"""Configuration-only policy published to supported cmshopee clients."""

from datetime import datetime

from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.utils.dateparse import parse_datetime
from django.utils.timezone import is_aware


CLIENT_SUBSCRIPTION_POLICY_VERSION = 1
CLIENT_SUBSCRIPTION_POLICY_MODES = frozenset({"off", "observe", "enforce"})
DEFAULT_CLIENT_SUBSCRIPTION_POLICY_UPDATED_AT = "2026-07-28T00:00:00+08:00"


def build_client_subscription_policy(*, mode, updated_at) -> dict:
    normalized_mode = str(mode or "").strip().lower()
    if normalized_mode not in CLIENT_SUBSCRIPTION_POLICY_MODES:
        raise ImproperlyConfigured(
            "CMSHOPEE_CLIENT_SUBSCRIPTION_POLICY must be one of: "
            "off, observe, enforce"
        )

    if isinstance(updated_at, datetime):
        parsed_updated_at = updated_at
    else:
        raw_updated_at = str(updated_at or "").strip()
        if not raw_updated_at:
            if normalized_mode != "off":
                raise ImproperlyConfigured(
                    "CMSHOPEE_CLIENT_SUBSCRIPTION_POLICY_UPDATED_AT is required "
                    "when CMSHOPEE_CLIENT_SUBSCRIPTION_POLICY is observe or enforce"
                )
            raw_updated_at = DEFAULT_CLIENT_SUBSCRIPTION_POLICY_UPDATED_AT
        if "T" not in raw_updated_at:
            raise ImproperlyConfigured(
                "CMSHOPEE_CLIENT_SUBSCRIPTION_POLICY_UPDATED_AT must be an "
                "ISO 8601 datetime with timezone"
            )
        parsed_updated_at = parse_datetime(raw_updated_at)

    if parsed_updated_at is None or not is_aware(parsed_updated_at):
        raise ImproperlyConfigured(
            "CMSHOPEE_CLIENT_SUBSCRIPTION_POLICY_UPDATED_AT must be an "
            "ISO 8601 datetime with timezone"
        )

    return {
        "policy_version": CLIENT_SUBSCRIPTION_POLICY_VERSION,
        "subscription_check_enabled": normalized_mode != "off",
        "subscription_enforcement_enabled": normalized_mode == "enforce",
        "updated_at": parsed_updated_at.isoformat(),
    }


def get_client_subscription_policy() -> dict:
    return build_client_subscription_policy(
        mode=getattr(settings, "CMSHOPEE_CLIENT_SUBSCRIPTION_POLICY", "off"),
        updated_at=getattr(
            settings,
            "CMSHOPEE_CLIENT_SUBSCRIPTION_POLICY_UPDATED_AT",
            "",
        ),
    )