feat: Implement Telegram alerts for catalog updates and failures

server/index.js

@@ -11,6 +11,8 @@ import { createHash } from "node:crypto";
 import { timetable } from "./timetable.js";
 import { catalogDiagnostics } from "./diagnostics.js";
 import { securityHeaders, requestTimeout } from "./protect.js";
+import { startWatch, watchOnce, watchStatus } from "./watch.js";
+import { telegram } from "./alerts.js";
 import {
   getIndex,
   indexStatus,
@@ -67,8 +69,9 @@ app.use("/api", (_req, res, next) => {
 // 7 — /api/diagnostics, cells the parser could not read with confidence;
 // 8 — /api/ready, and `ready` in /api/health;
 // 9 — a request limit on /api (429 too_many_requests), a 30 s time limit (504 timeout), security headers;
-// 10 — parserVersion in /api/catalog.
-const API_VERSION = 10;
+// 10 — parserVersion in /api/catalog;
+// 11 — the catalog is checked by ETag every 5 minutes; `watch`, `telegram` and `catalog.lastCrawl` in /api/health.
+const API_VERSION = 11;
 
 /**
  * What the server still waits for before it answers from memory: the catalog, the week table
@@ -89,6 +92,9 @@ app.get("/api/health", async (req, res) => {
     parserVersion: PARSER_VERSION,
     ...sources,
     directory: indexStatus(),
+    // The server's own checks of the catalog and its messages to the owner.
+    watch: watchStatus,
+    telegram: { enabled: telegram.enabled, sent: telegram.sent, lastSentAt: telegram.lastSentAt, lastError: telegram.lastError },
   });
 });
 // Readiness for Docker and a proxy: 503 until the catalog, the week table and the index are
@@ -309,7 +315,13 @@ export function start(port = Number(process.env.PORT || 3001), host = process.en
     console.log(`API и PWA: http://127.0.0.1:${port}`);
     // So the first visit and the first search do not wait for the university.
     getCalendar().catch((e) => console.error(`Таблица недель: ${e.message}`));
-    getIndex().catch((e) => console.error(`Индекс: ${e.message}`));
+    getIndex()
+      .catch((e) => console.error(`Индекс: ${e.message}`))
+      // Then the catalog is watched every few minutes, with messages in Telegram if set up.
+      .finally(() => {
+        watchOnce();
+        startWatch();
+      });
   });
   // A client must send its headers within 15 s and the whole request (a Word upload of up to
   // 10 MB on a slow phone) within two minutes, so slow connections cannot pile up.