"""Schemata für wiederkehrende Posten, Preisversionen und Vorschau."""

from datetime import date, datetime

from pydantic import Field, model_validator

from app.models.enums import BusinessDayShift, EntryKind
from app.schemas.common import ApiModel, InputModel, Money, PositiveMoney
from app.schemas.merchant import MerchantOut
from app.services.recurrence import InvalidRRuleError, validate_rrule


class RecurrenceBase(InputModel):
    kind: EntryKind
    title: str = Field(min_length=1, max_length=160, examples=["Netflix Standard"])
    merchant_id: int | None = None
    category_id: int
    account_id: int
    amount: PositiveMoney = Field(
        description="Aktueller Betrag. Immer positiv – die Richtung steckt in `kind`."
    )
    is_variable: bool = Field(
        default=False, description="Geschätzter Betrag, das Ist weicht regelmäßig ab."
    )
    currency: str = Field(default="EUR", pattern=r"^[A-Z]{3}$")

    rrule: str = Field(
        max_length=500,
        examples=["FREQ=MONTHLY;BYMONTHDAY=1"],
        description="Vollständige RFC-5545-RRULE ohne DTSTART.",
    )
    dtstart: date = Field(description="Erste mögliche Fälligkeit der Serie.")
    until: date | None = Field(default=None, description="Hartes Serienende, einschließlich.")

    business_day_shift: BusinessDayShift = Field(
        default=BusinessDayShift.NEXT,
        description="Verschiebung, wenn der Termin auf Wochenende oder Feiertag fällt.",
    )
    holiday_region: str = Field(default="DE-NW", max_length=8, examples=["DE-NW"])

    installments_total: int | None = Field(
        default=None, ge=1, description="Anzahl Raten; beendet die Serie unabhängig von der RRULE."
    )
    principal_amount: PositiveMoney | None = Field(
        default=None, description="Ursprüngliche Darlehenssumme für die Restschuldberechnung."
    )

    contract_start: date | None = None
    contract_min_term_months: int | None = Field(default=None, ge=1)
    contract_notice_period_days: int | None = Field(default=None, ge=0)
    contract_auto_renew_months: int | None = Field(default=None, ge=1)

    reserve_enabled: bool = Field(
        default=False, description="Bildet monatliche Rücklagen für nicht-monatliche Posten."
    )
    notes: str | None = None
    tags: list[str] = Field(default_factory=list)
    is_active: bool = True

    @model_validator(mode="after")
    def _check_rule_and_dates(self) -> "RecurrenceBase":
        try:
            validate_rrule(self.rrule, self.dtstart)
        except InvalidRRuleError as exc:
            raise ValueError(str(exc)) from exc
        if self.until is not None and self.until < self.dtstart:
            raise ValueError("Das Serienende darf nicht vor dem Start liegen.")
        return self


class RecurrenceCreate(RecurrenceBase):
    pass


class RecurrenceUpdate(InputModel):
    """Alle Felder optional. RRULE und `dtstart` werden zusammen geprüft."""

    kind: EntryKind | None = None
    title: str | None = Field(default=None, min_length=1, max_length=160)
    merchant_id: int | None = None
    category_id: int | None = None
    account_id: int | None = None
    amount: PositiveMoney | None = None
    is_variable: bool | None = None
    currency: str | None = Field(default=None, pattern=r"^[A-Z]{3}$")
    rrule: str | None = Field(default=None, max_length=500)
    dtstart: date | None = None
    until: date | None = None
    business_day_shift: BusinessDayShift | None = None
    holiday_region: str | None = Field(default=None, max_length=8)
    installments_total: int | None = Field(default=None, ge=1)
    principal_amount: PositiveMoney | None = None
    contract_start: date | None = None
    contract_min_term_months: int | None = Field(default=None, ge=1)
    contract_notice_period_days: int | None = Field(default=None, ge=0)
    contract_auto_renew_months: int | None = Field(default=None, ge=1)
    contract_cancelled_at: date | None = None
    reserve_enabled: bool | None = None
    notes: str | None = None
    tags: list[str] | None = None
    is_active: bool | None = None


class AmountVersionCreate(InputModel):
    amount: PositiveMoney
    valid_from: date = Field(description="Gilt für alle Fälligkeiten ab diesem Tag.")
    note: str | None = Field(default=None, examples=["Preiserhöhung laut Schreiben vom 01.06."])


class AmountVersionOut(ApiModel):
    id: int
    recurrence_id: int
    amount: Money
    valid_from: date
    note: str | None
    created_at: datetime


class ContractTermOut(ApiModel):
    """Laufende Vertragsperiode und Kündigungstermin."""

    term_start: date
    term_end: date
    notice_deadline: date | None
    renews_on: date | None
    is_cancelled: bool


class InstallmentStatusOut(ApiModel):
    """Stand einer Ratenzahlung."""

    total: int
    paid: int
    remaining: int
    paid_amount: Money
    remaining_amount: Money
    final_due_date: date | None


class RecurrenceOut(ApiModel):
    id: int
    kind: EntryKind
    title: str
    merchant_id: int | None
    category_id: int
    account_id: int
    amount: Money
    is_variable: bool
    currency: str
    rrule: str
    dtstart: date
    until: date | None
    business_day_shift: BusinessDayShift
    holiday_region: str
    installments_total: int | None
    principal_amount: Money | None
    contract_start: date | None
    contract_min_term_months: int | None
    contract_notice_period_days: int | None
    contract_auto_renew_months: int | None
    contract_cancelled_at: date | None
    reserve_enabled: bool
    notes: str | None
    tags: list[str]
    is_active: bool
    created_at: datetime
    updated_at: datetime


class RecurrenceDetailOut(RecurrenceOut):
    """Posten samt berechneter Zusatzangaben für die Detailansicht."""

    merchant: MerchantOut | None = None
    amount_versions: list[AmountVersionOut] = Field(default_factory=list)
    next_dates: list[date] = Field(
        default_factory=list, description="Die nächsten fünf nominalen Termine."
    )
    monthly_reserve: Money | None = Field(
        default=None, description="Rücklage pro Monat, wenn `reserve_enabled` gesetzt ist."
    )
    annual_burden: Money = Field(description="Belastung der kommenden zwölf Monate.")
    contract_term: ContractTermOut | None = None
    installments: InstallmentStatusOut | None = None