Mini Shell

import argparse
import ipaddress
import sys
from functools import lru_cache, partial
from itertools import chain
from typing import Any, Dict, Iterable, Iterator, Mapping, Tuple

from defence360agent.application import app
from defence360agent.contracts.config import Core as Config
from defence360agent.rpc_tools.utils import prepare_schema
from defence360agent.simple_rpc import RpcClient
from defence360agent.utils.cli import EXITCODE_NOT_FOUND


class SchemaToArgparse:
    # NOTE: 'default' is a normalization rule, 'required' is a validation rule
    OptionType = Iterator[Tuple[str, Any]]

    def __init__(self, argument, options):
        self._argument: str = argument

        self._allowed: Iterable = options.get("allowed")
        self._default: Any = options.get("default")
        self._envvar: str = options.get("envvar", False)
        self._help: str = options.get("help")
        self._positional: bool = options.get("positional", False)
        self._rename: str = options.get("rename")
        self._required: bool = options.get("required", False)
        self._type: str = options.get("type")

    @property
    def argname(self) -> str:
        if self._positional:
            return self._argument
        return "--" + self._argument.replace("_", "-")

    @property
    def options(self):
        argparse_options = dict(
            chain(
                self.choices(),
                self.default(),
                self.help(),
                self.metavar(),
                self.nargs(),
                self.required(),
            ),
        )
        return argparse_options

    def nargs(self) -> OptionType:
        option = "nargs"
        if self._type == "list":
            # FIXME: all positional arguments are not required
            #  to support `rename`
            if not self._positional and self._required and not self._envvar:
                yield option, "+"
            else:
                yield option, "*"
        elif self._positional and (self._envvar or self._default is None):
            yield option, "?"

    def choices(self) -> OptionType:
        yield "choices", self._allowed

    def help(self) -> OptionType:
        yield "help", self._help

    def metavar(self) -> OptionType:
        option = "metavar"
        if self._rename:
            yield option, self._rename.upper()
        elif self._type == "list":
            yield option, self._argument.upper()

    def default(self) -> OptionType:
        if (
            self._default is not None
            and not self._envvar
            and (self._type == "list" or not self._positional)
        ):
            yield "default", self._default

    def required(self):
        if (
            self._required
            and self._type != "list"
            and not self._envvar
            # 'required' is an invalid argument for positionals
            and not self._positional
        ):
            yield "required", True


def schema_to_argparse(parser, argument, options):
    if options.get("type") == "boolean":
        required = options.get("required") and not options.get("envvar", False)
        bool_parser = parser.add_mutually_exclusive_group(required=required)
        bool_parser.add_argument(
            "--" + argument.replace("_", "-"),
            dest=argument,
            action="store_true",
        )
        bool_parser.add_argument(
            "--no-" + argument.replace("_", "-"),
            dest=argument,
            action="store_false",
        )
        bool_parser.set_defaults(**{argument: options.get("default")})
    else:
        converter = SchemaToArgparse(argument, options)
        parser.add_argument(converter.argname, **converter.options)


class EnvParser:
    @staticmethod
    def format_help(envvar_parameter_options: Mapping):
        if not envvar_parameter_options:
            return ""

        def format_arg(options):
            if "help" in options:
                return f"{options['envvar']}\t\t{options['help']}"
            return options["envvar"]

        return "\nenvironment variables: \n  {}".format(
            "\n  ".join(
                format_arg(options)
                for options in envvar_parameter_options.values()
            )
        )

    @staticmethod
    def _validate(envvar, value, options):
        if "isascii" in options:
            try:
                value.encode("ascii")
            except UnicodeEncodeError:
                return (
                    f"error: {envvar}={value} must only contain ascii symbols",
                )
        return None

    @classmethod
    def parse(
        cls,
        environ: Mapping,
        command,
        envvar_parameter_options,
        exclude: Iterable[str],
    ) -> Dict[str, str]:
        kwargs = {}
        for parameter, options in envvar_parameter_options.items():
            if parameter in exclude:
                continue
            envvar_name = options["envvar"]
            try:
                value = kwargs[parameter] = environ[envvar_name]
            except KeyError:
                if "default" in options:
                    kwargs[parameter] = options["default"]
                    continue
                if not options.get("required"):
                    continue
                msg = cls._format_error(
                    command,
                    envvar_parameter_options,
                    "error: environment variable {} is not defined".format(
                        envvar_name
                    ),
                )
                print(msg, file=sys.stderr)
                sys.exit(EXITCODE_NOT_FOUND)
            else:
                if err := cls._validate(envvar_name, value, options):
                    msg = cls._format_error(
                        command, envvar_parameter_options, err
                    )
                    print(msg, file=sys.stderr)
                    sys.exit(EXITCODE_NOT_FOUND)
        return kwargs

    @classmethod
    def _format_error(cls, command, envvar_parameter_options, msg):
        return "{command}:\n{help}\n\n{message}".format(
            command=" ".join(command),
            help=cls.format_help(envvar_parameter_options),
            message=msg,
        )


def is_valid_ipv4_addr(addr):
    try:
        ipaddress.IPv4Address(addr)
    except ipaddress.AddressValueError:
        return False
    return True


def _filter_user(schema, user):
    for key, values in schema.items():
        if user in values.get("cli", {}).get("users", []):
            yield key, values


def rpc_endpoint(command, require_rpc, **params):
    return RpcClient(require_svc_is_running=require_rpc).cmd(*command)(
        **params
    )


def generate_endpoint_params(arg_parser_namespace, arguments):
    kwargs = {}
    for argument in arguments:
        arg_parser_argument = argument.replace("-", "_")
        value = getattr(arg_parser_namespace, arg_parser_argument, None)
        if value is not None:
            kwargs[argument] = value

    return kwargs


def apply_parser(subparsers, schema):
    _subparsers = {}
    commands = sorted(schema.keys())
    for methods in commands:
        values = schema[methods]
        assert isinstance(methods, (tuple, list))
        parser = None

        # generate subparsers
        subparser = subparsers
        for i, command in enumerate(methods):
            # last element
            if i == len(methods) - 1:
                parser = subparser.add_parser(
                    name=command,
                    help=values.get("help"),
                    formatter_class=argparse.RawDescriptionHelpFormatter,
                )
                if any(
                    (c != methods and methods == c[: len(methods)])
                    for c in commands
                ):
                    _subparsers[methods] = parser.add_subparsers(
                        help="Available commands"
                    )
            else:
                # Need to reuse created subparsers for sub-commands, otherwise
                # they will be overwritten.
                #
                # Example:
                #   For both of the commands:
                #     * malware on-demand queue put
                #     * malware on-demand queue remove
                # only one subparser is created. We should add `queue`
                # subparser only once in order to keep both `put` and `remove`.

                hashable = tuple(methods[: i + 1])
                exists_subparser = _subparsers.get(hashable)
                if not exists_subparser:
                    subparser = _subparsers[hashable] = subparser.add_parser(
                        name=command,
                        help=values.get("help"),
                    ).add_subparsers(help="Available commands")
                else:
                    subparser = exists_subparser

        assert parser, "parser is not defined"

        # generate arguments
        envvar_parameter_options = {}
        for argument, options in values.get("schema", {}).items():
            if "envvar" in options:
                envvar_parameter_options[argument] = options
                if options.get("envvar_only", False):
                    continue
            if "rename" in options:
                options.update(**values["schema"][options["rename"]])
                options["required"] = False
                options["positional"] = False
            schema_to_argparse(parser, argument, options)

        parser.epilog = EnvParser.format_help(envvar_parameter_options)

        parser.add_argument(
            "--json", action="store_true", help="return data in JSON format"
        )
        parser.add_argument("--verbose", "-v", action="count")

        require_rpc = values.get("cli", {}).get("require_rpc", "running")

        parser.set_defaults(
            # Initializing `RpcClient` here for each command will
            # inevitably lead to the `ServiceStateError`,
            # because some endpoints require the agent to be stopped and
            # some require it to be running. So we use `partial` to
            # defer initialization until the command is selected.
            endpoint=partial(rpc_endpoint, methods, require_rpc),
            generate_endpoint_params=partial(
                generate_endpoint_params,
                arguments=values.get("schema", {}).keys(),
            ),
            envvar_parameter_options=envvar_parameter_options,
            command=methods,
        )


def _apply_subparsers(subparsers, user):
    schema = dict(_filter_user(prepare_schema(app.SCHEMA_PATHS), user))
    apply_parser(subparsers, schema)


@lru_cache(maxsize=1)
def create_cli_parser():
    parser = argparse.ArgumentParser(description="CLI for %s." % Config.NAME)

    parser.add_argument("--log-config", help="logging config filename")
    parser.add_argument(
        "--console-log-level",
        choices=["ERROR", "WARNING", "INFO", "DEBUG"],
        help="Level of logging input to the console",
    )
    parser.add_argument(
        "--remote-addr",
        type=lambda ip: ip if is_valid_ipv4_addr(ip) else None,
        help="Client's IP address for adding it to the whitelist",
    )
    subparsers = parser.add_subparsers(help="Available commands")
    _apply_subparsers(subparsers, "root")
    return parser