[refactor] Introduce ThemingService (#2943)

* [refactor] Introduce ThemingService

* [refactor] Implement ThemingService for web

* [refactor] Implement ThemingService on browser

* [refactor] Implement ThemingService for desktop

* [refactor] Remove deprecated platformUtils.service theme methods

* [fix] Move ThemingService from libs/common to libs/angular

* [fix] Simplify ThemeBuilder's constructor

* [fix] Dont notify subscribers of null values from theme$

* [fix] Always notify PaymentComponent of theme changes

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

@@ -1,5 +1,7 @@
 import { InjectionToken, Injector, LOCALE_ID, NgModule } from "@angular/core";
 
+import { ThemingService } from "@bitwarden/angular/services/theming/theming.service";
+import { AbstractThemingService } from "@bitwarden/angular/services/theming/theming.service.abstraction";
 import { ApiService as ApiServiceAbstraction } from "@bitwarden/common/abstractions/api.service";
 import { AppIdService as AppIdServiceAbstraction } from "@bitwarden/common/abstractions/appId.service";
 import { AuditService as AuditServiceAbstraction } from "@bitwarden/common/abstractions/audit.service";
@@ -423,6 +425,10 @@ export const SYSTEM_LANGUAGE = new InjectionToken<string>("SYSTEM_LANGUAGE");
       useClass: TwoFactorService,
       deps: [I18nServiceAbstraction, PlatformUtilsServiceAbstraction],
     },
+    {
+      provide: AbstractThemingService,
+      useClass: ThemingService,
+    },
   ],
 })
 export class JslibServicesModule {}

libs/angular/src/services/theming/theme.ts

@@ -0,0 +1,6 @@
+import { ThemeType } from "@bitwarden/common/enums/themeType";
+
+export interface Theme {
+  configuredTheme: ThemeType;
+  effectiveTheme: ThemeType;
+}

libs/angular/src/services/theming/themeBuilder.ts

@@ -0,0 +1,19 @@
+import { ThemeType } from "@bitwarden/common/enums/themeType";
+
+import { Theme } from "./theme";
+
+export class ThemeBuilder implements Theme {
+  get effectiveTheme(): ThemeType {
+    return this.configuredTheme != ThemeType.System ? this.configuredTheme : this.systemTheme;
+  }
+
+  constructor(readonly configuredTheme: ThemeType, readonly systemTheme: ThemeType) {}
+
+  updateSystemTheme(systemTheme: ThemeType): ThemeBuilder {
+    return new ThemeBuilder(this.configuredTheme, systemTheme);
+  }
+
+  updateConfiguredTheme(configuredTheme: ThemeType): ThemeBuilder {
+    return new ThemeBuilder(configuredTheme, this.systemTheme);
+  }
+}

libs/angular/src/services/theming/theming.service.abstraction.ts

@@ -0,0 +1,12 @@
+import { Observable } from "rxjs";
+
+import { ThemeType } from "@bitwarden/common/enums/themeType";
+
+import { Theme } from "./theme";
+
+export abstract class AbstractThemingService {
+  theme$: Observable<Theme>;
+  monitorThemeChanges: () => Promise<void>;
+  updateSystemTheme: (systemTheme: ThemeType) => void;
+  updateConfiguredTheme: (theme: ThemeType) => Promise<void>;
+}

libs/angular/src/services/theming/theming.service.ts

@@ -0,0 +1,71 @@
+import { MediaMatcher } from "@angular/cdk/layout";
+import { DOCUMENT } from "@angular/common";
+import { Inject, Injectable } from "@angular/core";
+import { BehaviorSubject, filter, fromEvent, Observable } from "rxjs";
+
+import { StateService } from "@bitwarden/common/abstractions/state.service";
+import { ThemeType } from "@bitwarden/common/enums/themeType";
+
+import { Theme } from "./theme";
+import { ThemeBuilder } from "./themeBuilder";
+import { AbstractThemingService } from "./theming.service.abstraction";
+
+@Injectable()
+export class ThemingService implements AbstractThemingService {
+  private _theme = new BehaviorSubject<ThemeBuilder | null>(null);
+  theme$: Observable<Theme> = this._theme.pipe(filter((x) => x !== null));
+
+  constructor(
+    private stateService: StateService,
+    private mediaMatcher: MediaMatcher,
+    @Inject(DOCUMENT) private document: Document
+  ) {
+    this.monitorThemeChanges();
+  }
+
+  async monitorThemeChanges(): Promise<void> {
+    this._theme.next(
+      new ThemeBuilder(await this.stateService.getTheme(), await this.getSystemTheme())
+    );
+    this.monitorConfiguredThemeChanges();
+    this.monitorSystemThemeChanges();
+  }
+
+  updateSystemTheme(systemTheme: ThemeType): void {
+    this._theme.next(this._theme.getValue().updateSystemTheme(systemTheme));
+  }
+
+  async updateConfiguredTheme(theme: ThemeType): Promise<void> {
+    await this.stateService.setTheme(theme);
+    this._theme.next(this._theme.getValue().updateConfiguredTheme(theme));
+  }
+
+  protected monitorConfiguredThemeChanges(): void {
+    this.theme$.subscribe((theme: Theme) => {
+      this.document.documentElement.classList.remove(
+        "theme_" + ThemeType.Light,
+        "theme_" + ThemeType.Dark,
+        "theme_" + ThemeType.Nord,
+        "theme_" + ThemeType.SolarizedDark
+      );
+      this.document.documentElement.classList.add("theme_" + theme.effectiveTheme);
+    });
+  }
+
+  // We use a media match query for monitoring the system theme on web and browser, but this doesn't work for electron apps on Linux.
+  // In desktop we override these methods to track systemTheme with the electron renderer instead, which works for all OSs.
+  protected async getSystemTheme(): Promise<ThemeType> {
+    return this.mediaMatcher.matchMedia("(prefers-color-scheme: dark)").matches
+      ? ThemeType.Dark
+      : ThemeType.Light;
+  }
+
+  protected monitorSystemThemeChanges(): void {
+    fromEvent<MediaQueryListEvent>(
+      this.mediaMatcher.matchMedia("(prefers-color-scheme: dark)"),
+      "change"
+    ).subscribe((event) => {
+      this.updateSystemTheme(event.matches ? ThemeType.Dark : ThemeType.Light);
+    });
+  }
+}