perf(calendar): pre-filter ICS data before parsing

Author: KristjanESPERANTO

cspell.config.json

@@ -257,6 +257,7 @@
 		"pubdate",
 		"radokristof",
 		"rajniszp",
+		"RDATE",
 		"rebuilded",
 		"Reis",
 		"rejas",
@@ -364,7 +365,8 @@
 		"xxxe",
 		"Ybbet",
 		"yearmatch",
-		"yearmatchgroup"
+		"yearmatchgroup",
+		"YYYYMMDDTHHMMSSZ"
 	],
 	"ignorePaths": [
 		"css/roboto.css",

defaultmodules/calendar/calendarfetcher.js

@@ -1,4 +1,5 @@
 const ical = require("node-ical");
+const moment = require("moment-timezone");
 const Log = require("logger");
 const CalendarFetcherUtils = require("./calendarfetcherutils");
 const HTTPFetcher = require("#http_fetcher");
@@ -59,7 +60,13 @@ class CalendarFetcher {
 			}
 
 			const responseData = await response.text();
-			const parsed = await ical.async.parseICS(responseData);
+
+			// ics-filter is ESM-only, so we import it dynamically from this CommonJS file.
+			const { icsFilter } = await import("ics-filter");
+			const [windowStart, windowEnd] = this.#filterWindow();
+			const filteredData = icsFilter(responseData, windowStart, windowEnd);
+
+			const parsed = await ical.async.parseICS(filteredData);
 
 			Log.debug(`Parsed iCal data from ${this.url} with ${Object.keys(parsed).length} entries.`);
 
@@ -94,6 +101,21 @@ class CalendarFetcher {
 		this.httpFetcher.startPeriodicFetch();
 	}
 
+	/**
+	 * Time window of events to keep, as [start, end].
+	 * Without includePastEvents the window starts now; otherwise it also
+	 * reaches maximumNumberOfDays into the past.
+	 * @returns {[Date, Date]} The inclusive start and end of the window.
+	 */
+	#filterWindow () {
+		const today = moment().startOf("day");
+		const start = this.includePastEvents
+			? today.clone().subtract(this.maximumNumberOfDays, "days").toDate()
+			: new Date();
+		const end = today.clone().add(this.maximumNumberOfDays, "days").toDate();
+		return [start, end];
+	}
+
 	/**
 	 * Check if enough time has passed since the last fetch to warrant a new one.
 	 * Uses reloadInterval as the threshold to respect user's configured fetchInterval.

package-lock.json

@@ -93,6 +93,7 @@
 		"helmet": "^8.2.0",
 		"html-to-text": "^10.0.0",
 		"iconv-lite": "^0.7.2",
+		"ics-filter": "^1.0.2",
 		"ipaddr.js": "^2.4.0",
 		"moment": "^2.30.1",
 		"moment-timezone": "^0.6.2",