#
# Copyright 2007 Google Inc. Released under the GPL v2

"""
This module defines the base classes for the server Host hierarchy.

Implementation details:
You should import the "hosts" package instead of importing each type of host.

        Host: a machine on which you can run programs
        RemoteHost: a remote machine on which you can run programs
"""

__author__ = """
mbligh@google.com (Martin J. Bligh),
poirier@google.com (Benjamin Poirier),
stutsman@google.com (Ryan Stutsman)
"""

from autotest_lib.client.bin import utils
from autotest_lib.client.common_lib import hosts
from autotest_lib.server import utils as server_utils
try:
    from chromite.lib import metrics
except ImportError:
    metrics = utils.metrics_mock


class Host(hosts.Host):
    """
    This class represents a machine on which you can run programs.

    It may be a local machine, the one autoserv is running on, a remote
    machine or a virtual machine.

    Implementation details:
    This is an abstract class, leaf subclasses must implement the methods
    listed here. You must not instantiate this class but should
    instantiate one of those leaf subclasses.

    When overriding methods that raise NotImplementedError, the leaf class
    is fully responsible for the implementation and should not chain calls
    to super. When overriding methods that are a NOP in Host, the subclass
    should chain calls to super(). The criteria for fitting a new method into
    one category or the other should be:
        1. If two separate generic implementations could reasonably be
           concatenated, then the abstract implementation should pass and
           subclasses should chain calls to super.
        2. If only one class could reasonably perform the stated function
           (e.g. two separate run() implementations cannot both be executed)
           then the method should raise NotImplementedError in Host, and
           the implementor should NOT chain calls to super, to ensure that
           only one implementation ever gets executed.
    """

    bootloader = None
    support_devserver_provision = False


    def __init__(self, *args, **dargs):
        super(Host, self).__init__(*args, **dargs)

        self.start_loggers()
        if self.job:
            self.job.hosts.add(self)


    def _initialize(self, *args, **dargs):
        super(Host, self)._initialize(*args, **dargs)

        self.serverdir = server_utils.get_server_dir()
        self.env = {}


    def close(self):
        super(Host, self).close()

        if self.job:
            self.job.hosts.discard(self)


_CREATION_METRIC_WHITELIST = {
        'AbstractSSHHost',
        'ADBHost',
        'CastOSHost',
        'ChameleonHost',
        'CrosHost',
        'EmulatedAdbHost',
        'GceHost',
        'JetstreamHost',
        'MoblabHost',
        'PlanktonHost',
        'ServoHost',
        'SonicHost',
        'SSHHost',
        'TestBed',
        'TestStationHost',
}
_CREATION_METRIC = '/chrome/infra/chromeos/autotest/host/class_instantiated'


def send_creation_metric(host, context=''):
    """Send a metric about which host class we ended up creating.

    Creating host classes is black magic. Once a host class has been created
    through the various channels, use this function to report what got created.

    @param host: An instace of one of the host classes to send a report about.
    @param context: Optional context for who created the host instance.
    """
    bases = {b.__name__ for b in host.__class__.__bases__}
    bases = bases & _CREATION_METRIC_WHITELIST
    for base in bases:
        metrics.Counter(_CREATION_METRIC).increment(fields={
                'class': base,
                'context': context,
        })