# (c) 2012-2014, Michael DeHaan <michael.dehaan@gmail.com>
#
# This file is part of Ansible
#
# 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/>.

# Make coding more python3-ish
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type

import threading
import time

from collections import deque
from multiprocessing import Lock
from jinja2.exceptions import UndefinedError

from ansible import constants as C
from ansible.compat.six.moves import queue as Queue
from ansible.compat.six import iteritems, string_types
from ansible.errors import AnsibleError, AnsibleParserError, AnsibleUndefinedVariable
from ansible.executor import action_write_locks
from ansible.executor.process.worker import WorkerProcess
from ansible.executor.task_result import TaskResult
from ansible.inventory.host import Host
from ansible.inventory.group import Group
from ansible.playbook.helpers import load_list_of_blocks
from ansible.playbook.included_file import IncludedFile
from ansible.playbook.task_include import TaskInclude
from ansible.playbook.role_include import IncludeRole
from ansible.plugins import action_loader, connection_loader, filter_loader, lookup_loader, module_loader, test_loader
from ansible.template import Templar
from ansible.vars import combine_vars, strip_internal_keys
from ansible.module_utils._text import to_text


try:
    from __main__ import display
except ImportError:
    from ansible.utils.display import Display
    display = Display()

__all__ = ['StrategyBase']

# TODO: this should probably be in the plugins/__init__.py, with
#       a smarter mechanism to set all of the attributes based on
#       the loaders created there
class SharedPluginLoaderObj:
    '''
    A simple object to make pass the various plugin loaders to
    the forked processes over the queue easier
    '''
    def __init__(self):
        self.action_loader = action_loader
        self.connection_loader = connection_loader
        self.filter_loader = filter_loader
        self.test_loader   = test_loader
        self.lookup_loader = lookup_loader
        self.module_loader = module_loader


_sentinel = object()
def results_thread_main(strategy):
    while True:
        try:
            result = strategy._final_q.get()
            if type(result) == object:
                break
            else:
                strategy._results_lock.acquire()
                strategy._results.append(result)
                strategy._results_lock.release()
        except (IOError, EOFError):
            break
        except Queue.Empty:
            pass

class StrategyBase:

    '''
    This is the base class for strategy plugins, which contains some common
    code useful to all strategies like running handlers, cleanup actions, etc.
    '''

    def __init__(self, tqm):
        self._tqm               = tqm
        self._inventory         = tqm.get_inventory()
        self._workers           = tqm.get_workers()
        self._notified_handlers = tqm._notified_handlers
        self._listening_handlers = tqm._listening_handlers
        self._variable_manager  = tqm.get_variable_manager()
        self._loader            = tqm.get_loader()
        self._final_q           = tqm._final_q
        self._step              = getattr(tqm._options, 'step', False)
        self._diff              = getattr(tqm._options, 'diff', False)

        # Backwards compat: self._display isn't really needed, just import the global display and use that.
        self._display           = display

        # internal counters
        self._pending_results   = 0
        self._cur_worker        = 0

        # this dictionary is used to keep track of hosts that have
        # outstanding tasks still in queue
        self._blocked_hosts     = dict()

        self._results = deque()
        self._results_lock = threading.Condition(threading.Lock())

        # create the result processing thread for reading results in the background
        self._results_thread = threading.Thread(target=results_thread_main, args=(self,))
        self._results_thread.daemon = True
        self._results_thread.start()

    def cleanup(self):
        self._final_q.put(_sentinel)
        self._results_thread.join()

    def run(self, iterator, play_context, result=0):
        # execute one more pass through the iterator without peeking, to
        # make sure that all of the hosts are advanced to their final task.
        # This should be safe, as everything should be ITERATING_COMPLETE by
        # this point, though the strategy may not advance the hosts itself.
        [iterator.get_next_task_for_host(host) for host in self._inventory.get_hosts(iterator._play.hosts) if host.name not in self._tqm._unreachable_hosts]

        # save the failed/unreachable hosts, as the run_handlers()
        # method will clear that information during its execution
        failed_hosts      = iterator.get_failed_hosts()
        unreachable_hosts = self._tqm._unreachable_hosts.keys()

        display.debug("running handlers")
        handler_result = self.run_handlers(iterator, play_context)
        if isinstance(handler_result, bool) and not handler_result:
            result |= self._tqm.RUN_ERROR
        elif not handler_result:
            result |= handler_result

        # now update with the hosts (if any) that failed or were
        # unreachable during the handler execution phase
        failed_hosts      = set(failed_hosts).union(iterator.get_failed_hosts())
        unreachable_hosts = set(unreachable_hosts).union(self._tqm._unreachable_hosts.keys())

        # return the appropriate code, depending on the status hosts after the run
        if not isinstance(result, bool) and result != self._tqm.RUN_OK:
            return result
        elif len(unreachable_hosts) > 0:
            return self._tqm.RUN_UNREACHABLE_HOSTS
        elif len(failed_hosts) > 0:
            return self._tqm.RUN_FAILED_HOSTS
        else:
            return self._tqm.RUN_OK

    def get_hosts_remaining(self, play):
        return [host for host in self._inventory.get_hosts(play.hosts)
                if host.name not in self._tqm._failed_hosts and host.name not in self._tqm._unreachable_hosts]

    def get_failed_hosts(self, play):
        return [host for host in self._inventory.get_hosts(play.hosts) if host.name in self._tqm._failed_hosts]

    def add_tqm_variables(self, vars, play):
        '''
        Base class method to add extra variables/information to the list of task
        vars sent through the executor engine regarding the task queue manager state.
        '''
        vars['ansible_current_hosts'] = [h.name for h in self.get_hosts_remaining(play)]
        vars['ansible_failed_hosts'] = [h.name for h in self.get_failed_hosts(play)]

    def _queue_task(self, host, task, task_vars, play_context):
        ''' handles queueing the task up to be sent to a worker '''

        display.debug("entering _queue_task() for %s/%s" % (host.name, task.action))

        # Add a write lock for tasks.
        # Maybe this should be added somewhere further up the call stack but
        # this is the earliest in the code where we have task (1) extracted
        # into its own variable and (2) there's only a single code path
        # leading to the module being run.  This is called by three
        # functions: __init__.py::_do_handler_run(), linear.py::run(), and
        # free.py::run() so we'd have to add to all three to do it there.
        # The next common higher level is __init__.py::run() and that has
        # tasks inside of play_iterator so we'd have to extract them to do it
        # there.

        if task.action not in action_write_locks.action_write_locks:
            display.debug('Creating lock for %s' % task.action)
            action_write_locks.action_write_locks[task.action] = Lock()

        # and then queue the new task
        try:

            # create a dummy object with plugin loaders set as an easier
            # way to share them with the forked processes
            shared_loader_obj = SharedPluginLoaderObj()

            queued = False
            starting_worker = self._cur_worker
            while True:
                (worker_prc, rslt_q) = self._workers[self._cur_worker]
                if worker_prc is None or not worker_prc.is_alive():
                    worker_prc = WorkerProcess(self._final_q, task_vars, host, task, play_context, self._loader, self._variable_manager, shared_loader_obj)
                    self._workers[self._cur_worker][0] = worker_prc
                    worker_prc.start()
                    display.debug("worker is %d (out of %d available)" % (self._cur_worker+1, len(self._workers)))
                    queued = True
                self._cur_worker += 1
                if self._cur_worker >= len(self._workers):
                    self._cur_worker = 0
                if queued:
                    break
                elif self._cur_worker == starting_worker:
                    time.sleep(0.0001)

            self._pending_results += 1
        except (EOFError, IOError, AssertionError) as e:
            # most likely an abort
            display.debug("got an error while queuing: %s" % e)
            return
        display.debug("exiting _queue_task() for %s/%s" % (host.name, task.action))

    def _process_pending_results(self, iterator, one_pass=False, max_passes=None):
        '''
        Reads results off the final queue and takes appropriate action
        based on the result (executing callbacks, updating state, etc.).
        '''

        ret_results = []

        def get_original_host(host_name):
            host_name = to_text(host_name)
            if host_name in self._inventory._hosts_cache:
                return self._inventory._hosts_cache[host_name]
            else:
                return self._inventory.get_host(host_name)

        def search_handler_blocks(handler_name, handler_blocks):
            for handler_block in handler_blocks:
                for handler_task in handler_block.block:
                    if handler_task.name:
                        handler_vars = self._variable_manager.get_vars(loader=self._loader, play=iterator._play, task=handler_task)
                        templar = Templar(loader=self._loader, variables=handler_vars)
                        try:
                            # first we check with the full result of get_name(), which may
                            # include the role name (if the handler is from a role). If that
                            # is not found, we resort to the simple name field, which doesn't
                            # have anything extra added to it.
                            target_handler_name = templar.template(handler_task.name)
                            if target_handler_name == handler_name:
                                return handler_task
                            else:
                                target_handler_name = templar.template(handler_task.get_name())
                                if target_handler_name == handler_name:
                                    return handler_task
                        except (UndefinedError, AnsibleUndefinedVariable):
                            # We skip this handler due to the fact that it may be using
                            # a variable in the name that was conditionally included via
                            # set_fact or some other method, and we don't want to error
                            # out unnecessarily
                            continue
                    else:
                        # if the handler name is not set, we check via the handlers uuid.
                        # this is mainly used by listening handlers only
                        if handler_name == handler_task._uuid:
                            return handler_task
            return None

        def parent_handler_match(target_handler, handler_name):
            if target_handler:
                if isinstance(target_handler, (TaskInclude, IncludeRole)):
                    try:
                        handler_vars = self._variable_manager.get_vars(loader=self._loader, play=iterator._play, task=target_handler)
                        templar = Templar(loader=self._loader, variables=handler_vars)
                        target_handler_name = templar.template(target_handler.name)
                        if target_handler_name == handler_name:
                            return True
                        else:
                            target_handler_name = templar.template(target_handler.get_name())
                            if target_handler_name == handler_name:
                                return True
                    except (UndefinedError, AnsibleUndefinedVariable):
                        pass
                return parent_handler_match(target_handler._parent, handler_name)
            else:
                return False

        cur_pass = 0
        while True:
            try:
                self._results_lock.acquire()
                task_result = self._results.pop()
            except IndexError:
                break
            finally:
                self._results_lock.release()

            original_host = get_original_host(task_result._host)
            original_task = iterator.get_original_task(original_host, task_result._task)
            task_result._host = original_host
            task_result._task = original_task

            # send callbacks for 'non final' results
            if '_ansible_retry' in task_result._result:
                self._tqm.send_callback('v2_runner_retry', task_result)
                continue
            elif '_ansible_item_result' in task_result._result:
                if task_result.is_failed() or task_result.is_unreachable():
                    self._tqm.send_callback('v2_runner_item_on_failed', task_result)
                elif task_result.is_skipped():
                    self._tqm.send_callback('v2_runner_item_on_skipped', task_result)
                else:
                    if 'diff' in task_result._result:
                        if self._diff:
                            self._tqm.send_callback('v2_on_file_diff', task_result)
                    self._tqm.send_callback('v2_runner_item_on_ok', task_result)
                continue

            if original_task.register:
                if original_task.run_once:
                    host_list = [host for host in self._inventory.get_hosts(iterator._play.hosts) if host.name not in self._tqm._unreachable_hosts]
                else:
                    host_list = [original_host]

                clean_copy = strip_internal_keys(task_result._result)
                if 'invocation' in clean_copy:
                    del clean_copy['invocation']

                for target_host in host_list:
                    self._variable_manager.set_nonpersistent_facts(target_host, {original_task.register: clean_copy})

            # all host status messages contain 2 entries: (msg, task_result)
            role_ran = False
            if task_result.is_failed():
                role_ran = True
                if not original_task.ignore_errors:
                    display.debug("marking %s as failed" % original_host.name)
                    if original_task.run_once:
                        # if we're using run_once, we have to fail every host here
                        for h in self._inventory.get_hosts(iterator._play.hosts):
                            if h.name not in self._tqm._unreachable_hosts:
                                state, _ = iterator.get_next_task_for_host(h, peek=True)
                                iterator.mark_host_failed(h)
                                state, new_task = iterator.get_next_task_for_host(h, peek=True)
                    else:
                        iterator.mark_host_failed(original_host)

                    # increment the failed count for this host
                    self._tqm._stats.increment('failures', original_host.name)

                    # grab the current state and if we're iterating on the rescue portion
                    # of a block then we save the failed task in a special var for use 
                    # within the rescue/always
                    state, _ = iterator.get_next_task_for_host(original_host, peek=True)

                    if iterator.is_failed(original_host) and state and state.run_state == iterator.ITERATING_COMPLETE:
                        self._tqm._failed_hosts[original_host.name] = True

                    if state and state.run_state == iterator.ITERATING_RESCUE:
                        self._variable_manager.set_nonpersistent_facts(
                            original_host,
                            dict(
                                ansible_failed_task=original_task.serialize(),
                                ansible_failed_result=task_result._result,
                            ),
                        )
                else:
                    self._tqm._stats.increment('ok', original_host.name)
                    if 'changed' in task_result._result and task_result._result['changed']:
                        self._tqm._stats.increment('changed', original_host.name)
                self._tqm.send_callback('v2_runner_on_failed', task_result, ignore_errors=original_task.ignore_errors)
            elif task_result.is_unreachable():
                self._tqm._unreachable_hosts[original_host.name] = True
                iterator._play._removed_hosts.append(original_host.name)
                self._tqm._stats.increment('dark', original_host.name)
                self._tqm.send_callback('v2_runner_on_unreachable', task_result)
            elif task_result.is_skipped():
                self._tqm._stats.increment('skipped', original_host.name)
                self._tqm.send_callback('v2_runner_on_skipped', task_result)
            else:
                role_ran = True

                if original_task.loop:
                    # this task had a loop, and has more than one result, so
                    # loop over all of them instead of a single result
                    result_items = task_result._result.get('results', [])
                else:
                    result_items = [ task_result._result ]

                for result_item in result_items:
                    if '_ansible_notify' in result_item:
                        if task_result.is_changed():
                            # The shared dictionary for notified handlers is a proxy, which
                            # does not detect when sub-objects within the proxy are modified.
                            # So, per the docs, we reassign the list so the proxy picks up and
                            # notifies all other threads
                            for handler_name in result_item['_ansible_notify']:
                                found = False
                                # Find the handler using the above helper.  First we look up the
                                # dependency chain of the current task (if it's from a role), otherwise
                                # we just look through the list of handlers in the current play/all
                                # roles and use the first one that matches the notify name
                                target_handler = search_handler_blocks(handler_name, iterator._play.handlers)
                                if target_handler is not None:
                                    found = True
                                    if original_host not in self._notified_handlers[target_handler]:
                                        self._notified_handlers[target_handler].append(original_host)
                                        # FIXME: should this be a callback?
                                        display.vv("NOTIFIED HANDLER %s" % (handler_name,))
                                else:
                                    # As there may be more than one handler with the notified name as the
                                    # parent, so we just keep track of whether or not we found one at all
                                    for target_handler in self._notified_handlers:
                                        if parent_handler_match(target_handler, handler_name):
                                            self._notified_handlers[target_handler].append(original_host)
                                            display.vv("NOTIFIED HANDLER %s" % (target_handler.get_name(),))
                                            found = True

                                if handler_name in self._listening_handlers:
                                    for listening_handler_name in self._listening_handlers[handler_name]:
                                        listening_handler = search_handler_blocks(listening_handler_name, iterator._play.handlers)
                                        if listening_handler is not None:
                                            found = True
                                        else:
                                            continue
                                        if original_host not in self._notified_handlers[listening_handler]:
                                            self._notified_handlers[listening_handler].append(original_host)
                                            display.vv("NOTIFIED HANDLER %s" % (listening_handler_name,))

                                # and if none were found, then we raise an error
                                if not found:
                                  msg = "The requested handler '%s' was not found in either the main handlers list nor in the listening handlers list" % handler_name
                                  if C.ERROR_ON_MISSING_HANDLER:
                                      raise AnsibleError(msg)
                                  else:
                                      display.warning(msg)

                    if 'add_host' in result_item:
                        # this task added a new host (add_host module)
                        new_host_info = result_item.get('add_host', dict())
                        self._add_host(new_host_info, iterator)

                    elif 'add_group' in result_item:
                        # this task added a new group (group_by module)
                        self._add_group(original_host, result_item)

                    elif 'ansible_facts' in result_item:

                        # set correct loop var
                        if original_task.loop_control:
                            loop_var = original_task.loop_control.loop_var or 'item'
                        else:
                            loop_var = 'item'

                        item = result_item.get(loop_var, None)

                        # if delegated fact and we are delegating facts, we need to change target host for them
                        if original_task.delegate_to is not None and original_task.delegate_facts:
                            task_vars = self._variable_manager.get_vars(loader=self._loader, play=iterator._play, host=original_host, task=original_task)
                            self.add_tqm_variables(task_vars, play=iterator._play)
                            if item is not None:
                                task_vars[loop_var] = item
                            templar = Templar(loader=self._loader, variables=task_vars)
                            host_name = templar.template(original_task.delegate_to)
                            actual_host = self._inventory.get_host(host_name)
                            if actual_host is None:
                                actual_host = Host(name=host_name)
                        else:
                            actual_host = original_host

                        if original_task.action == 'include_vars':
                            for (var_name, var_value) in iteritems(result_item['ansible_facts']):
                                # find the host we're actually refering too here, which may
                                # be a host that is not really in inventory at all

                                if original_task.run_once:
                                    host_list = [host for host in self._inventory.get_hosts(iterator._play.hosts) if host.name not in self._tqm._unreachable_hosts]
                                else:
                                    host_list = [actual_host]

                                for target_host in host_list:
                                    self._variable_manager.set_host_variable(target_host, var_name, var_value)
                        else:
                            if original_task.run_once:
                                host_list = [host for host in self._inventory.get_hosts(iterator._play.hosts) if host.name not in self._tqm._unreachable_hosts]
                            else:
                                host_list = [actual_host]

                            for target_host in host_list:
                                if original_task.action == 'set_fact':
                                    self._variable_manager.set_nonpersistent_facts(target_host, result_item['ansible_facts'].copy())
                                else:
                                    self._variable_manager.set_host_facts(target_host, result_item['ansible_facts'].copy())

                if 'diff' in task_result._result:
                    if self._diff:
                        self._tqm.send_callback('v2_on_file_diff', task_result)

                if original_task.action not in ['include', 'include_role']:
                    self._tqm._stats.increment('ok', original_host.name)
                    if 'changed' in task_result._result and task_result._result['changed']:
                        self._tqm._stats.increment('changed', original_host.name)

                # finally, send the ok for this task
                self._tqm.send_callback('v2_runner_on_ok', task_result)

            self._pending_results -= 1
            if original_host.name in self._blocked_hosts:
                del self._blocked_hosts[original_host.name]

            # If this is a role task, mark the parent role as being run (if
            # the task was ok or failed, but not skipped or unreachable)
            if original_task._role is not None and role_ran: #TODO:  and original_task.action != 'include_role':?
                # lookup the role in the ROLE_CACHE to make sure we're dealing
                # with the correct object and mark it as executed
                for (entry, role_obj) in iteritems(iterator._play.ROLE_CACHE[original_task._role._role_name]):
                    if role_obj._uuid == original_task._role._uuid:
                        role_obj._had_task_run[original_host.name] = True

            ret_results.append(task_result)

            if one_pass or max_passes is not None and (cur_pass+1) >= max_passes:
                break

            cur_pass += 1

        return ret_results

    def _wait_on_pending_results(self, iterator):
        '''
        Wait for the shared counter to drop to zero, using a short sleep
        between checks to ensure we don't spin lock
        '''

        ret_results = []

        display.debug("waiting for pending results...")
        while self._pending_results > 0 and not self._tqm._terminated:

            if self._tqm.has_dead_workers():
                raise AnsibleError("A worker was found in a dead state")

            results = self._process_pending_results(iterator)
            ret_results.extend(results)
            if self._pending_results > 0:
                time.sleep(C.DEFAULT_INTERNAL_POLL_INTERVAL)

        display.debug("no more pending results, returning what we have")

        return ret_results

    def _add_host(self, host_info, iterator):
        '''
        Helper function to add a new host to inventory based on a task result.
        '''

        host_name = host_info.get('host_name')

        # Check if host in inventory, add if not
        new_host = self._inventory.get_host(host_name)
        if not new_host:
            new_host = Host(name=host_name)
            self._inventory._hosts_cache[host_name] = new_host
            self._inventory.get_host_vars(new_host)

            allgroup = self._inventory.get_group('all')
            allgroup.add_host(new_host)

        # Set/update the vars for this host
        new_host.vars = combine_vars(new_host.vars, self._inventory.get_host_vars(new_host))
        new_host.vars = combine_vars(new_host.vars,  host_info.get('host_vars', dict()))

        new_groups = host_info.get('groups', [])
        for group_name in new_groups:
            if not self._inventory.get_group(group_name):
                new_group = Group(group_name)
                self._inventory.add_group(new_group)
                self._inventory.get_group_vars(new_group)
                new_group.vars = self._inventory.get_group_variables(group_name)
            else:
                new_group = self._inventory.get_group(group_name)

            new_group.add_host(new_host)

            # add this host to the group cache
            if self._inventory.groups is not None:
                if group_name in self._inventory.groups:
                    if new_host not in self._inventory.get_group(group_name).hosts:
                        self._inventory.get_group(group_name).hosts.append(new_host.name)

        # clear pattern caching completely since it's unpredictable what
        # patterns may have referenced the group
        self._inventory.clear_pattern_cache()

        # clear cache of group dict, which is used in magic host variables
        self._inventory.clear_group_dict_cache()

        # also clear the hostvar cache entry for the given play, so that
        # the new hosts are available if hostvars are referenced
        self._variable_manager.invalidate_hostvars_cache(play=iterator._play)

    def _add_group(self, host, result_item):
        '''
        Helper function to add a group (if it does not exist), and to assign the
        specified host to that group.
        '''

        changed = False

        # the host here is from the executor side, which means it was a
        # serialized/cloned copy and we'll need to look up the proper
        # host object from the master inventory
        real_host = self._inventory.get_host(host.name)

        group_name = result_item.get('add_group')
        new_group = self._inventory.get_group(group_name)
        if not new_group:
            # create the new group and add it to inventory
            new_group = Group(name=group_name)
            self._inventory.add_group(new_group)
            new_group.vars = self._inventory.get_group_vars(new_group)

            # and add the group to the proper hierarchy
            allgroup = self._inventory.get_group('all')
            allgroup.add_child_group(new_group)
            changed = True

        if group_name not in host.get_groups():
            new_group.add_host(real_host)
            changed = True
            
        if changed:
            # clear cache of group dict, which is used in magic host variables
            self._inventory.clear_group_dict_cache()

        return changed

    def _load_included_file(self, included_file, iterator, is_handler=False):
        '''
        Loads an included YAML file of tasks, applying the optional set of variables.
        '''

        display.debug("loading included file: %s" % included_file._filename)
        try:
            data = self._loader.load_from_file(included_file._filename)
            if data is None:
                return []
            elif not isinstance(data, list):
                raise AnsibleError("included task files must contain a list of tasks")

            ti_copy = included_file._task.copy()
            temp_vars = ti_copy.vars.copy()
            temp_vars.update(included_file._args)
            # pop tags out of the include args, if they were specified there, and assign
            # them to the include. If the include already had tags specified, we raise an
            # error so that users know not to specify them both ways
            tags = included_file._task.vars.pop('tags', [])
            if isinstance(tags, string_types):
                tags = tags.split(',')
            if len(tags) > 0:
                if len(included_file._task.tags) > 0:
                    raise AnsibleParserError("Include tasks should not specify tags in more than one way (both via args and directly on the task). Mixing tag specify styles is prohibited for whole import hierarchy, not only for single import statement",
                            obj=included_file._task._ds)
                display.deprecated("You should not specify tags in the include parameters. All tags should be specified using the task-level option")
                included_file._task.tags = tags

            ti_copy.vars = temp_vars

            block_list = load_list_of_blocks(
                data,
                play=iterator._play,
                parent_block=None,
                task_include=ti_copy,
                role=included_file._task._role,
                use_handlers=is_handler,
                loader=self._loader,
                variable_manager=self._variable_manager,
            )

            # since we skip incrementing the stats when the task result is
            # first processed, we do so now for each host in the list
            for host in included_file._hosts:
                self._tqm._stats.increment('ok', host.name)

        except AnsibleError as e:
            # mark all of the hosts including this file as failed, send callbacks,
            # and increment the stats for this host
            for host in included_file._hosts:
                tr = TaskResult(host=host, task=included_file._task, return_data=dict(failed=True, reason=to_text(e)))
                iterator.mark_host_failed(host)
                self._tqm._failed_hosts[host.name] = True
                self._tqm._stats.increment('failures', host.name)
                self._tqm.send_callback('v2_runner_on_failed', tr)
            return []

        # finally, send the callback and return the list of blocks loaded
        self._tqm.send_callback('v2_playbook_on_include', included_file)
        display.debug("done processing included file")
        return block_list

    def run_handlers(self, iterator, play_context):
        '''
        Runs handlers on those hosts which have been notified.
        '''

        result = self._tqm.RUN_OK

        for handler_block in iterator._play.handlers:
            # FIXME: handlers need to support the rescue/always portions of blocks too,
            #        but this may take some work in the iterator and gets tricky when
            #        we consider the ability of meta tasks to flush handlers
            for handler in handler_block.block:
                if handler in self._notified_handlers and len(self._notified_handlers[handler]):
                    result = self._do_handler_run(handler, handler.get_name(), iterator=iterator, play_context=play_context)
                    if not result:
                        break
        return result

    def _do_handler_run(self, handler, handler_name, iterator, play_context, notified_hosts=None):

        # FIXME: need to use iterator.get_failed_hosts() instead?
        #if not len(self.get_hosts_remaining(iterator._play)):
        #    self._tqm.send_callback('v2_playbook_on_no_hosts_remaining')
        #    result = False
        #    break
        saved_name = handler.name
        handler.name = handler_name
        self._tqm.send_callback('v2_playbook_on_handler_task_start', handler)
        handler.name = saved_name

        if notified_hosts is None:
            notified_hosts = self._notified_handlers[handler]

        run_once = False
        try:
            action = action_loader.get(handler.action, class_only=True)
            if handler.run_once or getattr(action, 'BYPASS_HOST_LOOP', False):
                run_once = True
        except KeyError:
            # we don't care here, because the action may simply not have a
            # corresponding action plugin
            pass

        host_results = []
        for host in notified_hosts:
            if not handler.has_triggered(host) and (not iterator.is_failed(host) or play_context.force_handlers):
                task_vars = self._variable_manager.get_vars(loader=self._loader, play=iterator._play, host=host, task=handler)
                self.add_tqm_variables(task_vars, play=iterator._play)
                self._queue_task(host, handler, task_vars, play_context)
                if run_once:
                    break

        # collect the results from the handler run
        host_results = self._wait_on_pending_results(iterator)

        try:
            included_files = IncludedFile.process_include_results(
                host_results,
                self._tqm,
                iterator=iterator,
                inventory=self._inventory,
                loader=self._loader,
                variable_manager=self._variable_manager
            )
        except AnsibleError as e:
            return False

        result = True
        if len(included_files) > 0:
            for included_file in included_files:
                try:
                    new_blocks = self._load_included_file(included_file, iterator=iterator, is_handler=True)
                    # for every task in each block brought in by the include, add the list
                    # of hosts which included the file to the notified_handlers dict
                    for block in new_blocks:
                        iterator._play.handlers.append(block)
                        iterator.cache_block_tasks(block)
                        for task in block.block:
                            result = self._do_handler_run(
                                handler=task,
                                handler_name=None,
                                iterator=iterator,
                                play_context=play_context,
                                notified_hosts=included_file._hosts[:],
                            )
                            if not result:
                                break
                except AnsibleError as e:
                    for host in included_file._hosts:
                        iterator.mark_host_failed(host)
                        self._tqm._failed_hosts[host.name] = True
                    display.warning(str(e))
                    continue

        # wipe the notification list
        self._notified_handlers[handler] = []
        display.debug("done running handlers, result is: %s" % result)
        return result

    def _take_step(self, task, host=None):

        ret=False
        msg=u'Perform task: %s ' % task
        if host:
            msg += u'on %s ' % host
        msg += u'(N)o/(y)es/(c)ontinue: '
        resp = display.prompt(msg)

        if resp.lower() in ['y','yes']:
            display.debug("User ran task")
            ret = True
        elif resp.lower() in ['c', 'continue']:
            display.debug("User ran task and canceled step mode")
            self._step = False
            ret = True
        else:
            display.debug("User skipped task")

        display.banner(msg)

        return ret

    def _execute_meta(self, task, play_context, iterator, target_host=None):

        # meta tasks store their args in the _raw_params field of args,
        # since they do not use k=v pairs, so get that
        meta_action = task.args.get('_raw_params')

        # FIXME(s):
        # * raise an error or show a warning when a conditional is used
        #   on a meta task that doesn't support them

        def _evaluate_conditional(h):
            all_vars = self._variable_manager.get_vars(loader=self._loader, play=iterator._play, host=host, task=task)
            templar = Templar(loader=self._loader, variables=all_vars)
            return task.evaluate_conditional(templar, all_vars)

        if target_host:
            host_list = [target_host]
        else:
            host_list = [host for host in self._inventory.get_hosts(iterator._play.hosts) if host.name not in self._tqm._unreachable_hosts]

        results = []
        for host in host_list:
            result = None
            if meta_action == 'noop':
                # FIXME: issue a callback for the noop here?
                result = TaskResult(host, task, dict(changed=False, msg="noop"))
            elif meta_action == 'flush_handlers':
                self.run_handlers(iterator, play_context)
            elif meta_action == 'refresh_inventory':
                self._inventory.refresh_inventory()
                result = TaskResult(host, task, dict(changed=False, msg="inventory successfully refreshed"))
            elif meta_action == 'clear_facts':
                if _evaluate_conditional(host):
                    self._variable_manager.clear_facts(target_host)
                    result = TaskResult(host, task, dict(changed=True, msg="inventory successfully refreshed"))
                else:
                    result = TaskResult(host, task, dict(changed=False, skipped=True))
            elif meta_action == 'clear_host_errors':
                if _evaluate_conditional(host):
                    self._tqm._failed_hosts.pop(host.name, False)
                    self._tqm._unreachable_hosts.pop(host.name, False)
                    iterator._host_states[host.name].fail_state = iterator.FAILED_NONE
                    result = TaskResult(host, task, dict(changed=True, msg="successfully cleared host errors"))
                else:
                    result = TaskResult(host, task, dict(changed=False, skipped=True))
            elif meta_action == 'end_play':
                if _evaluate_conditional(host):
                    iterator._host_states[host.name].run_state = iterator.ITERATING_COMPLETE
                    result = TaskResult(host, task, dict(changed=True, msg="ending play"))
                else:
                    result = TaskResult(host, task, dict(changed=False, skipped=True))
            #elif meta_action == 'reset_connection':
            #    connection_info.connection.close()
            else:
                raise AnsibleError("invalid meta action requested: %s" % meta_action, obj=task._ds)

            if result is not None:
                results.append(result)

        return results
