import type { MdHeading } from '../types/markdown';

export function getDisplayedHeadings(
  headings: Array<MdHeading | null> | null | undefined,
  tocDepth: number,
): Array<MdHeading | null> {
  if (!headings) {
    return [];
  }
  return headings.filter((heading, idx) => {
    if (!heading) {
      return false;
    }
    if (idx === 0 && heading.depth === 1) {
      return false;
    }
    return !(heading.depth && heading.depth > tocDepth);
  });
}

export function getDisplayedHeadingsIds(
  headings: Array<MdHeading | null> | null | undefined,
): Array<string | undefined> {
  if (!headings) {
    return [];
  }
  return headings.map((header) => header?.id);
}

export function getLeastDepth(headings: Array<MdHeading | null> | null | undefined): number {
  if (!headings || headings.length === 0) {
    return 1;
  }
  let depth = null;
  for (const heading of headings) {
    if (!heading) continue;
    if (depth === null || depth > heading.depth) {
      depth = heading.depth;
    }
  }
  return depth ?? 1;
}