refactor: unify logic

packages/utils/src/date-utils/checkIsNextDay.ts

@@ -1,13 +1,40 @@
+import { dayInMs } from './conversionUtils.js';
+
 /**
  * Utility function checks whether a given event is the day after from its predecessor
  * We consider an event to be the day after, if it begins before the start of the previous
  * @example day after
  * 09:00 - 10:00
  * 08:00 - 10:30
+ * @example day after
+ * 23:00 - 00:00
+ * 02:00 - 03:00
  * @example same day
  * 09:00 - 10:00
  * 09:30 - 10:30
+ * @example same day, but previous crosses midnight
+ * 23:00 - 01:00
+ * 02:00 - 03:00
+ * @example same day, but previous crosses midnight (with overlap)
+ * 22:00 - 02:00
+ * 01:00 - 03:00
  */
 export function checkIsNextDay(previousStart: number, timeStart: number, previousDuration: number): boolean {
-  return previousDuration === 0 ? false : timeStart <= previousStart;
+  if (previousDuration === 0) {
+    return false;
+  }
+
+  if (timeStart <= previousStart) {
+    const normalisedPreviousEnd = previousStart + previousDuration;
+    if (normalisedPreviousEnd === dayInMs) {
+      return true;
+    }
+    // handle exception for an event that finishes exactly at midnight
+    if (normalisedPreviousEnd > dayInMs) {
+      return false;
+    }
+    return true;
+  }
+
+  return false;
 }