import re
import uuid

from django.db import transaction

from apps.account.models import User
from apps.banker.models import Contact
from apps.messaging.api.services import BulkMessageService
from apps.messaging.models import Channel
from apps.orders.models import Order, OrderStage, OrderStageLog

_FIELD_PATTERN = re.compile(r"\{(.*?)\}")


class OrderStageService:
    @staticmethod
    def _render(order: Order, stage: OrderStage, extra_input_value: str = "") -> str:
        body = stage.template.body if stage.template else ""
        values = {
            "نام": order.customer_name,
            "شماره": order.customer_phone,
            "کد پیگیری": order.tracking_code,
            "مرحله": stage.label,
            "ورودی": extra_input_value,
        }
        return _FIELD_PATTERN.sub(lambda m: values.get(m.group(1), m.group(0)), body)

    @staticmethod
    def _upsert_contact(user: User, order: Order) -> Contact:
        contact = Contact.objects.filter(user=user, phone=order.customer_phone).first()
        if contact:
            return contact
        return Contact.objects.create(
            id=str(uuid.uuid4()), user=user, name=order.customer_name, phone=order.customer_phone
        )

    @staticmethod
    @transaction.atomic
    def advance(user: User, order_id: str, extra_input_value: str = "") -> Order:
        order = Order.objects.select_for_update().get(pk=order_id, user=user)
        if order.is_completed:
            raise ValueError("این سفارش قبلا به آخرین مرحله رسیده است.")

        stages = list(OrderStage.objects.filter(user=user).order_by("sort_order"))
        if not stages:
            raise ValueError("اول باید حداقل یک مرحله برای پیگیری سفارش تعریف کنی.")

        if order.current_stage_id is None:
            next_stage = stages[0]
        else:
            current_index = next((i for i, s in enumerate(stages) if s.id == order.current_stage_id), None)
            if current_index is None or current_index + 1 >= len(stages):
                raise ValueError("این سفارش قبلا به آخرین مرحله رسیده است.")
            next_stage = stages[current_index + 1]

        extra_input_value = (extra_input_value or "").strip()
        if next_stage.requires_extra_input and not extra_input_value:
            label = next_stage.extra_input_label or "ورودی این مرحله"
            raise ValueError(f"برای این مرحله باید «{label}» را وارد کنی.")

        contact = OrderStageService._upsert_contact(user, order)
        rendered = OrderStageService._render(order, next_stage, extra_input_value)
        if rendered:
            BulkMessageService.create_and_dispatch(
                user=user,
                channels=[Channel.SMS],
                contact_ids=[contact.id],
                body_override=rendered,
            )

        order.current_stage = next_stage
        order.is_completed = next_stage.id == stages[-1].id
        order.save(update_fields=["current_stage", "is_completed", "updated_at"])

        OrderStageLog.objects.create(
            id=str(uuid.uuid4()),
            order=order,
            stage=next_stage,
            stage_label=next_stage.label,
            message_body=rendered,
            extra_input_value=extra_input_value,
        )
        return order