStateProvider } from "../user-state.provider";
 
-import { DefaultUserState } from "./default-user-state";
+import { DefaultActiveUserState } from "./default-active-user-state";
 
-export class DefaultUserStateProvider implements UserStateProvider {
-  private userStateCache: Record<string, UserState<unknown>> = {};
+export class DefaultActiveUserStateProvider implements ActiveUserStateProvider {
+  private cache: Record<string, ActiveUserState<unknown>> = {};
 
   constructor(
     protected accountService: AccountService,
@@ -22,22 +22,22 @@ export class DefaultUserStateProvider implements UserStateProvider {
     protected diskStorage: AbstractStorageService & ObservableStorageService,
   ) {}
 
-  get<T>(keyDefinition: KeyDefinition<T>): UserState<T> {
-    const cacheKey = keyDefinition.buildCacheKey();
-    const existingUserState = this.userStateCache[cacheKey];
+  get<T>(keyDefinition: KeyDefinition<T>): ActiveUserState<T> {
+    const cacheKey = keyDefinition.buildCacheKey("user", "active");
+    const existingUserState = this.cache[cacheKey];
     if (existingUserState != null) {
       // I have to cast out of the unknown generic but this should be safe if rules
       // around domain token are made
-      return existingUserState as DefaultUserState<T>;
+      return existingUserState as ActiveUserState<T>;
     }
 
-    const newUserState = this.buildUserState(keyDefinition);
-    this.userStateCache[cacheKey] = newUserState;
+    const newUserState = this.buildActiveUserState(keyDefinition);
+    this.cache[cacheKey] = newUserState;
     return newUserState;
   }
 
-  protected buildUserState<T>(keyDefinition: KeyDefinition<T>): UserState<T> {
-    return new DefaultUserState<T>(
+  protected buildActiveUserState<T>(keyDefinition: KeyDefinition<T>): ActiveUserState<T> {
+    return new DefaultActiveUserState<T>(
       keyDefinition,
       this.accountService,
       this.encryptService,

libs/common/src/platform/state/implementations/default-active-user-state.spec.ts

@@ -14,7 +14,7 @@ import { UserId } from "../../../types/guid";
 import { KeyDefinition } from "../key-definition";
 import { StateDefinition } from "../state-definition";
 
-import { DefaultUserState } from "./default-user-state";
+import { DefaultActiveUserState } from "./default-active-user-state";
 
 class TestState {
   date: Date;
@@ -37,18 +37,18 @@ const testKeyDefinition = new KeyDefinition<TestState>(testStateDefinition, "fak
   deserializer: TestState.fromJSON,
 });
 
-describe("DefaultUserState", () => {
+describe("DefaultActiveUserState", () => {
   const accountService = mock<AccountService>();
   let diskStorageService: FakeStorageService;
   let activeAccountSubject: BehaviorSubject<{ id: UserId } & AccountInfo>;
-  let userState: DefaultUserState<TestState>;
+  let userState: DefaultActiveUserState<TestState>;
 
   beforeEach(() => {
     activeAccountSubject = new BehaviorSubject<{ id: UserId } & AccountInfo>(undefined);
     accountService.activeAccount$ = activeAccountSubject;
 
     diskStorageService = new FakeStorageService();
-    userState = new DefaultUserState(
+    userState = new DefaultActiveUserState(
       testKeyDefinition,
       accountService,
       null, // Not testing anything with encrypt service

libs/common/src/platform/state/implementations/default-active-user-state.ts

@@ -13,7 +13,6 @@ import {
 } from "rxjs";
 
 import { AccountService } from "../../../auth/abstractions/account.service";
-import { UserId } from "../../../types/guid";
 import { EncryptService } from "../../abstractions/encrypt.service";
 import {
   AbstractStorageService,
@@ -22,14 +21,15 @@ import {
 import { DerivedUserState } from "../derived-user-state";
 import { KeyDefinition, userKeyBuilder } from "../key-definition";
 import { StateUpdateOptions, populateOptionsWithDefault } from "../state-update-options";
-import { Converter, UserState } from "../user-state";
+import { Converter, ActiveUserState, activeMarker } from "../user-state";
 
 import { DefaultDerivedUserState } from "./default-derived-state";
 import { getStoredValue } from "./util";
 
 const FAKE_DEFAULT = Symbol("fakeDefault");
 
-export class DefaultUserState<T> implements UserState<T> {
+export class DefaultActiveUserState<T> implements ActiveUserState<T> {
+  [activeMarker]: true;
   private formattedKey$: Observable<string>;
 
   protected stateSubject: BehaviorSubject<T | typeof FAKE_DEFAULT> = new BehaviorSubject<
@@ -130,37 +130,6 @@ export class DefaultUserState<T> implements UserState<T> {
     return newState;
   }
 
-  async updateFor<TCombine>(
-    userId: UserId,
-    configureState: (state: T, dependencies: TCombine) => T,
-    options: StateUpdateOptions<T, TCombine> = {},
-  ): Promise<T> {
-    if (userId == null) {
-      throw new Error("Attempting to update user state, but no userId has been supplied.");
-    }
-    options = populateOptionsWithDefault(options);
-
-    const key = userKeyBuilder(userId, this.keyDefinition);
-    const currentState = await getStoredValue(
-      key,
-      this.chosenStorageLocation,
-      this.keyDefinition.deserializer,
-    );
-    const combinedDependencies =
-      options.combineLatestWith != null
-        ? await firstValueFrom(options.combineLatestWith.pipe(timeout(options.msTimeout)))
-        : null;
-
-    if (!options.shouldUpdate(currentState, combinedDependencies)) {
-      return;
-    }
-
-    const newState = configureState(currentState, combinedDependencies);
-    await this.saveToStorage(key, newState);
-
-    return newState;
-  }
-
   async getFromState(): Promise<T> {
     const key = await this.createKey();
     return await getStoredValue(key, this.chosenStorageLocation, this.keyDefinition.deserializer);

libs/common/src/platform/state/implementations/default-global-state.provider.ts

@@ -19,7 +19,7 @@ export class DefaultGlobalStateProvider implements GlobalStateProvider {
   ) {}
 
   get<T>(keyDefinition: KeyDefinition<T>): GlobalState<T> {
-    const cacheKey = keyDefinition.buildCacheKey();
+    const cacheKey = keyDefinition.buildCacheKey("global");
     const existingGlobalState = this.globalStateCache[cacheKey];
     if (existingGlobalState != null) {
       // The cast into the actual generic is safe because of rules around key definitions

libs/common/src/platform/state/implementations/default-single-user-state.provider.ts

@@ -0,0 +1,58 @@
+import { UserId } from "../../../types/guid";
+import { EncryptService } from "../../abstractions/encrypt.service";
+import {
+  AbstractMemoryStorageService,
+  AbstractStorageService,
+  ObservableStorageService,
+} from "../../abstractions/storage.service";
+import { KeyDefinition } from "../key-definition";
+import { StorageLocation } from "../state-definition";
+import { SingleUserState } from "../user-state";
+import { SingleUserStateProvider } from "../user-state.provider";
+
+import { DefaultSingleUserState } from "./default-single-user-state";
+
+export class DefaultSingleUserStateProvider implements SingleUserStateProvider {
+  private cache: Record<string, SingleUserState<unknown>> = {};
+
+  constructor(
+    protected encryptService: EncryptService,
+    protected memoryStorage: AbstractMemoryStorageService & ObservableStorageService,
+    protected diskStorage: AbstractStorageService & ObservableStorageService,
+  ) {}
+
+  get<T>(userId: UserId, keyDefinition: KeyDefinition<T>): SingleUserState<T> {
+    const cacheKey = keyDefinition.buildCacheKey("user", userId);
+    const existingUserState = this.cache[cacheKey];
+    if (existingUserState != null) {
+      // I have to cast out of the unknown generic but this should be safe if rules
+      // around domain token are made
+      return existingUserState as SingleUserState<T>;
+    }
+
+    const newUserState = this.buildSingleUserState(userId, keyDefinition);
+    this.cache[cacheKey] = newUserState;
+    return newUserState;
+  }
+
+  protected buildSingleUserState<T>(
+    userId: UserId,
+    keyDefinition: KeyDefinition<T>,
+  ): SingleUserState<T> {
+    return new DefaultSingleUserState<T>(
+      userId,
+      keyDefinition,
+      this.encryptService,
+      this.getLocation(keyDefinition.stateDefinition.storageLocation),
+    );
+  }
+
+  private getLocation(location: StorageLocation) {
+    switch (location) {
+      case "disk":
+        return this.diskStorage;
+      case "memory":
+        return this.memoryStorage;
+    }
+  }
+}

libs/common/src/platform/state/implementations/default-single-user-state.spec.ts

@@ -0,0 +1,212 @@
+/**
+ * need to update test environment so trackEmissions works appropriately
+ * @jest-environment ../shared/test.environment.ts
+ */
+
+import { firstValueFrom, of } from "rxjs";
+import { Jsonify } from "type-fest";
+
+import { trackEmissions, awaitAsync } from "../../../../spec";
+import { FakeStorageService } from "../../../../spec/fake-storage.service";
+import { UserId } from "../../../types/guid";
+import { Utils } from "../../misc/utils";
+import { KeyDefinition, userKeyBuilder } from "../key-definition";
+import { StateDefinition } from "../state-definition";
+
+import { DefaultSingleUserState } from "./default-single-user-state";
+
+class TestState {
+  date: Date;
+
+  static fromJSON(jsonState: Jsonify<TestState>) {
+    if (jsonState == null) {
+      return null;
+    }
+
+    return Object.assign(new TestState(), jsonState, {
+      date: new Date(jsonState.date),
+    });
+  }
+}
+
+const testStateDefinition = new StateDefinition("fake", "disk");
+
+const testKeyDefinition = new KeyDefinition<TestState>(testStateDefinition, "fake", {
+  deserializer: TestState.fromJSON,
+});
+const userId = Utils.newGuid() as UserId;
+const userKey = userKeyBuilder(userId, testKeyDefinition);
+
+describe("DefaultSingleUserState", () => {
+  let diskStorageService: FakeStorageService;
+  let globalState: DefaultSingleUserState<TestState>;
+  const newData = { date: new Date() };
+
+  beforeEach(() => {
+    diskStorageService = new FakeStorageService();
+    globalState = new DefaultSingleUserState(
+      userId,
+      testKeyDefinition,
+      null, // Not testing anything with encrypt service
+      diskStorageService,
+    );
+  });
+
+  afterEach(() => {
+    jest.resetAllMocks();
+  });
+
+  describe("state$", () => {
+    it("should emit when storage updates", async () => {
+      const emissions = trackEmissions(globalState.state$);
+      await diskStorageService.save(userKey, newData);
+      await awaitAsync();
+
+      expect(emissions).toEqual([
+        null, // Initial value
+        newData,
+      ]);
+    });
+
+    it("should not emit when update key does not match", async () => {
+      const emissions = trackEmissions(globalState.state$);
+      await diskStorageService.save("wrong_key", newData);
+
+      expect(emissions).toHaveLength(0);
+    });
+
+    it("should emit initial storage value on first subscribe", async () => {
+      const initialStorage: Record<string, TestState> = {};
+      initialStorage[userKey] = TestState.fromJSON({
+        date: "2022-09-21T13:14:17.648Z",
+      });
+      diskStorageService.internalUpdateStore(initialStorage);
+
+      const state = await firstValueFrom(globalState.state$);
+      expect(diskStorageService.mock.get).toHaveBeenCalledTimes(1);
+      expect(diskStorageService.mock.get).toHaveBeenCalledWith(
+        `user_${userId}_fake_fake`,
+        undefined,
+      );
+      expect(state).toBeTruthy();
+    });
+  });
+
+  describe("update", () => {
+    it("should save on update", async () => {
+      const result = await globalState.update((state) => {
+        return newData;
+      });
+
+      expect(diskStorageService.mock.save).toHaveBeenCalledTimes(1);
+      expect(result).toEqual(newData);
+    });
+
+    it("should emit once per update", async () => {
+      const emissions = trackEmissions(globalState.state$);
+      await awaitAsync(); // storage updates are behind a promise
+
+      await globalState.update((state) => {
+        return newData;
+      });
+
+      await awaitAsync();
+
+      expect(emissions).toEqual([
+        null, // Initial value
+        newData,
+      ]);
+    });
+
+    it("should provided combined dependencies", async () => {
+      const emissions = trackEmissions(globalState.state$);
+      await awaitAsync(); // storage updates are behind a promise
+
+      const combinedDependencies = { date: new Date() };
+
+      await globalState.update(
+        (state, dependencies) => {
+          expect(dependencies).toEqual(combinedDependencies);
+          return newData;
+        },
+        {
+          combineLatestWith: of(combinedDependencies),
+        },
+      );
+
+      await awaitAsync();
+
+      expect(emissions).toEqual([
+        null, // Initial value
+        newData,
+      ]);
+    });
+
+    it("should not update if shouldUpdate returns false", async () => {
+      const emissions = trackEmissions(globalState.state$);
+
+      const result = await globalState.update(
+        (state) => {
+          return newData;
+        },
+        {
+          shouldUpdate: () => false,
+        },
+      );
+
+      expect(diskStorageService.mock.save).not.toHaveBeenCalled();
+      expect(emissions).toEqual([null]); // Initial value
+      expect(result).toBeUndefined();
+    });
+
+    it("should provide the update callback with the current State", async () => {
+      const emissions = trackEmissions(globalState.state$);
+      await awaitAsync(); // storage updates are behind a promise
+
+      // Seed with interesting data
+      const initialData = { date: new Date(2020, 1, 1) };
+      await globalState.update((state, dependencies) => {
+        return initialData;
+      });
+
+      await awaitAsync();
+
+      await globalState.update((state) => {
+        expect(state).toEqual(initialData);
+        return newData;
+      });
+
+      await awaitAsync();
+
+      expect(emissions).toEqual([
+        null, // Initial value
+        initialData,
+        newData,
+      ]);
+    });
+
+    it("should give initial state for update call", async () => {
+      const initialStorage: Record<string, TestState> = {};
+      const initialState = TestState.fromJSON({
+        date: "2022-09-21T13:14:17.648Z",
+      });
+      initialStorage[userKey] = initialState;
+      diskStorageService.internalUpdateStore(initialStorage);
+
+      const emissions = trackEmissions(globalState.state$);
+      await awaitAsync(); // storage updates are behind a promise
+
+      const newState = {
+        ...initialState,
+        date: new Date(initialState.date.getFullYear(), initialState.date.getMonth() + 1),
+      };
+      const actual = await globalState.update((existingState) => newState);
+
+      await awaitAsync();
+
+      expect(actual).toEqual(newState);
+      expect(emissions).toHaveLength(2);
+      expect(emissions).toEqual(expect.arrayContaining([initialState, newState]));
+    });
+  });
+});

libs/common/src/platform/state/implementations/default-single-user-state.ts

@@ -0,0 +1,118 @@
+import {
+  BehaviorSubject,
+  Observable,
+  defer,
+  filter,
+  firstValueFrom,
+  shareReplay,
+  switchMap,
+  tap,
+  timeout,
+} from "rxjs";
+
+import { UserId } from "../../../types/guid";
+import { EncryptService } from "../../abstractions/encrypt.service";
+import {
+  AbstractStorageService,
+  ObservableStorageService,
+} from "../../abstractions/storage.service";
+import { DerivedUserState } from "../derived-user-state";
+import { KeyDefinition, userKeyBuilder } from "../key-definition";
+import { StateUpdateOptions, populateOptionsWithDefault } from "../state-update-options";
+import { Converter, SingleUserState } from "../user-state";
+
+import { DefaultDerivedUserState } from "./default-derived-state";
+import { getStoredValue } from "./util";
+const FAKE_DEFAULT = Symbol("fakeDefault");
+
+export class DefaultSingleUserState<T> implements SingleUserState<T> {
+  private storageKey: string;
+
+  protected stateSubject: BehaviorSubject<T | typeof FAKE_DEFAULT> = new BehaviorSubject<
+    T | typeof FAKE_DEFAULT
+  >(FAKE_DEFAULT);
+
+  state$: Observable<T>;
+
+  constructor(
+    readonly userId: UserId,
+    private keyDefinition: KeyDefinition<T>,
+    private encryptService: EncryptService,
+    private chosenLocation: AbstractStorageService & ObservableStorageService,
+  ) {
+    this.storageKey = userKeyBuilder(this.userId, this.keyDefinition);
+
+    const storageUpdates$ = this.chosenLocation.updates$.pipe(
+      filter((update) => update.key === this.storageKey),
+      switchMap(async (update) => {
+        if (update.updateType === "remove") {
+          return null;
+        }
+        return await getStoredValue(
+          this.storageKey,
+          this.chosenLocation,
+          this.keyDefinition.deserializer,
+        );
+      }),
+      shareReplay({ bufferSize: 1, refCount: false }),
+    );
+
+    this.state$ = defer(() => {
+      const storageUpdateSubscription = storageUpdates$.subscribe((value) => {
+        this.stateSubject.next(value);
+      });
+
+      this.getFromState().then((s) => {
+        this.stateSubject.next(s);
+      });
+
+      return this.stateSubject.pipe(
+        tap({
+          complete: () => {
+            storageUpdateSubscription.unsubscribe();
+          },
+        }),
+      );
+    }).pipe(
+      shareReplay({ refCount: false, bufferSize: 1 }),
+      filter<T>((i) => i != FAKE_DEFAULT),
+    );
+  }
+
+  async update<TCombine>(
+    configureState: (state: T, dependency: TCombine) => T,
+    options: StateUpdateOptions<T, TCombine> = {},
+  ): Promise<T> {
+    options = populateOptionsWithDefault(options);
+    const currentState = await this.getGuaranteedState();
+    const combinedDependencies =
+      options.combineLatestWith != null
+        ? await firstValueFrom(options.combineLatestWith.pipe(timeout(options.msTimeout)))
+        : null;
+
+    if (!options.shouldUpdate(currentState, combinedDependencies)) {
+      return;
+    }
+
+    const newState = configureState(currentState, combinedDependencies);
+    await this.chosenLocation.save(this.storageKey, newState);
+    return newState;
+  }
+
+  createDerived<TTo>(converter: Converter<T, TTo>): DerivedUserState<TTo> {
+    return new DefaultDerivedUserState<T, TTo>(converter, this.encryptService, this);
+  }
+
+  private async getGuaranteedState() {
+    const currentValue = this.stateSubject.getValue();
+    return currentValue === FAKE_DEFAULT ? await this.getFromState() : currentValue;
+  }
+
+  async getFromState(): Promise<T> {
+    return await getStoredValue(
+      this.storageKey,
+      this.chosenLocation,
+      this.keyDefinition.deserializer,
+    );
+  }
+}

libs/common/src/platform/state/implementations/default-state.provider.spec.ts

@@ -0,0 +1,56 @@
+import {
+  FakeActiveUserStateProvider,
+  FakeGlobalStateProvider,
+  FakeSingleUserStateProvider,
+} from "../../../../spec/fake-state-provider";
+import { UserId } from "../../../types/guid";
+import { KeyDefinition } from "../key-definition";
+import { StateDefinition } from "../state-definition";
+
+import { DefaultStateProvider } from "./default-state.provider";
+
+describe("DefaultStateProvider", () => {
+  let sut: DefaultStateProvider;
+  let activeUserStateProvider: FakeActiveUserStateProvider;
+  let singleUserStateProvider: FakeSingleUserStateProvider;
+  let globalStateProvider: FakeGlobalStateProvider;
+
+  beforeEach(() => {
+    activeUserStateProvider = new FakeActiveUserStateProvider();
+    singleUserStateProvider = new FakeSingleUserStateProvider();
+    globalStateProvider = new FakeGlobalStateProvider();
+    sut = new DefaultStateProvider(
+      activeUserStateProvider,
+      singleUserStateProvider,
+      globalStateProvider,
+    );
+  });
+
+  it("should bind the activeUserStateProvider", () => {
+    const keyDefinition = new KeyDefinition(new StateDefinition("test", "disk"), "test", {
+      deserializer: () => null,
+    });
+    const existing = activeUserStateProvider.get(keyDefinition);
+    const actual = sut.getActive(keyDefinition);
+    expect(actual).toBe(existing);
+  });
+
+  it("should bind the singleUserStateProvider", () => {
+    const userId = "user" as UserId;
+    const keyDefinition = new KeyDefinition(new StateDefinition("test", "disk"), "test", {
+      deserializer: () => null,
+    });
+    const existing = singleUserStateProvider.get(userId, keyDefinition);
+    const actual = sut.getUser(userId, keyDefinition);
+    expect(actual).toBe(existing);
+  });
+
+  it("should bind the globalStateProvider", () => {
+    const keyDefinition = new KeyDefinition(new StateDefinition("test", "disk"), "test", {
+      deserializer: () => null,
+    });
+    const existing = globalStateProvider.get(keyDefinition);
+    const actual = sut.getGlobal(keyDefinition);
+    expect(actual).toBe(existing);
+  });
+});

libs/common/src/platform/state/implementations/default-state.provider.ts

@@ -0,0 +1,19 @@
+import { GlobalStateProvider } from "../global-state.provider";
+import { StateProvider } from "../state.provider";
+import { ActiveUserStateProvider, SingleUserStateProvider } from "../user-state.provider";
+
+export class DefaultStateProvider implements StateProvider {
+  constructor(
+    private readonly activeUserStateProvider: ActiveUserStateProvider,
+    private readonly singleUserStateProvider: SingleUserStateProvider,
+    private readonly globalStateProvider: GlobalStateProvider,
+  ) {}
+
+  getActive: InstanceType<typeof ActiveUserStateProvider>["get"] =
+    this.activeUserStateProvider.get.bind(this.activeUserStateProvider);
+  getUser: InstanceType<typeof SingleUserStateProvider>["get"] =
+    this.singleUserStateProvider.get.bind(this.singleUserStateProvider);
+  getGlobal: InstanceType<typeof GlobalStateProvider>["get"] = this.globalStateProvider.get.bind(
+    this.globalStateProvider,
+  );
+}

libs/common/src/platform/state/index.ts

@@ -1,8 +1,9 @@
 export { DerivedUserState } from "./derived-user-state";
 export { GlobalState } from "./global-state";
+export { StateProvider } from "./state.provider";
 export { GlobalStateProvider } from "./global-state.provider";
-export { UserState } from "./user-state";
-export { UserStateProvider } from "./user-state.provider";
+export { ActiveUserState, SingleUserState } from "./user-state";
+export { ActiveUserStateProvider, SingleUserStateProvider } from "./user-state.provider";
 export { KeyDefinition } from "./key-definition";
 
 export * from "./state-definitions";

libs/common/src/platform/state/key-definition.ts

@@ -129,8 +129,13 @@ export class KeyDefinition<T> {
    * Create a string that should be unique across the entire application.
    * @returns A string that can be used to cache instances created via this key.
    */
-  buildCacheKey(): string {
-    return `${this.stateDefinition.storageLocation}_${this.stateDefinition.name}_${this.key}`;
+  buildCacheKey(scope: "user" | "global", userId?: "active" | UserId): string {
+    if (scope === "user" && userId == null) {
+      throw new Error("You must provide a userId when building a user scoped cache key.");
+    }
+    return userId === null
+      ? `${scope}_${userId}_${this.stateDefinition.name}_${this.key}`
+      : `${scope}_${this.stateDefinition.name}_${this.key}`;
   }
 }
 

libs/common/src/platform/state/state.provider.ts

@@ -0,0 +1,21 @@
+import { UserId } from "../../types/guid";
+
+import { GlobalState } from "./global-state";
+// eslint-disable-next-line @typescript-eslint/no-unused-vars -- used in docs
+import { GlobalStateProvider } from "./global-state.provider";
+import { KeyDefinition } from "./key-definition";
+import { ActiveUserState, SingleUserState } from "./user-state";
+// eslint-disable-next-line @typescript-eslint/no-unused-vars -- used in docs
+import { ActiveUserStateProvider, SingleUserStateProvider } from "./user-state.provider";
+
+/** Convenience wrapper class for {@link ActiveUserStateProvider}, {@link SingleUserStateProvider},
+ * and {@link GlobalStateProvider}.
+ */
+export abstract class StateProvider {
+  /** @see{@link ActiveUserStateProvider.get} */
+  getActive: <T>(keyDefinition: KeyDefinition<T>) => ActiveUserState<T>;
+  /** @see{@link SingleUserStateProvider.get} */
+  getUser: <T>(userId: UserId, keyDefinition: KeyDefinition<T>) => SingleUserState<T>;
+  /** @see{@link GlobalStateProvider.get} */
+  getGlobal: <T>(keyDefinition: KeyDefinition<T>) => GlobalState<T>;
+}

libs/common/src/platform/state/user-state.provider.ts

@@ -1,13 +1,28 @@
-import { KeyDefinition } from "./key-definition";
-import { UserState } from "./user-state";
+import { UserId } from "../../types/guid";
 
-/**
- * A provider for getting an implementation of user scoped state for the given key.
- */
-export abstract class UserStateProvider {
+import { KeyDefinition } from "./key-definition";
+import { ActiveUserState, SingleUserState } from "./user-state";
+
+/** A provider for getting an implementation of state scoped to a given key and userId */
+export abstract class SingleUserStateProvider {
   /**
-   * Gets a {@link GlobalState} scoped to the given {@link KeyDefinition}
+   * Gets a {@link SingleUserState} scoped to the given {@link KeyDefinition} and {@link UserId}
+   *
+   * @param userId - The {@link UserId} for which you want the user state for.
    * @param keyDefinition - The {@link KeyDefinition} for which you want the user state for.
    */
-  get: <T>(keyDefinition: KeyDefinition<T>) => UserState<T>;
+  get: <T>(userId: UserId, keyDefinition: KeyDefinition<T>) => SingleUserState<T>;
+}
+
+/** A provider for getting an implementation of state scoped to a given key, but always pointing
+ * to the currently active user
+ */
+export abstract class ActiveUserStateProvider {
+  /**
+   * Gets a {@link ActiveUserState} scoped to the given {@link KeyDefinition}, but updates when active user changes such
+   * that the emitted values always represents the state for the currently active user.
+   *
+   * @param keyDefinition - The {@link KeyDefinition} for which you want the user state for.
+   */
+  get: <T>(keyDefinition: KeyDefinition<T>) => ActiveUserState<T>;
 }

libs/common/src/platform/state/user-state.ts

@@ -37,22 +37,6 @@ export interface UserState<T> {
     configureState: (state: T, dependencies: TCombine) => T,
     options?: StateUpdateOptions<T, TCombine>,
   ) => Promise<T>;
-  /**
-   * Updates backing stores for the given userId, which may or may not be active.
-   * @param userId the UserId to target the update for
-   * @param configureState function that takes the current state for the targeted user and returns the new state
-   * @param options Defaults given by @see {module:state-update-options#DEFAULT_OPTIONS}
-   * @param options.shouldUpdate A callback for determining if you want to update state. Defaults to () => true
-   * @param options.combineLatestWith An observable that you want to combine with the current state for callbacks. Defaults to null
-   * @param options.msTimeout A timeout for how long you are willing to wait for a `combineLatestWith` option to complete. Defaults to 1000ms. Only applies if `combineLatestWith` is set.
-
-   * @returns The new state
-   */
-  readonly updateFor: <TCombine>(
-    userId: UserId,
-    configureState: (state: T, dependencies: TCombine) => T,
-    options?: StateUpdateOptions<T, TCombine>,
-  ) => Promise<T>;
 
   /**
    * Creates a derives state from the current state. Derived states are always tied to the active user.
@@ -61,3 +45,11 @@ export interface UserState<T> {
    */
   createDerived: <TTo>(converter: Converter<T, TTo>) => DerivedUserState<TTo>;
 }
+
+export const activeMarker: unique symbol = Symbol("active");
+export interface ActiveUserState<T> extends UserState<T> {
+  readonly [activeMarker]: true;
+}
+export interface SingleUserState<T> extends UserState<T> {
+  readonly userId: UserId;
+}