# -*- coding: utf-8 -*- #
# Copyright 2016 Google LLC. 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.

"""Connects to a serial port gateway using SSH."""


import sys

from googlecloudsdk.api_lib.compute import base_classes
from googlecloudsdk.api_lib.compute import daisy_utils
from googlecloudsdk.calliope import arg_parsers
from googlecloudsdk.calliope import base
from googlecloudsdk.command_lib.compute import completers
from googlecloudsdk.command_lib.compute import flags
from googlecloudsdk.command_lib.compute import scope as compute_scope
from googlecloudsdk.command_lib.compute import ssh_utils
from googlecloudsdk.command_lib.compute.instances import flags as instance_flags
from googlecloudsdk.command_lib.util.ssh import ssh
from googlecloudsdk.core import log
from googlecloudsdk.core import properties
from googlecloudsdk.core import requests


SERIAL_PORT_HELP = (
    'https://cloud.google.com/compute/docs/'
    'instances/interacting-with-serial-console'
)
CONNECTION_PORT = '9600'

# Regional ISPAC Constants and Templates

REGIONAL_SERIAL_PORT_GATEWAY_TEMPLATE = '{0}-ssh-serialport.{1}'

REGIONAL_HOST_KEY_URL_TEMPLATE = (
    'https://www.gstatic.com/vm_serial_port/{0}/{0}.pub'
)
REGIONAL_HOST_KEY_URL_TEMPLATE_V2 = (
    'https://www.gstatic.com/vm_serial_port_public_keys/{0}/{0}.pub'
)


@base.UniverseCompatible
@base.ReleaseTracks(base.ReleaseTrack.GA, base.ReleaseTrack.PREVIEW)
class ConnectToSerialPort(base.Command):
  """Connect to the serial port of an instance.

  *{command}* allows users to connect to, and interact with, a VM's
  virtual serial port using ssh as the secure, authenticated transport
  protocol.

  The user must first enable serial port access to a given VM by setting
  the 'serial-port-enable=true' metadata key-value pair. Setting
  'serial-port-enable' on the project-level metadata enables serial port
  access to all VMs in the project.

  This command uses the same SSH key pair as the `gcloud compute ssh`
  command and also ensures that the user's public SSH key is present in
  the project's metadata. If the user does not have a public SSH key,
  one is generated using ssh-keygen.

  ## EXAMPLES
  To connect to the serial port of the instance 'my-instance' in zone
  'us-central1-f', run:

    $ {command} my-instance --zone=us-central1-f
  """

  category = base.TOOLS_CATEGORY
  use_v2_host_key_endpoint = True

  @staticmethod
  def Args(parser):
    """Set up arguments for this command.

    Args:
      parser: An argparse.ArgumentParser.
    """
    ssh_utils.BaseSSHHelper.Args(parser)

    parser.add_argument(
        '--dry-run',
        action='store_true',
        help=(
            'If provided, the ssh command is printed to standard out '
            'rather than being executed.'
        ),
    )

    parser.add_argument(
        'user_host',
        completer=completers.InstancesCompleter,
        metavar='[USER@]INSTANCE',
        help="""\
        Specifies the user/instance for the serial port connection.

        ``USER'' specifies the username to authenticate as. If omitted,
        the current OS user is selected.
        """,
    )

    parser.add_argument(
        '--port',
        default=1,
        help="""\
        The number of the requested serial port. Can be 1-4, default is 1.

        Instances can support up to four serial ports. By default, this
        command will connect to the first serial port. Setting this flag
        will connect to the requested serial port.
        """,
    )

    parser.add_argument(
        '--extra-args',
        type=arg_parsers.ArgDict(min_length=1),
        default={},
        metavar='KEY=VALUE',
        help="""\
        Optional arguments can be passed to the serial port connection by
        passing key-value pairs to this flag, such as max-connections=N or
        replay-lines=N. See {0} for additional options.
        """.format(SERIAL_PORT_HELP),
    )

    parser.add_argument(
        '--location',
        help="""\
        If provided, the region in which the serial console connection will
        occur. Must be the region of the VM to connect to.
        """,
    )

    flags.AddZoneFlag(
        parser, resource_type='instance', operation_type='connect to'
    )

    ssh_utils.AddSSHKeyExpirationArgs(parser)

  def Run(self, args):
    """See ssh_utils.BaseSSHCommand.Run."""
    holder = base_classes.ComputeApiHolder(self.ReleaseTrack())
    client = holder.client

    ssh_helper = ssh_utils.BaseSSHHelper()
    ssh_helper.Run(args)
    ssh_helper.keys.EnsureKeysExist(
        args.force_key_file_overwrite, allow_passphrase=True
    )

    remote = ssh.Remote.FromArg(args.user_host)
    if not remote:
      raise ssh_utils.ArgumentError(
          'Expected argument of the form [USER@]INSTANCE. Received [{0}].'
          .format(args.user_host)
      )
    if not remote.user:
      remote.user = ssh.GetDefaultSshUsername()
    public_key = ssh_helper.keys.GetPublicKey().ToEntry(include_comment=True)

    instance_ref = instance_flags.SSH_INSTANCE_RESOLVER.ResolveResources(
        [remote.host],
        compute_scope.ScopeEnum.ZONE,
        args.zone,
        holder.resources,
        scope_lister=instance_flags.GetInstanceZoneScopeLister(client),
    )[0]

    # Attempt to determine the region from the zone flag if possible.
    if not args.location:
      location = daisy_utils.GetRegionFromZone(instance_ref.zone)
      log.info('Determined region from zone: {0}'.format(location))
    else:
      location = args.location

    gateway = REGIONAL_SERIAL_PORT_GATEWAY_TEMPLATE.format(
        location, properties.GetUniverseDomain()
    )
    hostkey_url = REGIONAL_HOST_KEY_URL_TEMPLATE.format(location)
    hostkey_url_v2 = REGIONAL_HOST_KEY_URL_TEMPLATE_V2.format(location)
    log.info('Connecting to serialport via server in {0}'.format(location))

    hostname = '[{0}]:{1}'.format(gateway, CONNECTION_PORT)
    # Update google_compute_known_hosts file with published host key
    known_hosts = ssh.KnownHosts.FromDefaultFile()

    def _GetHostKey(endpoint):
      """Get host key from endpoint."""
      session = requests.GetSession()
      resp = session.get(endpoint)
      log.info('http_response: {0}'.format(resp.text))

      host_keys = []
      if resp.ok:
        # There can be multiple public host keys for the same region,
        # in the response separated by newlines.
        retrieved_host_keys = (
            resp.text.strip().split('\n')
        )
        for host_key in retrieved_host_keys:
          host_keys.append(host_key)
        log.info(
            'Successfully acquired hostkey for {0} from {1}'.format(
                gateway, endpoint
            )
        )
      else:
        log.warning(
            'Failed to acquire hostkey for {0} from {1}'.format(
                gateway, endpoint
            )
        )
      return host_keys

    host_keys = []
    if self.use_v2_host_key_endpoint:
      host_keys.extend(_GetHostKey(hostkey_url_v2))
    host_keys.extend(_GetHostKey(hostkey_url))

    if host_keys:
      if self.use_v2_host_key_endpoint:
        known_hosts.AddMultiple(hostname, host_keys, overwrite=True)
      else:
        known_hosts.Add(hostname, host_keys[0], overwrite=True)
      known_hosts.Write()
      log.info('Successfully written hostkey for {0}'.format(gateway))
    elif known_hosts.ContainsAlias(hostname):
      log.warning(
          'Unable to download and update Host Key for [{0}]'
          ' . Attempting to connect using existing Host Key in [{1}]. If'
          ' the connection fails, please try again to update the Host Key.'
          .format(gateway, known_hosts.file_path)
      )
    else:
      log.warning(
          'Unable to download Host Key for [{0}]. No Host'
          ' Key found in known_hosts file [{1}]. gcloud does not have a'
          ' fallback Host Key and will therefore terminate the connection'
          ' attempt. If the problem persists, try updating gcloud and'
          ' connecting again.'.format(gateway, known_hosts.file_path)
      )
      # We shouldn't allow a connection without the correct host key
      return

    instance = ssh_helper.GetInstance(client, instance_ref)
    project = ssh_helper.GetProject(client, instance_ref.project)
    expiration, expiration_micros = ssh_utils.GetSSHKeyExpirationFromArgs(args)

    oslogin_state = ssh.GetOsloginState(
        instance,
        project,
        remote.user,
        public_key,
        expiration_micros,
        self.ReleaseTrack(),
        messages=holder.client.messages,
    )
    remote.user = oslogin_state.user

    # Determine the serial user, host tuple (remote)
    port = 'port={0}'.format(args.port)
    constructed_username_list = [
        instance_ref.project,
        instance_ref.zone,
        instance_ref.Name(),
        remote.user,
        port,
    ]

    if not args.dry_run:
      source = 'source={0}'.format('gcloud')
      constructed_username_list.append(source)

    if args.extra_args:
      for k, v in args.extra_args.items():
        constructed_username_list.append('{0}={1}'.format(k, v))
    serial_user = '.'.join(constructed_username_list)
    serial_remote = ssh.Remote(gateway, user=serial_user)

    identity_file = ssh_helper.keys.key_file
    options = ssh_helper.GetConfig(hostname, strict_host_key_checking='yes')
    del options['HostKeyAlias']
    options['ControlPath'] = 'none'
    cmd = ssh.SSHCommand(
        serial_remote,
        identity_file=identity_file,
        port=CONNECTION_PORT,
        options=options,
    )
    if args.dry_run:
      log.out.Print(' '.join(cmd.Build(ssh_helper.env)))
      return
    if not oslogin_state.oslogin_enabled:
      ssh_helper.EnsureSSHKeyExists(
          client, remote.user, instance, project, expiration
      )

    # TODO(b/35355795): Don't force connect in general.
    # At a minimum, avoid injecting 'y' if PuTTY will prompt for a 2FA
    # authentication method (since we know that won't work), or if the user has
    # disabled the property.
    putty_force_connect = (
        not oslogin_state.oslogin_2fa_enabled
        and properties.VALUES.ssh.putty_force_connect.GetBool()
    )

    # Don't wait for the instance to become SSHable. We are not connecting to
    # the instance itself through SSH, so the instance doesn't need to have
    # fully booted to connect to the serial port. Also, ignore exit code 255,
    # since the normal way to terminate the serial port connection is ~. and
    # that causes ssh to exit with 255.
    try:
      return_code = cmd.Run(
          ssh_helper.env, putty_force_connect=putty_force_connect
      )
    except ssh.CommandError:
      return_code = 255
    if return_code:
      sys.exit(return_code)


# Alpha and Beta ISPAC don't currently do anything different, but this method
# has been left in for convenience with any future alpha/beta features.
@base.ReleaseTracks(base.ReleaseTrack.BETA, base.ReleaseTrack.ALPHA)
class ConnectToSerialPortAlphaBeta(ConnectToSerialPort):
  """Connect to the serial port of an instance.

  *{command}* allows users to connect to, and interact with, a VM's
  virtual serial port using ssh as the secure, authenticated transport
  protocol.

  The user must first enable serial port access to a given VM by setting
  the 'serial-port-enable=true' metadata key-value pair. Setting
  'serial-port-enable' on the project-level metadata enables serial port
  access to all VMs in the project.

  This command uses the same SSH key pair as the `gcloud compute ssh`
  command and also ensures that the user's public SSH key is present in
  the project's metadata. If the user does not have a public SSH key,
  one is generated using ssh-keygen.

  ## EXAMPLES
  To connect to the serial port of the instance 'my-instance' in zone
  'us-central1-f', run:

    $ {command} my-instance --zone=us-central1-f
  """

  @classmethod
  def Args(cls, parser):
    cls.use_v2_host_key_endpoint = True
    super(ConnectToSerialPortAlphaBeta, cls).Args(parser)
