perf: Remove isAfter/isBefore in date-ranges:subtract (calcom#22549)

* perf: Remove isAfter/isBefore in date-ranges:subtract

* Small amend to also use valueOf here

* Addressed issue with utc offset in non-utc mode

* test: add failing test demonstrating timezone offset bug in subtract function

This test shows that when mixing UTC and timezone-aware dayjs objects,
the timezone offset adjustment (date.valueOf() + date.utcOffset() * 60000)
creates incorrect chronological comparisons that prevent proper exclusion.

The test expects 0 results but gets 6, reproducing the issue causing
futureLimit.timezone.test.ts to fail with extra time slots.

Co-Authored-By: alex@cal.com <me@alexvanandel.com>

* Fixed failing tests that proved the logic wasn't working correctly

* test: add scheduling pipeline reproduction test for futureLimit.timezone.test.ts failures

This test reproduces the exact scenario from getBusyTimes.ts that causes
the 6 extra slots (12:30-17:30 UTC) to appear in futureLimit.timezone.test.ts.

The test simulates:
- calendarBusyTimes from external calendar sources (converted to dayjs objects)
- openSeatsDateRanges from booking data with mixed timezone contexts
- The specific timezone mixing pattern that causes exclusion to fail

This demonstrates the remaining issue in the subtract function after
the timezone offset bug was fixed.

Co-Authored-By: alex@cal.com <me@alexvanandel.com>

* test: add getUserAvailability reproduction test showing subtract extends ranges instead of excluding busy times

This test reproduces the exact scenario from futureLimit.timezone.test.ts where the subtract function incorrectly extends available range end times to match busy time start times instead of properly subtracting the busy times from the available ranges.

Co-Authored-By: alex@cal.com <me@alexvanandel.com>

* test: fix getUserAvailability reproduction test to expect actual buggy behavior

The test now expects the current buggy behavior (5 ranges with 2024-06-02 missing)
instead of correct behavior, so it passes with current logic and would fail once
the subtract function is fixed to properly handle non-overlapping busy times.

Co-Authored-By: alex@cal.com <me@alexvanandel.com>

* test: fix getUserAvailability reproduction test to expect correct behavior and fail with buggy logic

The test now expects the correct behavior (ranges should remain at 12:30:00.000Z and all 6 ranges should be present) so it fails with the current buggy subtract function logic that incorrectly extends ranges to 18:30:00.000Z. Once the subtract function is fixed, this test will pass.

Co-Authored-By: alex@cal.com <me@alexvanandel.com>

* Push the valid fix for the futureLimits test failure

* test: update getUserAvailability test console output to match corrected behavior

The test now correctly expects 5 ranges (with June 2 properly excluded due to overlapping busy time) and the console output reflects this corrected behavior.

Co-Authored-By: alex@cal.com <me@alexvanandel.com>

* Remove console.log calls

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: emrysal

packages/lib/date-ranges.test.ts

@@ -957,14 +957,6 @@ describe("intersect function comprehensive tests", () => {
       const endTime = performance.now();
       const executionTime = endTime - startTime;
 
-      console.log(`Intersect function execution time: ${executionTime.toFixed(2)}ms`);
-      console.log(
-        `Processed ${
-          commonAvailability.length + userRanges1.length + userRanges2.length + userRanges3.length
-        } total date ranges`
-      );
-      console.log(`Found ${result.length} intersections`);
-
       expect(executionTime).toBeLessThan(100);
       expect(result.length).toBeGreaterThanOrEqual(0);
 
@@ -1038,4 +1030,80 @@ describe("intersect function comprehensive tests", () => {
       expect(result).toEqual([]);
     });
   });
+
+  describe("timezone offset exclusion bug", () => {
+    it("should succesfully mix UTC and timezone-aware dayjs objects in subtract", () => {
+      const TIMEZONE = "Asia/Kolkata"; // IST timezone (+05:30)
+
+      const sourceRanges = [
+        { start: dayjs.utc("2024-05-31T12:30:00.000Z"), end: dayjs.utc("2024-05-31T13:30:00.000Z") },
+        { start: dayjs.utc("2024-05-31T13:30:00.000Z"), end: dayjs.utc("2024-05-31T14:30:00.000Z") },
+        { start: dayjs.utc("2024-05-31T14:30:00.000Z"), end: dayjs.utc("2024-05-31T15:30:00.000Z") },
+        { start: dayjs.utc("2024-05-31T15:30:00.000Z"), end: dayjs.utc("2024-05-31T16:30:00.000Z") },
+        { start: dayjs.utc("2024-05-31T16:30:00.000Z"), end: dayjs.utc("2024-05-31T17:30:00.000Z") },
+        { start: dayjs.utc("2024-05-31T17:30:00.000Z"), end: dayjs.utc("2024-05-31T18:30:00.000Z") },
+      ];
+
+      const excludedRanges = [
+        {
+          start: dayjs("2024-05-31T12:30:00.000Z").tz(TIMEZONE),
+          end: dayjs("2024-05-31T23:59:59.999Z").tz(TIMEZONE),
+        },
+      ];
+
+      const result = subtract(sourceRanges, excludedRanges);
+
+      expect(result).toHaveLength(0);
+    });
+
+    it("should demonstrate timezone handling when same timezone", () => {
+      const TIMEZONE = "Asia/Kolkata";
+
+      const sourceRange = {
+        start: dayjs("2024-05-31T12:30:00.000Z").tz(TIMEZONE),
+        end: dayjs("2024-05-31T13:30:00.000Z").tz(TIMEZONE),
+      };
+
+      const excludedRange = {
+        start: dayjs("2024-05-31T12:30:00.000Z").tz(TIMEZONE),
+        end: dayjs("2024-05-31T18:00:00.000Z").tz(TIMEZONE),
+      };
+
+      const result = subtract([sourceRange], [excludedRange]);
+
+      expect(result).toHaveLength(0);
+    });
+
+    it("should not extend ranges instead of excluding busy times", () => {
+      const dateRanges = [
+        { start: dayjs("2024-05-31T04:00:00.000Z"), end: dayjs("2024-05-31T12:30:00.000Z") },
+        { start: dayjs("2024-06-01T04:00:00.000Z"), end: dayjs("2024-06-01T12:30:00.000Z") },
+        { start: dayjs("2024-06-02T04:00:00.000Z"), end: dayjs("2024-06-02T12:30:00.000Z") },
+        { start: dayjs("2024-06-03T04:00:00.000Z"), end: dayjs("2024-06-03T12:30:00.000Z") },
+        { start: dayjs("2024-06-04T04:00:00.000Z"), end: dayjs("2024-06-04T12:30:00.000Z") },
+        { start: dayjs("2024-06-05T04:00:00.000Z"), end: dayjs("2024-06-05T12:30:00.000Z") },
+      ];
+
+      // formattedBusyTimes from failing ROLLING_WINDOW test - this is the booking that should NOT affect dateRanges
+      const formattedBusyTimes = [
+        { start: dayjs("2024-06-01T18:30:00.000Z"), end: dayjs("2024-06-02T18:30:00.000Z") },
+      ];
+
+      const result = subtract(dateRanges, formattedBusyTimes);
+
+      // What the result SHOULD be (correct behavior): June 2 range is properly excluded due to overlapping busy time
+      const expectedCorrectedOutput = [
+        { start: dayjs("2024-05-31T04:00:00.000Z"), end: dayjs("2024-05-31T12:30:00.000Z") },
+        { start: dayjs("2024-06-01T04:00:00.000Z"), end: dayjs("2024-06-01T12:30:00.000Z") },
+        { start: dayjs("2024-06-03T04:00:00.000Z"), end: dayjs("2024-06-03T12:30:00.000Z") },
+        { start: dayjs("2024-06-04T04:00:00.000Z"), end: dayjs("2024-06-04T12:30:00.000Z") },
+        { start: dayjs("2024-06-05T04:00:00.000Z"), end: dayjs("2024-06-05T12:30:00.000Z") },
+      ];
+
+      expect(result).toHaveLength(5); // Correct: June 2 range is properly excluded
+      expect(result[0].end.toISOString()).toBe("2024-05-31T12:30:00.000Z"); // Correct: no extension
+      expect(result[1].end.toISOString()).toBe("2024-06-01T12:30:00.000Z"); // Correct: no extension
+      expect(result.find((r) => r.start.toISOString() === "2024-06-02T04:00:00.000Z")).toBeUndefined(); // Correct: June 2 excluded
+    });
+  });
 });

packages/lib/date-ranges.ts

@@ -307,25 +307,26 @@ export function subtract(
   sourceRanges: (DateRange & { [x: string]: unknown })[],
   excludedRanges: DateRange[]
 ) {
-  const result: DateRange[] = [];
+  const result = [];
+  const sortedExcludedRanges = [...excludedRanges].sort((a, b) => a.start.valueOf() - b.start.valueOf());
 
   for (const { start: sourceStart, end: sourceEnd, ...passThrough } of sourceRanges) {
     let currentStart = sourceStart;
 
-    const overlappingRanges = excludedRanges.filter(
-      ({ start, end }) => start.isBefore(sourceEnd) && end.isAfter(sourceStart)
-    );
+    for (const excludedRange of sortedExcludedRanges) {
+      if (excludedRange.start.valueOf() >= sourceEnd.valueOf()) break;
+      if (excludedRange.end.valueOf() <= currentStart.valueOf()) continue;
 
-    overlappingRanges.sort((a, b) => (a.start.isAfter(b.start) ? 1 : -1));
+      if (excludedRange.start.valueOf() > currentStart.valueOf()) {
+        result.push({ start: currentStart, end: excludedRange.start, ...passThrough });
+      }
 
-    for (const { start: excludedStart, end: excludedEnd } of overlappingRanges) {
-      if (excludedStart.isAfter(currentStart)) {
-        result.push({ start: currentStart, end: excludedStart });
+      if (excludedRange.end.valueOf() > currentStart.valueOf()) {
+        currentStart = excludedRange.end;
       }
-      currentStart = excludedEnd.isAfter(currentStart) ? excludedEnd : currentStart;
     }
 
-    if (sourceEnd.isAfter(currentStart)) {
+    if (sourceEnd.valueOf() > currentStart.valueOf()) {
       result.push({ start: currentStart, end: sourceEnd, ...passThrough });
     }
   }