src/utils/sortSearchResults.ts

import { InitialSearchResult, SearchResult } from "../../shared/interfaces";

export function sortSearchResults(results: InitialSearchResult[]): void {
  results.forEach((item, index) => {
    item.index = index;
  });

  // Put search results of headings and contents just after
  // their belonged page's title, if existed.
  (results as SearchResult[]).sort((a, b) => {
    let aPageIndex =
      a.type > 0 && a.page
        ? results.findIndex((item) => item.document === a.page)
        : a.index;

    let bPageIndex =
      b.type > 0 && b.page
        ? results.findIndex((item) => item.document === b.page)
        : b.index;

    if (aPageIndex === -1) {
      aPageIndex = a.index;
    }

    if (bPageIndex === -1) {
      bPageIndex = b.index;
    }

    if (aPageIndex === bPageIndex) {
      if (a.type === 0) {
        return -1;
      }
      if (b.type === 0) {
        return 1;
      }
      return a.index - b.index;
    }
    return aPageIndex - bPageIndex;
  });
}