from datetime import date
from decimal import Decimal

from app.engine.loans import loan_schedule
from app.engine.scenario import (PlainModifier, PlainPlanned, PlainRecurring,
                                 build_cashflows)

W = (date(2026, 8, 1), date(2026, 10, 31))


def test_recurring_with_percent_cut():
    rec = [PlainRecurring(id=1, name="Marketing", amount=Decimal("-1000"),
                          rhythm="monthly", due_day=5, start_date=None,
                          end_date=None, category_id=7)]
    mods = [PlainModifier(target_type="category", target_id=7,
                          kind="percent", value=Decimal("50"))]
    flows = build_cashflows(rec, [], [], [], mods, *W)
    assert flows == [(date(2026, 8, 5), Decimal("-500.00")),
                     (date(2026, 9, 5), Decimal("-500.00")),
                     (date(2026, 10, 5), Decimal("-500.00"))]


def test_remove_modifier_and_planned_and_loan():
    rec = [PlainRecurring(id=2, name="Abo", amount=Decimal("-50"),
                          rhythm="monthly", due_day=1, start_date=None,
                          end_date=None, category_id=None)]
    mods = [PlainModifier(target_type="recurring", target_id=2,
                          kind="remove", value=Decimal("0"))]
    planned = [PlainPlanned(name="Steuer", amount=Decimal("-2000"),
                            due=date(2026, 9, 15), category_id=None)]
    sched = loan_schedule(Decimal("10000"), Decimal("6"), 48, date(2026, 8, 1), "annuity")
    flows = build_cashflows(rec, planned, [sched],
                            [(date(2026, 8, 1), Decimal("10000"))], mods, *W)
    days = [d for d, _ in flows]
    assert date(2026, 8, 1) in days            # Kredit-Auszahlung
    assert date(2026, 9, 15) in days           # Einmalposten
    assert all(a != Decimal("-50") for _, a in flows)  # Abo entfernt


def test_absolute_modifier_reduces_outflow():
    """Test absolute modifier for outflows: -200 - 50 = -150"""
    rec = [PlainRecurring(id=1, name="Marketing", amount=Decimal("-200"),
                          rhythm="monthly", due_day=10, start_date=None,
                          end_date=None, category_id=3)]
    mods = [PlainModifier(target_type="category", target_id=3,
                          kind="absolute", value=Decimal("50"))]
    flows = build_cashflows(rec, [], [], [], mods, date(2026, 8, 1), date(2026, 8, 31))
    assert flows == [(date(2026, 8, 10), Decimal("-150.00"))]


def test_absolute_modifier_clamps_to_zero():
    """Test absolute modifier clamping: -200 + 300 = 0 (never flips sign)"""
    rec = [PlainRecurring(id=1, name="Marketing", amount=Decimal("-200"),
                          rhythm="monthly", due_day=10, start_date=None,
                          end_date=None, category_id=3)]
    mods = [PlainModifier(target_type="category", target_id=3,
                          kind="absolute", value=Decimal("300"))]
    flows = build_cashflows(rec, [], [], [], mods, date(2026, 8, 1), date(2026, 8, 31))
    assert flows == [(date(2026, 8, 10), Decimal("0.00"))]