# Copyright 2017, David Wilson
#
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from __future__ import absolute_import
from __future__ import unicode_literals

"""
Mitogen extends Ansible's target configuration mechanism in several ways that
require some care:

* Per-task configurables in Ansible like ansible_python_interpreter are
  connection-layer configurables in Mitogen. They must be extracted during each
  task execution to form the complete connection-layer configuration.

* Mitogen has extra configurables not supported by Ansible at all, such as
  mitogen_ssh_debug_level. These are extracted the same way as
  ansible_python_interpreter.

* Mitogen allows connections to be delegated to other machines. Ansible has no
  internal framework for this, and so Mitogen must figure out a delegated
  connection configuration all on its own. It cannot reuse much of the Ansible
  machinery for building a connection configuration, as that machinery is
  deeply spread out and hard-wired to expect Ansible's usual mode of operation.

For normal and delegate_to connections, Ansible's PlayContext is reused where
possible to maximize compatibility, but for proxy hops, configurations are
built up using the HostVars magic class to call VariableManager.get_vars()
behind the scenes on our behalf. Where Ansible has multiple sources of a
configuration item, for example, ansible_ssh_extra_args, Mitogen must (ideally
perfectly) reproduce how Ansible arrives at its value, without using mechanisms
that are hard-wired or change across Ansible versions.

That is what this file is for. It exports two spec classes, one that takes all
information from PlayContext, and another that takes (almost) all information
from HostVars.
"""

import abc
import os
import ansible.utils.shlex
import ansible.constants as C

from ansible.module_utils.six import with_metaclass


import mitogen.core


def parse_python_path(s):
    """
    Given the string set for ansible_python_interpeter, parse it using shell
    syntax and return an appropriate argument vector.
    """
    if s:
        return ansible.utils.shlex.shlex_split(s)


def optional_secret(value):
    """
    Wrap `value` in :class:`mitogen.core.Secret` if it is not :data:`None`,
    otherwise return :data:`None`.
    """
    if value is not None:
        return mitogen.core.Secret(value)


def first_true(it, default=None):
    """
    Return the first truthy element from `it`.
    """
    for elem in it:
        if elem:
            return elem
    return default


class Spec(with_metaclass(abc.ABCMeta, object)):
    """
    A source for variables that comprise a connection configuration.
    """

    @abc.abstractmethod
    def transport(self):
        """
        The name of the Ansible plug-in implementing the connection.
        """

    @abc.abstractmethod
    def inventory_name(self):
        """
        The name of the target being connected to as it appears in Ansible's
        inventory.
        """

    @abc.abstractmethod
    def remote_addr(self):
        """
        The network address of the target, or for container and other special
        targets, some other unique identifier.
        """

    @abc.abstractmethod
    def remote_user(self):
        """
        The username of the login account on the target.
        """

    @abc.abstractmethod
    def password(self):
        """
        The password of the login account on the target.
        """

    @abc.abstractmethod
    def become(self):
        """
        :data:`True` if privilege escalation should be active.
        """

    @abc.abstractmethod
    def become_method(self):
        """
        The name of the Ansible become method to use.
        """

    @abc.abstractmethod
    def become_user(self):
        """
        The username of the target account for become.
        """

    @abc.abstractmethod
    def become_pass(self):
        """
        The password of the target account for become.
        """

    @abc.abstractmethod
    def port(self):
        """
        The port of the login service on the target machine.
        """

    @abc.abstractmethod
    def python_path(self):
        """
        Path to the Python interpreter on the target machine.
        """

    @abc.abstractmethod
    def private_key_file(self):
        """
        Path to the SSH private key file to use to login.
        """

    @abc.abstractmethod
    def ssh_executable(self):
        """
        Path to the SSH executable.
        """

    @abc.abstractmethod
    def timeout(self):
        """
        The generic timeout for all connections.
        """

    @abc.abstractmethod
    def ansible_ssh_timeout(self):
        """
        The SSH-specific timeout for a connection.
        """

    @abc.abstractmethod
    def ssh_args(self):
        """
        The list of additional arguments that should be included in an SSH
        invocation.
        """

    @abc.abstractmethod
    def become_exe(self):
        """
        The path to the executable implementing the become method on the remote
        machine.
        """

    @abc.abstractmethod
    def sudo_args(self):
        """
        The list of additional arguments that should be included in a become
        invocation.
        """
        # TODO: split out into sudo_args/become_args.

    @abc.abstractmethod
    def mitogen_via(self):
        """
        The value of the mitogen_via= variable for this connection. Indicates
        the connection should be established via an intermediary.
        """

    @abc.abstractmethod
    def mitogen_kind(self):
        """
        The type of container to use with the "setns" transport.
        """

    @abc.abstractmethod
    def mitogen_docker_path(self):
        """
        The path to the "docker" program for the 'docker' transport.
        """

    @abc.abstractmethod
    def mitogen_kubectl_path(self):
        """
        The path to the "kubectl" program for the 'docker' transport.
        """

    @abc.abstractmethod
    def mitogen_lxc_path(self):
        """
        The path to the "lxc" program for the 'lxd' transport.
        """

    @abc.abstractmethod
    def mitogen_lxc_attach_path(self):
        """
        The path to the "lxc-attach" program for the 'lxc' transport.
        """

    @abc.abstractmethod
    def mitogen_lxc_info_path(self):
        """
        The path to the "lxc-info" program for the 'lxc' transport.
        """

    @abc.abstractmethod
    def mitogen_machinectl_path(self):
        """
        The path to the "machinectl" program for the 'setns' transport.
        """

    @abc.abstractmethod
    def mitogen_ssh_debug_level(self):
        """
        The SSH debug level.
        """

    @abc.abstractmethod
    def mitogen_ssh_compression(self):
        """
        Whether SSH compression is enabled.
        """

    @abc.abstractmethod
    def extra_args(self):
        """
        Connection-specific arguments.
        """


class PlayContextSpec(Spec):
    """
    PlayContextSpec takes almost all its information as-is from Ansible's
    PlayContext. It is used for normal connections and delegate_to connections,
    and should always be accurate.
    """
    def __init__(self, connection, play_context, transport, inventory_name):
        self._connection = connection
        self._play_context = play_context
        self._transport = transport
        self._inventory_name = inventory_name

    def transport(self):
        return self._transport

    def inventory_name(self):
        return self._inventory_name

    def remote_addr(self):
        return self._play_context.remote_addr

    def remote_user(self):
        return self._play_context.remote_user

    def become(self):
        return self._play_context.become

    def become_method(self):
        return self._play_context.become_method

    def become_user(self):
        return self._play_context.become_user

    def become_pass(self):
        return optional_secret(self._play_context.become_pass)

    def password(self):
        return optional_secret(self._play_context.password)

    def port(self):
        return self._play_context.port

    def python_path(self):
        return parse_python_path(
            self._connection.get_task_var('ansible_python_interpreter')
        )

    def private_key_file(self):
        return self._play_context.private_key_file

    def ssh_executable(self):
        return self._play_context.ssh_executable

    def timeout(self):
        return self._play_context.timeout

    def ansible_ssh_timeout(self):
        return (
            self._connection.get_task_var('ansible_timeout') or
            self._connection.get_task_var('ansible_ssh_timeout') or
            self.timeout()
        )

    def ssh_args(self):
        return [
            mitogen.core.to_text(term)
            for s in (
                getattr(self._play_context, 'ssh_args', ''),
                getattr(self._play_context, 'ssh_common_args', ''),
                getattr(self._play_context, 'ssh_extra_args', '')
            )
            for term in ansible.utils.shlex.shlex_split(s or '')
        ]

    def become_exe(self):
        return self._play_context.become_exe

    def sudo_args(self):
        return [
            mitogen.core.to_text(term)
            for term in ansible.utils.shlex.shlex_split(
                first_true((
                    self._play_context.become_flags,
                    self._play_context.sudo_flags,
                    # Ansible 2.3.
                    getattr(C, 'DEFAULT_BECOME_FLAGS', ''),
                    getattr(C, 'DEFAULT_SUDO_FLAGS', '')
                ), default='')
            )
        ]

    def mitogen_via(self):
        return self._connection.get_task_var('mitogen_via')

    def mitogen_kind(self):
        return self._connection.get_task_var('mitogen_kind')

    def mitogen_docker_path(self):
        return self._connection.get_task_var('mitogen_docker_path')

    def mitogen_kubectl_path(self):
        return self._connection.get_task_var('mitogen_kubectl_path')

    def mitogen_lxc_path(self):
        return self._connection.get_task_var('mitogen_lxc_path')

    def mitogen_lxc_attach_path(self):
        return self._connection.get_task_var('mitogen_lxc_attach_path')

    def mitogen_lxc_info_path(self):
        return self._connection.get_task_var('mitogen_lxc_info_path')

    def mitogen_machinectl_path(self):
        return self._connection.get_task_var('mitogen_machinectl_path')

    def mitogen_ssh_debug_level(self):
        return self._connection.get_task_var('mitogen_ssh_debug_level')

    def mitogen_ssh_compression(self):
        return self._connection.get_task_var('mitogen_ssh_compression')

    def extra_args(self):
        return self._connection.get_extra_args()


class MitogenViaSpec(Spec):
    """
    MitogenViaSpec takes most of its information from the HostVars of the
    running task. HostVars is a lightweight wrapper around VariableManager, so
    it is better to say that VariableManager.get_vars() is the ultimate source
    of MitogenViaSpec's information.

    Due to this, mitogen_via= hosts must have all their configuration
    information represented as host and group variables. We cannot use any
    per-task configuration, as all that data belongs to the real target host.

    Ansible uses all kinds of strange historical logic for calculating
    variables, including making their precedence configurable. MitogenViaSpec
    must ultimately reimplement all of that logic. It is likely that if you are
    having a configruation problem with connection delegation, the answer to
    your problem lies in the method implementations below!
    """
    def __init__(self, inventory_name, host_vars,
                 become_method, become_user):
        self._inventory_name = inventory_name
        self._host_vars = host_vars
        self._become_method = become_method
        self._become_user = become_user

    def transport(self):
        return (
            self._host_vars.get('ansible_connection') or
            C.DEFAULT_TRANSPORT
        )

    def inventory_name(self):
        return self._inventory_name

    def remote_addr(self):
        return (
            self._host_vars.get('ansible_host') or
            self._inventory_name
        )

    def remote_user(self):
        return (
            self._host_vars.get('ansible_user') or
            self._host_vars.get('ansible_ssh_user') or
            C.DEFAULT_REMOTE_USER
        )

    def become(self):
        return bool(self._become_user)

    def become_method(self):
        return self._become_method or C.DEFAULT_BECOME_METHOD

    def become_user(self):
        return self._become_user

    def become_pass(self):
        return optional_secret(
            # TODO: Might have to come from PlayContext.
            self._host_vars.get('ansible_become_password') or
            self._host_vars.get('ansible_become_pass')
        )

    def password(self):
        return optional_secret(
            # TODO: Might have to come from PlayContext.
            self._host_vars.get('ansible_ssh_pass') or
            self._host_vars.get('ansible_password')
        )

    def port(self):
        return (
            self._host_vars.get('ansible_port') or
            C.DEFAULT_REMOTE_PORT
        )

    def python_path(self):
        return parse_python_path(
            self._host_vars.get('ansible_python_interpreter')
            # This variable has no default for remote hosts. For local hosts it
            # is sys.executable.
        )

    def private_key_file(self):
        # TODO: must come from PlayContext too.
        return (
            self._host_vars.get('ansible_ssh_private_key_file') or
            self._host_vars.get('ansible_private_key_file') or
            C.DEFAULT_PRIVATE_KEY_FILE
        )

    def ssh_executable(self):
        return (
            self._host_vars.get('ansible_ssh_executable') or
            C.ANSIBLE_SSH_EXECUTABLE
        )

    def timeout(self):
        # TODO: must come from PlayContext too.
        return C.DEFAULT_TIMEOUT

    def ansible_ssh_timeout(self):
        return (
            self._host_vars.get('ansible_timeout') or
            self._host_vars.get('ansible_ssh_timeout') or
            self.timeout()
        )

    def ssh_args(self):
        return [
            mitogen.core.to_text(term)
            for s in (
                (
                    self._host_vars.get('ansible_ssh_args') or
                    getattr(C, 'ANSIBLE_SSH_ARGS', None) or
                    os.environ.get('ANSIBLE_SSH_ARGS')
                    # TODO: ini entry. older versions.
                ),
                (
                    self._host_vars.get('ansible_ssh_common_args') or
                    os.environ.get('ANSIBLE_SSH_COMMON_ARGS')
                    # TODO: ini entry.
                ),
                (
                    self._host_vars.get('ansible_ssh_extra_args') or
                    os.environ.get('ANSIBLE_SSH_EXTRA_ARGS')
                    # TODO: ini entry.
                ),
            )
            for term in ansible.utils.shlex.shlex_split(s)
            if s
        ]

    def become_exe(self):
        return (
            self._host_vars.get('ansible_become_exe') or
            C.DEFAULT_BECOME_EXE
        )

    def sudo_args(self):
        return [
            mitogen.core.to_text(term)
            for s in (
                self._host_vars.get('ansible_sudo_flags') or '',
                self._host_vars.get('ansible_become_flags') or '',
            )
            for term in ansible.utils.shlex.shlex_split(s)
        ]

    def mitogen_via(self):
        return self._host_vars.get('mitogen_via')

    def mitogen_kind(self):
        return self._host_vars.get('mitogen_kind')

    def mitogen_docker_path(self):
        return self._host_vars.get('mitogen_docker_path')

    def mitogen_kubectl_path(self):
        return self._host_vars.get('mitogen_kubectl_path')

    def mitogen_lxc_path(self):
        return self.host_vars.get('mitogen_lxc_path')

    def mitogen_lxc_attach_path(self):
        return self._host_vars.get('mitogen_lxc_attach_path')

    def mitogen_lxc_info_path(self):
        return self._host_vars.get('mitogen_lxc_info_path')

    def mitogen_machinectl_path(self):
        return self._host_vars.get('mitogen_machinectl_path')

    def mitogen_ssh_debug_level(self):
        return self._host_vars.get('mitogen_ssh_debug_level')

    def mitogen_ssh_compression(self):
        return self._host_vars.get('mitogen_ssh_compression')

    def extra_args(self):
        return []  # TODO