from datetime import date, timedelta
from decimal import Decimal

from sqlalchemy import select

from factories import make_cbr_rate, make_txn
from fintracker.analytics import today_local
from fintracker.db import get_sessionmaker
from fintracker.models import FxRateDaily
from fintracker.pricing.fx import FxTable, rebuild_fx_daily


def last_friday(before_days: int = 7) -> date:
    d = today_local() - timedelta(days=before_days)
    return d - timedelta(days=(d.weekday() - 4) % 7)


async def rebuild() -> None:
    async with get_sessionmaker()() as session:
        await rebuild_fx_daily(session)
        await session.commit()


async def rates_on(d: date) -> dict[str, tuple[Decimal, bool]]:
    async with get_sessionmaker()() as session:
        rows = (await session.execute(select(FxRateDaily).where(FxRateDaily.d == d))).scalars()
        return {r.ccy: (r.rate_rub, r.is_carried) for r in rows}


async def test_nominal_is_divided_out(app):
    friday = last_friday()
    await make_cbr_rate(friday, "JPY", "65.0", nominal=100)
    await rebuild()

    rate, is_carried = (await rates_on(friday))["JPY"]
    assert rate == Decimal("0.65")
    assert is_carried is False


async def test_weekend_carries_friday_forward(app):
    friday = last_friday()
    await make_cbr_rate(friday, "USD", "90.5")
    await rebuild()

    for offset in (1, 2):  # Saturday, Sunday
        rate, is_carried = (await rates_on(friday + timedelta(days=offset)))["USD"]
        assert rate == Decimal("90.5")
        assert is_carried is True


async def test_days_before_the_first_quote_are_back_filled(app):
    friday = last_friday()
    earlier = friday - timedelta(days=10)
    await make_txn(earlier, outcome="100", outcome_currency="USD")
    await make_cbr_rate(friday, "USD", "90.5")
    await rebuild()

    rate, is_carried = (await rates_on(earlier))["USD"]
    assert rate == Decimal("90.5")
    assert is_carried is True


async def test_rub_is_one_on_every_day_and_outside_the_spine(app):
    friday = last_friday()
    await make_cbr_rate(friday, "USD", "90.5")
    await rebuild()

    assert (await rates_on(friday))["RUB"] == (Decimal(1), False)
    assert (await rates_on(today_local()))["RUB"] == (Decimal(1), False)

    async with get_sessionmaker()() as session:
        fx = await FxTable.load(session)
    assert fx.rate(date(1999, 1, 1), "RUB") == Decimal(1)
    assert fx.rate(date(1999, 1, 1), "USD") is None
    assert fx.to_rub(Decimal("10"), "USD", friday) == Decimal("905.0")
    assert fx.to_rub(Decimal("10"), "XBT", friday) is None


async def test_spine_covers_future_rates_and_future_transactions(app):
    """The CBR publishes tomorrow's rate the evening before, and a transaction may be dated
    in the future — both days must be convertible."""
    t = today_local()
    await make_cbr_rate(t, "USD", "90")
    await make_cbr_rate(t + timedelta(days=1), "USD", "95")
    await make_txn(t + timedelta(days=3), outcome="10", outcome_currency="USD")
    await rebuild()

    assert (await rates_on(t + timedelta(days=1)))["USD"] == (Decimal("95"), False)
    # the txn is dated past the last quote: the spine still reaches it, carried forward
    assert (await rates_on(t + timedelta(days=3)))["USD"] == (Decimal("95"), True)

    async with get_sessionmaker()() as session:
        fx = await FxTable.load(session)
    assert fx.to_rub(Decimal("10"), "USD", t + timedelta(days=3)) == Decimal("950")


async def test_deleted_txn_does_not_stretch_the_spine(app):
    """ZenMoney hands out a zero date (1970-01-01) for some deleted rows.

    Counting it would build the daily grid over five extra decades of carried-forward rates.
    """
    friday = last_friday()
    await make_cbr_rate(friday, "USD", "90.5")
    await make_txn(friday, outcome=100, outcome_currency="RUB")
    await make_txn(date(1970, 1, 1), income=15000, income_currency="RUB", deleted=True)
    await rebuild()

    async with get_sessionmaker()() as session:
        earliest = (
            (await session.execute(select(FxRateDaily.d).order_by(FxRateDaily.d))).scalars().first()
        )
    assert earliest is not None
    assert earliest >= friday - timedelta(days=1)