import uuid
from datetime import date, datetime, timezone
from decimal import Decimal

from sqlalchemy import CheckConstraint, Date, DateTime, ForeignKey, Numeric, String, Text, UniqueConstraint
from sqlalchemy.dialects.postgresql import UUID
from sqlalchemy.orm import Mapped, mapped_column

from app.db.base import Base


class Receivable(Base):
    __tablename__ = "receivables"
    __table_args__ = (
        UniqueConstraint("sale_id", name="uq_receivable_sale"),
        CheckConstraint("original_amount >= 0 AND amount_paid >= 0 AND balance >= 0", name="ck_receivable_nonnegative"),
    )
    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    business_id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), ForeignKey("businesses.id", ondelete="CASCADE"), nullable=False, index=True)
    customer_id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), ForeignKey("customers.id", ondelete="RESTRICT"), nullable=False, index=True)
    sale_id: Mapped[uuid.UUID | None] = mapped_column(UUID(as_uuid=True), ForeignKey("sales.id", ondelete="RESTRICT"), nullable=True)
    invoice_id: Mapped[uuid.UUID | None] = mapped_column(UUID(as_uuid=True), ForeignKey("invoices.id", ondelete="RESTRICT"), nullable=True, unique=True)
    original_amount: Mapped[Decimal] = mapped_column(Numeric(14, 2), nullable=False)
    amount_paid: Mapped[Decimal] = mapped_column(Numeric(14, 2), default=Decimal("0"), nullable=False)
    balance: Mapped[Decimal] = mapped_column(Numeric(14, 2), nullable=False)
    due_date: Mapped[date | None] = mapped_column(Date, nullable=True)
    status: Mapped[str] = mapped_column(String(20), nullable=False, default="OPEN")
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=lambda: datetime.now(timezone.utc), nullable=False)
    updated_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=lambda: datetime.now(timezone.utc), onupdate=lambda: datetime.now(timezone.utc), nullable=False)


class ReceivableCollection(Base):
    __tablename__ = "receivable_collections"
    __table_args__ = (CheckConstraint("amount > 0", name="ck_receivable_collection_positive"),)
    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
    business_id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), ForeignKey("businesses.id", ondelete="CASCADE"), nullable=False, index=True)
    receivable_id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), ForeignKey("receivables.id", ondelete="RESTRICT"), nullable=False, index=True)
    customer_id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), ForeignKey("customers.id", ondelete="RESTRICT"), nullable=False, index=True)
    amount: Mapped[Decimal] = mapped_column(Numeric(14, 2), nullable=False)
    payment_method: Mapped[str] = mapped_column(String(20), nullable=False)
    reference: Mapped[str | None] = mapped_column(String(150), nullable=True)
    collected_by: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), ForeignKey("users.id", ondelete="RESTRICT"), nullable=False)
    collected_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=lambda: datetime.now(timezone.utc), nullable=False)



class DebtReminder(Base):
    __tablename__ = "debt_reminders"
    __table_args__ = (
        CheckConstraint(
            "amount_outstanding > 0",
            name="ck_debt_reminder_positive_amount",
        ),
    )

    id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        primary_key=True,
        default=uuid.uuid4,
    )
    business_id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("businesses.id", ondelete="CASCADE"),
        nullable=False,
        index=True,
    )
    customer_id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("customers.id", ondelete="RESTRICT"),
        nullable=False,
        index=True,
    )
    created_by: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        ForeignKey("users.id", ondelete="RESTRICT"),
        nullable=False,
    )
    channel: Mapped[str] = mapped_column(
        String(20),
        nullable=False,
        default="EMAIL",
    )
    recipient: Mapped[str] = mapped_column(
        String(320),
        nullable=False,
    )
    amount_outstanding: Mapped[Decimal] = mapped_column(
        Numeric(14, 2),
        nullable=False,
    )
    message: Mapped[str | None] = mapped_column(
        Text,
        nullable=True,
    )
    status: Mapped[str] = mapped_column(
        String(20),
        nullable=False,
        default="PENDING",
        index=True,
    )
    error_code: Mapped[str | None] = mapped_column(
        String(100),
        nullable=True,
    )
    sent_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True),
        nullable=True,
    )
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True),
        default=lambda: datetime.now(timezone.utc),
        nullable=False,
        index=True,
    )