Polish Holidays ICS

package.json

@@ -16,6 +16,7 @@
     "cheerio": "^1.0.0-rc.10",
     "clsx": "^1.1.1",
     "eslint-config-next": "^15.1.6",
+    "ics": "^3.8.1",
     "jotai": "^2.9.2",
     "next": "15.3.7",
     "next-themes": "^0.4.4",

src/app/api/holidays/route.ts

@@ -0,0 +1,149 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getHolidays, type Holiday } from "@/lib/scrapeHolidays";
+import { generateICS } from "@/lib/generateICS";
+
+// Cache configuration constants
+const SECONDS_IN_DAY = 86400;
+const SECONDS_IN_MONTH = 30 * SECONDS_IN_DAY; // 2,592,000 seconds
+const SECONDS_IN_WEEK = 7 * SECONDS_IN_DAY; // 604,800 seconds
+
+// Cache headers configuration
+const CACHE_MAX_AGE = SECONDS_IN_DAY; // 1 day for browsers
+const CACHE_S_MAXAGE = SECONDS_IN_MONTH; // 1 month for edge cache
+const CACHE_STALE_WHILE_REVALIDATE = SECONDS_IN_WEEK; // 1 week stale-while-revalidate
+
+// Month constants (1-indexed)
+const MONTHS = {
+  JANUARY: 1,
+  FEBRUARY: 2,
+  MARCH: 3,
+  APRIL: 4,
+  MAY: 5,
+  JUNE: 6,
+  JULY: 7,
+  AUGUST: 8,
+  SEPTEMBER: 9,
+  OCTOBER: 10,
+  NOVEMBER: 11,
+  DECEMBER: 12,
+} as const;
+
+// We fetch next year's holidays when we're 1 month away from the new year
+const MONTH_TO_START_FETCHING_NEXT_YEAR = MONTHS.NOVEMBER;
+
+/**
+ * Gets the current date information
+ */
+const getCurrentDateInfo = () => {
+  const now = new Date();
+  return {
+    year: now.getFullYear(),
+    month: now.getMonth() + 1, // Convert from 0-indexed to 1-indexed
+  };
+};
+
+/**
+ * Determines which years to fetch based on current date
+ * If we're in November or December, also fetch next year's holidays
+ * This ensures we have next year's data ready before the year transition
+ */
+const getYearsToFetch = (): number[] => {
+  const { year, month } = getCurrentDateInfo();
+  const years: number[] = [year];
+
+  // If we're 1 month or less away from the new year, also fetch next year
+  if (month >= MONTH_TO_START_FETCHING_NEXT_YEAR) {
+    years.push(year + 1);
+  }
+
+  return years;
+};
+
+/**
+ * Fetches holidays for a single year
+ * Throws error if fetch fails (to preserve error context)
+ */
+const fetchHolidaysForYear = async (year: number): Promise<Holiday[]> => {
+  return await getHolidays(year);
+};
+
+/**
+ * Fetches holidays for multiple years, ensuring current year is always included
+ */
+const fetchHolidaysForYears = async (years: number[]): Promise<Holiday[]> => {
+  const currentYear = getCurrentDateInfo().year;
+  const allHolidays: Holiday[] = [];
+
+  for (const year of years) {
+    try {
+      const holidays = await fetchHolidaysForYear(year);
+      allHolidays.push(...holidays);
+    } catch (error) {
+      // If current year fails to fetch, re-throw the error
+      if (year === currentYear) {
+        throw error;
+      }
+      // For next year, log but continue (it might not be available yet)
+      console.error(`Failed to fetch holidays for year ${year} (non-critical):`, error);
+    }
+  }
+
+  return allHolidays;
+};
+
+/**
+ * Sorts holidays by date in ascending order
+ */
+const sortHolidaysByDate = (holidays: Holiday[]): Holiday[] => {
+  return [...holidays].sort((a, b) => a.date.localeCompare(b.date));
+};
+
+/**
+ * Builds cache control header value
+ */
+const buildCacheControlHeader = (): string => {
+  return `public, max-age=${CACHE_MAX_AGE}, s-maxage=${CACHE_S_MAXAGE}, stale-while-revalidate=${CACHE_STALE_WHILE_REVALIDATE}`;
+};
+
+/**
+ * Builds response headers for ICS file
+ */
+const buildICSHeaders = (year: number) => {
+  return {
+    "Content-Type": "text/calendar; charset=utf-8",
+    "Content-Disposition": `attachment; filename="polish-holidays-${year}.ics"`,
+    "Cache-Control": buildCacheControlHeader(),
+  };
+};
+
+/**
+ * Creates a successful ICS response
+ */
+const createICSSuccessResponse = (holidays: Holiday[], year: number): NextResponse => {
+  const icsContent = generateICS(holidays);
+  return new NextResponse(icsContent, {
+    status: 200,
+    headers: buildICSHeaders(year),
+  });
+};
+
+/**
+ * Creates an error response
+ */
+const createErrorResponse = (message: string, status: number = 500): NextResponse => {
+  return NextResponse.json({ message }, { status });
+};
+
+export async function GET(request: NextRequest) {
+  try {
+    const years = getYearsToFetch();
+    const holidays = await fetchHolidaysForYears(years);
+    const sortedHolidays = sortHolidaysByDate(holidays);
+    const currentYear = getCurrentDateInfo().year;
+
+    return createICSSuccessResponse(sortedHolidays, currentYear);
+  } catch (error) {
+    console.error("Error generating holidays ICS:", error);
+    return createErrorResponse("Failed to generate holidays calendar", 500);
+  }
+}

src/lib/generateICS.ts

@@ -0,0 +1,58 @@
+import { createEvents, type EventAttributes } from "ics";
+import type { Holiday } from "./scrapeHolidays";
+
+/**
+ * Parses a date string (YYYY-MM-DD) into [year, month, day] array
+ * Month is 1-indexed (1-12) as required by the ics library
+ */
+const parseDateToArray = (dateStr: string): [number, number, number] => {
+  const [year, month, day] = dateStr.split("-").map(Number);
+  return [year, month, day];
+};
+
+/**
+ * Calculates the next day for all-day events
+ * The ics library requires end date to be the day after for all-day events
+ */
+const getNextDay = (dateArray: [number, number, number]): [number, number, number] => {
+  const [year, month, day] = dateArray;
+  const date = new Date(year, month - 1, day); // month is 0-indexed in Date
+  date.setDate(date.getDate() + 1);
+  return [date.getFullYear(), date.getMonth() + 1, date.getDate()];
+};
+
+/**
+ * Transforms a holiday into an ICS event attribute
+ */
+const holidayToEvent = (holiday: Holiday): EventAttributes => {
+  const start = parseDateToArray(holiday.date);
+  const end = getNextDay(start);
+
+  return {
+    title: holiday.name,
+    start,
+    end,
+    startInputType: "local",
+    endInputType: "local",
+    productId: "dudek.sh//Polish Holidays//EN",
+  };
+};
+
+/**
+ * Generates ICS calendar content from holidays using the ics library
+ */
+export const generateICS = (holidays: Holiday[]): string => {
+  const events = holidays.map(holidayToEvent);
+
+  const { error, value } = createEvents(events);
+
+  if (error) {
+    throw new Error(`Failed to generate ICS: ${error.message}`);
+  }
+
+  if (!value) {
+    throw new Error("ICS generation returned no value");
+  }
+
+  return value;
+};