from django.contrib.auth.hashers import check_password
from django.utils import timezone
from rest_framework.authentication import BaseAuthentication
from rest_framework.exceptions import AuthenticationFailed

from ..models import APIKey


class SystemUser:
    """Anonymous system user with scopes as permissions."""

    def __init__(self, scopes=None):
        self.scopes = scopes or []
        self.is_authenticated = True
        self.is_superuser = False
        self.pk = None
        self.id = None

    @property
    def is_anonymous(self):
        return False

    def __str__(self):
        return f"SystemUser(scopes={self.scopes})"


class APIKeyAuthentication(BaseAuthentication):
    """Service-to-service authentication via X-API-Key header."""

    keyword = "X-API-Key"

    def authenticate(self, request):
        raw_key = request.META.get(f"HTTP_{self.keyword.replace('-', '_').upper()}")
        if not raw_key:
            return None
        try:
            prefix, secret = raw_key.split(".", 1)
        except ValueError:
            raise AuthenticationFailed("Invalid API key format.")
        api_key = APIKey.objects.filter(prefix=prefix, is_active=True).first()
        if not api_key:
            raise AuthenticationFailed("API key not found.")
        if not check_password(secret, api_key.key_hash):
            raise AuthenticationFailed("Invalid API key.")
        if api_key.expires_at and api_key.expires_at < timezone.now():
            raise AuthenticationFailed("API key expired.")
        api_key.last_used_at = timezone.now()
        api_key.save(update_fields=["last_used_at"])
        return (SystemUser(scopes=api_key.scopes), api_key)