"""
Unit tests for app.services.news.session_window.

Critical invariant: `post` must end at the next trading day's premarket
start (04:00 ET) — NOT next session's open (09:30 ET) — to avoid 4-hour
overlap with the next session's `premarket` window.
"""
from datetime import date, datetime, time
from zoneinfo import ZoneInfo

import pytest

from app.services.news.session_window import session_window

ET = ZoneInfo("America/New_York")
UTC = ZoneInfo("UTC")


def _et(d: date, t: time) -> datetime:
    return datetime.combine(d, t, tzinfo=ET).astimezone(UTC)


def test_premarket_bounds_basic_weekday():
    # Wednesday 2026-04-22 (Tue 2026-04-21 prev day, both weekdays)
    target = date(2026, 4, 22)
    start, end = session_window(target, "premarket")
    # Premarket starts at the previous session's *close*, not 04:00
    expected_start = _et(date(2026, 4, 21), time(16, 0))
    expected_end = _et(target, time(9, 30))
    assert start == expected_start
    assert end == expected_end


def test_intraday_bounds_basic_weekday():
    target = date(2026, 4, 22)
    start, end = session_window(target, "intraday")
    assert start == _et(target, time(9, 30))
    assert end == _et(target, time(16, 0))


def test_post_ends_at_next_premarket_start_not_next_open():
    """post must NOT extend to next session's 09:30 — that would overlap T+1 premarket."""
    target = date(2026, 4, 22)  # Wed; next trading day Thu 2026-04-23
    _, end = session_window(target, "post")
    expected_end = _et(date(2026, 4, 23), time(4, 0))
    assert end == expected_end, f"post should end at next premarket start (04:00 ET), got {end.astimezone(ET)}"


def test_post_and_next_premarket_are_disjoint():
    target = date(2026, 4, 22)
    _, post_end = session_window(target, "post")
    next_pm_start, _ = session_window(date(2026, 4, 23), "premarket")
    # premarket starts at *previous close* (16:00), so they don't share boundary;
    # the contract is post_end <= 04:00 ET while next premarket fully overlaps that
    # zone. We assert the no-double-count guarantee: a 04:30 ET headline lands in
    # premarket (Thu) only, not in post (Wed).
    sample_dt = _et(date(2026, 4, 23), time(4, 30))
    assert sample_dt >= post_end, "04:30 ET headline should be past post-window end"
    assert sample_dt > next_pm_start  # premarket window includes 04:30


def test_full_session_spans_prev_close_to_next_premarket_start():
    target = date(2026, 4, 22)
    start, end = session_window(target, "full_session")
    assert start == _et(date(2026, 4, 21), time(16, 0))
    assert end == _et(date(2026, 4, 23), time(4, 0))


def test_premarket_after_weekend_uses_friday_close():
    """Monday's premarket starts at the previous *Friday*'s close, not Sunday."""
    target = date(2026, 4, 27)  # Monday
    start, _ = session_window(target, "premarket")
    expected_start = _et(date(2026, 4, 24), time(16, 0))  # Friday
    assert start == expected_start


def test_friday_post_extends_to_monday_premarket_start():
    """Friday's `post` window must extend across the weekend to Monday 04:00 ET."""
    target = date(2026, 4, 24)  # Friday
    _, end = session_window(target, "post")
    expected_end = _et(date(2026, 4, 27), time(4, 0))  # Monday 04:00
    assert end == expected_end


def test_unknown_window_raises():
    with pytest.raises(ValueError):
        session_window(date(2026, 4, 22), "lunch")  # type: ignore[arg-type]


def test_returned_datetimes_are_utc_aware():
    start, end = session_window(date(2026, 4, 22), "premarket")
    assert start.tzinfo is not None
    assert end.tzinfo is not None
    assert start.utcoffset().total_seconds() == 0  # type: ignore[union-attr]
    assert end.utcoffset().total_seconds() == 0  # type: ignore[union-attr]