refactoring

backend/src/utils/timeUtils.ts

@@ -0,0 +1,29 @@
+import { prisma } from "../prisma/client";
+
+/**
+ * Checks whether a user already has a time entry that overlaps with the given
+ * [startTime, endTime] interval.
+ *
+ * @param userId    - The user whose entries are checked.
+ * @param startTime - Start of the interval to check.
+ * @param endTime   - End of the interval to check.
+ * @param excludeId - Optional time-entry id to exclude (used when updating an
+ *                    existing entry so it does not collide with itself).
+ */
+export async function hasOverlappingEntries(
+  userId: string,
+  startTime: Date,
+  endTime: Date,
+  excludeId?: string,
+): Promise<boolean> {
+  const count = await prisma.timeEntry.count({
+    where: {
+      userId,
+      ...(excludeId ? { id: { not: excludeId } } : {}),
+      // An entry overlaps when it starts before our end AND ends after our start.
+      startTime: { lt: endTime },
+      endTime: { gt: startTime },
+    },
+  });
+  return count > 0;
+}