import { describe, it, expect } from 'vitest';
import { withUtf8Locale, DEFAULT_UTF8_LOCALE } from '../src/session/locale.js';

/**
 * locale.ts — UTF-8 locale guarantee for the spawned PTY.
 *
 * Why this exists: when the server is launched from Finder / launchd (the Mac
 * desktop app) the process env has NO `LANG`/`LC_*`. tmux then runs in its
 * non-UTF-8 mode and rewrites every wide character to `_` and downgrades
 * double-line box drawing (`═║╔╗`) to DEC Special Graphics single lines — so all
 * CJK output in the Claude Code TUI is destroyed before it ever reaches xterm.
 */
describe('withUtf8Locale', () => {
  it('adds LANG when no locale variable is set at all', () => {
    const out = withUtf8Locale({ PATH: '/usr/bin' });

    expect(out.LANG).toBe(DEFAULT_UTF8_LOCALE);
    expect(out.PATH).toBe('/usr/bin');
  });

  it('keeps a UTF-8 LANG the user already has', () => {
    const out = withUtf8Locale({ LANG: 'zh_CN.UTF-8' });

    expect(out.LANG).toBe('zh_CN.UTF-8');
  });

  it('accepts lowercase / hyphen-less spellings of utf8', () => {
    expect(withUtf8Locale({ LANG: 'en_US.utf8' }).LANG).toBe('en_US.utf8');
    expect(withUtf8Locale({ LANG: 'C.UTF8' }).LANG).toBe('C.UTF8');
  });

  it('replaces a non-UTF-8 LANG (C / POSIX / latin1) with the default', () => {
    expect(withUtf8Locale({ LANG: 'C' }).LANG).toBe(DEFAULT_UTF8_LOCALE);
    expect(withUtf8Locale({ LANG: 'POSIX' }).LANG).toBe(DEFAULT_UTF8_LOCALE);
    expect(withUtf8Locale({ LANG: 'en_US.ISO8859-1' }).LANG).toBe(DEFAULT_UTF8_LOCALE);
  });

  it('respects LC_ALL — it outranks LANG, so a UTF-8 LC_ALL is enough', () => {
    const out = withUtf8Locale({ LC_ALL: 'ja_JP.UTF-8', LANG: 'C' });

    expect(out.LC_ALL).toBe('ja_JP.UTF-8');
    expect(out.LANG).toBe('C'); // untouched — LC_ALL already decides the charset
  });

  it('respects a UTF-8 LC_CTYPE (macOS Terminal.app sets only this)', () => {
    const out = withUtf8Locale({ LC_CTYPE: 'UTF-8' });

    expect(out.LC_CTYPE).toBe('UTF-8');
    expect(out.LANG).toBeUndefined();
  });

  it('overrides LANG when LC_CTYPE is present but not UTF-8', () => {
    const out = withUtf8Locale({ LC_CTYPE: 'C' });

    expect(out.LANG).toBe(DEFAULT_UTF8_LOCALE);
  });

  it('does not mutate the input env (immutability)', () => {
    const input = { PATH: '/usr/bin' };
    const out = withUtf8Locale(input);

    expect(input).toEqual({ PATH: '/usr/bin' });
    expect(out).not.toBe(input);
  });

  it('ignores an empty-string locale (unset in practice)', () => {
    expect(withUtf8Locale({ LANG: '' }).LANG).toBe(DEFAULT_UTF8_LOCALE);
    expect(withUtf8Locale({ LC_ALL: '' }).LANG).toBe(DEFAULT_UTF8_LOCALE);
  });
});