/**
 * i18n key parity tests — ensures `en.json` and `vi.json` stay in sync.
 *
 * Rules enforced:
 *  1. Both files must have the same set of flattened leaf keys.
 *  2. No key value may be an empty string in either locale.
 *  3. Locale metadata keys must be present in both files.
 */
import { describe, expect, it } from 'vitest';
import enMessages from '../messages/en.json';
import viMessages from '../messages/vi.json';

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------
type MessageDict = Record<string, unknown>;

function flattenKeys(obj: MessageDict, prefix = ''): string[] {
  return Object.entries(obj).flatMap(([key, value]) => {
    const fullKey = prefix ? `${prefix}.${key}` : key;
    if (value !== null && typeof value === 'object' && !Array.isArray(value)) {
      return flattenKeys(value as MessageDict, fullKey);
    }
    return [fullKey];
  });
}

function flattenEntries(obj: MessageDict, prefix = ''): Array<[string, string]> {
  return Object.entries(obj).flatMap(([key, value]) => {
    const fullKey = prefix ? `${prefix}.${key}` : key;
    if (value !== null && typeof value === 'object' && !Array.isArray(value)) {
      return flattenEntries(value as MessageDict, fullKey);
    }
    return [[fullKey, String(value)]];
  });
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------
describe('i18n message key parity (en ↔ vi)', () => {
  const enKeys = new Set(flattenKeys(enMessages));
  const viKeys = new Set(flattenKeys(viMessages));

  it('vi.json has no extra keys missing from en.json', () => {
    const extraInVi = [...viKeys].filter((k) => !enKeys.has(k));
    expect(extraInVi, `Keys present in vi.json but not en.json: ${JSON.stringify(extraInVi)}`).toHaveLength(0);
  });

  it('en.json has no extra keys missing from vi.json', () => {
    const extraInEn = [...enKeys].filter((k) => !viKeys.has(k));
    expect(extraInEn, `Keys present in en.json but not vi.json: ${JSON.stringify(extraInEn)}`).toHaveLength(0);
  });

  it('en.json has no empty string values', () => {
    const empty = flattenEntries(enMessages).filter(([, v]) => v.trim() === '');
    expect(empty, `Empty values in en.json: ${JSON.stringify(empty.map(([k]) => k))}`).toHaveLength(0);
  });

  it('vi.json has no empty string values', () => {
    const empty = flattenEntries(viMessages).filter(([, v]) => v.trim() === '');
    expect(empty, `Empty values in vi.json: ${JSON.stringify(empty.map(([k]) => k))}`).toHaveLength(0);
  });

  it('both locales define the same top-level namespace keys', () => {
    const enTopLevel = Object.keys(enMessages).sort();
    const viTopLevel = Object.keys(viMessages).sort();
    expect(viTopLevel).toEqual(enTopLevel);
  });
});

describe('i18n locale config', () => {
  it('language namespace exists in en.json with the expected locale keys', () => {
    const lang = (enMessages as MessageDict).language as MessageDict | undefined;
    expect(lang).toBeDefined();
    expect(Object.keys(lang ?? {})).toContain('vi');
    expect(Object.keys(lang ?? {})).toContain('en');
  });

  it('language namespace exists in vi.json with the expected locale keys', () => {
    const lang = (viMessages as MessageDict).language as MessageDict | undefined;
    expect(lang).toBeDefined();
    expect(Object.keys(lang ?? {})).toContain('vi');
    expect(Object.keys(lang ?? {})).toContain('en');
  });
});