first commit

src/current/current-events.service.ts

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+import { Injectable } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import { distinctUntilChanged, from, map, Observable, switchMap, timer } from 'rxjs';
+import { getIntegerConfig } from '../common/config-number';
+import { CurrentResponseDto } from './dto/current-response.dto';
+import { GetCurrentDto } from './dto/get-current.dto';
+import { CurrentService } from './current.service';
+
+type CurrentSseMessage = {
+  data: CurrentResponseDto;
+};
+
+type CurrentSnapshot = {
+  signature: string;
+  response: CurrentResponseDto;
+};
+
+const DEFAULT_CURRENT_EVENTS_POLL_MS = 1_000;
+
+@Injectable()
+export class CurrentEventsService {
+  constructor(
+    private readonly current: CurrentService,
+    private readonly config: ConfigService,
+  ) {}
+
+  /** Отправляет SSE-события current только при изменении снимка данных по edge/tags. */
+  stream(query: GetCurrentDto): Observable<CurrentSseMessage> {
+    const pollMs = Math.max(
+      getIntegerConfig(this.config, 'CURRENT_EVENTS_POLL_MS', DEFAULT_CURRENT_EVENTS_POLL_MS),
+      250,
+    );
+
+    return timer(0, pollMs).pipe(
+      switchMap(() => from(this.createSnapshot(query))),
+      distinctUntilChanged((previous, current) => previous.signature === current.signature),
+      map((snapshot) => ({ data: snapshot.response })),
+    );
+  }
+
+  /** Собирает стабильную подпись ответа, чтобы не слать одинаковые SSE-события повторно. */
+  private async createSnapshot(query: GetCurrentDto): Promise<CurrentSnapshot> {
+    const response = await this.current.findByEdge(query);
+    return {
+      response,
+      signature: JSON.stringify(response),
+    };
+  }
+}