[PM-5606] Add reactive generator service (#7446)

libs/common/src/tools/generator/default-generator.service.ts

@@ -0,0 +1,64 @@
+import { firstValueFrom, map, share, timer, ReplaySubject, Observable } from "rxjs";
+
+// FIXME: use index.ts imports once policy abstractions and models
+// implement ADR-0002
+import { PolicyService } from "../../admin-console/abstractions/policy/policy.service.abstraction";
+import { ActiveUserStateProvider } from "../../platform/state";
+
+import { GeneratorStrategy, GeneratorService, PolicyEvaluator } from "./abstractions";
+
+/** {@link GeneratorServiceAbstraction} */
+export class DefaultGeneratorService<Options, Policy> implements GeneratorService<Options, Policy> {
+  /** Instantiates the generator service
+   * @param strategy tailors the service to a specific generator type
+   *            (e.g. password, passphrase)
+   * @param policy provides the policy to enforce
+   * @param state saves and loads password generation options to the location
+   *             specified by the strategy
+   */
+  constructor(
+    private strategy: GeneratorStrategy<Options, Policy>,
+    private policy: PolicyService,
+    private state: ActiveUserStateProvider,
+  ) {
+    this._policy$ = this.policy.get$(this.strategy.policy).pipe(
+      map((policy) => this.strategy.evaluator(policy)),
+      share({
+        // cache evaluator in a replay subject to amortize creation cost
+        // and reduce GC pressure.
+        connector: () => new ReplaySubject(1),
+        resetOnRefCountZero: () => timer(this.strategy.cache_ms),
+      }),
+    );
+  }
+
+  private _policy$: Observable<PolicyEvaluator<Policy, Options>>;
+
+  /** {@link GeneratorService.options$} */
+  get options$() {
+    return this.state.get(this.strategy.disk).state$;
+  }
+
+  /** {@link GeneratorService.saveOptions} */
+  async saveOptions(options: Options): Promise<void> {
+    await this.state.get(this.strategy.disk).update(() => options);
+  }
+
+  /** {@link GeneratorService.policy$} */
+  get policy$() {
+    return this._policy$;
+  }
+
+  /** {@link GeneratorService.enforcePolicy} */
+  async enforcePolicy(options: Options): Promise<Options> {
+    const policy = await firstValueFrom(this._policy$);
+    const evaluated = policy.applyPolicy(options);
+    const sanitized = policy.sanitize(evaluated);
+    return sanitized;
+  }
+
+  /** {@link GeneratorService.generate} */
+  async generate(options: Options): Promise<string> {
+    return await this.strategy.generate(options);
+  }
+}