from datetime import datetime
from typing import Any
from xml.etree.ElementTree import Element, SubElement

from constance import config
from django.conf import settings
from django.db.models import QuerySet

from engine.core.feeds.base import BaseFeedGenerator
from engine.core.models import Product


class GoogleMerchantFeedGenerator(BaseFeedGenerator):
    """
    Google Merchant Center feed generator.

    Generates product feeds in Atom/RSS format compatible with Google Shopping.
    Reference: https://support.google.com/merchants/answer/7052112
    """

    name: str = "google_merchant"
    supported_formats: tuple[str, ...] = ("xml", "json")
    default_format: str = "xml"

    GOOGLE_NS = "http://base.google.com/ns/1.0"

    def generate_feed_data(self, products: QuerySet[Product]) -> list[dict[str, Any]]:
        """Generate feed data as a list of product dictionaries."""
        items = []

        for product in products:
            item = self._build_product_item(product)
            if item:
                items.append(item)

        return items

    def _build_product_item(self, product: Product) -> dict[str, Any] | None:
        """Build a product item dictionary for the feed."""
        if not product.price or product.price <= 0:
            return None

        images = self.get_product_images(product)
        primary_image = images[0] if images else ""
        additional_images = images[1:10] if len(images) > 1 else []

        item = {
            "id": product.sku,
            "title": product.name[:150],
            "description": (product.description or "")[:5000],
            "link": self.get_product_url(product),
            "image_link": primary_image,
            "availability": self.get_availability(product),
            "price": f"{product.price:.2f} {self.get_currency()}",
            "brand": product.brand.name if product.brand else "",
            "condition": "new",
            "product_type": self._get_product_type(product),
        }

        if additional_images:
            item["additional_image_link"] = additional_images

        if product.partnumber:
            item["mpn"] = product.partnumber

        if product.discount_price:
            sale_price = product.price - product.discount_price
            if sale_price > 0:
                item["sale_price"] = f"{sale_price:.2f} {self.get_currency()}"

        gtin = self._get_gtin(product)
        if gtin:
            item["gtin"] = gtin
        else:
            item["identifier_exists"] = "no"

        return item

    def _get_product_type(self, product: Product) -> str:
        """Build the product type hierarchy from category."""
        if not product.category:
            return ""

        ancestors = product.category.get_ancestors(include_self=True)
        return " > ".join([cat.name for cat in ancestors])

    def _get_gtin(self, product: Product) -> str | None:
        """Extract GTIN/EAN/UPC from product attributes."""
        gtin_names = ["gtin", "ean", "upc", "isbn", "barcode"]

        for attr_value in product.attributes.all():
            if attr_value.attribute.name.lower() in gtin_names:
                return attr_value.value

        return None

    def to_xml(self, data: list[dict[str, Any]]) -> str:
        """Convert feed data to Google Merchant XML format."""
        rss = Element("rss")
        rss.set("version", "2.0")
        rss.set("xmlns:g", self.GOOGLE_NS)

        channel = SubElement(rss, "channel")

        title = SubElement(channel, "title")
        title.text = config.COMPANY_NAME or settings.PROJECT_NAME

        link = SubElement(channel, "link")
        link.text = f"https://{settings.STOREFRONT_DOMAIN}"

        description = SubElement(channel, "description")
        description.text = (
            f"Product feed for {config.COMPANY_NAME or settings.PROJECT_NAME}"
        )

        for product_data in data:
            item = SubElement(channel, "item")
            self._add_product_to_xml(item, product_data)

        return self.prettify_xml(rss)

    def _add_product_to_xml(self, item: Element, product_data: dict[str, Any]) -> None:
        """Add a product's data to an XML item element."""
        simple_fields = [
            ("id", "g:id"),
            ("title", "g:title"),
            ("description", "g:description"),
            ("link", "g:link"),
            ("image_link", "g:image_link"),
            ("availability", "g:availability"),
            ("price", "g:price"),
            ("brand", "g:brand"),
            ("condition", "g:condition"),
            ("product_type", "g:product_type"),
            ("mpn", "g:mpn"),
            ("gtin", "g:gtin"),
            ("sale_price", "g:sale_price"),
            ("identifier_exists", "g:identifier_exists"),
        ]

        for data_key, xml_tag in simple_fields:
            if data_key in product_data and product_data[data_key]:
                elem = SubElement(item, xml_tag)
                elem.text = str(product_data[data_key])

        additional_images = product_data.get("additional_image_link", [])
        for img_url in additional_images:
            elem = SubElement(item, "g:additional_image_link")
            elem.text = img_url

    def to_json(self, data: list[dict[str, Any]]) -> str:
        """Convert feed data to JSON format."""
        feed = {
            "channel": {
                "title": config.COMPANY_NAME or settings.PROJECT_NAME,
                "link": f"https://{settings.STOREFRONT_DOMAIN}",
                "description": f"Product feed for {config.COMPANY_NAME or settings.PROJECT_NAME}",
                "generated_at": datetime.now().isoformat(),
            },
            "items": data,
        }
        return super().to_json(feed)