import uuid
from celery import shared_task
from datetime import date, timedelta
from infrastructure.paperless_client import PaperlessGateway
from core.utils import format_currency, parse_iso_date
from django.contrib.auth import get_user_model
import logging
from decimal import Decimal
from modules.crm.models import Client

logger = logging.getLogger(__name__)

@shared_task(bind=True, max_retries=3)
def process_paperless_document_task(self, document_id):
    """
    Celery zadatak koji povezuje infrastrukturu i poslovnu logiku.
    """
    gateway = PaperlessGateway()  # rename so we don't overwrite 'client'
    
    try:
        User = get_user_model()
        # 1. Dohvat iz infrastrukture
        raw_data = gateway.get_document_metadata(document_id)
        raw_created = parse_iso_date(raw_data.get("created"))
        correspondent_name = raw_data.get("correspondent")

        # pokušaj dohvatiti crm klijenta
        try:
            crm_client = Client.objects.get(name=correspondent_name)
        except Client.DoesNotExist:
            logger.error(f"Klijent {correspondent_name} nije pronađen!")
            # Kreiramo fallback klijenta ali popunimo UNIQUE polja jedinstvenim vrijednostima
            unique_email = f"client+{uuid.uuid4()}@example.test"
            unique_tax_id = str(uuid.uuid4())
            crm_client, created = Client.objects.get_or_create(
                name=correspondent_name,
                defaults={
                    "email": unique_email,
                    "tax_id": unique_tax_id,
                }
            )
            if created:
                logger.info(f"Fallback klijent kreiran za '{correspondent_name}' (id={crm_client.id}).")

        # 2. Transformacija i čišćenje podataka
        total_raw = raw_data.get("total_amount", "0")
        try:
            amount_decimal = Decimal(str(total_raw))
        except Exception:
            amount_decimal = Decimal("0")

        processed_data = {
            "client": crm_client,
            "invoice_number": raw_data.get("invoice_number") or raw_data.get("correspondent"),
            "due_date": (raw_created or date.today()) + timedelta(days=30),
            "amount": amount_decimal,
            "created_at": raw_created,
        }

        from modules.invoicing.services import InvoiceService

        lookup_field = User.USERNAME_FIELD
        system_user = User.objects.filter(**{lookup_field: "bot@erp.hr"}).first()

        if not system_user:
            system_user = User(**{lookup_field: "bot@erp.hr"})
            system_user.email = "bot@erp.hr"
            system_user.first_name = "Paperless"
            system_user.last_name = "Bot"
            system_user.set_unusable_password()
            system_user.save()

        # Pozovi servis uvijek nakon što garantujemo da system_user postoji
        InvoiceService.create_full_invoice(user=system_user, **processed_data)

        logger.info(f"Dokument {document_id} uspješno obrađen.")

    except Exception as exc:
        logger.error(f"Greška pri obradi dokumenta {document_id}: {exc}")
        # Automatski retry ako padne
        raise self.retry(exc=exc, countdown=60)