"""Unit tests for unified DateService."""
from datetime import date
import pytest

from app.utils.date_service import date_service


def test_date_service_parse_iso():
    d = date_service.parse("2026-09-16")
    assert d == date(2026, 9, 16)


def test_date_service_parse_jalali():
    # 1405/06/25 -> 2026-09-16
    d = date_service.parse("1405/06/25")
    assert d == date(2026, 9, 16)


def test_date_service_to_jalali():
    d = date(2026, 9, 16)
    assert date_service.to_jalali(d) == "1405/06/25"


def test_date_service_duration_calculation():
    d1 = date(2026, 9, 10)
    d2 = date(2026, 9, 15)
    # gap between the dates: the end date is not counted
    assert date_service.calculate_duration(d1, d2) == 5
    assert date_service.calculate_duration(d1, d1) == 0
    assert date_service.calculate_duration(None, d2) == 0
    # inverted range is not a duration
    assert date_service.calculate_duration(d2, d1) == 0


def test_date_service_compute_end_date():
    d1 = date(2026, 9, 10)
    # 0 days means start and end are the same day
    assert date_service.compute_end_date(d1, 0) == d1
    # 5 days is the gap, so the end date is 5 days later
    assert date_service.compute_end_date(d1, 5) == date(2026, 9, 15)


def test_duration_and_end_date_are_inverses():
    """The pair must round-trip, otherwise saved values drift on reload."""
    d1 = date(2026, 9, 10)
    for gap in (0, 1, 4, 5, 30):
        end = date_service.compute_end_date(d1, gap)
        assert date_service.calculate_duration(d1, end) == gap