"""Utilities for all Let's Encrypt."""
import argparse
import collections
import errno
import logging
import os
import platform
import re
import stat
import subprocess
import sys

from letsencrypt 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), 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():
    """
    Get Operating System type/distribution and major version

    :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]
        os_ver = os_ver.partition(".")[0]
    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))

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