# -*- coding: utf-8 -*-
#
# (c) 2016, Yanis Guenane <yanis+ansible@guenane.org>
#
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Ansible is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.


try:
    from OpenSSL import crypto
except ImportError:
    # An error will be raised in the calling class to let the end
    # user know that OpenSSL couldn't be found.
    pass

import abc
import datetime
import errno
import hashlib
import os
import re

from ansible.module_utils import six
from ansible.module_utils._text import to_bytes


class OpenSSLObjectError(Exception):
    pass


def get_fingerprint_of_bytes(source):
    """Generate the fingerprint of the given bytes."""

    fingerprint = {}

    try:
        algorithms = hashlib.algorithms
    except AttributeError:
        try:
            algorithms = hashlib.algorithms_guaranteed
        except AttributeError:
            return None

    for algo in algorithms:
        f = getattr(hashlib, algo)
        h = f(source)
        try:
            # Certain hash functions have a hexdigest() which expects a length parameter
            pubkey_digest = h.hexdigest()
        except TypeError:
            pubkey_digest = h.hexdigest(32)
        fingerprint[algo] = ':'.join(pubkey_digest[i:i + 2] for i in range(0, len(pubkey_digest), 2))

    return fingerprint


def get_fingerprint(path, passphrase=None):
    """Generate the fingerprint of the public key. """

    privatekey = load_privatekey(path, passphrase)
    try:
        publickey = crypto.dump_publickey(crypto.FILETYPE_ASN1, privatekey)
        return get_fingerprint_of_bytes(publickey)
    except AttributeError:
        # If PyOpenSSL < 16.0 crypto.dump_publickey() will fail.
        # By doing this we prevent the code from raising an error
        # yet we return no value in the fingerprint hash.
        return None


def load_privatekey(path, passphrase=None):
    """Load the specified OpenSSL private key."""

    try:
        with open(path, 'rb') as b_priv_key_fh:
            priv_key_detail = b_priv_key_fh.read()

        if passphrase:
            return crypto.load_privatekey(crypto.FILETYPE_PEM,
                                          priv_key_detail,
                                          to_bytes(passphrase))
        else:
            return crypto.load_privatekey(crypto.FILETYPE_PEM,
                                          priv_key_detail)
    except (IOError, OSError) as exc:
        raise OpenSSLObjectError(exc)


def load_certificate(path):
    """Load the specified certificate."""

    try:
        with open(path, 'rb') as cert_fh:
            cert_content = cert_fh.read()
        return crypto.load_certificate(crypto.FILETYPE_PEM, cert_content)
    except (IOError, OSError) as exc:
        raise OpenSSLObjectError(exc)


def load_certificate_request(path):
    """Load the specified certificate signing request."""

    try:
        with open(path, 'rb') as csr_fh:
            csr_content = csr_fh.read()
        return crypto.load_certificate_request(crypto.FILETYPE_PEM, csr_content)
    except (IOError, OSError) as exc:
        raise OpenSSLObjectError(exc)


def parse_name_field(input_dict):
    """Take a dict with key: value or key: list_of_values mappings and return a list of tuples"""

    result = []
    for key in input_dict:
        if isinstance(input_dict[key], list):
            for entry in input_dict[key]:
                result.append((key, entry))
        else:
            result.append((key, input_dict[key]))
    return result


def convert_relative_to_datetime(relative_time_string):
    """Get a datetime.datetime or None from a string in the time format described in sshd_config(5)"""

    parsed_result = re.match(
        r"^(?P<prefix>[+-])((?P<weeks>\d+)[wW])?((?P<days>\d+)[dD])?((?P<hours>\d+)[hH])?((?P<minutes>\d+)[mM])?((?P<seconds>\d+)[sS]?)?$",
        relative_time_string)

    if parsed_result is None or len(relative_time_string) == 1:
        # not matched or only a single "+" or "-"
        return None

    offset = datetime.timedelta(0)
    if parsed_result.group("weeks") is not None:
        offset += datetime.timedelta(weeks=int(parsed_result.group("weeks")))
    if parsed_result.group("days") is not None:
        offset += datetime.timedelta(days=int(parsed_result.group("days")))
    if parsed_result.group("hours") is not None:
        offset += datetime.timedelta(hours=int(parsed_result.group("hours")))
    if parsed_result.group("minutes") is not None:
        offset += datetime.timedelta(
            minutes=int(parsed_result.group("minutes")))
    if parsed_result.group("seconds") is not None:
        offset += datetime.timedelta(
            seconds=int(parsed_result.group("seconds")))

    if parsed_result.group("prefix") == "+":
        return datetime.datetime.utcnow() + offset
    else:
        return datetime.datetime.utcnow() - offset


@six.add_metaclass(abc.ABCMeta)
class OpenSSLObject(object):

    def __init__(self, path, state, force, check_mode):
        self.path = path
        self.state = state
        self.force = force
        self.name = os.path.basename(path)
        self.changed = False
        self.check_mode = check_mode

    def check(self, module, perms_required=True):
        """Ensure the resource is in its desired state."""

        def _check_state():
            return os.path.exists(self.path)

        def _check_perms(module):
            file_args = module.load_file_common_arguments(module.params)
            return not module.set_fs_attributes_if_different(file_args, False)

        if not perms_required:
            return _check_state()

        return _check_state() and _check_perms(module)

    @abc.abstractmethod
    def dump(self):
        """Serialize the object into a dictionary."""

        pass

    @abc.abstractmethod
    def generate(self):
        """Generate the resource."""

        pass

    def remove(self):
        """Remove the resource from the filesystem."""

        try:
            os.remove(self.path)
            self.changed = True
        except OSError as exc:
            if exc.errno != errno.ENOENT:
                raise OpenSSLObjectError(exc)
            else:
                pass