# FILE: src/apps/billing/models/invoice.py
from __future__ import annotations

import datetime as dt
from decimal import Decimal
from typing import TYPE_CHECKING, List, Optional
from uuid import UUID

from sqlalchemy import Date, DateTime, ForeignKey, Integer, Numeric, String, UniqueConstraint
from sqlalchemy.dialects.postgresql import UUID as PG_UUID
from sqlalchemy.orm import Mapped, mapped_column, relationship

from src.database.base import TenantModel

if TYPE_CHECKING:
    from src.apps.sales.models.contract import Contract
    from src.apps.billing.models.invoice_payment import InvoicePayment


class Invoice(TenantModel):
    __tablename__ = "invoices"

    __table_args__ = (
        UniqueConstraint("tenant_id", "invoice_number", name="uq_invoices_tenant_number"),
    )

    # Override tenant_id with explicit FK
    tenant_id: Mapped[UUID] = mapped_column(
        PG_UUID(as_uuid=True),
        ForeignKey("accounts.id", ondelete="CASCADE"),
        nullable=False,
        index=True,
    )

    contract_id: Mapped[Optional[UUID]] = mapped_column(
        PG_UUID(as_uuid=True),
        ForeignKey("contracts.id", ondelete="SET NULL"),
        nullable=True,
        index=True,
    )

    invoice_number: Mapped[str] = mapped_column(String(50), nullable=False)
    status: Mapped[str] = mapped_column(String(50), nullable=False, default="outstanding")
    total_amount: Mapped[Decimal] = mapped_column(
        Numeric(12, 2), nullable=False, default=Decimal("0")
    )
    paid_amount: Mapped[Decimal] = mapped_column(
        Numeric(12, 2), nullable=False, default=Decimal("0")
    )
    balance_due: Mapped[Decimal] = mapped_column(
        Numeric(12, 2), nullable=False, default=Decimal("0")
    )
    due_date: Mapped[Optional[dt.date]] = mapped_column(Date, nullable=True)
    reminder_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
    last_reminder_at: Mapped[Optional[dt.datetime]] = mapped_column(
        DateTime(timezone=True), nullable=True
    )

    # Relationships
    contract: Mapped[Optional["Contract"]] = relationship(
        "Contract", back_populates="invoices"
    )
    payments: Mapped[List["InvoicePayment"]] = relationship(
        "InvoicePayment", back_populates="invoice"
    )