# Copyright 2019 Canonical Ltd.
#
# 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 logging
import os
import re
import shlex
import tempfile
import time
import uuid
from subprocess import CalledProcessError

import paramiko
import n2vc.exceptions

from juju.client import client

arches = [
    [re.compile(r"amd64|x86_64"), "amd64"],
    [re.compile(r"i?[3-9]86"), "i386"],
    [re.compile(r"(arm$)|(armv.*)"), "armhf"],
    [re.compile(r"aarch64"), "arm64"],
    [re.compile(r"ppc64|ppc64el|ppc64le"), "ppc64el"],
    [re.compile(r"s390x?"), "s390x"],

]


def normalize_arch(rawArch):
    """Normalize the architecture string."""
    for arch in arches:
        if arch[0].match(rawArch):
            return arch[1]


DETECTION_SCRIPT = """#!/bin/bash
set -e
os_id=$(grep '^ID=' /etc/os-release | tr -d '"' | cut -d= -f2)
if [ "$os_id" = 'centos' ]; then
  os_version=$(grep '^VERSION_ID=' /etc/os-release | tr -d '"' | cut -d= -f2)
  echo "centos$os_version"
else
  lsb_release -cs
fi
uname -m
grep MemTotal /proc/meminfo
cat /proc/cpuinfo
"""

INITIALIZE_UBUNTU_SCRIPT = """set -e
(id ubuntu &> /dev/null) || useradd -m ubuntu -s /bin/bash
umask 0077
temp=$(mktemp)
echo 'ubuntu ALL=(ALL) NOPASSWD:ALL' > $temp
install -m 0440 $temp /etc/sudoers.d/90-juju-ubuntu
rm $temp
su ubuntu -c 'install -D -m 0600 /dev/null ~/.ssh/authorized_keys'
export authorized_keys="{}"
if [ ! -z "$authorized_keys" ]; then
    su ubuntu -c 'echo $authorized_keys >> ~/.ssh/authorized_keys'
fi
"""

IPTABLES_SCRIPT = """#!/bin/bash
set -e
apt-get update
DEBIAN_FRONTEND=noninteractive apt-get install -yqq iptables-persistent
iptables -t nat -A OUTPUT -p tcp -d {} -j DNAT --to-destination {}
netfilter-persistent save
"""

class SSHProvisioner:
    """Provision a manually created machine via SSH."""

    def __init__(self, user, host, private_key_path, log=None):

        self.host = host
        self.user = user
        self.private_key_path = private_key_path

        if log:
            self.log = log
        else:
            self.log = logging.getLogger(__name__)

    def _get_ssh_client(self, host=None, user=None, private_key_path=None):
        """Return a connected Paramiko ssh object.

        :param str host: The host to connect to.
        :param str user: The user to connect as.
        :param str key: The private key to authenticate with.

        :return: object: A paramiko.SSHClient
        :raises: :class:`paramiko.ssh_exception.SSHException` if the
            connection failed
        """

        if not host:
            host = self.host

        if not user:
            user = self.user

        if not private_key_path:
            private_key_path = self.private_key_path

        ssh = paramiko.SSHClient()
        ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())

        pkey = None

        # Read the private key into a paramiko.RSAKey
        if os.path.exists(private_key_path):
            with open(private_key_path, 'r') as f:
                pkey = paramiko.RSAKey.from_private_key(f)

        #######################################################################
        # There is a bug in some versions of OpenSSH 4.3 (CentOS/RHEL5) where #
        # the server may not send the SSH_MSG_USERAUTH_BANNER message except  #
        # when responding to an auth_none request. For example, paramiko will #
        # attempt to use password authentication when a password is set, but  #
        # the server could deny that, instead requesting keyboard-interactive.#
        # The hack to workaround this is to attempt a reconnect, which will   #
        # receive the right banner, and authentication can proceed. See the   #
        # following for more info:                                            #
        # https://github.com/paramiko/paramiko/issues/432                     #
        # https://github.com/paramiko/paramiko/pull/438                       #
        #######################################################################

        retry = 10
        attempts = 0
        delay = 15
        while attempts <= retry:
            try:
                attempts += 1

                # Attempt to establish a SSH connection
                ssh.connect(
                    host,
                    port=22,
                    username=user,
                    pkey=pkey,
                    # allow_agent=False,
                    # look_for_keys=False,
                )
                break
            except paramiko.ssh_exception.SSHException as e:
                if 'Error reading SSH protocol banner' == str(e):
                    # Once more, with feeling
                    ssh.connect(host, port=22, username=user, pkey=pkey)
                else:
                    # Reraise the original exception
                    self.log.debug("Unhandled exception caught: {}".format(e))
                    raise e
            except Exception as e:
                if 'Unable to connect to port' in str(e):
                    self.log.debug("Waiting for VM to boot, sleeping {} seconds".format(delay))
                    if attempts > retry:
                        raise e
                    else:
                        time.sleep(delay)
                        # Slowly back off the retry
                        delay += 15
                else:
                    self.log.debug(e)
                    raise e
        return ssh

    def _run_command(self, ssh, cmd, pty=True):
        """Run a command remotely via SSH.

        :param object ssh: The SSHClient
        :param str cmd: The command to execute
        :param list cmd: The `shlex.split` command to execute
        :param bool pty: Whether to allocate a pty

        :return: tuple: The stdout and stderr of the command execution
        :raises: :class:`CalledProcessError` if the command fails
        """

        if isinstance(cmd, str):
            cmd = shlex.split(cmd)

        if type(cmd) is not list:
            cmd = [cmd]

        cmds = ' '.join(cmd)
        stdin, stdout, stderr = ssh.exec_command(cmds, get_pty=pty)
        retcode = stdout.channel.recv_exit_status()

        if retcode > 0:
            output = stderr.read().strip()
            raise CalledProcessError(returncode=retcode, cmd=cmd,
                                     output=output)
        return (
            stdout.read().decode('utf-8').strip(),
            stderr.read().decode('utf-8').strip()
        )

    def _init_ubuntu_user(self):
        """Initialize the ubuntu user.

        :return: bool: If the initialization was successful
        :raises: :class:`paramiko.ssh_exception.AuthenticationException`
            if the authentication fails
        """
        ssh = None
        try:
            # Run w/o allocating a pty, so we fail if sudo prompts for a passwd
            ssh = self._get_ssh_client()
            stdout, stderr = self._run_command(ssh, "sudo -n true", pty=False)
        except paramiko.ssh_exception.AuthenticationException:
            raise n2vc.exceptions.AuthenticationFailed(self.user)
        except paramiko.ssh_exception.NoValidConnectionsError:
            raise n2vc.exceptions.NoRouteToHost(self.host)
        finally:
            if ssh:
                ssh.close()

        # Infer the public key
        public_key = None
        public_key_path = "{}.pub".format(self.private_key_path)

        if not os.path.exists(public_key_path):
            raise FileNotFoundError(
                "Public key '{}' doesn't exist.".format(public_key_path)
            )

        with open(public_key_path, "r") as f:
            public_key = f.readline()

        script = INITIALIZE_UBUNTU_SCRIPT.format(public_key)

        try:
            ssh = self._get_ssh_client()

            self._run_command(
                ssh,
                ["sudo", "/bin/bash -c " + shlex.quote(script)],
                pty=True
            )
        except paramiko.ssh_exception.AuthenticationException as e:
            raise e
        finally:
            ssh.close()

        return True

    def _detect_hardware_and_os(self, ssh):
        """Detect the target hardware capabilities and OS series.

        :param object ssh: The SSHClient
        :return: str: A raw string containing OS and hardware information.
        """

        info = {
            'series': '',
            'arch': '',
            'cpu-cores': '',
            'mem': '',
        }

        stdout, stderr = self._run_command(
            ssh,
            ["sudo", "/bin/bash -c " + shlex.quote(DETECTION_SCRIPT)],
            pty=True,
        )

        lines = stdout.split("\n")

        # Remove extraneous line if DNS resolution of hostname famils
        # i.e. sudo: unable to resolve host test-1-mgmtvm-1: Connection timed out
        if 'unable to resolve host' in lines[0]:
            lines = lines[1:]

        info['series'] = lines[0].strip()
        info['arch'] = normalize_arch(lines[1].strip())

        memKb = re.split(r'\s+', lines[2])[1]

        # Convert megabytes -> kilobytes
        info['mem'] = round(int(memKb) / 1024)

        # Detect available CPUs
        recorded = {}
        for line in lines[3:]:
            physical_id = ""

            if line.find("physical id") == 0:
                physical_id = line.split(":")[1].strip()
            elif line.find("cpu cores") == 0:
                cores = line.split(":")[1].strip()

                if physical_id not in recorded.keys():
                    info['cpu-cores'] += cores
                    recorded[physical_id] = True

        return info

    def provision_machine(self):
        """Perform the initial provisioning of the target machine.

        :return: bool: The client.AddMachineParams
        :raises: :class:`paramiko.ssh_exception.AuthenticationException`
            if the upload fails
        """
        params = client.AddMachineParams()

        if self._init_ubuntu_user():
            try:
                ssh = self._get_ssh_client()

                hw = self._detect_hardware_and_os(ssh)
                params.series = hw['series']
                params.instance_id = "manual:{}".format(self.host)
                params.nonce = "manual:{}:{}".format(
                    self.host,
                    str(uuid.uuid4()),  # a nop for Juju w/manual machines
                )
                params.hardware_characteristics = {
                    'arch': hw['arch'],
                    'mem': int(hw['mem']),
                    'cpu-cores': int(hw['cpu-cores']),
                }
                params.addresses = [{
                    'value': self.host,
                    'type': 'ipv4',
                    'scope': 'public',
                }]

            except paramiko.ssh_exception.AuthenticationException as e:
                raise e
            finally:
                ssh.close()

        return params

    async def install_agent(self, connection, nonce, machine_id, api):
        """
        :param object connection: Connection to Juju API
        :param str nonce: The nonce machine specification
        :param str machine_id: The id assigned to the machine

        :return: bool: If the initialization was successful
        """
        # The path where the Juju agent should be installed.
        data_dir = "/var/lib/juju"

        # Disabling this prevents `apt-get update` from running initially, so
        # charms will fail to deploy
        disable_package_commands = False

        client_facade = client.ClientFacade.from_connection(connection)
        results = await client_facade.ProvisioningScript(
            data_dir=data_dir,
            disable_package_commands=disable_package_commands,
            machine_id=machine_id,
            nonce=nonce,
        )

        """Get the IP of the controller

        Parse the provisioning script, looking for the first apiaddress.

        Example:
            apiaddresses:
            - 10.195.8.2:17070
            - 127.0.0.1:17070
            - '[::1]:17070'
        """
        m = re.search('apiaddresses:\n- (\d+\.\d+\.\d+\.\d+):17070', results.script)
        apiaddress = m.group(1)

        """Add IP Table rule

        In order to route the traffic to the private ip of the Juju controller
        we use a DNAT rule to tell the machine that the destination for the
        private address is the public address of the machine where the Juju
        controller is running in LXD. That machine will have a complimentary
        iptables rule, routing traffic to the appropriate LXD container.
        """

        script = IPTABLES_SCRIPT.format(apiaddress, api)

        # Run this in a retry loop, because dpkg may be running and cause the
        # script to fail.
        retry = 10
        attempts = 0
        delay = 15

        while attempts <= retry:
            try:
                attempts += 1

                self._run_configure_script(script)
                break
            except Exception as e:
                    self.log.debug("Waiting for dpkg, sleeping {} seconds".format(delay))
                    if attempts > retry:
                        raise e
                    else:
                        time.sleep(delay)
                        # Slowly back off the retry
                        delay += 15

        # self.log.debug("Running configure script")
        self._run_configure_script(results.script)
        # self.log.debug("Configure script finished")


    def _run_configure_script(self, script: str):
        """Run the script to install the Juju agent on the target machine.

        :param str script: The script returned by the ProvisioningScript API
        :raises: :class:`paramiko.ssh_exception.AuthenticationException`
            if the upload fails
        """
        _, tmpFile = tempfile.mkstemp()
        with open(tmpFile, 'w') as f:
            f.write(script)
        try:
            # get ssh client
            ssh = self._get_ssh_client(
                user="ubuntu",
            )

            # copy the local copy of the script to the remote machine
            sftp = paramiko.SFTPClient.from_transport(ssh.get_transport())
            sftp.put(
                tmpFile,
                tmpFile,
            )

            # run the provisioning script
            stdout, stderr = self._run_command(
                ssh,
                "sudo /bin/bash {}".format(tmpFile),
            )

        except paramiko.ssh_exception.AuthenticationException as e:
            raise e
        finally:
            os.remove(tmpFile)
            ssh.close()