gui-video-clipper/src/lib/utils/clipRange.ts

export type QuickClipPosition = 'at' | 'before';

export function computeQuickClipRange(
  currentTime: number,
  duration: number,
  position: QuickClipPosition,
  clipDuration = 10,
): { start: number; end: number } | null {
  if (duration === 0) return null;

  let start: number;
  let end: number;

  switch (position) {
    case 'at':
      start = currentTime;
      end = Math.min(currentTime + clipDuration, duration);
      break;
    case 'before':
      start = Math.max(currentTime - clipDuration, 0);
      end = currentTime;
      break;
    default: {
      const _exhaustive: never = position;
      void _exhaustive;
      return null;
    }
  }

  if (start >= end) return null;
  return { start, end };
}