fix: support RDATE for events with explicit future dates

ics/with-rdate.ics

@@ -0,0 +1,32 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Test//Test//EN
+BEGIN:VEVENT
+UID:rdate-future@test
+DTSTART:20200101T100000Z
+DTEND:20200101T110000Z
+RDATE:20300101T100000Z,20310101T100000Z
+SUMMARY:RDATE with future dates - should be kept
+END:VEVENT
+BEGIN:VEVENT
+UID:rdate-past@test
+DTSTART:20180101T100000Z
+DTEND:20180101T110000Z
+RDATE:20190101T100000Z,20200101T100000Z
+SUMMARY:RDATE with only past dates - should be dropped
+END:VEVENT
+BEGIN:VEVENT
+UID:rdate-value-date@test
+DTSTART:20200601T100000Z
+DTEND:20200601T110000Z
+RDATE;VALUE=DATE:20300601,20310601
+SUMMARY:RDATE with VALUE=DATE format - should be kept
+END:VEVENT
+BEGIN:VEVENT
+UID:rdate-period@test
+DTSTART:20200601T100000Z
+DTEND:20200601T120000Z
+RDATE;VALUE=PERIOD:20300601T100000Z/20300601T120000Z
+SUMMARY:RDATE with VALUE=PERIOD format - should be kept
+END:VEVENT
+END:VCALENDAR

src/index.ts

@@ -18,6 +18,8 @@ export const icsFilter = (content: string, now: Date, max?: Date): string => {
 
   let keep: boolean = true;
   let hasRrule: boolean = false;
+  let hasRdate: boolean = false;
+  let rdateKeep: boolean = false;
   let hasKeptRecurrenceId: boolean = false;
   let rruleKeep: boolean = true;
 
@@ -57,6 +59,8 @@ export const icsFilter = (content: string, now: Date, max?: Date): string => {
 
       keep = true;
       hasRrule = false;
+      hasRdate = false;
+      rdateKeep = false;
       hasKeptRecurrenceId = false;
       rruleKeep = true;
       return;
@@ -142,6 +146,14 @@ export const icsFilter = (content: string, now: Date, max?: Date): string => {
           return;
         }
 
+        if (hasRdate && rdateKeep) {
+          if (isDevRun) {
+            console.log("DTEND lower than now, but rdate keeps it:", dtEnd, nowStr, "-->", line);
+          }
+
+          return;
+        }
+
         if (hasKeptRecurrenceId) {
           if (isDevRun) {
             console.log("DTEND lower than now, but recurrenceId keeps it:", dtEnd, nowStr, "-->", line);
@@ -188,6 +200,39 @@ export const icsFilter = (content: string, now: Date, max?: Date): string => {
       return;
     }
 
+    if (lineUpper.startsWith("RDATE")) {
+      const value: string | null = extractValue(line);
+      if (!value) {
+        return;
+      }
+
+      hasRdate = true;
+
+      for (const dateRaw of value.split(",")) {
+        const date: string | null = normalizeICSDateStr(dateRaw.trim());
+        if (!date) {
+          continue;
+        }
+
+        if (date >= nowStr && (!maxStr || date <= maxStr)) {
+          rdateKeep = true;
+          keep = true;
+
+          if (isDevRun) {
+            console.log("RDATE date in range:", date, "-->", line);
+          }
+
+          break;
+        }
+      }
+
+      if (isDevRun && !rdateKeep) {
+        console.log("RDATE: no dates in range", "-->", line);
+      }
+
+      return;
+    }
+
     if (lineUpper.startsWith("RECURRENCE-ID")) {
       const value: string | null = extractValue(line);
       const dtRecurrence: string | null = normalizeICSDateStr(value);

src/tests/rdate-support.test.ts

@@ -0,0 +1,37 @@
+import assert from "node:assert";
+import { readFileSync } from "node:fs";
+import { describe, test } from "node:test";
+
+import { icsFilter } from "../index.js";
+
+const content: string = readFileSync("./ics/with-rdate.ics", "utf-8");
+const now: Date = new Date();
+const max: Date = new Date(now.getTime() + 365 * 24 * 60 * 60 * 1000); // 1 year from now
+const filteredContent: string = icsFilter(content, now);
+const filteredMaxContent: string = icsFilter(content, now, max);
+
+describe("icsFilter on ics content with RDATE properties", () => {
+  test("should keep event with RDATE dates in the future", () => {
+    assert.ok(filteredContent.includes("rdate-future@test"), "Event with future RDATE dates should be kept");
+  });
+
+  test("should drop event with only past RDATE dates", () => {
+    assert.ok(!filteredContent.includes("rdate-past@test"), "Event with only past RDATE dates should be dropped");
+  });
+
+  test("should keep event with RDATE;VALUE=DATE format dates in the future", () => {
+    assert.ok(filteredContent.includes("rdate-value-date@test"), "Event with future RDATE;VALUE=DATE dates should be kept");
+  });
+
+  test("should keep event with RDATE;VALUE=PERIOD format dates in the future", () => {
+    assert.ok(filteredContent.includes("rdate-period@test"), "Event with future RDATE;VALUE=PERIOD dates should be kept");
+  });
+});
+
+describe("icsFilter on ics content with RDATE properties and max limit", () => {
+  test("should drop events whose RDATE dates are all beyond max", () => {
+    assert.ok(!filteredMaxContent.includes("rdate-future@test"), "Event with RDATE dates beyond max should be dropped");
+    assert.ok(!filteredMaxContent.includes("rdate-value-date@test"), "Event with RDATE;VALUE=DATE dates beyond max should be dropped");
+    assert.ok(!filteredMaxContent.includes("rdate-period@test"), "Event with RDATE;VALUE=PERIOD dates beyond max should be dropped");
+  });
+});