from __future__ import annotations

from datetime import datetime, timedelta, timezone
from pathlib import Path

import pytest

from somafm_tui.widgets import common

BERLIN = Path("/usr/share/zoneinfo/Europe/Berlin")
UTC_FILE = Path("/usr/share/zoneinfo/UTC")


@pytest.fixture(autouse=True)
def clear_zone_cache():
    common.local_zone.cache_clear()
    yield
    common.local_zone.cache_clear()


def _copy_zone(tmp_path: Path, source: Path) -> Path:
    target = tmp_path / "localtime"
    target.write_bytes(source.read_bytes())
    return target


def test_build_time_tz_utc_does_not_hide_the_system_zone(tmp_path, monkeypatch) -> None:
    if not BERLIN.exists():
        pytest.skip("system tzdata is not installed")
    monkeypatch.setattr(common, "LOCALTIME_PATH", str(_copy_zone(tmp_path, BERLIN)))
    monkeypatch.setenv("TZ", "UTC")

    zone = common.local_zone()
    assert zone.utcoffset(datetime(2026, 1, 1)) == timedelta(hours=1)

    aware = datetime(2026, 1, 1, 12, 0, tzinfo=timezone.utc)
    assert common.local_time(aware) == "13:00"


def test_explicit_non_utc_tz_is_respected(tmp_path, monkeypatch) -> None:
    if not BERLIN.exists() or not UTC_FILE.exists():
        pytest.skip("system tzdata is not installed")
    monkeypatch.setattr(common, "LOCALTIME_PATH", str(_copy_zone(tmp_path, UTC_FILE)))
    monkeypatch.setenv("TZ", "Europe/Berlin")

    zone = common.local_zone()
    assert zone.utcoffset(datetime(2026, 1, 1)) == timedelta(hours=1)
    assert common.local_time(datetime(2026, 1, 1, 12, 0, tzinfo=timezone.utc)) == "13:00"