import ulid
from sqlalchemy import Column, String, Numeric, DateTime, Text, Index
from sqlalchemy.sql import func
from app.core.database.db_session import Base

class Invoice(Base):
    __tablename__ = "invoices"

    invoice_id = Column(String(26), primary_key=True, default=lambda: str(ulid.new()))
    invoice_no = Column(String(16), unique=True, nullable=False, index=True) # CBIC 16-char limit format: C1P2-26-000452
    order_id = Column(String(26), nullable=True, index=True)
    pos_transaction_id = Column(String(26), nullable=True, index=True)
    customer_id = Column(String(26), nullable=False, index=True)
    
    subtotal = Column(Numeric(10, 2), nullable=False)
    discount_amount = Column(Numeric(10, 2), default=0.00)
    cgst = Column(Numeric(10, 2), default=0.00)
    sgst = Column(Numeric(10, 2), default=0.00)
    igst = Column(Numeric(10, 2), default=0.00)
    total_amount = Column(Numeric(10, 2), nullable=False)
    
    pdf_path = Column(String(500), nullable=True)
    status = Column(String(30), default="GENERATED") # GENERATED, CANCELLED, REFUNDED
    created_at = Column(DateTime, server_default=func.now(), index=True)

    __table_args__ = (
        Index('idx_invoices_customer_date', 'customer_id', 'created_at'),
    )