"""Plugin common functions."""
from abc import ABCMeta
from abc import abstractmethod
import argparse
import logging
import re
import shutil
import tempfile
from typing import Any
from typing import Callable
from typing import Iterable
from typing import List
from typing import Optional
from typing import Set
from typing import Tuple
from typing import Type
from typing import TypeVar

import pkg_resources

from acme import challenges
from certbot import achallenges
from certbot import configuration
from certbot import crypto_util
from certbot import errors
from certbot import interfaces
from certbot import reverter
from certbot._internal import constants
from certbot.compat import filesystem
from certbot.compat import os
from certbot.interfaces import Installer as AbstractInstaller
from certbot.interfaces import Plugin as AbstractPlugin
from certbot.plugins.storage import PluginStorage

logger = logging.getLogger(__name__)


def option_namespace(name: str) -> str:
    """ArgumentParser options namespace (prefix of all options)."""
    return name + "-"


def dest_namespace(name: str) -> str:
    """ArgumentParser dest namespace (prefix of all destinations)."""
    return name.replace("-", "_") + "_"


private_ips_regex = re.compile(
    r"(^127\.0\.0\.1)|(^10\.)|(^172\.1[6-9]\.)|"
    r"(^172\.2[0-9]\.)|(^172\.3[0-1]\.)|(^192\.168\.)")
hostname_regex = re.compile(
    r"^(([a-z0-9]|[a-z0-9][a-z0-9\-]*[a-z0-9])\.)*[a-z]+$", re.IGNORECASE)


class Plugin(AbstractPlugin, metaclass=ABCMeta):
    """Generic plugin."""

    def __init__(self, config: configuration.NamespaceConfig, name: str) -> None:
        super().__init__(config, name)
        self.config = config
        self.name = name

    @classmethod
    @abstractmethod
    def add_parser_arguments(cls, add: Callable[..., None]) -> None:
        """Add plugin arguments to the CLI argument parser.

        :param callable add: Function that proxies calls to
            `argparse.ArgumentParser.add_argument` prepending options
            with unique plugin name prefix.

        """

    @classmethod
    def inject_parser_options(cls, parser: argparse.ArgumentParser, name: str) -> None:
        """Inject parser options.

        See `~.certbot.interfaces.Plugin.inject_parser_options` for docs.

        """
        # dummy function, doesn't check if dest.startswith(self.dest_namespace)
        def add(arg_name_no_prefix: str, *args: Any, **kwargs: Any) -> None:
            parser.add_argument(
                "--{0}{1}".format(option_namespace(name), arg_name_no_prefix),
                *args, **kwargs)
        return cls.add_parser_arguments(add)

    @property
    def option_namespace(self) -> str:
        """ArgumentParser options namespace (prefix of all options)."""
        return option_namespace(self.name)

    def option_name(self, name: str) -> str:
        """Option name (include plugin namespace)."""
        return self.option_namespace + name

    @property
    def dest_namespace(self) -> str:
        """ArgumentParser dest namespace (prefix of all destinations)."""
        return dest_namespace(self.name)

    def dest(self, var: str) -> str:
        """Find a destination for given variable ``var``."""
        # this should do exactly the same what ArgumentParser(arg),
        # does to "arg" to compute "dest"
        return self.dest_namespace + var.replace("-", "_")

    def conf(self, var: str) -> Any:
        """Find a configuration value for variable ``var``."""
        return getattr(self.config, self.dest(var))

    def auth_hint(self, failed_achalls: List[achallenges.AnnotatedChallenge]) -> str:
        """Human-readable string to help the user troubleshoot the authenticator.

        Shown to the user if one or more of the attempted challenges were not a success.

        Should describe, in simple language, what the authenticator tried to do, what went
        wrong and what the user should try as their "next steps".

        TODO: auth_hint belongs in Authenticator but can't be added until the next major
        version of Certbot. For now, it lives in .Plugin and auth_handler will only call it
        on authenticators that subclass .Plugin. For now, inherit from `.Plugin` to implement
        and/or override the method.

        :param list failed_achalls: List of one or more failed challenges
                                    (:class:`achallenges.AnnotatedChallenge` subclasses).

        :rtype str:
        """
        # This is a fallback hint. Authenticators should implement their own auth_hint that
        # addresses the specific mechanics of that authenticator.
        challs = " and ".join(sorted({achall.typ for achall in failed_achalls}))
        return ("The Certificate Authority couldn't externally verify that the {name} plugin "
                "completed the required {challs} challenges. Ensure the plugin is configured "
                "correctly and that the changes it makes are accessible from the internet."
                .format(name=self.name, challs=challs))


class Installer(AbstractInstaller, Plugin, metaclass=ABCMeta):
    """An installer base class with reverter and ssl_dhparam methods defined.

    Installer plugins do not have to inherit from this class.

    """
    def __init__(self, *args: Any, **kwargs: Any) -> None:
        super().__init__(*args, **kwargs)
        self.storage = PluginStorage(self.config, self.name)
        self.reverter = reverter.Reverter(self.config)

    def add_to_checkpoint(self, save_files: Set[str], save_notes: str,
                          temporary: bool = False) -> None:
        """Add files to a checkpoint.

        :param set save_files: set of filepaths to save
        :param str save_notes: notes about changes during the save
        :param bool temporary: True if the files should be added to a
            temporary checkpoint rather than a permanent one. This is
            usually used for changes that will soon be reverted.

        :raises .errors.PluginError: when unable to add to checkpoint

        """
        if temporary:
            checkpoint_func = self.reverter.add_to_temp_checkpoint
        else:
            checkpoint_func = self.reverter.add_to_checkpoint

        try:
            checkpoint_func(save_files, save_notes)
        except errors.ReverterError as err:
            raise errors.PluginError(str(err))

    def finalize_checkpoint(self, title: str) -> None:
        """Timestamp and save changes made through the reverter.

        :param str title: Title describing checkpoint

        :raises .errors.PluginError: when an error occurs

        """
        try:
            self.reverter.finalize_checkpoint(title)
        except errors.ReverterError as err:
            raise errors.PluginError(str(err))

    def recovery_routine(self) -> None:
        """Revert all previously modified files.

        Reverts all modified files that have not been saved as a checkpoint

        :raises .errors.PluginError: If unable to recover the configuration

        """
        try:
            self.reverter.recovery_routine()
        except errors.ReverterError as err:
            raise errors.PluginError(str(err))

    def revert_temporary_config(self) -> None:
        """Rollback temporary checkpoint.

        :raises .errors.PluginError: when unable to revert config

        """
        try:
            self.reverter.revert_temporary_config()
        except errors.ReverterError as err:
            raise errors.PluginError(str(err))

    def rollback_checkpoints(self, rollback: int = 1) -> None:
        """Rollback saved checkpoints.

        :param int rollback: Number of checkpoints to revert

        :raises .errors.PluginError: If there is a problem with the input or
            the function is unable to correctly revert the configuration

        """
        try:
            self.reverter.rollback_checkpoints(rollback)
        except errors.ReverterError as err:
            raise errors.PluginError(str(err))

    @property
    def ssl_dhparams(self) -> str:
        """Full absolute path to ssl_dhparams file."""
        return os.path.join(self.config.config_dir, constants.SSL_DHPARAMS_DEST)

    @property
    def updated_ssl_dhparams_digest(self) -> str:
        """Full absolute path to digest of updated ssl_dhparams file."""
        return os.path.join(self.config.config_dir, constants.UPDATED_SSL_DHPARAMS_DIGEST)

    def install_ssl_dhparams(self) -> None:
        """Copy Certbot's ssl_dhparams file into the system's config dir if required."""
        install_version_controlled_file(
            self.ssl_dhparams,
            self.updated_ssl_dhparams_digest,
            constants.SSL_DHPARAMS_SRC,
            constants.ALL_SSL_DHPARAMS_HASHES)


class Configurator(Installer, interfaces.Authenticator, metaclass=ABCMeta):
    """
    A plugin that extends certbot.plugins.common.Installer
    and implements certbot.interfaces.Authenticator
    """


GenericAddr = TypeVar("GenericAddr", bound="Addr")


class Addr:
    r"""Represents an virtual host address.

    :param str addr: addr part of vhost address
    :param str port: port number or \*, or ""

    """
    def __init__(self, tup: Tuple[str, str], ipv6: bool = False):
        self.tup = tup
        self.ipv6 = ipv6

    @classmethod
    def fromstring(cls: Type[GenericAddr], str_addr: str) -> Optional[GenericAddr]:
        """Initialize Addr from string."""
        if str_addr.startswith('['):
            # ipv6 addresses starts with [
            endIndex = str_addr.rfind(']')
            host = str_addr[:endIndex + 1]
            port = ''
            if len(str_addr) > endIndex + 2 and str_addr[endIndex + 1] == ':':
                port = str_addr[endIndex + 2:]
            return cls((host, port), ipv6=True)
        else:
            tup = str_addr.partition(':')
            return cls((tup[0], tup[2]))

    def __str__(self) -> str:
        if self.tup[1]:
            return "%s:%s" % self.tup
        return self.tup[0]

    def normalized_tuple(self) -> Tuple[str, str]:
        """Normalized representation of addr/port tuple
        """
        if self.ipv6:
            return self.get_ipv6_exploded(), self.tup[1]
        return self.tup

    def __eq__(self, other: Any) -> bool:
        if isinstance(other, self.__class__):
            # compare normalized to take different
            # styles of representation into account
            return self.normalized_tuple() == other.normalized_tuple()

        return False

    def __hash__(self) -> int:
        return hash(self.tup)

    def get_addr(self) -> str:
        """Return addr part of Addr object."""
        return self.tup[0]

    def get_port(self) -> str:
        """Return port."""
        return self.tup[1]

    def get_addr_obj(self: GenericAddr, port: str) -> GenericAddr:
        """Return new address object with same addr and new port."""
        return self.__class__((self.tup[0], port), self.ipv6)

    def _normalize_ipv6(self, addr: str) -> List[str]:
        """Return IPv6 address in normalized form, helper function"""
        addr = addr.lstrip("[")
        addr = addr.rstrip("]")
        return self._explode_ipv6(addr)

    def get_ipv6_exploded(self) -> str:
        """Return IPv6 in normalized form"""
        if self.ipv6:
            return ":".join(self._normalize_ipv6(self.tup[0]))
        return ""

    def _explode_ipv6(self, addr: str) -> List[str]:
        """Explode IPv6 address for comparison"""
        result = ['0', '0', '0', '0', '0', '0', '0', '0']
        addr_list = addr.split(":")
        if len(addr_list) > len(result):
            # too long, truncate
            addr_list = addr_list[0:len(result)]
        append_to_end = False
        for i, block in enumerate(addr_list):
            if not block:
                # encountered ::, so rest of the blocks should be
                # appended to the end
                append_to_end = True
                continue
            if len(block) > 1:
                # remove leading zeros
                block = block.lstrip("0")
            if not append_to_end:
                result[i] = str(block)
            else:
                # count the location from the end using negative indices
                result[i-len(addr_list)] = str(block)
        return result


class ChallengePerformer:
    """Abstract base for challenge performers.

    :ivar configurator: Authenticator and installer plugin
    :ivar achalls: Annotated challenges
    :vartype achalls: `list` of `.KeyAuthorizationAnnotatedChallenge`
    :ivar indices: Holds the indices of challenges from a larger array
        so the user of the class doesn't have to.
    :vartype indices: `list` of `int`

    """

    def __init__(self, configurator: Configurator):
        self.configurator = configurator
        self.achalls: List[achallenges.KeyAuthorizationAnnotatedChallenge] = []
        self.indices: List[int] = []

    def add_chall(self, achall: achallenges.KeyAuthorizationAnnotatedChallenge,
                  idx: Optional[int] = None) -> None:
        """Store challenge to be performed when perform() is called.

        :param .KeyAuthorizationAnnotatedChallenge achall: Annotated
            challenge.
        :param int idx: index to challenge in a larger array

        """
        self.achalls.append(achall)
        if idx is not None:
            self.indices.append(idx)

    def perform(self) -> List[challenges.KeyAuthorizationChallengeResponse]:
        """Perform all added challenges.

        :returns: challenge responses
        :rtype: `list` of `acme.challenges.KeyAuthorizationChallengeResponse`


        """
        raise NotImplementedError()


def install_version_controlled_file(dest_path: str, digest_path: str, src_path: str,
                                    all_hashes: Iterable[str]) -> None:
    """Copy a file into an active location (likely the system's config dir) if required.

       :param str dest_path: destination path for version controlled file
       :param str digest_path: path to save a digest of the file in
       :param str src_path: path to version controlled file found in distribution
       :param list all_hashes: hashes of every released version of the file
    """
    current_hash = crypto_util.sha256sum(src_path)

    def _write_current_hash() -> None:
        with open(digest_path, "w") as file_h:
            file_h.write(current_hash)

    def _install_current_file() -> None:
        shutil.copyfile(src_path, dest_path)
        _write_current_hash()

    # Check to make sure options-ssl.conf is installed
    if not os.path.isfile(dest_path):
        _install_current_file()
        return
    # there's already a file there. if it's up to date, do nothing. if it's not but
    # it matches a known file hash, we can update it.
    # otherwise, print a warning once per new version.
    active_file_digest = crypto_util.sha256sum(dest_path)
    if active_file_digest == current_hash: # already up to date
        return
    if active_file_digest in all_hashes: # safe to update
        _install_current_file()
    else:  # has been manually modified, not safe to update
        # did they modify the current version or an old version?
        if os.path.isfile(digest_path):
            with open(digest_path, "r") as f:
                saved_digest = f.read()
            # they modified it after we either installed or told them about this version, so return
            if saved_digest == current_hash:
                return
        # there's a new version but we couldn't update the file, or they deleted the digest.
        # save the current digest so we only print this once, and print a warning
        _write_current_hash()
        logger.warning("%s has been manually modified; updated file "
            "saved to %s. We recommend updating %s for security purposes.",
            dest_path, src_path, dest_path)


# test utils used by certbot_apache/certbot_nginx (hence
# "pragma: no cover") TODO: this might quickly lead to dead code (also
# c.f. #383)

def dir_setup(test_dir: str, pkg: str) -> Tuple[str, str, str]:  # pragma: no cover
    """Setup the directories necessary for the configurator."""
    def expanded_tempdir(prefix: str) -> str:
        """Return the real path of a temp directory with the specified prefix

        Some plugins rely on real paths of symlinks for working correctly. For
        example, certbot-apache uses real paths of configuration files to tell
        a virtual host from another. On systems where TMP itself is a symbolic
        link, (ex: OS X) such plugins will be confused. This function prevents
        such a case.
        """
        return filesystem.realpath(tempfile.mkdtemp(prefix))

    temp_dir = expanded_tempdir("temp")
    config_dir = expanded_tempdir("config")
    work_dir = expanded_tempdir("work")

    filesystem.chmod(temp_dir, constants.CONFIG_DIRS_MODE)
    filesystem.chmod(config_dir, constants.CONFIG_DIRS_MODE)
    filesystem.chmod(work_dir, constants.CONFIG_DIRS_MODE)

    test_configs = pkg_resources.resource_filename(
        pkg, os.path.join("testdata", test_dir))

    shutil.copytree(
        test_configs, os.path.join(temp_dir, test_dir), symlinks=True)

    return temp_dir, config_dir, work_dir
