"""Open Food Facts Lookup-Client."""

from __future__ import annotations

import json
import re

import httpx

from .config import get_settings

settings = get_settings()

# Faktoren, um eine Einheit in die Basiseinheit (Gramm bzw. Milliliter) umzurechnen.
_UNIT_TO_BASE: dict[str, tuple[str, float]] = {
    "kg": ("gram", 1000.0),
    "g": ("gram", 1.0),
    "mg": ("gram", 0.001),
    "l": ("milliliter", 1000.0),
    "dl": ("milliliter", 100.0),
    "cl": ("milliliter", 10.0),
    "ml": ("milliliter", 1.0),
}

_QUANTITY_RE = re.compile(r"([\d]+(?:[.,]\d+)?)\s*(kg|mg|g|dl|cl|ml|l)\b", re.IGNORECASE)


def parse_quantity(quantity: str | None) -> tuple[str, float | None]:
    """Ermittelt Basiseinheit und Packungsgröße aus dem OFF-Feld 'quantity'.

    Beispiele: '500 g' -> ('gram', 500), '1 kg' -> ('gram', 1000),
    '1,5 l' -> ('milliliter', 1500), '6 Stück' -> ('piece', None).
    """
    if not quantity:
        return "piece", None
    match = _QUANTITY_RE.search(quantity)
    if not match:
        return "piece", None
    amount = float(match.group(1).replace(",", "."))
    base_unit, factor = _UNIT_TO_BASE[match.group(2).lower()]
    package_size = round(amount * factor, 3)
    return base_unit, (package_size if package_size > 0 else None)


def lookup_barcode(barcode: str) -> dict | None:
    """Fragt Open Food Facts nach einem Barcode.

    Gibt ein vorbefülltes Produkt-Dict zurück oder None, wenn nicht gefunden.
    """
    # v0-API: liefert bei Treffer status=1 + product, bei Nicht-Treffer status=0
    # (HTTP 200). Die v2-API hat kein status-Feld und antwortet mit HTTP 404,
    # weshalb wir bewusst v0 nutzen.
    url = f"{settings.off_base_url}/api/v0/product/{barcode}.json"
    try:
        resp = httpx.get(
            url,
            timeout=settings.off_timeout_seconds,
            headers={"User-Agent": "Vorrania-Selfhosted/1.0"},
            follow_redirects=True,
        )
    except httpx.HTTPError:
        return None

    if resp.status_code != 200:
        return None

    try:
        data = resp.json()
    except ValueError:
        return None
    if data.get("status") != 1:
        return None

    product = data.get("product", {})
    name = (
        product.get("product_name_de")
        or product.get("product_name")
        or product.get("generic_name")
        or ""
    ).strip()
    if not name:
        return None

    categories = product.get("categories") or ""
    category_tags = product.get("categories_tags") or []

    base_unit, package_size = parse_quantity(product.get("quantity"))

    return {
        "barcode": barcode,
        "name": name,
        "brand": (product.get("brands") or "").strip() or None,
        "image_url": product.get("image_front_url") or product.get("image_url") or None,
        "base_unit": base_unit,
        "package_size": package_size,
        "quantity_text": product.get("quantity"),
        "category_suggestion": categories.split(",")[0].strip() if categories else None,
        "category_tags": category_tags,
        "source": "off",
        "off_raw": json.dumps(product)[:20000],
    }