/** Shared timeline zoom/pan math for Timeline and MovementBands. */
export function zoomTimelineView(
  clientX: number,
  rectLeft: number,
  rectWidth: number,
  deltaY: number,
  viewStart: number,
  viewEnd: number,
  absoluteMin: number,
  absoluteMax: number
): { start: number; end: number } {
  const span = viewEnd - viewStart;
  const ratio = (clientX - rectLeft) / rectWidth;
  const centerYear = viewStart + ratio * span;
  const factor = deltaY > 0 ? 1.15 : 0.85;
  const newSpan = Math.max(10, Math.min(absoluteMax - absoluteMin, span * factor));
  let newStart = centerYear - ratio * newSpan;
  let newEnd = centerYear + (1 - ratio) * newSpan;
  if (newStart < absoluteMin) {
    newEnd += absoluteMin - newStart;
    newStart = absoluteMin;
  }
  if (newEnd > absoluteMax) {
    newStart -= newEnd - absoluteMax;
    newEnd = absoluteMax;
  }
  return { start: Math.round(newStart), end: Math.round(newEnd) };
}

export function panTimelineView(
  deltaX: number,
  rectWidth: number,
  viewStart: number,
  viewEnd: number,
  absoluteMin: number,
  absoluteMax: number
): { start: number; end: number } {
  const span = viewEnd - viewStart;
  const yearDelta = (deltaX / rectWidth) * span;
  let newStart = viewStart - yearDelta;
  let newEnd = viewEnd - yearDelta;
  if (newStart < absoluteMin) {
    newEnd += absoluteMin - newStart;
    newStart = absoluteMin;
  }
  if (newEnd > absoluteMax) {
    newStart -= newEnd - absoluteMax;
    newEnd = absoluteMax;
  }
  return { start: Math.round(newStart), end: Math.round(newEnd) };
}