feat(approvals): live pending-count badges on every Approval Center tab and the Approvals menu

The badges are pushed, not polled. ApprovalCountsService opens one Server-Sent Events stream (/approvals/counts/stream) through HttpClient so the login and tenant headers apply; the server writes a `counts` event the moment the numbers change. - Total badge on the Approvals menu, count badge on 26 Approval Center tabs (Reject Account and Terminated Account are lists, not requests: no badge). - Last numbers are kept per login in localStorage, so a page refresh shows them at once until the stream's first event makes them exact. - Stream recycles every few minutes and reconnects at once; after a failure it retries with a growing wait and reads /approvals/counts meanwhile. - NO_PROGRESS_BAR token: the background stream does not run the top progress bar. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
2026-10-15 15:49:36 +05:30
parent ab8ed7e67e
commit 4d205672df
9 changed files with 368 additions and 3 deletions
@@ -0,0 +1,193 @@
+/**
+ * Copyright since 2025 Mifos Initiative
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+import { Injectable, OnDestroy, inject } from '@angular/core';
+import { HttpClient, HttpContext, HttpDownloadProgressEvent, HttpEvent, HttpEventType } from '@angular/common/http';
+import { BehaviorSubject, Subscription } from 'rxjs';
+import { AuthenticationService } from '../core/authentication/authentication.service';
+import { SILENT_HTTP_ERROR } from '../core/http/silent-error.token';
+import { NO_PROGRESS_BAR } from '../core/progress-bar/no-progress.token';
+
+/** What the server pushes: the total and, for each Approval Center tab with something waiting, its number. */
+interface ApprovalCounts {
+  total: number;
+  counts: Record<string, number>;
+}
+
+/** After a stream drops, the first wait before reconnecting; it doubles up to the cap. */
+const RETRY_MS = 2_000;
+const RETRY_MAX_MS = 60_000;
+
+/** A stream that ends sooner than this after opening is treated as a failure. */
+const MIN_STREAM_MS = 3_000;
+
+/**
+ * How many requests wait on each Approval Center tab, and the total for the Approvals menu.
+ *
+ * The numbers are pushed, not polled: the service opens one Server-Sent Events stream, GET /approvals/counts/stream, and
+ * the server writes a `counts` event the moment the numbers change, so a request raised or actioned by anyone moves the
+ * badge within about a second with no reloads and no traffic while nothing changes. The server answers numbers only
+ * (no rows); a tab still loads its own list when it is opened, and applies its own table, status, office scope and
+ * permission, so a tab the login may not see is absent.
+ *
+ * The stream goes through HttpClient (not EventSource, which cannot send the login's headers), so the usual
+ * authentication and tenant headers apply. It is silent (see SILENT_HTTP_ERROR, NO_PROGRESS_BAR): no error popup and no
+ * progress bar. The server ends a stream every few minutes and the service reconnects at once; after a failure it keeps
+ * the last numbers and retries with a growing wait.
+ *
+ * A browser tab that is hidden keeps its stream: it is one idle connection, and the badge is right when it is shown.
+ */
+@Injectable({ providedIn: 'root' })
+export class ApprovalCountsService implements OnDestroy {
+  private http = inject(HttpClient);
+  private authenticationService = inject(AuthenticationService);
+
+  private readonly countsSubject = new BehaviorSubject<Record<string, number>>({});
+  private readonly totalSubject = new BehaviorSubject<number>(0);
+  /** Pending count per tab key; a tab with nothing waiting is absent. */
+  readonly counts$ = this.countsSubject.asObservable();
+  /** Everything waiting across all the tabs the signed-in user can see. */
+  readonly total$ = this.totalSubject.asObservable();
+
+  private active = false;
+  private failures = 0;
+  private stream: Subscription | null = null;
+  private retryTimer: ReturnType<typeof setTimeout> | null = null;
+
+  /** Whether this login reaches the Approval Center at all, so nothing is asked for everyone else. */
+  get canSeeApprovals(): boolean {
+    const permissions = this.authenticationService.getCredentials()?.permissions ?? [];
+    return permissions.includes('ALL_FUNCTIONS') || permissions.includes('MENU_TASKS');
+  }
+
+  /** Opens the stream (once; a second call changes nothing). */
+  start(): void {
+    if (this.active || !this.canSeeApprovals) return;
+    this.active = true;
+    // After a page refresh the last numbers show at once; the stream's first event (a moment later) makes them exact.
+    this.restore();
+    this.connect();
+  }
+
+  stop(): void {
+    this.active = false;
+    this.stream?.unsubscribe();
+    this.stream = null;
+    if (this.retryTimer) clearTimeout(this.retryTimer);
+    this.retryTimer = null;
+    this.failures = 0;
+  }
+
+  ngOnDestroy(): void {
+    this.stop();
+  }
+
+  private connect(): void {
+    if (!this.active) return;
+    // Text already handled, so each progress event is only read from where the last one ended.
+    let consumed = 0;
+    const startedAt = Date.now();
+    this.stream = this.http
+      .get('/approvals/counts/stream', {
+        observe: 'events',
+        reportProgress: true,
+        responseType: 'text',
+        headers: { Accept: 'text/event-stream' },
+        context: new HttpContext().set(SILENT_HTTP_ERROR, true).set(NO_PROGRESS_BAR, true)
+      })
+      .subscribe({
+        next: (event: HttpEvent<string>) => {
+          if (event.type !== HttpEventType.DownloadProgress) return;
+          const text = (event as HttpDownloadProgressEvent).partialText ?? '';
+          consumed = this.read(text, consumed);
+        },
+        // The server closes a stream after a few minutes: connect again straight away. One that ended almost at once
+        // was not a stream at all (a proxy answering for it, say), so that is a failure and backs off.
+        complete: () => (Date.now() - startedAt < MIN_STREAM_MS ? this.retryLater() : this.connect()),
+        error: () => this.retryLater()
+      });
+  }
+
+  private retryLater(): void {
+    this.failures += 1;
+    // While the stream is down (an older server without it, a proxy that blocks it) the badge is still kept right by a
+    // plain read each time the retry comes round; the stream takes over again as soon as it connects.
+    this.http
+      .get<ApprovalCounts>('/approvals/counts', {
+        params: { fresh: 'true' },
+        context: new HttpContext().set(SILENT_HTTP_ERROR, true).set(NO_PROGRESS_BAR, true)
+      })
+      .subscribe({
+        next: (answer) => {
+          this.countsSubject.next(answer.counts ?? {});
+          this.totalSubject.next(answer.total ?? 0);
+          this.remember(answer);
+        },
+        error: () => undefined
+      });
+    const wait = Math.min(RETRY_MAX_MS, RETRY_MS * 2 ** (this.failures - 1));
+    this.retryTimer = setTimeout(() => this.connect(), wait);
+  }
+
+  /** Reads every complete event after `from` (events end with a blank line) and returns how far it got. */
+  private read(text: string, from: number): number {
+    let position = from;
+    let end = text.indexOf('\n\n', position);
+    while (end !== -1) {
+      this.handle(text.slice(position, end));
+      position = end + 2;
+      end = text.indexOf('\n\n', position);
+    }
+    return position;
+  }
+
+  private handle(block: string): void {
+    let name = 'message';
+    const data: string[] = [];
+    for (const line of block.split('\n')) {
+      if (line.startsWith('event:')) name = line.slice(6).trim();
+      else if (line.startsWith('data:')) data.push(line.slice(5).trimStart());
+    }
+    // Comment lines (the server's keep-alive pings) carry no event and are ignored.
+    if (name !== 'counts' || data.length === 0) return;
+    try {
+      const answer = JSON.parse(data.join('\n')) as ApprovalCounts;
+      this.failures = 0;
+      this.countsSubject.next(answer.counts ?? {});
+      this.totalSubject.next(answer.total ?? 0);
+      this.remember(answer);
+    } catch {
+      // A damaged event is skipped; the next change sends the numbers again.
+    }
+  }
+
+  /** Storage is per login, so one user's numbers are never shown to the next person on the same browser. */
+  private storageKey(): string {
+    return `approvalCounts:${this.authenticationService.getCredentials()?.username ?? ''}`;
+  }
+
+  private remember(answer: ApprovalCounts): void {
+    try {
+      localStorage.setItem(this.storageKey(), JSON.stringify({ total: answer.total, counts: answer.counts }));
+    } catch {
+      // Storage can be blocked or full; the badge simply starts empty after a refresh.
+    }
+  }
+
+  private restore(): void {
+    try {
+      const saved = JSON.parse(localStorage.getItem(this.storageKey()) ?? 'null') as ApprovalCounts | null;
+      if (saved && typeof saved.total === 'number' && saved.counts) {
+        this.countsSubject.next(saved.counts);
+        this.totalSubject.next(saved.total);
+      }
+    } catch {
+      // Unreadable or missing: start empty and wait for the first event.
+    }
+  }
+}