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"))]


def test_ende_modifier_beendet_posten_im_szenario():
    r = PlainRecurring(1, "Miete", Decimal("-2000.00"), "monthly", 1, None, None, None)
    m = PlainModifier("recurring", 1, "ende", Decimal("0"), date(2026, 8, 31))
    flows = build_cashflows([r], [], [], [], [m], date(2026, 7, 1), date(2026, 12, 31))
    assert [d for d, _ in flows] == [date(2026, 7, 1), date(2026, 8, 1)]
    assert all(a == Decimal("-2000.00") for _, a in flows)


def test_ende_modifier_minimum_mit_eigenem_ende():
    # Posten endet selbst am 15.10.; Szenario-Ende 31.08. ist frueher -> gewinnt.
    r = PlainRecurring(1, "Miete", Decimal("-100.00"), "monthly", 1,
                       None, date(2026, 10, 15), None)
    m = PlainModifier("recurring", 1, "ende", Decimal("0"), date(2026, 8, 31))
    flows = build_cashflows([r], [], [], [], [m], date(2026, 7, 1), date(2026, 12, 31))
    assert [d for d, _ in flows] == [date(2026, 7, 1), date(2026, 8, 1)]
    # Umgekehrt: Szenario-Ende NACH eigenem Ende aendert nichts.
    m_spaet = PlainModifier("recurring", 1, "ende", Decimal("0"), date(2026, 12, 31))
    flows2 = build_cashflows([r], [], [], [], [m_spaet], date(2026, 7, 1), date(2026, 12, 31))
    assert [d for d, _ in flows2][-1] == date(2026, 10, 1)


def test_ende_modifier_auf_kategorie_trifft_alle_posten_der_kategorie():
    r1 = PlainRecurring(1, "Miete A", Decimal("-10.00"), "monthly", 1, None, None, 7)
    r2 = PlainRecurring(2, "Miete B", Decimal("-20.00"), "monthly", 1, None, None, 7)
    r3 = PlainRecurring(3, "Strom", Decimal("-5.00"), "monthly", 1, None, None, 9)
    m = PlainModifier("category", 7, "ende", Decimal("0"), date(2026, 7, 31))
    flows = build_cashflows([r1, r2, r3], [], [], [], [m],
                            date(2026, 7, 1), date(2026, 9, 30))
    betraege = sorted(a for _, a in flows)
    # Miete A/B nur je 1x (Juli), Strom 3x (Juli-Sept).
    assert betraege == [Decimal("-20.00"), Decimal("-10.00"),
                        Decimal("-5.00"), Decimal("-5.00"), Decimal("-5.00")]


def test_ende_modifier_ohne_datum_wirkt_nicht():
    r = PlainRecurring(1, "Miete", Decimal("-10.00"), "monthly", 1, None, None, None)
    m = PlainModifier("recurring", 1, "ende", Decimal("0"), None)
    flows = build_cashflows([r], [], [], [], [m], date(2026, 7, 1), date(2026, 9, 30))
    assert len(flows) == 3


def test_ende_modifier_aendert_betraege_nicht():
    r = PlainRecurring(1, "Miete", Decimal("-2000.00"), "monthly", 1, None, None, None)
    m = PlainModifier("recurring", 1, "ende", Decimal("50"), date(2026, 12, 31))
    flows = build_cashflows([r], [], [], [], [m], date(2026, 7, 1), date(2026, 8, 31))
    assert all(a == Decimal("-2000.00") for _, a in flows)