"""
Tests for timezone utility module.

Validates centralized timezone helpers that ensure scheduling logic uses
explicit America/Chicago timezone rather than relying on OS defaults.
"""

import pytest
from datetime import datetime, timezone
from zoneinfo import ZoneInfo

from utils.timezone import (
    CHICAGO_TZ,
    now_utc,
    now_chicago,
    to_chicago,
    to_discord_timestamp,
)


class TestChicagoTZ:
    """Tests for the CHICAGO_TZ constant."""

    def test_chicago_tz_is_zoneinfo(self):
        """CHICAGO_TZ should be a ZoneInfo instance for America/Chicago."""
        assert isinstance(CHICAGO_TZ, ZoneInfo)
        assert str(CHICAGO_TZ) == "America/Chicago"


class TestNowUtc:
    """Tests for now_utc()."""

    def test_returns_aware_datetime(self):
        """now_utc() should return a timezone-aware datetime."""
        result = now_utc()
        assert result.tzinfo is not None

    def test_returns_utc(self):
        """now_utc() should return a datetime in UTC."""
        result = now_utc()
        assert result.tzinfo == timezone.utc


class TestNowChicago:
    """Tests for now_chicago()."""

    def test_returns_aware_datetime(self):
        """now_chicago() should return a timezone-aware datetime."""
        result = now_chicago()
        assert result.tzinfo is not None

    def test_returns_chicago_tz(self):
        """now_chicago() should return a datetime in America/Chicago timezone."""
        result = now_chicago()
        assert result.tzinfo == CHICAGO_TZ


class TestToChicago:
    """Tests for to_chicago()."""

    def test_converts_utc_datetime(self):
        """to_chicago() should correctly convert a UTC datetime to Chicago time."""
        # 2024-07-15 18:00 UTC = 2024-07-15 13:00 CDT (UTC-5 during summer)
        utc_dt = datetime(2024, 7, 15, 18, 0, 0, tzinfo=timezone.utc)
        result = to_chicago(utc_dt)
        assert result.hour == 13
        assert result.tzinfo == CHICAGO_TZ

    def test_handles_naive_datetime_assumes_utc(self):
        """to_chicago() should treat naive datetimes as UTC."""
        naive_dt = datetime(2024, 7, 15, 18, 0, 0)
        result = to_chicago(naive_dt)
        # Same as converting from UTC
        utc_dt = datetime(2024, 7, 15, 18, 0, 0, tzinfo=timezone.utc)
        expected = to_chicago(utc_dt)
        assert result.hour == expected.hour
        assert result.tzinfo == CHICAGO_TZ

    def test_preserves_already_chicago(self):
        """to_chicago() on an already-Chicago datetime should be a no-op."""
        chicago_dt = datetime(2024, 7, 15, 13, 0, 0, tzinfo=CHICAGO_TZ)
        result = to_chicago(chicago_dt)
        assert result.hour == 13
        assert result.tzinfo == CHICAGO_TZ

    def test_winter_offset(self):
        """to_chicago() should use CST (UTC-6) during winter months."""
        # 2024-01-15 18:00 UTC = 2024-01-15 12:00 CST (UTC-6 during winter)
        utc_dt = datetime(2024, 1, 15, 18, 0, 0, tzinfo=timezone.utc)
        result = to_chicago(utc_dt)
        assert result.hour == 12


class TestToDiscordTimestamp:
    """Tests for to_discord_timestamp()."""

    def test_default_style(self):
        """to_discord_timestamp() should use 'f' style by default."""
        dt = datetime(2024, 7, 15, 18, 0, 0, tzinfo=timezone.utc)
        result = to_discord_timestamp(dt)
        unix_ts = int(dt.timestamp())
        assert result == f"<t:{unix_ts}:f>"

    def test_relative_style(self):
        """to_discord_timestamp() with style='R' should produce relative format."""
        dt = datetime(2024, 7, 15, 18, 0, 0, tzinfo=timezone.utc)
        result = to_discord_timestamp(dt, style="R")
        unix_ts = int(dt.timestamp())
        assert result == f"<t:{unix_ts}:R>"

    def test_all_styles(self):
        """to_discord_timestamp() should support all Discord timestamp styles."""
        dt = datetime(2024, 7, 15, 18, 0, 0, tzinfo=timezone.utc)
        unix_ts = int(dt.timestamp())
        for style in ("R", "f", "F", "t", "T", "d", "D"):
            result = to_discord_timestamp(dt, style=style)
            assert result == f"<t:{unix_ts}:{style}>"

    def test_naive_datetime_assumes_utc(self):
        """to_discord_timestamp() should treat naive datetimes as UTC."""
        naive_dt = datetime(2024, 7, 15, 18, 0, 0)
        aware_dt = datetime(2024, 7, 15, 18, 0, 0, tzinfo=timezone.utc)
        assert to_discord_timestamp(naive_dt) == to_discord_timestamp(aware_dt)

    def test_chicago_datetime_same_instant(self):
        """to_discord_timestamp() should produce the same unix timestamp regardless of tz."""
        utc_dt = datetime(2024, 7, 15, 18, 0, 0, tzinfo=timezone.utc)
        chicago_dt = utc_dt.astimezone(CHICAGO_TZ)
        assert to_discord_timestamp(utc_dt) == to_discord_timestamp(chicago_dt)