# Copyright 2012 OpenStack Foundation
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.


import io
import select
import socket
import time
import warnings

from oslo_log import log as logging
from oslo_utils.secretutils import md5

from tempest.lib import exceptions


with warnings.catch_warnings():
    warnings.simplefilter("ignore")
    import paramiko


LOG = logging.getLogger(__name__)


def get_fingerprint(self):
    """Patch paramiko

    This method needs to be patched to allow paramiko to work under FIPS.
    Until the patch to do this merges, patch paramiko here.

    TODO(alee) Remove this when paramiko is patched.
    See https://github.com/paramiko/paramiko/pull/1928
    """
    return md5(self.asbytes(), usedforsecurity=False).digest()


paramiko.pkey.PKey.get_fingerprint = get_fingerprint


class Client(object):

    def __init__(self, host, username, password=None, timeout=300, pkey=None,
                 channel_timeout=10, look_for_keys=False, key_filename=None,
                 port=22, proxy_client=None, ssh_key_type='rsa'):
        """SSH client.

        Many of parameters are just passed to the underlying implementation
        as it is.  See the paramiko documentation for more details.
        http://docs.paramiko.org/en/2.1/api/client.html#paramiko.client.SSHClient.connect

        :param host: Host to login.
        :param username: SSH username.
        :param password: SSH password, or a password to unlock private key.
        :param timeout: Timeout in seconds, including retries.
            Default is 300 seconds.
        :param pkey: Private key.
        :param channel_timeout: Channel timeout in seconds, passed to the
            paramiko.  Default is 10 seconds.
        :param look_for_keys: Whether or not to search for private keys
            in ``~/.ssh``.  Default is False.
        :param key_filename: Filename for private key to use.
        :param port: SSH port number.
        :param proxy_client: Another SSH client to provide a transport
            for ssh-over-ssh.  The default is None, which means
            not to use ssh-over-ssh.
        :param ssh_key_type: ssh key type (rsa, ecdsa)
        :type proxy_client: ``tempest.lib.common.ssh.Client`` object
        """
        self.host = host
        self.username = username
        self.port = port
        self.password = password
        if isinstance(pkey, str):
            if ssh_key_type == 'rsa':
                pkey = paramiko.RSAKey.from_private_key(
                    io.StringIO(str(pkey)))
            elif ssh_key_type == 'ecdsa':
                pkey = paramiko.ECDSAKey.from_private_key(
                    io.StringIO(str(pkey)))
            else:
                raise exceptions.SSHClientUnsupportedKeyType(
                    key_type=ssh_key_type)
        self.pkey = pkey
        self.look_for_keys = look_for_keys
        self.key_filename = key_filename
        self.timeout = int(timeout)
        self.channel_timeout = float(channel_timeout)
        self.buf_size = 1024
        self.proxy_client = proxy_client
        if (self.proxy_client and self.proxy_client.host == self.host and
                self.proxy_client.port == self.port and
                self.proxy_client.username == self.username):
            raise exceptions.SSHClientProxyClientLoop(
                host=self.host, port=self.port, username=self.username)
        self._proxy_conn = None

    def _get_ssh_connection(self, sleep=1.5, backoff=1):
        """Returns an ssh connection to the specified host."""
        bsleep = sleep
        ssh = paramiko.SSHClient()
        ssh.set_missing_host_key_policy(
            paramiko.AutoAddPolicy())
        _start_time = time.time()
        if self.pkey is not None:
            LOG.info("Creating ssh connection to '%s:%d' as '%s'"
                     " with public key authentication",
                     self.host, self.port, self.username)
        else:
            LOG.info("Creating ssh connection to '%s:%d' as '%s'"
                     " with password %s",
                     self.host, self.port, self.username, str(self.password))
        attempts = 0
        while True:
            if self.proxy_client is not None:
                proxy_chan = self._get_proxy_channel()
            else:
                proxy_chan = None
            try:
                ssh.connect(self.host, port=self.port, username=self.username,
                            password=self.password,
                            look_for_keys=self.look_for_keys,
                            key_filename=self.key_filename,
                            timeout=self.channel_timeout, pkey=self.pkey,
                            sock=proxy_chan)
                LOG.info("ssh connection to %s@%s successfully created",
                         self.username, self.host)
                return ssh
            except (EOFError,
                    socket.error, socket.timeout,
                    paramiko.SSHException) as e:
                ssh.close()
                if self._is_timed_out(_start_time):
                    LOG.exception("Failed to establish authenticated ssh"
                                  " connection to %s@%s after %d attempts. "
                                  "Proxy client: %s",
                                  self.username, self.host, attempts,
                                  self._get_proxy_client_info())
                    raise exceptions.SSHTimeout(host=self.host,
                                                user=self.username,
                                                password=self.password)
                bsleep += backoff
                attempts += 1
                LOG.warning("Failed to establish authenticated ssh"
                            " connection to %s@%s (%s). Number attempts: %s."
                            " Retry after %d seconds.",
                            self.username, self.host, e, attempts, bsleep)
                time.sleep(bsleep)

    def _is_timed_out(self, start_time):
        return (time.time() - self.timeout) > start_time

    @staticmethod
    def _can_system_poll():
        return hasattr(select, 'poll')

    def exec_command(self, cmd, encoding="utf-8"):
        """Execute the specified command on the server

        Note that this method is reading whole command outputs to memory, thus
        shouldn't be used for large outputs.

        :param str cmd: Command to run at remote server.
        :param str encoding: Encoding for result from paramiko.
                             Result will not be decoded if None.
        :returns: data read from standard output of the command.
        :raises: SSHExecCommandFailed if command returns nonzero
                 status. The exception contains command status stderr content.
        :raises: TimeoutException if cmd doesn't end when timeout expires.
        """
        ssh = self._get_ssh_connection()
        transport = ssh.get_transport()
        with transport.open_session() as channel:
            channel.fileno()  # Register event pipe
            channel.exec_command(cmd)
            channel.shutdown_write()

            # If the executing host is linux-based, poll the channel
            if self._can_system_poll():
                out_data_chunks = []
                err_data_chunks = []
                poll = select.poll()
                poll.register(channel, select.POLLIN)
                start_time = time.time()

                while True:
                    ready = poll.poll(self.channel_timeout)
                    if not any(ready):
                        if not self._is_timed_out(start_time):
                            continue
                        raise exceptions.TimeoutException(
                            "Command: '{0}' executed on host '{1}'.".format(
                                cmd, self.host))
                    if not ready[0]:  # If there is nothing to read.
                        continue
                    out_chunk = err_chunk = None
                    if channel.recv_ready():
                        out_chunk = channel.recv(self.buf_size)
                        out_data_chunks += out_chunk,
                    if channel.recv_stderr_ready():
                        err_chunk = channel.recv_stderr(self.buf_size)
                        err_data_chunks += err_chunk,
                    if not err_chunk and not out_chunk:
                        break
                out_data = b''.join(out_data_chunks)
                err_data = b''.join(err_data_chunks)
            # Just read from the channels
            else:
                out_file = channel.makefile('rb', self.buf_size)
                err_file = channel.makefile_stderr('rb', self.buf_size)
                out_data = out_file.read()
                err_data = err_file.read()
            if encoding:
                out_data = out_data.decode(encoding)
                err_data = err_data.decode(encoding)

            exit_status = channel.recv_exit_status()

        ssh.close()

        if 0 != exit_status:
            raise exceptions.SSHExecCommandFailed(
                command=cmd, exit_status=exit_status,
                stderr=err_data, stdout=out_data)
        return out_data

    def test_connection_auth(self):
        """Raises an exception when we can not connect to server via ssh."""
        connection = self._get_ssh_connection()
        connection.close()

    def _get_proxy_channel(self):
        conn = self.proxy_client._get_ssh_connection()
        # Keep a reference to avoid g/c
        # https://github.com/paramiko/paramiko/issues/440
        self._proxy_conn = conn
        transport = conn.get_transport()
        chan = transport.open_session()
        cmd = 'nc %s %s' % (self.host, self.port)
        chan.exec_command(cmd)
        return chan

    def _get_proxy_client_info(self):
        if not self.proxy_client:
            return 'no proxy client'
        nested_pclient = self.proxy_client._get_proxy_client_info()
        return ('%(username)s@%(host)s:%(port)s, nested proxy client: '
                '%(nested_pclient)s' % {'username': self.proxy_client.username,
                                        'host': self.proxy_client.host,
                                        'port': self.proxy_client.port,
                                        'nested_pclient': nested_pclient})
