from ipaddress import IPv4Address, IPv4Network

from rest_framework import permissions


class IsActiveUser(permissions.BasePermission):
    """
    Allows access only to activated users.
    """

    def has_permission(self, request, view):
        # Authenticated users can have is_active = None (pending activation). Strictly require True here.
        return request.user and request.user.is_active == True


class IsOwner(permissions.BasePermission):
    """
    Custom permission to only allow owners of an object to view or edit it.
    """

    def has_object_permission(self, request, view, obj):
        return obj.owner == request.user


class IsDomainOwner(permissions.BasePermission):
    """
    Custom permission to only allow owners of a domain to view or edit an object owned by that domain.
    """

    def has_object_permission(self, request, view, obj):
        return obj.domain.owner == request.user


class TokenNoDomainPolicy(permissions.BasePermission):
    """
    Permission to check whether a token is unrestricted by any domain policy.
    """

    def has_permission(self, request, view):
        return request.auth.get_policy(domain=None) is None


class TokenDomainPolicyBasePermission(permissions.BasePermission):
    """
    Base permission to check whether a token authorizes specific actions on a domain.
    """

    perm_field = None

    def _has_object_permission(self, request, view, obj):
        policy = request.auth.get_policy(domain=obj)

        # If the token has no domain policy, there are no restrictions
        if policy is None:
            return True

        # Otherwise, return the requested permission
        return getattr(policy, self.perm_field)


class TokenHasDomainBasePermission(TokenDomainPolicyBasePermission):
    """
    Base permission for checking a token's domain policy, for the view domain.
    """

    def has_permission(self, request, view):
        return self._has_object_permission(request, view, view.domain)


class TokenHasDomainDynDNSPermission(TokenHasDomainBasePermission):
    """
    Custom permission to check whether a token authorizes using the dynDNS interface for the view domain.
    """

    perm_field = "perm_dyndns"


class TokenHasDomainRRsetsPermission(TokenHasDomainBasePermission):
    """
    Custom permission to check whether a token authorizes accessing RRsets for the view domain.
    """

    perm_field = "perm_rrsets"


class AuthTokenCorrespondsToViewToken(permissions.BasePermission):
    """
    Permission to check whether the view kwargs's token_id corresponds to the current token.
    """

    def has_permission(self, request, view):
        return view.kwargs["token_id"] == request.auth.pk


class IsVPNClient(permissions.BasePermission):
    """
    Permission that requires that the user is accessing using an IP from the VPN net.
    """

    message = "Inadmissible client IP."

    def has_permission(self, request, view):
        ip = IPv4Address(request.META.get("REMOTE_ADDR"))
        return ip in IPv4Network("10.8.0.0/24")


class HasManageTokensPermission(permissions.BasePermission):
    """
    Permission to check whether a token has "manage tokens" permission.
    """

    def has_permission(self, request, view):
        return request.auth.perm_manage_tokens


class WithinDomainLimit(permissions.BasePermission):
    """
    Permission that requires that the user still has domain limit quota available.
    """

    message = (
        "Domain limit exceeded. Please contact support to create additional domains."
    )

    def has_permission(self, request, view):
        return (
            request.user.limit_domains is None
            or request.user.domains.count() < request.user.limit_domains
        )