from sqlalchemy.orm import Session
from app.models.invoice import Invoice, InvoiceItem, InvoiceStatus
from app.schemas.invoice import InvoiceCreate, InvoiceUpdate
from typing import List, Optional
from decimal import Decimal
import uuid


class InvoiceService:
    def __init__(self, db: Session):
        self.db = db

    def get_invoices(
        self, user_id: int, skip: int = 0, limit: int = 100
    ) -> List[Invoice]:
        return (
            self.db.query(Invoice)
            .filter(Invoice.user_id == user_id)
            .offset(skip)
            .limit(limit)
            .all()
        )

    def get_invoice(self, invoice_id: int, user_id: int) -> Optional[Invoice]:
        return (
            self.db.query(Invoice)
            .filter(Invoice.id == invoice_id, Invoice.user_id == user_id)
            .first()
        )

    def create_invoice(self, invoice_data: InvoiceCreate, user_id: int) -> Invoice:
        # Generate unique invoice number
        invoice_number = f"INV-{uuid.uuid4().hex[:8].upper()}"

        # Calculate totals
        subtotal = sum(item.quantity * item.unit_price for item in invoice_data.items)
        tax_amount = (
            subtotal * (invoice_data.tax_rate / 100)
            if invoice_data.tax_rate
            else Decimal("0")
        )
        total = subtotal + tax_amount

        # Create invoice
        invoice = Invoice(
            invoice_number=invoice_number,
            customer_id=invoice_data.customer_id,
            user_id=user_id,
            due_date=invoice_data.due_date,
            tax_rate=invoice_data.tax_rate or Decimal("0"),
            subtotal=subtotal,
            tax_amount=tax_amount,
            total=total,
            notes=invoice_data.notes,
        )

        self.db.add(invoice)
        self.db.flush()  # Get the invoice ID

        # Create invoice items
        for item_data in invoice_data.items:
            item_total = item_data.quantity * item_data.unit_price
            item = InvoiceItem(
                invoice_id=invoice.id,
                description=item_data.description,
                quantity=item_data.quantity,
                unit_price=item_data.unit_price,
                total_price=item_total,
            )
            self.db.add(item)

        self.db.commit()
        self.db.refresh(invoice)
        return invoice

    def update_invoice(
        self, invoice_id: int, invoice_data: InvoiceUpdate, user_id: int
    ) -> Optional[Invoice]:
        invoice = self.get_invoice(invoice_id, user_id)
        if not invoice:
            return None

        # Update basic fields
        update_data = invoice_data.dict(exclude_unset=True, exclude={"items"})
        for field, value in update_data.items():
            setattr(invoice, field, value)

        # Update items if provided
        if invoice_data.items is not None:
            # Delete existing items
            self.db.query(InvoiceItem).filter(
                InvoiceItem.invoice_id == invoice_id
            ).delete()

            # Add new items
            subtotal = Decimal("0")
            for item_data in invoice_data.items:
                item_total = item_data.quantity * item_data.unit_price
                subtotal += item_total
                item = InvoiceItem(
                    invoice_id=invoice.id,
                    description=item_data.description,
                    quantity=item_data.quantity,
                    unit_price=item_data.unit_price,
                    total_price=item_total,
                )
                self.db.add(item)

            # Recalculate totals
            tax_amount = (
                subtotal * (invoice.tax_rate / 100)
                if invoice.tax_rate
                else Decimal("0")
            )
            invoice.subtotal = subtotal
            invoice.tax_amount = tax_amount
            invoice.total = subtotal + tax_amount

        self.db.commit()
        self.db.refresh(invoice)
        return invoice

    def delete_invoice(self, invoice_id: int, user_id: int) -> bool:
        invoice = self.get_invoice(invoice_id, user_id)
        if not invoice:
            return False

        self.db.delete(invoice)
        self.db.commit()
        return True

    def update_invoice_status(
        self, invoice_id: int, status: InvoiceStatus, user_id: int
    ) -> Optional[Invoice]:
        invoice = self.get_invoice(invoice_id, user_id)
        if not invoice:
            return None

        invoice.status = status
        self.db.commit()
        self.db.refresh(invoice)
        return invoice