#!/usr/bin/env node
// i18n parity check — keeps Julien's "every locale = same files + keys as en"
// DoD honest over time.
//
// What it checks per non-en locale:
//   1. File set parity: every domain file that exists in en/ must exist in this
//      locale's dir; no extra domain files allowed.
//   2. Key set parity: for each shared domain file, the top-level translation
//      keys must match exactly (no missing, no extra).
//
// Output: structured report grouped by locale, plus a `--strict` flag that
// returns exit-code 1 when any drift is present (intended for CI). Without
// `--strict` the script exits 0 and prints, so it can also run as a non-blocking
// audit during translation work.
//   3. Plural forms: a count-bearing string (`key` or `key.other`, plus at
//      least one of `key.zero|one|two|few|many` in en) is a plural group. Its
//      category keys are not compared with en's, since Russian needs `.few`
//      and `.many` and Japanese needs none. Instead every locale must spell
//      out each category whole counts reach in its language, and may not
//      carry one its language never selects. The rules come from
//      `Intl.PluralRules`, through the same helpers the client resolves with.
//
// Limitations: we only parse *top-level* string keys (those declared as the
// first column of the file, matching the regex below). Nested objects, function
// bodies, and inline comments are ignored. This matches how `t(key)` calls
// resolve at runtime in TranslationContext.

import { readdirSync, readFileSync, statSync } from 'node:fs';
import { dirname, join } from 'node:path';
import { fileURLToPath } from 'node:url';
import { getIntlLanguage } from '../src/i18n/languages.ts';
import { allPluralCategories, integerPluralCategories, pluralFormOf, pluralGroups } from '../src/i18n/plural.ts';

const here = dirname(fileURLToPath(import.meta.url));
const i18nRoot = join(here, '..', 'src', 'i18n');

// Match a top-level translation key declaration: leading whitespace, then a
// quoted key (must start with a lowercase letter), then a colon. This is the
// exact pattern every domain file uses. Keys may hold a colon themselves
// (admin.plugins.perm.db:read:trips); without it in the class those keys were
// never compared, and two locales lacked dozens of them unnoticed.
const TOP_LEVEL_KEY_RE = /^\s*'([a-z][a-zA-Z0-9.\-_:]*)'\s*:/gm;

function listLocales() {
  return readdirSync(i18nRoot)
    .filter((name) => statSync(join(i18nRoot, name)).isDirectory())
    // externalNotifications is a barrel module, not a locale.
    .filter((name) => name !== 'externalNotifications');
}

function listDomainFiles(locale) {
  return readdirSync(join(i18nRoot, locale))
    .filter((f) => f.endsWith('.ts') && f !== 'index.ts')
    .sort();
}

function extractKeys(locale, file) {
  const content = readFileSync(join(i18nRoot, locale, file), 'utf8');
  const keys = new Set();
  for (const match of content.matchAll(TOP_LEVEL_KEY_RE)) {
    keys.add(match[1]);
  }
  return keys;
}

function withoutVariants(keys, groups) {
  return new Set([...keys].filter((k) => !pluralFormOf(k, groups)));
}

/** What one locale owes the plural groups of one file. */
function checkPluralForms(locale, keys, groups) {
  const intl = getIntlLanguage(locale);
  const required = integerPluralCategories(intl).filter((c) => c !== 'other');
  const allowed = new Set(allPluralCategories(intl));
  const missing = [];
  const invalid = [];
  for (const base of groups) {
    for (const c of required) if (!keys.has(`${base}.${c}`)) missing.push(`${base}.${c}`);
  }
  for (const key of keys) {
    const form = pluralFormOf(key, groups);
    if (form && !allowed.has(form.category)) invalid.push(key);
  }
  return { missing, invalid };
}

function diffSets(reference, candidate) {
  const missing = [];
  const extra = [];
  for (const k of reference) if (!candidate.has(k)) missing.push(k);
  for (const k of candidate) if (!reference.has(k)) extra.push(k);
  return { missing, extra };
}

function checkParity() {
  const locales = listLocales();
  if (!locales.includes('en')) {
    throw new Error('shared/src/i18n/en is required as the reference locale');
  }
  const enFiles = listDomainFiles('en');
  const enKeysByDomain = new Map();
  for (const f of enFiles) enKeysByDomain.set(f, extractKeys('en', f));

  const report = { fileDrift: [], keyDrift: [], pluralDrift: [] };
  const groupsByDomain = new Map();
  for (const f of enFiles) {
    const groups = pluralGroups(enKeysByDomain.get(f));
    groupsByDomain.set(f, groups);
    const { missing, invalid } = checkPluralForms('en', enKeysByDomain.get(f), groups);
    if (missing.length || invalid.length) report.pluralDrift.push({ locale: 'en', file: f, missing, invalid });
  }

  for (const locale of locales) {
    if (locale === 'en') continue;

    const localeFiles = listDomainFiles(locale);
    const { missing: missingFiles, extra: extraFiles } = diffSets(
      new Set(enFiles),
      new Set(localeFiles),
    );

    if (missingFiles.length || extraFiles.length) {
      report.fileDrift.push({ locale, missing: missingFiles, extra: extraFiles });
    }

    for (const file of enFiles) {
      if (!localeFiles.includes(file)) continue;
      const localeKeys = extractKeys(locale, file);
      const groups = groupsByDomain.get(file);
      const { missing, extra } = diffSets(
        withoutVariants(enKeysByDomain.get(file), groups),
        withoutVariants(localeKeys, groups),
      );
      if (missing.length || extra.length) {
        report.keyDrift.push({ locale, file, missing, extra });
      }
      const plural = checkPluralForms(locale, localeKeys, groups);
      if (plural.missing.length || plural.invalid.length) {
        report.pluralDrift.push({ locale, file, ...plural });
      }
    }
  }

  return report;
}

function formatReport(report) {
  const lines = [];

  if (report.fileDrift.length === 0) {
    lines.push('File parity: OK');
  } else {
    lines.push(`File parity: ${report.fileDrift.length} locale(s) with file drift`);
    for (const { locale, missing, extra } of report.fileDrift) {
      if (missing.length) lines.push(`  ${locale}: missing ${missing.join(', ')}`);
      if (extra.length) lines.push(`  ${locale}: extra ${extra.join(', ')}`);
    }
  }

  if (report.keyDrift.length === 0) {
    lines.push('Key parity: OK');
  } else {
    lines.push(`Key parity: ${report.keyDrift.length} domain file(s) with key drift`);
    for (const { locale, file, missing, extra } of report.keyDrift) {
      const parts = [];
      if (missing.length) parts.push(`missing ${missing.length} (e.g. ${missing.slice(0, 3).join(', ')})`);
      if (extra.length) parts.push(`extra ${extra.length} (e.g. ${extra.slice(0, 3).join(', ')})`);
      lines.push(`  ${locale}/${file}: ${parts.join('; ')}`);
    }
  }

  if (report.pluralDrift.length === 0) {
    lines.push('Plural forms: OK');
  } else {
    lines.push(`Plural forms: ${report.pluralDrift.length} domain file(s) with missing or impossible forms`);
    for (const { locale, file, missing, invalid } of report.pluralDrift) {
      const parts = [];
      if (missing.length) parts.push(`missing ${missing.join(', ')}`);
      if (invalid.length) parts.push(`never selected ${invalid.join(', ')}`);
      lines.push(`  ${locale}/${file}: ${parts.join('; ')}`);
    }
  }

  return lines.join('\n');
}

// Export a structured API for vitest. The CLI entry point only runs when
// executed directly (`node scripts/i18n-parity.mjs`), so importing this file
// from a spec does not produce side effects.
export { checkParity, formatReport };

const isCli = process.argv[1] && process.argv[1].endsWith('i18n-parity.mjs');
if (isCli) {
  const strict = process.argv.includes('--strict');
  const filesOnly = process.argv.includes('--files-only');
  const report = checkParity();
  process.stdout.write(formatReport(filesOnly ? { ...report, keyDrift: [], pluralDrift: [] } : report) + '\n');

  if (strict) {
    const hasFileDrift = report.fileDrift.length > 0;
    const hasKeyDrift = filesOnly ? false : report.keyDrift.length > 0 || report.pluralDrift.length > 0;
    if (hasFileDrift || hasKeyDrift) process.exit(1);
  }
}