"""Unit tests for the i18n helper."""

import importlib

import pytest


@pytest.fixture
def reload_i18n(monkeypatch):
    """Reload the module after tweaking env vars so LANG is recomputed."""
    def _reload(env: dict[str, str]):
        for k, v in env.items():
            monkeypatch.setenv(k, v)
        import i18n
        return importlib.reload(i18n)
    return _reload


def test_default_language_is_english(reload_i18n):
    mod = reload_i18n({"HY_LANG": ""})
    assert mod.LANG == "en"
    assert mod.t("warn.empty_msg") == "Please enter a message"


def test_explicit_zh(reload_i18n):
    mod = reload_i18n({"HY_LANG": "zh-CN.UTF-8"})
    assert mod.LANG == "zh"
    assert mod.t("warn.empty_msg") == "请输入消息内容"


def test_falls_back_to_default_lang_for_unknown(reload_i18n):
    mod = reload_i18n({"HY_LANG": "fr"})
    assert mod.LANG == "en"


def test_format_args(reload_i18n):
    mod = reload_i18n({"HY_LANG": "en"})
    assert mod.t("tool.call_header", i=2, n=5) == "Function call (2/5)"


def test_falls_back_to_english_when_zh_missing(reload_i18n):
    mod = reload_i18n({"HY_LANG": "zh"})
    mod.TRANSLATIONS["zh"].pop("warn.empty_msg", None)
    assert mod.t("warn.empty_msg") == "Please enter a message"


def test_unknown_key_returns_key(reload_i18n):
    mod = reload_i18n({"HY_LANG": "en"})
    assert mod.t("does.not.exist") == "does.not.exist"