/**
 * A localisation key may be a LEAF or a BRANCH, never both.
 *
 * Foundry expands dotted keys into a nested object, so shipping both
 * "RINGBRP.Authority.Merge" (a string) and "RINGBRP.Authority.Merge.0" makes it try
 * to assign a property to a string. That throws inside the loader, and the loader
 * abandons the WHOLE FILE — one bad pair silently un-localises the entire system and
 * every sheet starts printing raw keys. It cost an hour to find once.
 *
 *   node tools/check-lang.mjs
 */
import { readFile, readdir } from "node:fs/promises";

const dir = new URL("../lang/", import.meta.url);
let failures = 0;

for (const file of (await readdir(dir)).filter(f => f.endsWith(".json"))) {
  const raw = await readFile(new URL(file, dir), "utf8");
  let json;
  try { json = JSON.parse(raw); }
  catch (e) { console.error(`${file}: not valid JSON — ${e.message}`); failures++; continue; }

  const keys = Object.keys(json);
  const set = new Set(keys);
  for (const k of keys) {
    const parts = k.split(".");
    for (let i = 1; i < parts.length; i++) {
      const prefix = parts.slice(0, i).join(".");
      if (set.has(prefix)) {
        console.error(`${file}: "${prefix}" is a value AND a prefix of "${k}" — Foundry cannot load this file`);
        failures++;
      }
    }
  }
  // duplicate keys survive JSON.parse by silently overwriting; catch them in the text
  const seen = new Set(), dupes = new Set();
  for (const m of raw.matchAll(/^\s*"([^"]+)"\s*:/gm)) {
    if (seen.has(m[1])) dupes.add(m[1]); else seen.add(m[1]);
  }
  for (const d of dupes) { console.error(`${file}: duplicate key "${d}"`); failures++; }
  if (!failures) console.log(`check-lang: OK — ${file}, ${keys.length} keys, no leaf/branch collisions`);
}

if (failures) { console.error(`\ncheck-lang: ${failures} failure(s)`); process.exit(1); }