# app/services/cart_service.py
"""
Shopping cart service.

This module provides:
- Session-based cart management
- Cart item operations (add, update, remove)
- Cart total calculations
"""

import logging

from sqlalchemy import and_
from sqlalchemy.orm import Session

from app.exceptions import (
    CartItemNotFoundException,
    InsufficientInventoryForCartException,
    InvalidCartQuantityException,
    ProductNotFoundException,
)
from models.database.cart import CartItem
from models.database.product import Product

logger = logging.getLogger(__name__)


class CartService:
    """Service for managing shopping carts."""

    def get_cart(self, db: Session, vendor_id: int, session_id: str) -> dict:
        """
        Get cart contents for a session.

        Args:
            db: Database session
            vendor_id: Vendor ID
            session_id: Session ID

        Returns:
            Cart data with items and totals
        """
        logger.info(
            "[CART_SERVICE] get_cart called",
            extra={
                "vendor_id": vendor_id,
                "session_id": session_id,
            },
        )

        # Fetch cart items from database
        cart_items = (
            db.query(CartItem)
            .filter(
                and_(CartItem.vendor_id == vendor_id, CartItem.session_id == session_id)
            )
            .all()
        )

        logger.info(
            f"[CART_SERVICE] Found {len(cart_items)} items in database",
            extra={"item_count": len(cart_items)},
        )

        # Build response
        items = []
        subtotal = 0.0

        for cart_item in cart_items:
            product = cart_item.product
            line_total = cart_item.line_total

            items.append(
                {
                    "product_id": product.id,
                    "product_name": product.marketplace_product.title,
                    "quantity": cart_item.quantity,
                    "price": cart_item.price_at_add,
                    "line_total": line_total,
                    "image_url": (
                        product.marketplace_product.image_link
                        if product.marketplace_product
                        else None
                    ),
                }
            )

            subtotal += line_total

        cart_data = {
            "vendor_id": vendor_id,
            "session_id": session_id,
            "items": items,
            "subtotal": subtotal,
            "total": subtotal,  # Could add tax/shipping later
        }

        logger.info(
            f"[CART_SERVICE] get_cart returning: {len(cart_data['items'])} items, total: {cart_data['total']}",
            extra={"cart": cart_data},
        )

        return cart_data

    def add_to_cart(
        self,
        db: Session,
        vendor_id: int,
        session_id: str,
        product_id: int,
        quantity: int = 1,
    ) -> dict:
        """
        Add product to cart.

        Args:
            db: Database session
            vendor_id: Vendor ID
            session_id: Session ID
            product_id: Product ID
            quantity: Quantity to add

        Returns:
            Updated cart

        Raises:
            ProductNotFoundException: If product not found
            InsufficientInventoryException: If not enough inventory
        """
        logger.info(
            "[CART_SERVICE] add_to_cart called",
            extra={
                "vendor_id": vendor_id,
                "session_id": session_id,
                "product_id": product_id,
                "quantity": quantity,
            },
        )

        # Verify product exists and belongs to vendor
        product = (
            db.query(Product)
            .filter(
                and_(
                    Product.id == product_id,
                    Product.vendor_id == vendor_id,
                    Product.is_active == True,
                )
            )
            .first()
        )

        if not product:
            logger.error(
                "[CART_SERVICE] Product not found",
                extra={"product_id": product_id, "vendor_id": vendor_id},
            )
            raise ProductNotFoundException(product_id=product_id, vendor_id=vendor_id)

        logger.info(
            f"[CART_SERVICE] Product found: {product.marketplace_product.title}",
            extra={
                "product_id": product_id,
                "product_name": product.marketplace_product.title,
                "available_inventory": product.available_inventory,
            },
        )

        # Get current price (use sale_price if available, otherwise regular price)
        current_price = product.sale_price if product.sale_price else product.price

        # Check if item already exists in cart
        existing_item = (
            db.query(CartItem)
            .filter(
                and_(
                    CartItem.vendor_id == vendor_id,
                    CartItem.session_id == session_id,
                    CartItem.product_id == product_id,
                )
            )
            .first()
        )

        if existing_item:
            # Update quantity
            new_quantity = existing_item.quantity + quantity

            # Check inventory for new total quantity
            if product.available_inventory < new_quantity:
                logger.warning(
                    "[CART_SERVICE] Insufficient inventory for update",
                    extra={
                        "product_id": product_id,
                        "current_in_cart": existing_item.quantity,
                        "adding": quantity,
                        "requested_total": new_quantity,
                        "available": product.available_inventory,
                    },
                )
                raise InsufficientInventoryForCartException(
                    product_id=product_id,
                    product_name=product.marketplace_product.title,
                    requested=new_quantity,
                    available=product.available_inventory,
                )

            existing_item.quantity = new_quantity
            db.flush()
            db.refresh(existing_item)

            logger.info(
                "[CART_SERVICE] Updated existing cart item",
                extra={"cart_item_id": existing_item.id, "new_quantity": new_quantity},
            )

            return {
                "message": "Product quantity updated in cart",
                "product_id": product_id,
                "quantity": new_quantity,
            }
        # Check inventory for new item
        if product.available_inventory < quantity:
            logger.warning(
                "[CART_SERVICE] Insufficient inventory",
                extra={
                    "product_id": product_id,
                    "requested": quantity,
                    "available": product.available_inventory,
                },
            )
            raise InsufficientInventoryForCartException(
                product_id=product_id,
                product_name=product.marketplace_product.title,
                requested=quantity,
                available=product.available_inventory,
            )

        # Create new cart item
        cart_item = CartItem(
            vendor_id=vendor_id,
            session_id=session_id,
            product_id=product_id,
            quantity=quantity,
            price_at_add=current_price,
        )
        db.add(cart_item)
        db.flush()
        db.refresh(cart_item)

        logger.info(
            "[CART_SERVICE] Created new cart item",
            extra={
                "cart_item_id": cart_item.id,
                "quantity": quantity,
                "price": current_price,
            },
        )

        return {
            "message": "Product added to cart",
            "product_id": product_id,
            "quantity": quantity,
        }

    def update_cart_item(
        self,
        db: Session,
        vendor_id: int,
        session_id: str,
        product_id: int,
        quantity: int,
    ) -> dict:
        """
        Update quantity of item in cart.

        Args:
            db: Database session
            vendor_id: Vendor ID
            session_id: Session ID
            product_id: Product ID
            quantity: New quantity (must be >= 1)

        Returns:
            Success message

        Raises:
            ValidationException: If quantity < 1
            ProductNotFoundException: If product not found
            InsufficientInventoryException: If not enough inventory
        """
        if quantity < 1:
            raise InvalidCartQuantityException(quantity=quantity, min_quantity=1)

        # Find cart item
        cart_item = (
            db.query(CartItem)
            .filter(
                and_(
                    CartItem.vendor_id == vendor_id,
                    CartItem.session_id == session_id,
                    CartItem.product_id == product_id,
                )
            )
            .first()
        )

        if not cart_item:
            raise CartItemNotFoundException(
                product_id=product_id, session_id=session_id
            )

        # Verify product still exists and is active
        product = (
            db.query(Product)
            .filter(
                and_(
                    Product.id == product_id,
                    Product.vendor_id == vendor_id,
                    Product.is_active == True,
                )
            )
            .first()
        )

        if not product:
            raise ProductNotFoundException(str(product_id))

        # Check inventory
        if product.available_inventory < quantity:
            raise InsufficientInventoryForCartException(
                product_id=product_id,
                product_name=product.marketplace_product.title,
                requested=quantity,
                available=product.available_inventory,
            )

        # Update quantity
        cart_item.quantity = quantity
        db.flush()
        db.refresh(cart_item)

        logger.info(
            "[CART_SERVICE] Updated cart item quantity",
            extra={
                "cart_item_id": cart_item.id,
                "product_id": product_id,
                "new_quantity": quantity,
            },
        )

        return {
            "message": "Cart updated",
            "product_id": product_id,
            "quantity": quantity,
        }

    def remove_from_cart(
        self, db: Session, vendor_id: int, session_id: str, product_id: int
    ) -> dict:
        """
        Remove item from cart.

        Args:
            db: Database session
            vendor_id: Vendor ID
            session_id: Session ID
            product_id: Product ID

        Returns:
            Success message

        Raises:
            ProductNotFoundException: If product not in cart
        """
        # Find and delete cart item
        cart_item = (
            db.query(CartItem)
            .filter(
                and_(
                    CartItem.vendor_id == vendor_id,
                    CartItem.session_id == session_id,
                    CartItem.product_id == product_id,
                )
            )
            .first()
        )

        if not cart_item:
            raise CartItemNotFoundException(
                product_id=product_id, session_id=session_id
            )

        db.delete(cart_item)

        logger.info(
            "[CART_SERVICE] Removed item from cart",
            extra={
                "cart_item_id": cart_item.id,
                "product_id": product_id,
                "session_id": session_id,
            },
        )

        return {"message": "Item removed from cart", "product_id": product_id}

    def clear_cart(self, db: Session, vendor_id: int, session_id: str) -> dict:
        """
        Clear all items from cart.

        Args:
            db: Database session
            vendor_id: Vendor ID
            session_id: Session ID

        Returns:
            Success message with count of items removed
        """
        # Delete all cart items for this session
        deleted_count = (
            db.query(CartItem)
            .filter(
                and_(CartItem.vendor_id == vendor_id, CartItem.session_id == session_id)
            )
            .delete()
        )

        logger.info(
            "[CART_SERVICE] Cleared cart",
            extra={
                "session_id": session_id,
                "vendor_id": vendor_id,
                "items_removed": deleted_count,
            },
        )

        return {"message": "Cart cleared", "items_removed": deleted_count}


# Create service instance
cart_service = CartService()