import uuid
from sqlalchemy import Column, String, Integer, Numeric, DateTime, Date, ForeignKey, CheckConstraint, Index
from sqlalchemy.orm import relationship
from utils.utils import Base, utc_now


class Loancalculation(Base):
    __tablename__ = "loan_calculations"

    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
    principal_amount = Column(Numeric(15, 2), nullable=False)
    annual_interest_rate = Column(Numeric(6, 4), nullable=False)
    loan_term_months = Column(Integer, nullable=False)
    monthly_payment = Column(Numeric(15, 2), nullable=False)
    total_amount_paid = Column(Numeric(15, 2), nullable=False)
    total_interest_paid = Column(Numeric(15, 2), nullable=False)
    created_at = Column(DateTime(timezone=True), default=utc_now, nullable=False)
    updated_at = Column(DateTime(timezone=True), default=utc_now, onupdate=utc_now, nullable=False)

    amortization_schedule_entries = relationship(
        "Amortizationscheduleentry",
        back_populates="loan_calculation",
        cascade="all, delete-orphan",
        passive_deletes=True,
    )

    __table_args__ = (
        CheckConstraint("principal_amount >= 1 AND principal_amount <= 100000000", name="ck_principal_amount_range"),
        CheckConstraint("annual_interest_rate >= 0.01 AND annual_interest_rate <= 99.99", name="ck_annual_interest_rate_range"),
        CheckConstraint("loan_term_months >= 1 AND loan_term_months <= 600", name="ck_loan_term_months_range"),
    )


class Amortizationscheduleentry(Base):
    __tablename__ = "amortization_schedule_entries"

    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
    calculation_id = Column(String(36), ForeignKey("loan_calculations.id", ondelete="CASCADE"), nullable=False, index=True)
    payment_number = Column(Integer, nullable=False)
    payment_date = Column(Date, nullable=True)
    payment_amount = Column(Numeric(15, 2), nullable=False)
    principal_portion = Column(Numeric(15, 2), nullable=False)
    interest_portion = Column(Numeric(15, 2), nullable=False)
    remaining_balance = Column(Numeric(15, 2), nullable=False)
    cumulative_interest = Column(Numeric(15, 2), nullable=False)
    cumulative_principal = Column(Numeric(15, 2), nullable=False)
    created_at = Column(DateTime(timezone=True), default=utc_now, nullable=False)
    updated_at = Column(DateTime(timezone=True), default=utc_now, onupdate=utc_now, nullable=False)

    loan_calculation = relationship("Loancalculation", back_populates="amortization_schedule_entries")

    __table_args__ = (
        CheckConstraint("payment_number > 0", name="ck_payment_number_positive"),
        CheckConstraint("remaining_balance >= 0", name="ck_remaining_balance_nonneg"),
        CheckConstraint("cumulative_interest >= 0", name="ck_cumulative_interest_nonneg"),
        CheckConstraint("cumulative_principal >= 0", name="ck_cumulative_principal_nonneg"),
        Index("ix_amortization_calculation_payment", "calculation_id", "payment_number"),
    )