"""Provides a factory method to create a host object."""

from contextlib import closing
from autotest_lib.client.common_lib import error, global_config
from autotest_lib.server import autotest, utils as server_utils
from autotest_lib.server.hosts import site_factory, cros_host, ssh_host, serial
from autotest_lib.server.hosts import adb_host, logfile_monitor


DEFAULT_FOLLOW_PATH = '/var/log/kern.log'
DEFAULT_PATTERNS_PATH = 'console_patterns'
SSH_ENGINE = global_config.global_config.get_config_value('AUTOSERV',
                                                          'ssh_engine',
                                                          type=str)

# Default ssh options used in creating a host.
DEFAULT_SSH_USER = 'root'
DEFAULT_SSH_PASS = ''
DEFAULT_SSH_PORT = 22
DEFAULT_SSH_VERBOSITY = ''
DEFAULT_SSH_OPTIONS = ''

# for tracking which hostnames have already had job_start called
_started_hostnames = set()


def _get_host_arguments():
    """Returns parameters needed to ssh into a host.

    There are currently 2 use cases for creating a host.
    1. Through the server_job, in which case the server_job injects
       the appropriate ssh parameters into our name space and they
       are available as the variables ssh_user, ssh_pass etc.
    2. Directly through factory.create_host, in which case we use
       the same defaults as used in the server job to create a host.

    @returns: A tuple of parameters needed to create an ssh connection, ordered
              as: ssh_user, ssh_pass, ssh_port, ssh_verbosity, ssh_options.
    """
    g = globals()
    return (g.get('ssh_user', DEFAULT_SSH_USER),
            g.get('ssh_pass', DEFAULT_SSH_PASS),
            g.get('ssh_port', DEFAULT_SSH_PORT),
            g.get('ssh_verbosity_flag', DEFAULT_SSH_VERBOSITY),
            g.get('ssh_options', DEFAULT_SSH_OPTIONS))


def _detect_host(connectivity_class, hostname, **args):
    """Detect host type.

    Currently checks if adb is on the host and if so returns ADBHost if not or
    if the check fails, it will return CrosHost.

    @param connectivity_class: connectivity class to use to talk to the host
                               (ParamikoHost or SSHHost)
    @param hostname: A string representing the host name of the device.
    @param args: Args that will be passed to the constructor of
                 the host class.

    @returns Class type to use for this host.
    """
    # Detect if adb is on the host. If so we are using an ADBHost. If not use,
    # CrosHost.
    try:
        # Attempt to find adb on the system. If that succeeds use ADBHost.
        with closing(connectivity_class(hostname, **args)) as host:
            # Send stderr to /dev/null which cleans up log spam about not
            # finding adb installed.
            result = host.run('which adb 2> /dev/null', timeout=10)
            return adb_host.ADBHost
    except (error.AutoservRunError, error.AutoservSSHTimeout):
        # If any errors occur use CrosHost.
        # TODO(fdeng): this method should should dynamically discover
        # and allocate host types, crbug.com/273843
        # TODO crbug.com/302026 (sbasi) - adjust this pathway for ADBHost in
        # the future should a host require verify/repair.
        return cros_host.CrosHost


def create_host(
    hostname, auto_monitor=False, follow_paths=None, pattern_paths=None,
    netconsole=False, **args):
    """Create a host object.

    This method mixes host classes that are needed into a new subclass
    and creates a instance of the new class.

    @param hostname: A string representing the host name of the device.
    @param auto_monitor: A boolean value, if True, will try to mix
                         SerialHost in. If the host supports use as SerialHost,
                         will not mix in LogfileMonitorMixin anymore.
                         If the host doesn't support it, will
                         fall back to direct demesg logging and mix
                         LogfileMonitorMixin in.
    @param follow_paths: A list, passed to LogfileMonitorMixin,
                         remote paths to monitor.
    @param pattern_paths: A list, passed to LogfileMonitorMixin,
                          local paths to alert pattern definition files.
    @param netconsole: A boolean value, if True, will mix NetconsoleHost in.
    @param args: Args that will be passed to the constructor of
                 the new host class.
    @param adb: If True creates an instance of adb_host not cros_host.

    @returns: A host object which is an instance of the newly created
              host class.
    """

    ssh_user, ssh_pass, ssh_port, ssh_verbosity_flag, ssh_options = \
            _get_host_arguments()

    hostname, args['user'], args['password'], args['port'] = \
            server_utils.parse_machine(hostname, ssh_user, ssh_pass, ssh_port)
    args['ssh_verbosity_flag'] = ssh_verbosity_flag
    args['ssh_options'] = ssh_options

    # by default assume we're using SSH support
    if SSH_ENGINE == 'paramiko':
        from autotest_lib.server.hosts import paramiko_host
        connectivity_class = paramiko_host.ParamikoHost
    elif SSH_ENGINE == 'raw_ssh':
        connectivity_class = ssh_host.SSHHost
    else:
        raise error.AutoServError("Unknown SSH engine %s. Please verify the "
                                  "value of the configuration key 'ssh_engine' "
                                  "on autotest's global_config.ini file." %
                                  SSH_ENGINE)

    classes = [_detect_host(connectivity_class, hostname, **args),
               connectivity_class]
    # by default mix in run_test support
    classes.append(autotest.AutotestHostMixin)

    # if the user really wants to use netconsole, let them
    if netconsole:
        classes.append(netconsole.NetconsoleHost)

    if auto_monitor:
        # use serial console support if it's available
        conmux_args = {}
        for key in ("conmux_server", "conmux_attach"):
            if key in args:
                conmux_args[key] = args[key]
        if serial.SerialHost.host_is_supported(hostname, **conmux_args):
            classes.append(serial.SerialHost)
        else:
            # no serial available, fall back to direct dmesg logging
            if follow_paths is None:
                follow_paths = [DEFAULT_FOLLOW_PATH]
            else:
                follow_paths = list(follow_paths) + [DEFAULT_FOLLOW_PATH]

            if pattern_paths is None:
                pattern_paths = [DEFAULT_PATTERNS_PATH]
            else:
                pattern_paths = (
                    list(pattern_paths) + [DEFAULT_PATTERNS_PATH])

            logfile_monitor_class = logfile_monitor.NewLogfileMonitorMixin(
                follow_paths, pattern_paths)
            classes.append(logfile_monitor_class)

    elif follow_paths:
        logfile_monitor_class = logfile_monitor.NewLogfileMonitorMixin(
            follow_paths, pattern_paths)
        classes.append(logfile_monitor_class)

    # do any site-specific processing of the classes list
    site_factory.postprocess_classes(classes, hostname,
                                     auto_monitor=auto_monitor, **args)

    # create a custom host class for this machine and return an instance of it
    host_class = type("%s_host" % hostname, tuple(classes), {})
    host_instance = host_class(hostname, **args)

    # call job_start if this is the first time this host is being used
    if hostname not in _started_hostnames:
        host_instance.job_start()
        _started_hostnames.add(hostname)

    return host_instance