"""Utilities for all Certbot."""
import argparse
import collections
# distutils.version under virtualenv confuses pylint
# For more info, see: https://github.com/PyCQA/pylint/issues/73
import distutils.version  # pylint: disable=import-error,no-name-in-module
import errno
import logging
import os
import platform
import re
import six
import socket
import stat
import subprocess
import sys

import configargparse

from certbot import errors


logger = logging.getLogger(__name__)


Key = collections.namedtuple("Key", "file pem")
# Note: form is the type of data, "pem" or "der"
CSR = collections.namedtuple("CSR", "file data form")


# ANSI SGR escape codes
# Formats text as bold or with increased intensity
ANSI_SGR_BOLD = '\033[1m'
# Colors text red
ANSI_SGR_RED = "\033[31m"
# Resets output format
ANSI_SGR_RESET = "\033[0m"


def run_script(params):
    """Run the script with the given params.

    :param list params: List of parameters to pass to Popen

    """
    try:
        proc = subprocess.Popen(params,
                                stdout=subprocess.PIPE,
                                stderr=subprocess.PIPE)

    except (OSError, ValueError):
        msg = "Unable to run the command: %s" % " ".join(params)
        logger.error(msg)
        raise errors.SubprocessError(msg)

    stdout, stderr = proc.communicate()

    if proc.returncode != 0:
        msg = "Error while running %s.\n%s\n%s" % (
            " ".join(params), stdout, stderr)
        # Enter recovery routine...
        logger.error(msg)
        raise errors.SubprocessError(msg)

    return stdout, stderr


def exe_exists(exe):
    """Determine whether path/name refers to an executable.

    :param str exe: Executable path or name

    :returns: If exe is a valid executable
    :rtype: bool

    """
    def is_exe(path):
        """Determine if path is an exe."""
        return os.path.isfile(path) and os.access(path, os.X_OK)

    path, _ = os.path.split(exe)
    if path:
        return is_exe(exe)
    else:
        for path in os.environ["PATH"].split(os.pathsep):
            if is_exe(os.path.join(path, exe)):
                return True

    return False


def make_or_verify_dir(directory, mode=0o755, uid=0, strict=False):
    """Make sure directory exists with proper permissions.

    :param str directory: Path to a directory.
    :param int mode: Directory mode.
    :param int uid: Directory owner.

    :raises .errors.Error: if a directory already exists,
        but has wrong permissions or owner

    :raises OSError: if invalid or inaccessible file names and
        paths, or other arguments that have the correct type,
        but are not accepted by the operating system.

    """
    try:
        os.makedirs(directory, mode)
    except OSError as exception:
        if exception.errno == errno.EEXIST:
            if strict and not check_permissions(directory, mode, uid):
                raise errors.Error(
                    "%s exists, but it should be owned by user %d with"
                    "permissions %s" % (directory, uid, oct(mode)))
        else:
            raise


def check_permissions(filepath, mode, uid=0):
    """Check file or directory permissions.

    :param str filepath: Path to the tested file (or directory).
    :param int mode: Expected file mode.
    :param int uid: Expected file owner.

    :returns: True if `mode` and `uid` match, False otherwise.
    :rtype: bool

    """
    file_stat = os.stat(filepath)
    return stat.S_IMODE(file_stat.st_mode) == mode and file_stat.st_uid == uid


def safe_open(path, mode="w", chmod=None, buffering=None):
    """Safely open a file.

    :param str path: Path to a file.
    :param str mode: Same os `mode` for `open`.
    :param int chmod: Same as `mode` for `os.open`, uses Python defaults
        if ``None``.
    :param int buffering: Same as `bufsize` for `os.fdopen`, uses Python
        defaults if ``None``.

    """
    # pylint: disable=star-args
    open_args = () if chmod is None else (chmod,)
    fdopen_args = () if buffering is None else (buffering,)
    return os.fdopen(
        os.open(path, os.O_CREAT | os.O_EXCL | os.O_RDWR, *open_args),
        mode, *fdopen_args)


def _unique_file(path, filename_pat, count, mode):
    while True:
        current_path = os.path.join(path, filename_pat(count))
        try:
            return safe_open(current_path, chmod=mode),\
                os.path.abspath(current_path)
        except OSError as err:
            # "File exists," is okay, try a different name.
            if err.errno != errno.EEXIST:
                raise
        count += 1


def unique_file(path, mode=0o777):
    """Safely finds a unique file.

    :param str path: path/filename.ext
    :param int mode: File mode

    :returns: tuple of file object and file name

    """
    path, tail = os.path.split(path)
    return _unique_file(
        path, filename_pat=(lambda count: "%04d_%s" % (count, tail)),
        count=0, mode=mode)


def unique_lineage_name(path, filename, mode=0o777):
    """Safely finds a unique file using lineage convention.

    :param str path: directory path
    :param str filename: proposed filename
    :param int mode: file mode

    :returns: tuple of file object and file name (which may be modified
        from the requested one by appending digits to ensure uniqueness)

    :raises OSError: if writing files fails for an unanticipated reason,
        such as a full disk or a lack of permission to write to
        specified location.

    """
    preferred_path = os.path.join(path, "%s.conf" % (filename))
    try:
        return safe_open(preferred_path, chmod=mode), preferred_path
    except OSError as err:
        if err.errno != errno.EEXIST:
            raise
    return _unique_file(
        path, filename_pat=(lambda count: "%s-%04d.conf" % (filename, count)),
        count=1, mode=mode)


def safely_remove(path):
    """Remove a file that may not exist."""
    try:
        os.remove(path)
    except OSError as err:
        if err.errno != errno.ENOENT:
            raise


def get_os_info(filepath="/etc/os-release"):
    """
    Get OS name and version

    :param str filepath: File path of os-release file
    :returns: (os_name, os_version)
    :rtype: `tuple` of `str`
    """

    if os.path.isfile(filepath):
        # Systemd os-release parsing might be viable
        os_name, os_version = get_systemd_os_info(filepath=filepath)
        if os_name:
            return (os_name, os_version)

    # Fallback to platform module
    return get_python_os_info()


def get_os_info_ua(filepath="/etc/os-release"):
    """
    Get OS name and version string for User Agent

    :param str filepath: File path of os-release file
    :returns: os_ua
    :rtype: `str`
    """

    if os.path.isfile(filepath):
        os_ua = _get_systemd_os_release_var("PRETTY_NAME", filepath=filepath)
        if not os_ua:
            os_ua = _get_systemd_os_release_var("NAME", filepath=filepath)
        if os_ua:
            return os_ua

    # Fallback
    return " ".join(get_python_os_info())


def get_systemd_os_info(filepath="/etc/os-release"):
    """
    Parse systemd /etc/os-release for distribution information

    :param str filepath: File path of os-release file
    :returns: (os_name, os_version)
    :rtype: `tuple` of `str`
    """

    os_name = _get_systemd_os_release_var("ID", filepath=filepath)
    os_version = _get_systemd_os_release_var("VERSION_ID", filepath=filepath)

    return (os_name, os_version)


def _get_systemd_os_release_var(varname, filepath="/etc/os-release"):
    """
    Get single value from systemd /etc/os-release

    :param str varname: Name of variable to fetch
    :param str filepath: File path of os-release file
    :returns: requested value
    :rtype: `str`
    """

    var_string = varname+"="
    if not os.path.isfile(filepath):
        return ""
    with open(filepath, 'r') as fh:
        contents = fh.readlines()

    for line in contents:
        if line.strip().startswith(var_string):
            # Return the value of var, normalized
            return _normalize_string(line.strip()[len(var_string):])
    return ""


def _normalize_string(orig):
    """
    Helper function for _get_systemd_os_release_var() to remove quotes
    and whitespaces
    """
    return orig.replace('"', '').replace("'", "").strip()


def get_python_os_info():
    """
    Get Operating System type/distribution and major version
    using python platform module

    :returns: (os_name, os_version)
    :rtype: `tuple` of `str`
    """
    info = platform.system_alias(
        platform.system(),
        platform.release(),
        platform.version()
    )
    os_type, os_ver, _ = info
    os_type = os_type.lower()
    if os_type.startswith('linux'):
        info = platform.linux_distribution()
        # On arch, platform.linux_distribution() is reportedly ('','',''),
        # so handle it defensively
        if info[0]:
            os_type = info[0]
        if info[1]:
            os_ver = info[1]
    elif os_type.startswith('darwin'):
        os_ver = subprocess.Popen(
            ["sw_vers", "-productVersion"],
            stdout=subprocess.PIPE
        ).communicate()[0].rstrip('\n')
    elif os_type.startswith('freebsd'):
        # eg "9.3-RC3-p1"
        os_ver = os_ver.partition("-")[0]
        os_ver = os_ver.partition(".")[0]
    elif platform.win32_ver()[1]:
        os_ver = platform.win32_ver()[1]
    else:
        # Cases known to fall here: Cygwin python
        os_ver = ''
    return os_type, os_ver

# Just make sure we don't get pwned... Make sure that it also doesn't
# start with a period or have two consecutive periods <- this needs to
# be done in addition to the regex
EMAIL_REGEX = re.compile("[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+$")


def safe_email(email):
    """Scrub email address before using it."""
    if EMAIL_REGEX.match(email) is not None:
        return not email.startswith(".") and ".." not in email
    else:
        logger.warn("Invalid email address: %s.", email)
        return False


def add_deprecated_argument(add_argument, argument_name, nargs):
    """Adds a deprecated argument with the name argument_name.

    Deprecated arguments are not shown in the help. If they are used on
    the command line, a warning is shown stating that the argument is
    deprecated and no other action is taken.

    :param callable add_argument: Function that adds arguments to an
        argument parser/group.
    :param str argument_name: Name of deprecated argument.
    :param nargs: Value for nargs when adding the argument to argparse.

    """
    class ShowWarning(argparse.Action):
        """Action to log a warning when an argument is used."""
        def __call__(self, unused1, unused2, unused3, option_string=None):
            sys.stderr.write(
                "Use of {0} is deprecated.\n".format(option_string))

    configargparse.ACTION_TYPES_THAT_DONT_NEED_A_VALUE.add(ShowWarning)
    add_argument(argument_name, action=ShowWarning,
                 help=argparse.SUPPRESS, nargs=nargs)


def enforce_domain_sanity(domain):
    """Method which validates domain value and errors out if
    the requirements are not met.

    :param domain: Domain to check
    :type domains: `str` or `unicode`
    :raises ConfigurationError: for invalid domains and cases where Let's
                                Encrypt currently will not issue certificates

    :returns: The domain cast to `str`, with ASCII-only contents
    :rtype: str
    """
    # Check if there's a wildcard domain
    if domain.startswith("*."):
        raise errors.ConfigurationError(
            "Wildcard domains are not supported: {0}".format(domain))
    # Punycode
    if "xn--" in domain:
        raise errors.ConfigurationError(
            "Punycode domains are not presently supported: {0}".format(domain))

    # Unicode
    try:
        domain = domain.encode('ascii').lower()
    except UnicodeError:
        error_fmt = (u"Internationalized domain names "
                     "are not presently supported: {0}")
        if isinstance(domain, six.text_type):
            raise errors.ConfigurationError(error_fmt.format(domain))
        else:
            raise errors.ConfigurationError(str(error_fmt).format(domain))

    # Remove trailing dot
    domain = domain[:-1] if domain.endswith('.') else domain

    # Explain separately that IP addresses aren't allowed (apart from not
    # being FQDNs) because hope springs eternal concerning this point
    try:
        socket.inet_aton(domain)
        raise errors.ConfigurationError(
            "Requested name {0} is an IP address. The Let's Encrypt "
            "certificate authority will not issue certificates for a "
            "bare IP address.".format(domain))
    except socket.error:
        # It wasn't an IP address, so that's good
        pass

    # FQDN checks from
    # http://www.mkyong.com/regular-expressions/domain-name-regular-expression-example/
    #  Characters used, domain parts < 63 chars, tld > 1 < 64 chars
    #  first and last char is not "-"
    fqdn = re.compile("^((?!-)[A-Za-z0-9-]{1,63}(?<!-)\\.)+[A-Za-z]{2,63}$")
    if not fqdn.match(domain):
        raise errors.ConfigurationError("Requested domain {0} is not a FQDN"
                                        .format(domain))
    return domain


def get_strict_version(normalized):
    """Converts a normalized version to a strict version.

    :param str normalized: normalized version string

    :returns: An equivalent strict version
    :rtype: distutils.version.StrictVersion

    """
    # strict version ending with "a" and a number designates a pre-release
    # pylint: disable=no-member
    return distutils.version.StrictVersion(normalized.replace(".dev", "a"))
