Optimized broadcast week calculation

src/week.ts

@@ -2,17 +2,6 @@ import { DateTime } from "luxon";
 
 import { IfValid, isValid } from "./helpers";
 
-const DAY = 24 * 60 * 60 * 1000;
-
-function isLastWeekOverflown(date: DateTime): boolean {
-  const yearEnd = date.endOf("year");
-  const yearEndWeekDay = yearEnd.weekday;
-  if (yearEndWeekDay === 7) {
-    return false;
-  }
-  return yearEnd.toMillis() - date.toMillis() <= yearEndWeekDay * DAY;
-}
-
 /**
  * returns broadcast week number (1-54) for a given date
  **/
@@ -23,19 +12,5 @@ export function getBroadcastWeek<IsValid extends boolean>(
     return null as IfValid<IsValid, number>;
   }
 
-  const day = date.startOf("day");
-
-  if (isLastWeekOverflown(day)) {
-    return 1 as IfValid<IsValid, number>;
-  }
-
-  const yearStart = day.startOf("year");
-  const yearStartWeekDay = yearStart.weekday - 1;
-  const weekNo = Math.ceil(
-    ((day.valueOf() - yearStart.toMillis() + yearStartWeekDay * DAY) / DAY +
-      1) /
-      7,
-  );
-
-  return weekNo as IfValid<IsValid, number>;
+  return Math.ceil(date.endOf("week").ordinal / 7) as IfValid<IsValid, number>;
 }