# Copyright 2008 Google Inc. All Rights Reserved.

"""
The host module contains the objects and method used to
manage a host in Autotest.

The valid actions are:
create:  adds host(s)
delete:  deletes host(s)
list:    lists host(s)
stat:    displays host(s) information
mod:     modifies host(s)
jobs:    lists all jobs that ran on host(s)

The common options are:
-M|--mlist:   file containing a list of machines


See topic_common.py for a High Level Design and Algorithm.

"""
import common
import json
import random
import re
import socket
import sys
import time

from autotest_lib.cli import action_common, rpc, topic_common, skylab_utils, skylab_migration
from autotest_lib.cli import fair_partition
from autotest_lib.client.bin import utils as bin_utils
from autotest_lib.cli.skylab_json_utils import process_labels, print_textpb, write, writeln
from autotest_lib.cli import skylab_rollback
from autotest_lib.cli.skylab_json_utils import process_labels, validate_required_fields_for_skylab
from autotest_lib.client.common_lib import error, host_protections
from autotest_lib.server import frontend, hosts
from autotest_lib.server.hosts import host_info
from autotest_lib.server.lib.status_history import HostJobHistory
from autotest_lib.server.lib.status_history import UNUSED, WORKING
from autotest_lib.server.lib.status_history import BROKEN, UNKNOWN


try:
    from skylab_inventory import text_manager
    from skylab_inventory.lib import device
    from skylab_inventory.lib import server as skylab_server
except ImportError:
    pass


MIGRATED_HOST_SUFFIX = '-migrated-do-not-use'


ID_AUTOGEN_MESSAGE = ("[IGNORED]. Do not edit (crbug.com/950553). ID is "
                      "auto-generated.")


class host(topic_common.atest):
    """Host class
    atest host [create|delete|list|stat|mod|jobs|rename|migrate|skylab_migrate|statjson] <options>"""
    usage_action = '[create|delete|list|stat|mod|jobs|rename|migrate|skylab_migrate|statjson]'
    topic = msg_topic = 'host'
    msg_items = '<hosts>'

    protections = host_protections.Protection.names


    def __init__(self):
        """Add to the parser the options common to all the
        host actions"""
        super(host, self).__init__()

        self.parser.add_option('-M', '--mlist',
                               help='File listing the machines',
                               type='string',
                               default=None,
                               metavar='MACHINE_FLIST')

        self.topic_parse_info = topic_common.item_parse_info(
            attribute_name='hosts',
            filename_option='mlist',
            use_leftover=True)


    def _parse_lock_options(self, options):
        if options.lock and options.unlock:
            self.invalid_syntax('Only specify one of '
                                '--lock and --unlock.')

        self.lock = options.lock
        self.unlock = options.unlock
        self.lock_reason = options.lock_reason

        if options.lock:
            self.data['locked'] = True
            self.messages.append('Locked host')
        elif options.unlock:
            self.data['locked'] = False
            self.data['lock_reason'] = ''
            self.messages.append('Unlocked host')

        if options.lock and options.lock_reason:
            self.data['lock_reason'] = options.lock_reason


    def _cleanup_labels(self, labels, platform=None):
        """Removes the platform label from the overall labels"""
        if platform:
            return [label for label in labels
                    if label != platform]
        else:
            try:
                return [label for label in labels
                        if not label['platform']]
            except TypeError:
                # This is a hack - the server will soon
                # do this, so all this code should be removed.
                return labels


    def get_items(self):
        return self.hosts


class host_help(host):
    """Just here to get the atest logic working.
    Usage is set by its parent"""
    pass


class host_list(action_common.atest_list, host):
    """atest host list [--mlist <file>|<hosts>] [--label <label>]
       [--status <status1,status2>] [--acl <ACL>] [--user <user>]"""

    def __init__(self):
        super(host_list, self).__init__()

        self.parser.add_option('-b', '--label',
                               default='',
                               help='Only list hosts with all these labels '
                               '(comma separated). When --skylab is provided, '
                               'a label must be in the format of '
                               'label-key:label-value (e.g., board:lumpy).')
        self.parser.add_option('-s', '--status',
                               default='',
                               help='Only list hosts with any of these '
                               'statuses (comma separated)')
        self.parser.add_option('-a', '--acl',
                               default='',
                               help=('Only list hosts within this ACL. %s' %
                                     skylab_utils.MSG_INVALID_IN_SKYLAB))
        self.parser.add_option('-u', '--user',
                               default='',
                               help=('Only list hosts available to this user. '
                                     '%s' % skylab_utils.MSG_INVALID_IN_SKYLAB))
        self.parser.add_option('-N', '--hostnames-only', help='Only return '
                               'hostnames for the machines queried.',
                               action='store_true')
        self.parser.add_option('--locked',
                               default=False,
                               help='Only list locked hosts',
                               action='store_true')
        self.parser.add_option('--unlocked',
                               default=False,
                               help='Only list unlocked hosts',
                               action='store_true')
        self.parser.add_option('--full-output',
                               default=False,
                               help=('Print out the full content of the hosts. '
                                     'Only supported with --skylab.'),
                               action='store_true',
                               dest='full_output')

        self.add_skylab_options()


    def parse(self):
        """Consume the specific options"""
        label_info = topic_common.item_parse_info(attribute_name='labels',
                                                  inline_option='label')

        (options, leftover) = super(host_list, self).parse([label_info])

        self.status = options.status
        self.acl = options.acl
        self.user = options.user
        self.hostnames_only = options.hostnames_only

        if options.locked and options.unlocked:
            self.invalid_syntax('--locked and --unlocked are '
                                'mutually exclusive')

        self.locked = options.locked
        self.unlocked = options.unlocked
        self.label_map = None

        if self.skylab:
            if options.user or options.acl or options.status:
                self.invalid_syntax('--user, --acl or --status is not '
                                    'supported with --skylab.')
            self.full_output = options.full_output
            if self.full_output and self.hostnames_only:
                self.invalid_syntax('--full-output is conflicted with '
                                    '--hostnames-only.')

            if self.labels:
                self.label_map = device.convert_to_label_map(self.labels)
        else:
            if options.full_output:
                self.invalid_syntax('--full_output is only supported with '
                                    '--skylab.')

        return (options, leftover)


    def execute_skylab(self):
        """Execute 'atest host list' with --skylab."""
        inventory_repo = skylab_utils.InventoryRepo(self.inventory_repo_dir)
        inventory_repo.initialize()
        lab = text_manager.load_lab(inventory_repo.get_data_dir())

        # TODO(nxia): support filtering on run-time labels and status.
        return device.get_devices(
            lab,
            'duts',
            self.environment,
            label_map=self.label_map,
            hostnames=self.hosts,
            locked=self.locked,
            unlocked=self.unlocked)


    def execute(self):
        """Execute 'atest host list'."""
        if self.skylab:
            return self.execute_skylab()

        filters = {}
        check_results = {}
        if self.hosts:
            filters['hostname__in'] = self.hosts
            check_results['hostname__in'] = 'hostname'

        if self.labels:
            if len(self.labels) == 1:
                # This is needed for labels with wildcards (x86*)
                filters['labels__name__in'] = self.labels
                check_results['labels__name__in'] = None
            else:
                filters['multiple_labels'] = self.labels
                check_results['multiple_labels'] = None

        if self.status:
            statuses = self.status.split(',')
            statuses = [status.strip() for status in statuses
                        if status.strip()]

            filters['status__in'] = statuses
            check_results['status__in'] = None

        if self.acl:
            filters['aclgroup__name'] = self.acl
            check_results['aclgroup__name'] = None
        if self.user:
            filters['aclgroup__users__login'] = self.user
            check_results['aclgroup__users__login'] = None

        if self.locked or self.unlocked:
            filters['locked'] = self.locked
            check_results['locked'] = None

        return super(host_list, self).execute(op='get_hosts',
                                              filters=filters,
                                              check_results=check_results)


    def output(self, results):
        """Print output of 'atest host list'.

        @param results: the results to be printed.
        """
        if results and not self.skylab:
            # Remove the platform from the labels.
            for result in results:
                result['labels'] = self._cleanup_labels(result['labels'],
                                                        result['platform'])
        if self.skylab and self.full_output:
            print results
            return

        if self.skylab:
            results = device.convert_to_autotest_hosts(results)

        if self.hostnames_only:
            self.print_list(results, key='hostname')
        else:
            keys = ['hostname', 'status', 'shard', 'locked', 'lock_reason',
                    'locked_by', 'platform', 'labels']
            super(host_list, self).output(results, keys=keys)


class host_stat(host):
    """atest host stat --mlist <file>|<hosts>"""
    usage_action = 'stat'

    def execute(self):
        """Execute 'atest host stat'."""
        results = []
        # Convert wildcards into real host stats.
        existing_hosts = []
        for host in self.hosts:
            if host.endswith('*'):
                stats = self.execute_rpc('get_hosts',
                                         hostname__startswith=host.rstrip('*'))
                if len(stats) == 0:
                    self.failure('No hosts matching %s' % host, item=host,
                                 what_failed='Failed to stat')
                    continue
            else:
                stats = self.execute_rpc('get_hosts', hostname=host)
                if len(stats) == 0:
                    self.failure('Unknown host %s' % host, item=host,
                                 what_failed='Failed to stat')
                    continue
            existing_hosts.extend(stats)

        for stat in existing_hosts:
            host = stat['hostname']
            # The host exists, these should succeed
            acls = self.execute_rpc('get_acl_groups', hosts__hostname=host)

            labels = self.execute_rpc('get_labels', host__hostname=host)
            results.append([[stat], acls, labels, stat['attributes']])
        return results


    def output(self, results):
        """Print output of 'atest host stat'.

        @param results: the results to be printed.
        """
        for stats, acls, labels, attributes in results:
            print '-'*5
            self.print_fields(stats,
                              keys=['hostname', 'id', 'platform',
                                    'status', 'locked', 'locked_by',
                                    'lock_time', 'lock_reason', 'protection',])
            self.print_by_ids(acls, 'ACLs', line_before=True)
            labels = self._cleanup_labels(labels)
            self.print_by_ids(labels, 'Labels', line_before=True)
            self.print_dict(attributes, 'Host Attributes', line_before=True)


class host_get_migration_plan(host_stat):
    """atest host get_migration_plan --mlist <file>|<hosts>"""
    usage_action = "get_migration_plan"

    def __init__(self):
        super(host_get_migration_plan, self).__init__()
        self.parser.add_option("--ratio", default=0.5, type=float, dest="ratio")
        self.add_skylab_options()

    def parse(self):
        (options, leftover) = super(host_get_migration_plan, self).parse()
        self.ratio = options.ratio
        return (options, leftover)

    def execute(self):
        afe = frontend.AFE()
        results = super(host_get_migration_plan, self).execute()
        working = []
        non_working = []
        for stats, _, _, _ in results:
            assert len(stats) == 1
            stats = stats[0]
            hostname = stats["hostname"]
            now = time.time()
            history = HostJobHistory.get_host_history(
                afe=afe,
                hostname=hostname,
                start_time=now,
                end_time=now - 24 * 60 * 60,
            )
            dut_status, _ = history.last_diagnosis()
            if dut_status in [UNUSED, WORKING]:
                working.append(hostname)
            elif dut_status == BROKEN:
                non_working.append(hostname)
            elif dut_status == UNKNOWN:
                # if it's unknown, randomly assign it to working or
                # nonworking, since we don't know.
                # The two choices aren't actually equiprobable, but it
                # should be fine.
                random.choice([working, non_working]).append(hostname)
            else:
                raise ValueError("unknown status %s" % dut_status)
        working_transfer, working_retain = fair_partition.partition(working, self.ratio)
        non_working_transfer, non_working_retain = \
            fair_partition.partition(non_working, self.ratio)
        return {
            "transfer": working_transfer + non_working_transfer,
            "retain": working_retain + non_working_retain,
        }

    def output(self, results):
        print json.dumps(results, indent=4, sort_keys=True)


class host_statjson(host_stat):
    """atest host statjson --mlist <file>|<hosts>

    exposes the same information that 'atest host stat' does, but in the json
    format that 'skylab add-dut' expects
    """

    usage_action = "statjson"

    def __init__(self):
        super(host_statjson, self).__init__()
        self.parser.add_option('--verify',
                               default=False,
                               help='Verify that required fields are provided',
                               action='store_true',
                               dest='verify')
        self.parser.add_option('--textpb',
                               default=False,
                               help='Print in best effort textpb format',
                               action='store_true',
                               dest='textpb')

    def parse(self):
        (options, leftover) = super(host_statjson, self).parse()
        self.verify = options.verify
        self.textpb = options.textpb
        return (options, leftover)

    def output(self, results):
        """Print output of 'atest host statjson <...>'"""
        for row in results:
            stats, acls, labels, attributes = row
            # TODO(gregorynisbet): under what circumstances is stats
            #    not a list of length 1?
            assert len(stats) == 1
            stats_map = stats[0]

            # Stripping the MIGRATED_HOST_SUFFIX makes it possible to
            # migrate a DUT from autotest to skylab even after its hostname
            # has been changed.
            # This enables the steps (renaming the host,
            # copying the inventory information to skylab) to be doable in
            # either order.
            hostname = _remove_hostname_suffix_if_present(
                stats_map["hostname"],
                MIGRATED_HOST_SUFFIX
            )

            # TODO(gregorynisbet): clean up servo information
            if "servo_host" not in attributes:
                attributes["servo_host"] = "dummy_host"
            if "servo_port" not in attributes:
                attributes["servo_port"] = "dummy_port"

            labels = self._cleanup_labels(labels)
            attrs = [{"key": k, "value": v} for k, v in attributes.iteritems()]
            out_labels = process_labels(labels, platform=stats_map["platform"])
            skylab_json = {
                "common": {
                    "attributes": attrs,
                    "environment": "ENVIRONMENT_PROD",
                    "hostname": hostname,
                    "id": ID_AUTOGEN_MESSAGE,
                    "labels": out_labels,
                    "serialNumber": attributes.get("serial_number", None),
                }
            }
            # if the validate flag is provided, check that a given json blob
            # has all the required fields for skylab.
            if self.verify:
                validate_required_fields_for_skylab(skylab_json)
            if self.textpb:
                # need leading "duts" preamble
                write("duts ")
                print_textpb(skylab_json)
            else:
                print json.dumps(skylab_json, indent=4, sort_keys=True)


class host_jobs(host):
    """atest host jobs [--max-query] --mlist <file>|<hosts>"""
    usage_action = 'jobs'

    def __init__(self):
        super(host_jobs, self).__init__()
        self.parser.add_option('-q', '--max-query',
                               help='Limits the number of results '
                               '(20 by default)',
                               type='int', default=20)


    def parse(self):
        """Consume the specific options"""
        (options, leftover) = super(host_jobs, self).parse()
        self.max_queries = options.max_query
        return (options, leftover)


    def execute(self):
        """Execute 'atest host jobs'."""
        results = []
        real_hosts = []
        for host in self.hosts:
            if host.endswith('*'):
                stats = self.execute_rpc('get_hosts',
                                         hostname__startswith=host.rstrip('*'))
                if len(stats) == 0:
                    self.failure('No host matching %s' % host, item=host,
                                 what_failed='Failed to stat')
                [real_hosts.append(stat['hostname']) for stat in stats]
            else:
                real_hosts.append(host)

        for host in real_hosts:
            queue_entries = self.execute_rpc('get_host_queue_entries',
                                             host__hostname=host,
                                             query_limit=self.max_queries,
                                             sort_by=['-job__id'])
            jobs = []
            for entry in queue_entries:
                job = {'job_id': entry['job']['id'],
                       'job_owner': entry['job']['owner'],
                       'job_name': entry['job']['name'],
                       'status': entry['status']}
                jobs.append(job)
            results.append((host, jobs))
        return results


    def output(self, results):
        """Print output of 'atest host jobs'.

        @param results: the results to be printed.
        """
        for host, jobs in results:
            print '-'*5
            print 'Hostname: %s' % host
            self.print_table(jobs, keys_header=['job_id',
                                                'job_owner',
                                                'job_name',
                                                'status'])

class BaseHostModCreate(host):
    """The base class for host_mod and host_create"""
    # Matches one attribute=value pair
    attribute_regex = r'(?P<attribute>\w+)=(?P<value>.+)?'

    def __init__(self):
        """Add the options shared between host mod and host create actions."""
        self.messages = []
        self.host_ids = {}
        super(BaseHostModCreate, self).__init__()
        self.parser.add_option('-l', '--lock',
                               help='Lock hosts.',
                               action='store_true')
        self.parser.add_option('-r', '--lock_reason',
                               help='Reason for locking hosts.',
                               default='')
        self.parser.add_option('-u', '--unlock',
                               help='Unlock hosts.',
                               action='store_true')

        self.parser.add_option('-p', '--protection', type='choice',
                               help=('Set the protection level on a host.  '
                                     'Must be one of: %s. %s' %
                                     (', '.join('"%s"' % p
                                               for p in self.protections),
                                      skylab_utils.MSG_INVALID_IN_SKYLAB)),
                               choices=self.protections)
        self._attributes = []
        self.parser.add_option('--attribute', '-i',
                               help=('Host attribute to add or change. Format '
                                     'is <attribute>=<value>. Multiple '
                                     'attributes can be set by passing the '
                                     'argument multiple times. Attributes can '
                                     'be unset by providing an empty value.'),
                               action='append')
        self.parser.add_option('-b', '--labels',
                               help=('Comma separated list of labels. '
                                     'When --skylab is provided, a label must '
                                     'be in the format of label-key:label-value'
                                     ' (e.g., board:lumpy).'))
        self.parser.add_option('-B', '--blist',
                               help='File listing the labels',
                               type='string',
                               metavar='LABEL_FLIST')
        self.parser.add_option('-a', '--acls',
                               help=('Comma separated list of ACLs. %s' %
                                     skylab_utils.MSG_INVALID_IN_SKYLAB))
        self.parser.add_option('-A', '--alist',
                               help=('File listing the acls. %s' %
                                     skylab_utils.MSG_INVALID_IN_SKYLAB),
                               type='string',
                               metavar='ACL_FLIST')
        self.parser.add_option('-t', '--platform',
                               help=('Sets the platform label. %s Please set '
                                     'platform in labels (e.g., -b '
                                     'platform:platform_name) with --skylab.' %
                                     skylab_utils.MSG_INVALID_IN_SKYLAB))


    def parse(self):
        """Consume the options common to host create and host mod.
        """
        label_info = topic_common.item_parse_info(attribute_name='labels',
                                                 inline_option='labels',
                                                 filename_option='blist')
        acl_info = topic_common.item_parse_info(attribute_name='acls',
                                                inline_option='acls',
                                                filename_option='alist')

        (options, leftover) = super(BaseHostModCreate, self).parse([label_info,
                                                              acl_info],
                                                             req_items='hosts')

        self._parse_lock_options(options)

        self.label_map = None
        if self.allow_skylab and self.skylab:
            # TODO(nxia): drop these flags when all hosts are migrated to skylab
            if (options.protection or options.acls or options.alist or
                options.platform):
                self.invalid_syntax(
                        '--protection, --acls, --alist or --platform is not '
                        'supported with --skylab.')

            if self.labels:
                self.label_map = device.convert_to_label_map(self.labels)

        if options.protection:
            self.data['protection'] = options.protection
            self.messages.append('Protection set to "%s"' % options.protection)

        self.attributes = {}
        if options.attribute:
            for pair in options.attribute:
                m = re.match(self.attribute_regex, pair)
                if not m:
                    raise topic_common.CliError('Attribute must be in key=value '
                                                'syntax.')
                elif m.group('attribute') in self.attributes:
                    raise topic_common.CliError(
                            'Multiple values provided for attribute '
                            '%s.' % m.group('attribute'))
                self.attributes[m.group('attribute')] = m.group('value')

        self.platform = options.platform
        return (options, leftover)


    def _set_acls(self, hosts, acls):
        """Add hosts to acls (and remove from all other acls).

        @param hosts: list of hostnames
        @param acls: list of acl names
        """
        # Remove from all ACLs except 'Everyone' and ACLs in list
        # Skip hosts that don't exist
        for host in hosts:
            if host not in self.host_ids:
                continue
            host_id = self.host_ids[host]
            for a in self.execute_rpc('get_acl_groups', hosts=host_id):
                if a['name'] not in self.acls and a['id'] != 1:
                    self.execute_rpc('acl_group_remove_hosts', id=a['id'],
                                     hosts=self.hosts)

        # Add hosts to the ACLs
        self.check_and_create_items('get_acl_groups', 'add_acl_group',
                                    self.acls)
        for a in acls:
            self.execute_rpc('acl_group_add_hosts', id=a, hosts=hosts)


    def _remove_labels(self, host, condition):
        """Remove all labels from host that meet condition(label).

        @param host: hostname
        @param condition: callable that returns bool when given a label
        """
        if host in self.host_ids:
            host_id = self.host_ids[host]
            labels_to_remove = []
            for l in self.execute_rpc('get_labels', host=host_id):
                if condition(l):
                    labels_to_remove.append(l['id'])
            if labels_to_remove:
                self.execute_rpc('host_remove_labels', id=host_id,
                                 labels=labels_to_remove)


    def _set_labels(self, host, labels):
        """Apply labels to host (and remove all other labels).

        @param host: hostname
        @param labels: list of label names
        """
        condition = lambda l: l['name'] not in labels and not l['platform']
        self._remove_labels(host, condition)
        self.check_and_create_items('get_labels', 'add_label', labels)
        self.execute_rpc('host_add_labels', id=host, labels=labels)


    def _set_platform_label(self, host, platform_label):
        """Apply the platform label to host (and remove existing).

        @param host: hostname
        @param platform_label: platform label's name
        """
        self._remove_labels(host, lambda l: l['platform'])
        self.check_and_create_items('get_labels', 'add_label', [platform_label],
                                    platform=True)
        self.execute_rpc('host_add_labels', id=host, labels=[platform_label])


    def _set_attributes(self, host, attributes):
        """Set attributes on host.

        @param host: hostname
        @param attributes: attribute dictionary
        """
        for attr, value in self.attributes.iteritems():
            self.execute_rpc('set_host_attribute', attribute=attr,
                             value=value, hostname=host)


class host_mod(BaseHostModCreate):
    """atest host mod [--lock|--unlock --force_modify_locking
    --platform <arch>
    --labels <labels>|--blist <label_file>
    --acls <acls>|--alist <acl_file>
    --protection <protection_type>
    --attributes <attr>=<value>;<attr>=<value>
    --mlist <mach_file>] <hosts>"""
    usage_action = 'mod'

    def __init__(self):
        """Add the options specific to the mod action"""
        super(host_mod, self).__init__()
        self.parser.add_option('--unlock-lock-id',
                               help=('Unlock the lock with the lock-id. %s' %
                                     skylab_utils.MSG_ONLY_VALID_IN_SKYLAB),
                               default=None)
        self.parser.add_option('-f', '--force_modify_locking',
                               help='Forcefully lock\unlock a host',
                               action='store_true')
        self.parser.add_option('--remove_acls',
                               help=('Remove all active acls. %s' %
                                     skylab_utils.MSG_INVALID_IN_SKYLAB),
                               action='store_true')
        self.parser.add_option('--remove_labels',
                               help='Remove all labels.',
                               action='store_true')

        self.add_skylab_options()
        self.parser.add_option('--new-env',
                               dest='new_env',
                               choices=['staging', 'prod'],
                               help=('The new environment ("staging" or '
                                     '"prod") of the hosts. %s' %
                                     skylab_utils.MSG_ONLY_VALID_IN_SKYLAB),
                               default=None)


    def _parse_unlock_options(self, options):
        """Parse unlock related options."""
        if self.skylab and options.unlock and options.unlock_lock_id is None:
            self.invalid_syntax('Must provide --unlock-lock-id with "--skylab '
                                '--unlock".')

        if (not (self.skylab and options.unlock) and
            options.unlock_lock_id is not None):
            self.invalid_syntax('--unlock-lock-id is only valid with '
                                '"--skylab --unlock".')

        self.unlock_lock_id = options.unlock_lock_id


    def parse(self):
        """Consume the specific options"""
        (options, leftover) = super(host_mod, self).parse()

        self._parse_unlock_options(options)

        if options.force_modify_locking:
             self.data['force_modify_locking'] = True

        if self.skylab and options.remove_acls:
            # TODO(nxia): drop the flag when all hosts are migrated to skylab
            self.invalid_syntax('--remove_acls is not supported with --skylab.')

        self.remove_acls = options.remove_acls
        self.remove_labels = options.remove_labels
        self.new_env = options.new_env

        return (options, leftover)


    def execute_skylab(self):
        """Execute atest host mod with --skylab.

        @return A list of hostnames which have been successfully modified.
        """
        inventory_repo = skylab_utils.InventoryRepo(self.inventory_repo_dir)
        inventory_repo.initialize()
        data_dir = inventory_repo.get_data_dir()
        lab = text_manager.load_lab(data_dir)

        locked_by = None
        if self.lock:
            locked_by = inventory_repo.git_repo.config('user.email')

        successes = []
        for hostname in self.hosts:
            try:
                device.modify(
                        lab,
                        'duts',
                        hostname,
                        self.environment,
                        lock=self.lock,
                        locked_by=locked_by,
                        lock_reason = self.lock_reason,
                        unlock=self.unlock,
                        unlock_lock_id=self.unlock_lock_id,
                        attributes=self.attributes,
                        remove_labels=self.remove_labels,
                        label_map=self.label_map,
                        new_env=self.new_env)
                successes.append(hostname)
            except device.SkylabDeviceActionError as e:
                print('Cannot modify host %s: %s' % (hostname, e))

        if successes:
            text_manager.dump_lab(data_dir, lab)

            status = inventory_repo.git_repo.status()
            if not status:
                print('Nothing is changed for hosts %s.' % successes)
                return []

            message = skylab_utils.construct_commit_message(
                    'Modify %d hosts.\n\n%s' % (len(successes), successes))
            self.change_number = inventory_repo.upload_change(
                    message, draft=self.draft, dryrun=self.dryrun,
                    submit=self.submit)

        return successes


    def execute(self):
        """Execute 'atest host mod'."""
        if self.skylab:
            return self.execute_skylab()

        successes = []
        for host in self.execute_rpc('get_hosts', hostname__in=self.hosts):
            self.host_ids[host['hostname']] = host['id']
        for host in self.hosts:
            if host not in self.host_ids:
                self.failure('Cannot modify non-existant host %s.' % host)
                continue
            host_id = self.host_ids[host]

            try:
                if self.data:
                    self.execute_rpc('modify_host', item=host,
                                     id=host, **self.data)

                if self.attributes:
                    self._set_attributes(host, self.attributes)

                if self.labels or self.remove_labels:
                    self._set_labels(host, self.labels)

                if self.platform:
                    self._set_platform_label(host, self.platform)

                # TODO: Make the AFE return True or False,
                # especially for lock
                successes.append(host)
            except topic_common.CliError, full_error:
                # Already logged by execute_rpc()
                pass

        if self.acls or self.remove_acls:
            self._set_acls(self.hosts, self.acls)

        return successes


    def output(self, hosts):
        """Print output of 'atest host mod'.

        @param hosts: the host list to be printed.
        """
        for msg in self.messages:
            self.print_wrapped(msg, hosts)

        if hosts and self.skylab:
            print('Modified hosts: %s.' % ', '.join(hosts))
            if self.skylab and not self.dryrun and not self.submit:
                print(skylab_utils.get_cl_message(self.change_number))


class HostInfo(object):
    """Store host information so we don't have to keep looking it up."""
    def __init__(self, hostname, platform, labels):
        self.hostname = hostname
        self.platform = platform
        self.labels = labels


class host_create(BaseHostModCreate):
    """atest host create [--lock|--unlock --platform <arch>
    --labels <labels>|--blist <label_file>
    --acls <acls>|--alist <acl_file>
    --protection <protection_type>
    --attributes <attr>=<value>;<attr>=<value>
    --mlist <mach_file>] <hosts>"""
    usage_action = 'create'

    def parse(self):
        """Option logic specific to create action.
        """
        (options, leftovers) = super(host_create, self).parse()
        self.locked = options.lock
        if 'serials' in self.attributes:
            if len(self.hosts) > 1:
                raise topic_common.CliError('Can not specify serials with '
                                            'multiple hosts.')


    @classmethod
    def construct_without_parse(
            cls, web_server, hosts, platform=None,
            locked=False, lock_reason='', labels=[], acls=[],
            protection=host_protections.Protection.NO_PROTECTION):
        """Construct a host_create object and fill in data from args.

        Do not need to call parse after the construction.

        Return an object of site_host_create ready to execute.

        @param web_server: A string specifies the autotest webserver url.
            It is needed to setup comm to make rpc.
        @param hosts: A list of hostnames as strings.
        @param platform: A string or None.
        @param locked: A boolean.
        @param lock_reason: A string.
        @param labels: A list of labels as strings.
        @param acls: A list of acls as strings.
        @param protection: An enum defined in host_protections.
        """
        obj = cls()
        obj.web_server = web_server
        try:
            # Setup stuff needed for afe comm.
            obj.afe = rpc.afe_comm(web_server)
        except rpc.AuthError, s:
            obj.failure(str(s), fatal=True)
        obj.hosts = hosts
        obj.platform = platform
        obj.locked = locked
        if locked and lock_reason.strip():
            obj.data['lock_reason'] = lock_reason.strip()
        obj.labels = labels
        obj.acls = acls
        if protection:
            obj.data['protection'] = protection
        obj.attributes = {}
        return obj


    def _detect_host_info(self, host):
        """Detect platform and labels from the host.

        @param host: hostname

        @return: HostInfo object
        """
        # Mock an afe_host object so that the host is constructed as if the
        # data was already in afe
        data = {'attributes': self.attributes, 'labels': self.labels}
        afe_host = frontend.Host(None, data)
        store = host_info.InMemoryHostInfoStore(
                host_info.HostInfo(labels=self.labels,
                                   attributes=self.attributes))
        machine = {
                'hostname': host,
                'afe_host': afe_host,
                'host_info_store': store
        }
        try:
            if bin_utils.ping(host, tries=1, deadline=1) == 0:
                serials = self.attributes.get('serials', '').split(',')
                adb_serial = self.attributes.get('serials')
                host_dut = hosts.create_host(machine,
                                             adb_serial=adb_serial)

                info = HostInfo(host, host_dut.get_platform(),
                                host_dut.get_labels())
                # Clean host to make sure nothing left after calling it,
                # e.g. tunnels.
                if hasattr(host_dut, 'close'):
                    host_dut.close()
            else:
                # Can't ping the host, use default information.
                info = HostInfo(host, None, [])
        except (socket.gaierror, error.AutoservRunError,
                error.AutoservSSHTimeout):
            # We may be adding a host that does not exist yet or we can't
            # reach due to hostname/address issues or if the host is down.
            info = HostInfo(host, None, [])
        return info


    def _execute_add_one_host(self, host):
        # Always add the hosts as locked to avoid the host
        # being picked up by the scheduler before it's ACL'ed.
        self.data['locked'] = True
        if not self.locked:
            self.data['lock_reason'] = 'Forced lock on device creation'
        self.execute_rpc('add_host', hostname=host, status="Ready", **self.data)

        # If there are labels avaliable for host, use them.
        info = self._detect_host_info(host)
        labels = set(self.labels)
        if info.labels:
            labels.update(info.labels)

        if labels:
            self._set_labels(host, list(labels))

        # Now add the platform label.
        # If a platform was not provided and we were able to retrieve it
        # from the host, use the retrieved platform.
        platform = self.platform if self.platform else info.platform
        if platform:
            self._set_platform_label(host, platform)

        if self.attributes:
            self._set_attributes(host, self.attributes)


    def execute(self):
        """Execute 'atest host create'."""
        successful_hosts = []
        for host in self.hosts:
            try:
                self._execute_add_one_host(host)
                successful_hosts.append(host)
            except topic_common.CliError:
                pass

        if successful_hosts:
            self._set_acls(successful_hosts, self.acls)

            if not self.locked:
                for host in successful_hosts:
                    self.execute_rpc('modify_host', id=host, locked=False,
                                     lock_reason='')
        return successful_hosts


    def output(self, hosts):
        """Print output of 'atest host create'.

        @param hosts: the added host list to be printed.
        """
        self.print_wrapped('Added host', hosts)


class host_delete(action_common.atest_delete, host):
    """atest host delete [--mlist <mach_file>] <hosts>"""

    def __init__(self):
        super(host_delete, self).__init__()

        self.add_skylab_options()


    def execute_skylab(self):
        """Execute 'atest host delete' with '--skylab'.

        @return A list of hostnames which have been successfully deleted.
        """
        inventory_repo = skylab_utils.InventoryRepo(self.inventory_repo_dir)
        inventory_repo.initialize()
        data_dir = inventory_repo.get_data_dir()
        lab = text_manager.load_lab(data_dir)

        successes = []
        for hostname in self.hosts:
            try:
                device.delete(
                        lab,
                        'duts',
                        hostname,
                        self.environment)
                successes.append(hostname)
            except device.SkylabDeviceActionError as e:
                print('Cannot delete host %s: %s' % (hostname, e))

        if successes:
            text_manager.dump_lab(data_dir, lab)
            message = skylab_utils.construct_commit_message(
                    'Delete %d hosts.\n\n%s' % (len(successes), successes))
            self.change_number = inventory_repo.upload_change(
                    message, draft=self.draft, dryrun=self.dryrun,
                    submit=self.submit)

        return successes


    def execute(self):
        """Execute 'atest host delete'.

        @return A list of hostnames which have been successfully deleted.
        """
        if self.skylab:
            return self.execute_skylab()

        return super(host_delete, self).execute()


class InvalidHostnameError(Exception):
    """Cannot perform actions on the host because of invalid hostname."""


def _add_hostname_suffix(hostname, suffix):
    """Add the suffix to the hostname."""
    if hostname.endswith(suffix):
        raise InvalidHostnameError(
              'Cannot add "%s" as it already contains the suffix.' % suffix)

    return hostname + suffix


def _remove_hostname_suffix_if_present(hostname, suffix):
    """Remove the suffix from the hostname."""
    if hostname.endswith(suffix):
        return hostname[:len(hostname) - len(suffix)]
    else:
        return hostname


class host_rename(host):
    """Host rename is only for migrating hosts between skylab and AFE DB."""

    usage_action = 'rename'

    def __init__(self):
        """Add the options specific to the rename action."""
        super(host_rename, self).__init__()

        self.parser.add_option('--for-migration',
                               help=('Rename hostnames for migration. Rename '
                                     'each "hostname" to "hostname%s". '
                                     'The original "hostname" must not contain '
                                     'suffix.' % MIGRATED_HOST_SUFFIX),
                               action='store_true',
                               default=False)
        self.parser.add_option('--for-rollback',
                               help=('Rename hostnames for migration rollback. '
                                     'Rename each "hostname%s" to its original '
                                     '"hostname".' % MIGRATED_HOST_SUFFIX),
                               action='store_true',
                               default=False)
        self.parser.add_option('--dryrun',
                               help='Execute the action as a dryrun.',
                               action='store_true',
                               default=False)
        self.parser.add_option('--non-interactive',
                               help='run non-interactively',
                               action='store_true',
                               default=False)


    def parse(self):
        """Consume the options common to host rename."""
        (options, leftovers) = super(host_rename, self).parse()
        self.for_migration = options.for_migration
        self.for_rollback = options.for_rollback
        self.dryrun = options.dryrun
        self.interactive = not options.non_interactive
        self.host_ids = {}

        if not (self.for_migration ^ self.for_rollback):
            self.invalid_syntax('--for-migration and --for-rollback are '
                                'exclusive, and one of them must be enabled.')

        if not self.hosts:
            self.invalid_syntax('Must provide hostname(s).')

        if self.dryrun:
            print('This will be a dryrun and will not rename hostnames.')

        return (options, leftovers)


    def execute(self):
        """Execute 'atest host rename'."""
        if self.interactive:
            if self.prompt_confirmation():
                pass
            else:
                return

        successes = []
        for host in self.execute_rpc('get_hosts', hostname__in=self.hosts):
            self.host_ids[host['hostname']] = host['id']
        for host in self.hosts:
            if host not in self.host_ids:
                self.failure('Cannot rename non-existant host %s.' % host,
                              item=host, what_failed='Failed to rename')
                continue
            try:
                host_id = self.host_ids[host]
                if self.for_migration:
                    new_hostname = _add_hostname_suffix(
                            host, MIGRATED_HOST_SUFFIX)
                else:
                    #for_rollback
                    new_hostname = _remove_hostname_suffix_if_present(
                            host, MIGRATED_HOST_SUFFIX)

                if not self.dryrun:
                    # TODO(crbug.com/850737): delete and abort HQE.
                    data = {'hostname': new_hostname}
                    self.execute_rpc('modify_host', item=host, id=host_id,
                                     **data)
                successes.append((host, new_hostname))
            except InvalidHostnameError as e:
                self.failure('Cannot rename host %s: %s' % (host, e), item=host,
                             what_failed='Failed to rename')
            except topic_common.CliError, full_error:
                # Already logged by execute_rpc()
                pass

        return successes


    def output(self, results):
        """Print output of 'atest host rename'."""
        if results:
            print('Successfully renamed:')
            for old_hostname, new_hostname in results:
                print('%s to %s' % (old_hostname, new_hostname))


class host_migrate(action_common.atest_list, host):
    """'atest host migrate' to migrate or rollback hosts."""

    usage_action = 'migrate'

    def __init__(self):
        super(host_migrate, self).__init__()

        self.parser.add_option('--migration',
                               dest='migration',
                               help='Migrate the hosts to skylab.',
                               action='store_true',
                               default=False)
        self.parser.add_option('--rollback',
                               dest='rollback',
                               help='Rollback the hosts migrated to skylab.',
                               action='store_true',
                               default=False)
        self.parser.add_option('--model',
                               help='Model of the hosts to migrate.',
                               dest='model',
                               default=None)
        self.parser.add_option('--board',
                               help='Board of the hosts to migrate.',
                               dest='board',
                               default=None)
        self.parser.add_option('--pool',
                               help=('Pool of the hosts to migrate. Must '
                                     'specify --model for the pool.'),
                               dest='pool',
                               default=None)

        self.add_skylab_options(enforce_skylab=True)


    def parse(self):
        """Consume the specific options"""
        (options, leftover) = super(host_migrate, self).parse()

        self.migration = options.migration
        self.rollback = options.rollback
        self.model = options.model
        self.pool = options.pool
        self.board = options.board
        self.host_ids = {}

        if not (self.migration ^ self.rollback):
            self.invalid_syntax('--migration and --rollback are exclusive, '
                                'and one of them must be enabled.')

        if self.pool is not None and (self.model is None and
                                      self.board is None):
            self.invalid_syntax('Must provide --model or --board with --pool.')

        if not self.hosts and not (self.model or self.board):
            self.invalid_syntax('Must provide hosts or --model or --board.')

        return (options, leftover)


    def _remove_invalid_hostnames(self, hostnames, log_failure=False):
        """Remove hostnames with MIGRATED_HOST_SUFFIX.

        @param hostnames: A list of hostnames.
        @param log_failure: Bool indicating whether to log invalid hostsnames.

        @return A list of valid hostnames.
        """
        invalid_hostnames = set()
        for hostname in hostnames:
            if hostname.endswith(MIGRATED_HOST_SUFFIX):
                if log_failure:
                    self.failure('Cannot migrate host with suffix "%s" %s.' %
                                 (MIGRATED_HOST_SUFFIX, hostname),
                                 item=hostname, what_failed='Failed to rename')
                invalid_hostnames.add(hostname)

        hostnames = list(set(hostnames) - invalid_hostnames)

        return hostnames


    def execute(self):
        """Execute 'atest host migrate'."""
        hostnames = self._remove_invalid_hostnames(self.hosts, log_failure=True)

        filters = {}
        check_results = {}
        if hostnames:
            check_results['hostname__in'] = 'hostname'
            if self.migration:
                filters['hostname__in'] = hostnames
            else:
                # rollback
                hostnames_with_suffix = [
                        _add_hostname_suffix(h, MIGRATED_HOST_SUFFIX)
                        for h in hostnames]
                filters['hostname__in'] = hostnames_with_suffix
        else:
            # TODO(nxia): add exclude_filter {'hostname__endswith':
            # MIGRATED_HOST_SUFFIX} for --migration
            if self.rollback:
                filters['hostname__endswith'] = MIGRATED_HOST_SUFFIX

        labels = []
        if self.model:
            labels.append('model:%s' % self.model)
        if self.pool:
            labels.append('pool:%s' % self.pool)
        if self.board:
            labels.append('board:%s' % self.board)

        if labels:
            if len(labels) == 1:
                filters['labels__name__in'] = labels
                check_results['labels__name__in'] = None
            else:
                filters['multiple_labels'] = labels
                check_results['multiple_labels'] = None

        results = super(host_migrate, self).execute(
                op='get_hosts', filters=filters, check_results=check_results)
        hostnames = [h['hostname'] for h in results]

        if self.migration:
            hostnames = self._remove_invalid_hostnames(hostnames)
        else:
            # rollback
            hostnames = [_remove_hostname_suffix(h, MIGRATED_HOST_SUFFIX)
                         for h in hostnames]

        return self.execute_skylab_migration(hostnames)


    def assign_duts_to_drone(self, infra, devices, environment):
        """Assign uids of the devices to a random skylab drone.

        @param infra: An instance of lab_pb2.Infrastructure.
        @param devices: A list of device_pb2.Device to be assigned to the drone.
        @param environment: 'staging' or 'prod'.
        """
        skylab_drones = skylab_server.get_servers(
                infra, environment, role='skylab_drone', status='primary')

        if len(skylab_drones) == 0:
            raise device.SkylabDeviceActionError(
                'No skylab drone is found in primary status and staging '
                'environment. Please confirm there is at least one valid skylab'
                ' drone added in skylab inventory.')

        for device in devices:
            # Randomly distribute each device to a skylab_drone.
            skylab_drone = random.choice(skylab_drones)
            skylab_server.add_dut_uids(skylab_drone, [device])


    def remove_duts_from_drone(self, infra, devices):
        """Remove uids of the devices from their skylab drones.

        @param infra: An instance of lab_pb2.Infrastructure.
        @devices: A list of device_pb2.Device to be remove from the drone.
        """
        skylab_drones = skylab_server.get_servers(
                infra, 'staging', role='skylab_drone', status='primary')

        for skylab_drone in skylab_drones:
            skylab_server.remove_dut_uids(skylab_drone, devices)


    def execute_skylab_migration(self, hostnames):
        """Execute migration in skylab_inventory.

        @param hostnames: A list of hostnames to migrate.
        @return If there're hosts to migrate, return a list of the hostnames and
                a message instructing actions after the migration; else return
                None.
        """
        if not hostnames:
            return

        inventory_repo = skylab_utils.InventoryRepo(self.inventory_repo_dir)
        inventory_repo.initialize()

        subdirs = ['skylab', 'prod', 'staging']
        data_dirs = skylab_data_dir, prod_data_dir, staging_data_dir = [
                inventory_repo.get_data_dir(data_subdir=d) for d in subdirs]
        skylab_lab, prod_lab, staging_lab = [
                text_manager.load_lab(d) for d in data_dirs]
        infra = text_manager.load_infrastructure(skylab_data_dir)

        label_map = None
        labels = []
        if self.board:
            labels.append('board:%s' % self.board)
        if self.model:
            labels.append('model:%s' % self.model)
        if self.pool:
            labels.append('critical_pool:%s' % self.pool)
        if labels:
            label_map = device.convert_to_label_map(labels)

        if self.migration:
            prod_devices = device.move_devices(
                    prod_lab, skylab_lab, 'duts', label_map=label_map,
                    hostnames=hostnames)
            staging_devices = device.move_devices(
                    staging_lab, skylab_lab, 'duts', label_map=label_map,
                    hostnames=hostnames)

            all_devices = prod_devices + staging_devices
            # Hostnames in afe_hosts tabel.
            device_hostnames = [str(d.common.hostname) for d in all_devices]
            message = (
                'Migration: move %s hosts into skylab_inventory.\n\n'
                'Please run this command after the CL is submitted:\n'
                'atest host rename --for-migration %s' %
                (len(all_devices), ' '.join(device_hostnames)))

            self.assign_duts_to_drone(infra, prod_devices, 'prod')
            self.assign_duts_to_drone(infra, staging_devices, 'staging')
        else:
            # rollback
            prod_devices = device.move_devices(
                    skylab_lab, prod_lab, 'duts', environment='prod',
                    label_map=label_map, hostnames=hostnames)
            staging_devices = device.move_devices(
                    skylab_lab, staging_lab, 'duts', environment='staging',
                    label_map=label_map, hostnames=hostnames)

            all_devices = prod_devices + staging_devices
            # Hostnames in afe_hosts tabel.
            device_hostnames = [_add_hostname_suffix(str(d.common.hostname),
                                                     MIGRATED_HOST_SUFFIX)
                                for d in all_devices]
            message = (
                'Rollback: remove %s hosts from skylab_inventory.\n\n'
                'Please run this command after the CL is submitted:\n'
                'atest host rename --for-rollback %s' %
                (len(all_devices), ' '.join(device_hostnames)))

            self.remove_duts_from_drone(infra, all_devices)

        if all_devices:
            text_manager.dump_infrastructure(skylab_data_dir, infra)

            if prod_devices:
                text_manager.dump_lab(prod_data_dir, prod_lab)

            if staging_devices:
                text_manager.dump_lab(staging_data_dir, staging_lab)

            text_manager.dump_lab(skylab_data_dir, skylab_lab)

            self.change_number = inventory_repo.upload_change(
                    message, draft=self.draft, dryrun=self.dryrun,
                    submit=self.submit)

            return all_devices, message


    def output(self, result):
        """Print output of 'atest host list'.

        @param result: the result to be printed.
        """
        if result:
            devices, message = result

            if devices:
                hostnames = [h.common.hostname for h in devices]
                if self.migration:
                    print('Migrating hosts: %s' % ','.join(hostnames))
                else:
                    # rollback
                    print('Rolling back hosts: %s' % ','.join(hostnames))

                if not self.dryrun:
                    if not self.submit:
                        print(skylab_utils.get_cl_message(self.change_number))
                    else:
                        # Print the instruction command for renaming hosts.
                        print('%s' % message)
        else:
            print('No hosts were migrated.')


def _host_skylab_migrate_get_hostnames(obj, class_, model=None, pool=None, board=None):
    """
    @params : in 'model', 'pool', 'board'

    """
    # TODO(gregorynisbet)
    # this just gets all the hostnames, it doesn't filter by
    # presence or absence of migrated-do-not-use.
    labels = []
    for key, value in ({'model': model, 'board': board, 'pool': pool}).items():
        if value:
            labels.append(key + ":" + value)
    filters = {}
    check_results = {}
    # Copy the filter and check_results initialization logic from
    # the 'execute' method of the class 'host_migrate'.
    if not labels:
        return []
    elif len(labels) == 1:
        filters['labels__name__in'] = labels
        check_results['labels__name__in'] = None
    elif len(labels) > 1:
        filters['multiple_labels'] = labels
        check_results['multiple_labels'] = None
    else:
        assert False

    results = super(class_, obj).execute(
        op='get_hosts', filters=filters, check_results=check_results)
    return [result['hostname'] for result in results]


class host_skylab_migrate(action_common.atest_list, host):
    usage_action = 'skylab_migrate'

    def __init__(self):
        super(host_skylab_migrate, self).__init__()
        self.parser.add_option('--dry-run',
                               help='Dry run. Show only candidate hosts.',
                               action='store_true',
                               dest='dry_run')
        self.parser.add_option('--ratio',
                               help='ratio of hosts to migrate as number from 0 to 1.',
                               type=float,
                               dest='ratio',
                               default=1)
        self.parser.add_option('--bug-number',
                               help='bug number for tracking purposes.',
                               dest='bug_number',
                               default=None)
        self.parser.add_option('--board',
                               help='Board of the hosts to migrate',
                               dest='board',
                               default=None)
        self.parser.add_option('--model',
                               help='Model of the hosts to migrate',
                               dest='model',
                               default=None)
        self.parser.add_option('--pool',
                               help='Pool of the hosts to migrate',
                               dest='pool',
                               default=None)
        self.parser.add_option('-q',
                               '--quick',
                               help='use quick-add-duts',
                               dest='use_quick_add',
                               action='store_true')
        self.parser.add_option('-s',
                               '--slow',
                               help='don\'t use quick-add-duts',
                               dest='no_use_quick_add',
                               action='store_true')
        self.parser.add_option('-b',
                               '--batch-size',
                               help='process n duts at a time',
                               dest="batch_size",
                               default=None)

    def parse(self):
        (options, leftover) = super(host_skylab_migrate, self).parse()
        self.dry_run = options.dry_run
        self.ratio = options.ratio
        self.bug_number = options.bug_number
        self.model = options.model
        self.pool = options.pool
        self.board = options.board
        self._reason = "migration to skylab: %s" % self.bug_number
        use_quick_add = options.use_quick_add
        no_use_quick_add = options.no_use_quick_add
        if use_quick_add:
            if no_use_quick_add:
                self.invalid_syntax('cannot supply both --quick and --slow.')
            else:
                self.use_quick_add = True
        else:
            if no_use_quick_add:
                self.use_quick_add = False
            else:
                self.invalid_syntax('must include either --quick or --slow.')
        self.batch_size = options.batch_size

        return (options, leftover)

    def _validate_one_hostname_source(self):
        """Validate that hostname source is explicit hostnames or valid query.

        Hostnames must either be provided explicitly or be the result of a
        query defined by 'model', 'board', and 'pool'.

        @returns : whether the hostnames come from exactly one valid source.
        """
        has_criteria = any([(self.model and self.board), self.board, self.pool])
        has_command_line_hosts = bool(self.hosts)
        if has_criteria != has_command_line_hosts:
            # all good, one data source
            return True
        if has_criteria and has_command_line_hosts:
            self.failure(
                '--model/host/board and explicit hostnames are alternatives. Provide exactly one.',
                item='cli',
                what_failed='user')
            return False
        self.failure(
            'no explicit hosts and no criteria provided.',
            item='cli',
            what_failed='user')
        return False


    def execute(self):
        if not self._validate_one_hostname_source():
            return None
        if self.hosts:
            hostnames = self.hosts
        else:
            hostnames = _host_skylab_migrate_get_hostnames(
                obj=self,
                class_=host_skylab_migrate,
                model=self.model,
                board=self.board,
                pool=self.pool,
            )
        if self.dry_run:
            return hostnames
        if not hostnames:
            return {'error': 'no hosts to migrate'}
        res = skylab_migration.migrate(
            ratio=self.ratio,
            reason=self._reason,
            hostnames=hostnames,
            max_duration=10 * 60,
            interval_len=2,
            min_ready_intervals=10,
            immediately=True,
            use_quick_add=self.use_quick_add,
            batch_size=self.batch_size,
        )
        return res


    def output(self, result):
        if result is not None:
            print json.dumps(result, indent=4, sort_keys=True)


class host_skylab_rollback(action_common.atest_list, host):
    usage_action = "skylab_rollback"

    def __init__(self):
        super(host_skylab_rollback, self).__init__()
        self.parser.add_option('--bug-number',
                               help='bug number for tracking purposes.',
                               dest='bug_number',
                               default=None)

    def parse(self):
        (options, leftover) = super(host_skylab_rollback, self).parse()
        self.bug_number = options.bug_number
        return (options, leftover)

    def execute(self):
        if self.hosts:
            hostnames = self.hosts
        else:
            hostnames = _host_skylab_migrate_get_hostnames(
                obj=self,
                class_=host_skylab_migrate,
                model=self.model,
                board=self.board,
                pool=self.pool,
            )
        if not hostnames:
            return {'error': 'no hosts to migrate'}
        res = skylab_rollback.rollback(
            hosts=hostnames,
            bug=self.bug_number,
            dry_run=False,
        )
        return res


    def output(self, result):
        print result


class host_skylab_verify(action_common.atest_list, host):
    usage_action = "skylab_verify"

    def __init__(self):
        super(host_skylab_verify, self).__init__()

    def parse(self):
        (options, leftover) = super(host_skylab_verify, self).parse()
        return (options, leftover)

    def execute(self):
        if self.hosts:
            hostnames = self.hosts
        else:
            hostnames = _host_skylab_migrate_get_hostnames(
                obj=self,
                class_=host_skylab_migrate,
                model=self.model,
                board=self.board,
                pool=self.pool,
            )
        if not hostnames:
            return {'error': 'no hosts to migrate'}
        res = skylab_migration.hostname_migrated_status(
            hostnames=hostnames,
        )
        return res


    def output(self, result):
        json.dump(result, sys.stdout, indent=4)