interface LineGeometry {
  readonly top: number;
  readonly height: number;
}

interface CenteredFileLineScrollInput {
  readonly scrollTop: number;
  readonly scrollHeight: number;
  readonly viewportTop: number;
  readonly viewportHeight: number;
  readonly fileTop: number;
  readonly estimatedLine: LineGeometry;
  readonly renderedLine?: LineGeometry;
}

export function resolveCenteredFileLineScrollTop(input: CenteredFileLineScrollInput): number {
  const lineTop =
    input.renderedLine === undefined
      ? input.fileTop + input.estimatedLine.top
      : input.scrollTop + input.renderedLine.top - input.viewportTop;
  const lineHeight = input.renderedLine?.height ?? input.estimatedLine.height;
  const centeredTop = Math.max(0, lineTop - Math.max(0, (input.viewportHeight - lineHeight) / 2));
  return Math.min(centeredTop, Math.max(0, input.scrollHeight - input.viewportHeight));
}