/**
 * Pure helpers for the navigation page facets / filters (#158).
 *
 * No DOM, no imports — usable straight from Node tests.
 * Mirrors the search page's facet mechanism (Vaults / Tags / Extensions)
 * over a plain directory listing instead of a search result set.
 */

/** Strip the leading dot and lowercase a file extension. */
function normExt(extension) {
  return String(extension || "").toLowerCase().replace(/^\./, "");
}

/** Display name used for labels and alphabetical sorting (.md removed). */
export function navDisplayName(file) {
  const name = file.name || String(file.path || "").split("/").pop() || "";
  return name.endsWith(".md") ? name.slice(0, -3) : name;
}

/**
 * Count vaults / tags / extensions over a file listing.
 * @param {Array<object>} files
 * @returns {{vaults: object, tags: object, extensions: object}} counts sorted desc
 */
export function buildNavFacets(files) {
  const facets = { vaults: {}, tags: {}, extensions: {} };
  for (const f of files || []) {
    if (f.vault) facets.vaults[f.vault] = (facets.vaults[f.vault] || 0) + 1;
    const ext = normExt(f.extension);
    if (ext) facets.extensions[ext] = (facets.extensions[ext] || 0) + 1;
    for (const tag of f.tags || []) {
      facets.tags[tag] = (facets.tags[tag] || 0) + 1;
    }
  }
  for (const key of Object.keys(facets)) {
    facets[key] = Object.fromEntries(
      Object.entries(facets[key]).sort((a, b) => b[1] - a[1]),
    );
  }
  return facets;
}

/**
 * Keep only the files matching the active tag / extension filters.
 * @param {Array<object>} files
 * @param {{tag?: string, ext?: string}} filters
 */
export function filterNavFiles(files, filters) {
  const tag = (filters && filters.tag) || "";
  const ext = normExt((filters && filters.ext) || "");
  if (!tag && !ext) return files || [];
  return (files || []).filter((f) => {
    if (ext && normExt(f.extension) !== ext) return false;
    if (tag && !(f.tags || []).includes(tag)) return false;
    return true;
  });
}

/**
 * Sort the listing: `modified` (newest first, server default) or
 * `relevance` (A→Z).
 *
 * ponytail: a directory listing carries no relevance signal, `relevance` is an
 * alphabetical stand-in — upgrade path: sort by scoped search score once the
 * navigation page owns a query.
 */
export function sortNavFiles(files, mode) {
  const out = (files || []).slice();
  if (mode === "relevance") {
    out.sort((a, b) =>
      navDisplayName(a).localeCompare(navDisplayName(b), undefined, { sensitivity: "base" }),
    );
  } else {
    out.sort((a, b) => (b.modified || 0) - (a.modified || 0));
  }
  return out;
}