"""
A Salt Util for working with the Registry.pol file. The Registry.pol file is the
source of truth for registry settings that are configured via LGPO.
"""
import logging
import os
import re
import struct

import salt.modules.win_file
import salt.utils.files
import salt.utils.win_reg
from salt.exceptions import CommandExecutionError

CLASS_INFO = {
    "User": {
        "policy_path": os.path.join(
            os.getenv("WINDIR", r"C:\Windows"),
            "System32",
            "GroupPolicy",
            "User",
            "Registry.pol",
        ),
        "hive": "HKEY_USERS",
        "lgpo_section": "User Configuration",
        "gpt_extension_location": "gPCUserExtensionNames",
        "gpt_extension_guid": "[{35378EAC-683F-11D2-A89A-00C04FBBCFA2}{D02B1F73-3407-48AE-BA88-E8213C6761F1}]",
    },
    "Machine": {
        "policy_path": os.path.join(
            os.getenv("WINDIR", r"C:\Windows"),
            "System32",
            "GroupPolicy",
            "Machine",
            "Registry.pol",
        ),
        "hive": "HKEY_LOCAL_MACHINE",
        "lgpo_section": "Computer Configuration",
        "gpt_extension_location": "gPCMachineExtensionNames",
        "gpt_extension_guid": "[{35378EAC-683F-11D2-A89A-00C04FBBCFA2}{D02B1F72-3407-48AE-BA88-E8213C6761F1}]",
    },
}
REG_POL_HEADER = "\u5250\u6765\x01\x00"
GPT_INI_PATH = os.path.join(
    os.getenv("WINDIR", "C:\\Windows"), "System32", "GroupPolicy", "gpt.ini"
)

log = logging.getLogger(__name__)

__virtualname__ = "lgpo_reg"


def __virtual__():
    """
    Only works on Windows with the lgpo_reg module
    """
    if not salt.utils.platform.is_windows():
        return False, "LGPO_REG Util: Only available on Windows"

    return __virtualname__


def search_reg_pol(search_string, policy_data):
    """
    Helper function to do a regex search of a string value in policy_data.
    This is used to search the policy data from a registry.pol file or from
    gpt.ini

    Args:
        search_string (str): The string to search for

        policy_data (str): The data to be searched

    Returns:
        bool: ``True`` if the regex search_string is found, otherwise ``False``
    """
    if policy_data:
        if search_string:
            log.debug("LGPO_REG Util: Searching for %s", search_string)
            match = re.search(search_string, policy_data, re.IGNORECASE)
            if match:
                log.debug("LGPO_REG Util: Found")
                return True
    return False


def read_reg_pol_file(reg_pol_path):
    """
    Helper function to read the content of the Registry.pol file

    Args:
        reg_pol_path (str): The path to the Registry.pol file

    Returns:
        bytes: The data as contained in the Registry.pol file
    """
    return_data = None
    if os.path.exists(reg_pol_path):
        log.debug("LGPO_REG Util: Reading from %s", reg_pol_path)
        with salt.utils.files.fopen(reg_pol_path, "rb") as pol_file:
            return_data = pol_file.read()
    return return_data


def write_reg_pol_data(
    data_to_write,
    policy_file_path,
    gpt_extension,
    gpt_extension_guid,
    gpt_ini_path=GPT_INI_PATH,
):
    """
    Helper function to actually write the data to a Registry.pol file

    Also updates/edits the gpt.ini file to include the ADM policy extensions
    to let the computer know user and/or machine registry policy files need
    to be processed

    Args:
        data_to_write (bytes): Data to write into the user/machine registry.pol
            file

        policy_file_path (str): Path to the registry.pol file

        gpt_extension (str): GPT extension list name from _policy_info class for
            this registry class gpt_extension_location

        gpt_extension_guid (str): ADMX registry extension guid for the class

        gpt_ini_path (str): The path to the gpt.ini file

    Returns:
        bool: True if successful

    Raises:
        CommandExecutionError: On failure
    """
    # Write Registry.pol file
    if not os.path.exists(policy_file_path):
        log.debug("LGPO_REG Util: Creating parent directories for Registry.pol")
        salt.modules.win_file.makedirs_(policy_file_path)
    if data_to_write is None:
        data_to_write = b""
    try:
        with salt.utils.files.fopen(policy_file_path, "wb") as pol_file:
            reg_pol_header = REG_POL_HEADER.encode("utf-16-le")
            if not data_to_write.startswith(reg_pol_header):
                log.debug("LGPO_REG Util: Writing header to %s", policy_file_path)
                pol_file.write(reg_pol_header)
            log.debug("LGPO_REG Util: Writing to %s", policy_file_path)
            pol_file.write(data_to_write)
    # TODO: This needs to be more specific
    except Exception as e:  # pylint: disable=broad-except
        msg = (
            "An error occurred attempting to write to {}, the exception was: {}".format(
                policy_file_path, e
            )
        )
        log.exception(msg)
        raise CommandExecutionError(msg)

    # Write the gpt.ini file
    gpt_ini_data = ""
    if os.path.exists(gpt_ini_path):
        with salt.utils.files.fopen(gpt_ini_path, "r") as gpt_file:
            gpt_ini_data = gpt_file.read()
        # Make sure it has Windows Style line endings
        gpt_ini_data = (
            gpt_ini_data.replace("\r\n", "_|-")
            .replace("\n", "_|-")
            .replace("_|-", "\r\n")
        )
    if not search_reg_pol(r"\[General\]\r\n", gpt_ini_data):
        log.debug("LGPO_REG Util: Adding [General] section to gpt.ini")
        gpt_ini_data = "[General]\r\n" + gpt_ini_data
    if search_reg_pol(rf"{re.escape(gpt_extension)}=", gpt_ini_data):
        # ensure the line contains the ADM guid
        gpt_ext_loc = re.search(
            rf"^{re.escape(gpt_extension)}=.*\r\n",
            gpt_ini_data,
            re.IGNORECASE | re.MULTILINE,
        )
        gpt_ext_str = gpt_ini_data[gpt_ext_loc.start() : gpt_ext_loc.end()]
        if not search_reg_pol(
            search_string=rf"{re.escape(gpt_extension_guid)}",
            policy_data=gpt_ext_str,
        ):
            log.debug("LGPO_REG Util: Inserting gpt extension GUID")
            gpt_ext_str = gpt_ext_str.split("=")
            gpt_ext_str[1] = gpt_extension_guid + gpt_ext_str[1]
            gpt_ext_str = "=".join(gpt_ext_str)
            gpt_ini_data = (
                gpt_ini_data[0 : gpt_ext_loc.start()]
                + gpt_ext_str
                + gpt_ini_data[gpt_ext_loc.end() :]
            )
    else:
        general_location = re.search(
            r"^\[General\]\r\n", gpt_ini_data, re.IGNORECASE | re.MULTILINE
        )
        gpt_ini_data = "{}{}={}\r\n{}".format(
            gpt_ini_data[general_location.start() : general_location.end()],
            gpt_extension,
            gpt_extension_guid,
            gpt_ini_data[general_location.end() :],
        )
    # https://technet.microsoft.com/en-us/library/cc978247.aspx
    if search_reg_pol(r"Version=", gpt_ini_data):
        version_loc = re.search(
            r"^Version=.*\r\n", gpt_ini_data, re.IGNORECASE | re.MULTILINE
        )
        version_str = gpt_ini_data[version_loc.start() : version_loc.end()]
        version_str = version_str.split("=")
        version_nums = struct.unpack(b">2H", struct.pack(b">I", int(version_str[1])))
        if gpt_extension.lower() == "gPCMachineExtensionNames".lower():
            version_nums = (version_nums[0], version_nums[1] + 1)
        elif gpt_extension.lower() == "gPCUserExtensionNames".lower():
            version_nums = (version_nums[0] + 1, version_nums[1])
        version_num = struct.unpack(b">I", struct.pack(b">2H", *version_nums))[0]
        gpt_ini_data = "{}{}={}\r\n{}".format(
            gpt_ini_data[0 : version_loc.start()],
            "Version",
            version_num,
            gpt_ini_data[version_loc.end() :],
        )
    else:
        general_location = re.search(
            r"^\[General\]\r\n", gpt_ini_data, re.IGNORECASE | re.MULTILINE
        )
        if gpt_extension.lower() == "gPCMachineExtensionNames".lower():
            version_nums = (0, 1)
        elif gpt_extension.lower() == "gPCUserExtensionNames".lower():
            version_nums = (1, 0)
        gpt_ini_data = "{}{}={}\r\n{}".format(
            gpt_ini_data[general_location.start() : general_location.end()],
            "Version",
            int(
                "{}{}".format(
                    str(version_nums[0]).zfill(4),
                    str(version_nums[1]).zfill(4),
                ),
                16,
            ),
            gpt_ini_data[general_location.end() :],
        )
    if gpt_ini_data:
        try:
            with salt.utils.files.fopen(gpt_ini_path, "w") as gpt_file:
                gpt_file.write(gpt_ini_data)
        # TODO: This needs to be more specific
        except Exception as e:  # pylint: disable=broad-except
            msg = (
                "An error occurred attempting to write the gpg.ini file.\n"
                "path: {}\n"
                "exception: {}".format(gpt_ini_path, e)
            )
            log.exception(msg)
            raise CommandExecutionError(msg)
    return True


def reg_pol_to_dict(policy_data):
    """
    Convert the data obtained from a Registry.pol file to a dictionary.

    Args:
        policy_data (bytes): The data as retrieved from the Registry.pol file

    Raises:
        SaltInvocationError: Invalid or corrupt policy data

    Returns:
        dict: A dictionary representation of the Registry.pol data
    """
    # https://learn.microsoft.com/en-us/previous-versions/windows/desktop/Policy/registry-policy-file-format
    # https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-gpreg/5c092c22-bf6b-4e7f-b180-b20743d368f5

    reg_pol_header = REG_POL_HEADER.encode("utf-16-le")

    # If policy_data is None, that means the Registry.pol file is missing
    # So, we'll create it
    if policy_data is None:
        policy_data = reg_pol_header

    if not policy_data.startswith(reg_pol_header):
        msg = "LGPO_REG Util: Invalid Header. Registry.pol may be corrupt"
        raise CommandExecutionError(msg)

    # Strip the header information, we don't care about it now
    pol_file_data = policy_data.lstrip(reg_pol_header)

    if not pol_file_data:
        log.debug("LGPO_REG Util: No registry.pol data to return")
        return {}

    def strip_field_end(value):
        while value[-2:] == b"\x00\x00":
            value = value[:-2]
        return value

    log.debug("LGPO_REG Util: Unpacking reg pol data")
    reg_pol = {}
    # Each policy is inside square braces. In this case they're encoded
    # utf-16-le, so there's a null-byte for each character
    for policy in pol_file_data.split(b"]\x00[\x00"):
        # Now remove the lingering square braces
        policy = policy.replace(b"]\x00", b"").replace(b"[\x00", b"")
        # Each policy element is delimited by a semi-colon, encoded utf-16-le
        # The first 4 are the key, name, type and size
        # all remaining is data
        key, v_name, v_type, v_size, v_data = policy.split(b";\x00", 4)
        # Removing trailing null-bytes
        key = strip_field_end(key).decode("utf-16-le")
        v_name = strip_field_end(v_name).decode("utf-16-le")
        # v_type is one of (0, 1, 2, 3, 4, 5, 7, 11) as 32-bit little-endian
        v_type = struct.unpack("<i", v_type)[0]
        if v_type == 0:
            # REG_NONE : No Type
            # We don't know what this data is, so don't do anything
            pass
        elif v_type in (1, 2):
            # REG_SZ : String Type
            # REG_EXPAND_SZ : String with Environment Variables, ie %PATH%
            v_data = strip_field_end(v_data).decode("utf-16-le")
        elif v_type == 4:
            # REG_DWORD : 32-bit little endian
            v_data = struct.unpack("<i", v_data)[0]
        elif v_type == 5:
            # REG_DWORD : 32-bit big endian
            v_data = struct.unpack(">i", v_data)[0]
        elif v_type == 7:
            # REG_MULTI_SZ : Multiple strings, delimited by \x00
            v_data = strip_field_end(v_data)
            if not v_data:
                v_data = None
            else:
                v_data = v_data.decode("utf-16-le").split("\x00")
        elif v_type == 11:
            # REG_QWORD : 64-bit little endian
            v_data = struct.unpack("<q", v_data)[0]
        else:
            msg = f"LGPO_REG Util: Found unknown registry type: {v_type}"
            raise CommandExecutionError(msg)

        # Lookup the REG Type from the number
        reg = salt.utils.win_reg.Registry()
        v_type = reg.vtype_reverse.get(v_type, "REG_NONE")

        # Make the dictionary entries
        reg_pol.setdefault(key, {})
        if not v_name:
            reg_pol[key]["*"] = "CREATEKEY"
        else:
            reg_pol[key][v_name] = {"type": v_type, "data": v_data}

    return reg_pol


def dict_to_reg_pol(data):
    """
    Convert a dictionary to the bytes format expected by the Registry.pol file

    Args:
        data (dict): A dictionary containing the contents to be converted

    Returns:
        bytes: The data to be written to the Registry.pol file
    """
    # https://learn.microsoft.com/en-us/previous-versions/windows/desktop/Policy/registry-policy-file-format
    # https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-gpreg/5c092c22-bf6b-4e7f-b180-b20743d368f5
    reg = salt.utils.win_reg.Registry()

    pol_enter_delim = "[".encode("utf-16-le")
    pol_exit_delim = "]".encode("utf-16-le")
    pol_section_delim = ";".encode("utf-16-le")
    pol_section_term = "\x00".encode("utf-16-le")

    policies = []
    for key, value in data.items():
        for v_name, d in value.items():
            # Handle CREATEKEY entry
            if v_name == "*" and d == "CREATEKEY":
                v_name = ""
                d = {"type": "REG_NONE"}

            try:
                v_type = reg.vtype[d["type"]]
            except KeyError:
                msg = "LGPO_REG Util: Found unknown registry type: {}".format(d["type"])
                raise CommandExecutionError(msg)

            # The first three items are pretty straight forward
            policy = [
                # Key followed by null byte
                f"{key}".encode("utf-16-le") + pol_section_term,
                # Value name followed by null byte
                f"{v_name}".encode("utf-16-le") + pol_section_term,
                # Type in 32-bit little-endian
                struct.pack("<i", v_type),
            ]
            # The data is encoded depending on the Type
            if v_type == 0:
                # REG_NONE : No value
                v_data = b""
            elif v_type in (1, 2):
                # REG_SZ : String Type
                # REG_EXPAND_SZ : String with Environment Variables, ie %PATH%
                # Value followed by null byte
                v_data = d["data"].encode("utf-16-le") + pol_section_term
            elif v_type == 4:
                # REG_DWORD : Little Endian
                # 32-bit little endian
                v_data = struct.pack("<i", int(d["data"]))
            elif v_type == 5:
                # REG_DWORD : Big Endian (not common)
                # 32-bit big endian
                v_data = struct.pack(">i", int(d["data"]))
            elif v_type == 7:
                # REG_MULTI_SZ : Multiple strings
                # Each element is delimited by \x00, terminated by \x00\x00
                # Then the entire output is terminated with a null byte
                if d["data"] is None:
                    # An None value just gets the section terminator
                    v_data = pol_section_term
                elif len(d["data"]) == 0:
                    # An empty list just gets the section terminator
                    v_data = pol_section_term
                elif len(d["data"]) == 1 and not d["data"][0]:
                    # An list with an empty value just gets the section terminator
                    v_data = pol_section_term
                else:
                    # All others will be joined with a null byte, the list
                    # terminated, and the entire section terminated
                    v_data = (
                        "\x00".join(d["data"]).encode("utf-16-le")
                        + pol_section_term
                        + pol_section_term
                    )
            elif v_type == 11:
                # REG_QWORD : Little Endian
                # 64-bit little endian
                v_data = struct.pack("<q", int(d["data"]))

            # Now that we have the data in the right format, let's calculate its size
            # 16-bit little endian with null terminator
            if len(v_data) > 65535:
                msg = "LGPO_REG Util: Size exceeds 65535 bytes"
                raise CommandExecutionError(msg)
            v_size = len(v_data).to_bytes(2, "little") + pol_section_term

            policy.append(v_size)
            policy.append(v_data)

            policies.append(pol_section_delim.join(policy))

    policy_file_data = REG_POL_HEADER.encode("utf-16-le")
    for policy in policies:
        policy_file_data += pol_enter_delim + policy + pol_exit_delim

    return policy_file_data
