"""
Module for managing SNMP service settings on Windows servers.
The Windows feature 'SNMP-Service' must be installed.
"""

import logging

import salt.utils.platform
from salt.exceptions import CommandExecutionError, SaltInvocationError

_HKEY = "HKLM"

_SNMP_KEY = r"SYSTEM\CurrentControlSet\Services\SNMP\Parameters"
_AGENT_KEY = rf"{_SNMP_KEY}\RFC1156Agent"
_COMMUNITIES_KEY = rf"{_SNMP_KEY}\ValidCommunities"

_SNMP_GPO_KEY = r"SOFTWARE\Policies\SNMP\Parameters"
_COMMUNITIES_GPO_KEY = rf"{_SNMP_GPO_KEY}\ValidCommunities"

_PERMISSION_TYPES = {
    "None": 1,
    "Notify": 2,
    "Read Only": 4,
    "Read Write": 8,
    "Read Create": 16,
}
_SERVICE_TYPES = {
    "None": 0,
    "Physical": 1,
    "Datalink and subnetwork": 2,
    "Internet": 4,
    "End-to-end": 8,
    "Applications": 64,
}

_LOG = logging.getLogger(__name__)

# Define the module's virtual name
__virtualname__ = "win_snmp"


def __virtual__():
    """
    Only works on Windows systems.
    """
    if not salt.utils.platform.is_windows():
        return False, "Module win_snmp: Requires Windows"

    if not __utils__["reg.key_exists"](_HKEY, _SNMP_KEY):
        return False, "Module win_snmp: SNMP not installed"

    return __virtualname__


def get_agent_service_types():
    """
    Get the sysServices types that can be configured.

    Returns:
        list: A list of service types.

    CLI Example:

    .. code-block:: bash

        salt '*' win_snmp.get_agent_service_types
    """
    return list(_SERVICE_TYPES)


def get_permission_types():
    """
    Get the permission types that can be configured for communities.

    Returns:
        list: A list of permission types.

    CLI Example:

    .. code-block:: bash

        salt '*' win_snmp.get_permission_types
    """
    return list(_PERMISSION_TYPES)


def get_agent_settings():
    """
    Determine the value of the SNMP sysContact, sysLocation, and sysServices
    settings.

    Returns:
        dict: A dictionary of the agent settings.

    CLI Example:

    .. code-block:: bash

        salt '*' win_snmp.get_agent_settings
    """
    ret = dict()
    sorted_types = sorted(_SERVICE_TYPES.items(), key=lambda x: (-x[1], x[0]))

    ret["services"] = list()
    ret["contact"] = (__utils__["reg.read_value"](_HKEY, _AGENT_KEY, "sysContact"))[
        "vdata"
    ]

    ret["location"] = (__utils__["reg.read_value"](_HKEY, _AGENT_KEY, "sysLocation"))[
        "vdata"
    ]

    current_bitmask = (__utils__["reg.read_value"](_HKEY, _AGENT_KEY, "sysServices"))[
        "vdata"
    ]

    if current_bitmask == 0:
        ret["services"].append(sorted_types[-1][0])
    else:
        # sorted_types is sorted from greatest to least bitmask.
        for service, bitmask in sorted_types:
            if current_bitmask is not None and current_bitmask > 0:
                remaining_bitmask = current_bitmask - bitmask

                if remaining_bitmask >= 0:
                    current_bitmask = remaining_bitmask
                    ret["services"].append(service)
            else:
                break

    ret["services"] = sorted(ret["services"])
    return ret


def set_agent_settings(contact=None, location=None, services=None):
    """
    Manage the SNMP sysContact, sysLocation, and sysServices settings.

    Args:
        contact (str, optional): The SNMP contact.

        location (str, optional): The SNMP location.

        services (list, optional): A list of selected services. The possible
            service names can be found via ``win_snmp.get_agent_service_types``.
            To disable all services pass a list of None, ie: ['None']

    Returns:
        bool: True if successful, otherwise False

    CLI Example:

    .. code-block:: bash

        salt '*' win_snmp.set_agent_settings contact='Contact Name' location='Place' services="['Physical']"
    """
    if services is not None:
        # Filter services for unique items, and sort them for comparison
        # purposes.
        services = sorted(set(services))

        # Validate the services.
        for service in services:
            if service not in _SERVICE_TYPES:
                message = "Invalid service '{}' specified. Valid services: {}".format(
                    service, get_agent_service_types()
                )
                raise SaltInvocationError(message)

    settings = {"contact": contact, "location": location, "services": services}

    current_settings = get_agent_settings()

    if settings == current_settings:
        _LOG.debug("Agent settings already contain the provided values.")
        return True

    if contact is not None:
        if contact != current_settings["contact"]:
            __utils__["reg.set_value"](
                _HKEY, _AGENT_KEY, "sysContact", contact, "REG_SZ"
            )

    if location is not None:
        if location != current_settings["location"]:
            __utils__["reg.set_value"](
                _HKEY, _AGENT_KEY, "sysLocation", location, "REG_SZ"
            )

    if services is not None:
        if set(services) != set(current_settings["services"]):
            # Calculate the total value. Produces 0 if an empty list was provided,
            # corresponding to the None _SERVICE_TYPES value.
            vdata = sum(_SERVICE_TYPES[service] for service in services)

            _LOG.debug("Setting sysServices vdata to: %s", vdata)

            __utils__["reg.set_value"](
                _HKEY, _AGENT_KEY, "sysServices", vdata, "REG_DWORD"
            )

    # Get the fields post-change so that we can verify tht all values
    # were modified successfully. Track the ones that weren't.
    new_settings = get_agent_settings()
    failed_settings = dict()

    for setting in settings:
        if settings[setting] is not None and settings[setting] != new_settings[setting]:
            failed_settings[setting] = settings[setting]

    if failed_settings:
        _LOG.error("Unable to configure agent settings: %s", failed_settings)
        return False

    _LOG.debug("Agent settings configured successfully: %s", settings.keys())
    return True


def get_auth_traps_enabled():
    """
    Determine whether the host is configured to send authentication traps.

    Returns:
        bool: True if traps are enabled, otherwise False

    CLI Example:

    .. code-block:: bash

        salt '*' win_snmp.get_auth_traps_enabled
    """
    reg_ret = __utils__["reg.read_value"](_HKEY, _SNMP_KEY, "EnableAuthenticationTraps")

    if reg_ret["vdata"] == "(value not set)":
        return False
    return bool(reg_ret["vdata"] or 0)


def set_auth_traps_enabled(status=True):
    """
    Manage the sending of authentication traps.

    Args:
        status (bool): True to enable traps. False to disable.

    Returns:
        bool: True if successful, otherwise False

    CLI Example:

    .. code-block:: bash

        salt '*' win_snmp.set_auth_traps_enabled status='True'
    """
    vname = "EnableAuthenticationTraps"
    current_status = get_auth_traps_enabled()

    if bool(status) == current_status:
        _LOG.debug("%s already contains the provided value.", vname)
        return True

    vdata = int(status)
    __utils__["reg.set_value"](_HKEY, _SNMP_KEY, vname, vdata, "REG_DWORD")

    new_status = get_auth_traps_enabled()

    if status == new_status:
        _LOG.debug("Setting %s configured successfully: %s", vname, vdata)
        return True
    _LOG.error("Unable to configure %s with value: %s", vname, vdata)
    return False


def get_community_names():
    """
    Get the current accepted SNMP community names and their permissions.

    If community names are being managed by Group Policy, those values will be
    returned instead like this:

    .. code-block:: bash

        TestCommunity:
            Managed by GPO

    Community names managed normally will denote the permission instead:

    .. code-block:: bash

        TestCommunity:
            Read Only

    Returns:
        dict: A dictionary of community names and permissions.

    CLI Example:

    .. code-block:: bash

        salt '*' win_snmp.get_community_names
    """
    ret = dict()

    # Look in GPO settings first
    if __utils__["reg.key_exists"](_HKEY, _COMMUNITIES_GPO_KEY):

        _LOG.debug("Loading communities from Group Policy settings")

        current_values = __utils__["reg.list_values"](_HKEY, _COMMUNITIES_GPO_KEY)

        # GPO settings are different in that they do not designate permissions
        # They are a numbered list of communities like so:
        #
        # {1: "community 1",
        #  2: "community 2"}
        #
        # Denote that it is being managed by Group Policy.
        #
        # community 1:
        #     Managed by GPO
        # community 2:
        #     Managed by GPO
        if isinstance(current_values, list):
            for current_value in current_values:

                # Ignore error values
                if not isinstance(current_value, dict):
                    continue

                ret[current_value["vdata"]] = "Managed by GPO"

    if not ret:

        _LOG.debug("Loading communities from SNMP settings")

        current_values = __utils__["reg.list_values"](_HKEY, _COMMUNITIES_KEY)

        # The communities are stored as the community name with a numeric
        # permission value. Like this (4 = Read Only):
        #
        # {"community 1": 4,
        #  "community 2": 4}
        #
        # Convert the numeric value to the text equivalent, as present in the
        # Windows SNMP service GUI.
        #
        # community 1:
        #     Read Only
        # community 2:
        #     Read Only
        if isinstance(current_values, list):
            for current_value in current_values:

                # Ignore error values
                if not isinstance(current_value, dict):
                    continue

                permissions = ""
                for permission_name in _PERMISSION_TYPES:
                    if current_value["vdata"] == _PERMISSION_TYPES[permission_name]:
                        permissions = permission_name
                        break
                ret[current_value["vname"]] = permissions

    if not ret:
        _LOG.debug("Unable to find existing communities.")
    return ret


def set_community_names(communities):
    """
    Manage the SNMP accepted community names and their permissions.

    .. note::
        Settings managed by Group Policy will always take precedence over those
        set using the SNMP interface. Therefore if this function finds Group
        Policy settings it will raise a CommandExecutionError

    Args:
        communities (dict): A dictionary of SNMP community names and
            permissions. The possible permissions can be found via
            ``win_snmp.get_permission_types``.

    Returns:
        bool: True if successful, otherwise False

    Raises:
        CommandExecutionError:
            If SNMP settings are being managed by Group Policy

    CLI Example:

    .. code-block:: bash

        salt '*' win_snmp.set_community_names communities="{'TestCommunity': 'Read Only'}'
    """
    values = dict()

    if __utils__["reg.key_exists"](_HKEY, _COMMUNITIES_GPO_KEY):
        _LOG.debug("Communities on this system are managed by Group Policy")
        raise CommandExecutionError(
            "Communities on this system are managed by Group Policy"
        )

    current_communities = get_community_names()

    if communities == current_communities:
        _LOG.debug("Communities already contain the provided values.")
        return True

    for vname in communities:
        if not communities[vname]:
            communities[vname] = "None"
        try:
            vdata = _PERMISSION_TYPES[communities[vname]]
        except KeyError:
            raise SaltInvocationError(
                "Invalid permission '{}' specified. Valid permissions: {}".format(
                    communities[vname], _PERMISSION_TYPES.keys()
                )
            )
        values[vname] = vdata

    # Check current communities.
    for current_vname in current_communities:
        if current_vname in values:
            # Modify existing communities that have a different permission value.
            if current_communities[current_vname] != values[current_vname]:
                __utils__["reg.set_value"](
                    _HKEY,
                    _COMMUNITIES_KEY,
                    current_vname,
                    values[current_vname],
                    "REG_DWORD",
                )
        else:
            # Remove current communities that weren't provided.
            __utils__["reg.delete_value"](_HKEY, _COMMUNITIES_KEY, current_vname)

    # Create any new communities.
    for vname in values:
        if vname not in current_communities:
            __utils__["reg.set_value"](
                _HKEY, _COMMUNITIES_KEY, vname, values[vname], "REG_DWORD"
            )

    # Get the fields post-change so that we can verify tht all values
    # were modified successfully. Track the ones that weren't.
    new_communities = get_community_names()
    failed_communities = dict()

    for new_vname in new_communities:
        if new_vname not in communities:
            failed_communities[new_vname] = None

    for vname in communities:
        if communities[vname] != new_communities[vname]:
            failed_communities[vname] = communities[vname]

    if failed_communities:
        _LOG.error("Unable to configure communities: %s", failed_communities)
        return False
    _LOG.debug("Communities configured successfully: %s", communities.keys())
    return True
