from datetime import date
from decimal import Decimal

import pytest

from finance.models import Account, Category, Transaction
from finance.reports import (
    ReportInputError,
    account_balances,
    available_currencies,
    monthly_summary,
    spending_by_category,
)


pytestmark = pytest.mark.django_db


def make_account(name="Synthetic Bank", *, kind=Account.Kind.BANK, currency="BRL"):
    return Account.objects.create(name=name, kind=kind, currency=currency)


def post(account, amount, kind, posting_date, *, category=None):
    return Transaction.objects.create(
        account=account,
        amount=Decimal(amount),
        kind=kind,
        posting_date=posting_date,
        category=category,
    )


def test_monthly_summary_counts_card_purchase_once_and_refund_in_posting_month():
    bank = make_account()
    card = make_account("Synthetic Card", kind=Account.Kind.CREDIT_CARD)
    post(bank, "500.00", Transaction.Kind.OPENING, date(2025, 12, 31))
    post(bank, "1000.00", Transaction.Kind.INCOME, date(2026, 1, 2))
    post(card, "-300.00", Transaction.Kind.EXPENSE, date(2026, 1, 3))
    post(bank, "-300.00", Transaction.Kind.TRANSFER, date(2026, 1, 20))
    post(card, "300.00", Transaction.Kind.TRANSFER, date(2026, 1, 20))
    post(card, "50.00", Transaction.Kind.REFUND, date(2026, 1, 25))
    post(card, "20.00", Transaction.Kind.REFUND, date(2026, 2, 1))

    result = monthly_summary(date(2026, 1, 1), "BRL")

    assert result.inflow == Decimal("1000.00")
    assert result.expense == Decimal("300.00")
    assert result.refund == Decimal("50.00")
    assert result.net_spending == Decimal("250.00")
    assert result.net_activity == Decimal("750.00")


def test_spending_has_uncategorized_bucket_and_never_combines_currency():
    bank = make_account()
    usd = make_account("Synthetic USD", currency="USD")
    food = Category.objects.create(name="Synthetic Food", kind=Category.Kind.EXPENSE)
    post(bank, "-100.00", Transaction.Kind.EXPENSE, date(2026, 1, 2), category=food)
    post(bank, "20.00", Transaction.Kind.REFUND, date(2026, 1, 3), category=food)
    post(bank, "-20.00", Transaction.Kind.EXPENSE, date(2026, 1, 4))
    post(usd, "-999.00", Transaction.Kind.EXPENSE, date(2026, 1, 5), category=food)

    rows = spending_by_category(date(2026, 1, 1), "BRL")

    assert [(row.category_name, row.net_spending) for row in rows] == [
        ("Synthetic Food", Decimal("80.00")),
        ("Uncategorized", Decimal("20.00")),
    ]
    assert rows[0].expense == Decimal("100.00")
    assert rows[0].refund == Decimal("20.00")


def test_empty_month_returns_explicit_zero_totals_and_no_spending_rows():
    result = monthly_summary(date(2026, 1, 1), "BRL")

    assert result.inflow == Decimal("0.00")
    assert result.expense == Decimal("0.00")
    assert result.refund == Decimal("0.00")
    assert result.net_spending == Decimal("0.00")
    assert result.net_activity == Decimal("0.00")
    assert spending_by_category(date(2026, 1, 1), "BRL") == ()


def test_account_balances_include_openings_and_transfers_through_month_end():
    beta = make_account("Synthetic Beta")
    alpha = make_account("Synthetic Alpha")
    usd = make_account("Synthetic USD", currency="USD")
    post(alpha, "100.00", Transaction.Kind.OPENING, date(2025, 12, 1))
    post(alpha, "-20.00", Transaction.Kind.TRANSFER, date(2026, 1, 20))
    post(beta, "20.00", Transaction.Kind.TRANSFER, date(2026, 1, 20))
    post(beta, "-5.00", Transaction.Kind.EXPENSE, date(2026, 2, 1))
    post(usd, "1000.00", Transaction.Kind.OPENING, date(2025, 12, 1))

    rows = account_balances(date(2026, 1, 1), "BRL")

    assert [(row.account_name, row.balance) for row in rows] == [
        ("Synthetic Alpha", Decimal("80.00")),
        ("Synthetic Beta", Decimal("20.00")),
    ]


def test_available_currencies_are_distinct_and_sorted():
    make_account("Synthetic BRL", currency="BRL")
    make_account("Synthetic USD", currency="USD")
    make_account("Synthetic BRL 2", currency="BRL")

    assert available_currencies() == ("BRL", "USD")


@pytest.mark.parametrize(
    ("month", "currency", "errors"),
    [
        (date(2026, 1, 2), "BRL", {"month": "must_be_first_day"}),
        (date(9999, 12, 1), "BRL", {"month": "invalid_month"}),
        (date(2026, 1, 1), "brl", {"currency": "invalid_currency"}),
        ("2026-01", "BRL", {"month": "invalid_date"}),
    ],
)
def test_report_inputs_are_validated(month, currency, errors):
    with pytest.raises(ReportInputError) as caught:
        monthly_summary(month, currency)

    assert caught.value.errors == errors