#
# Copyright (C) 2010, 2013 Red Hat, Inc.
# Copyright (C) 2010 Cole Robinson <crobinso@redhat.com>
#
# This program 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 2 of the License, or
# (at your option) any later version.
#
# This program 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 this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
# MA 02110-1301 USA.
#

import logging

from gi.repository import GObject

from .baseclass import vmmGObject


class vmmLibvirtObject(vmmGObject):
    __gsignals__ = {
        "state-changed": (GObject.SignalFlags.RUN_FIRST, None, []),
        "initialized": (GObject.SignalFlags.RUN_FIRST, None, [bool]),
    }

    _STATUS_ACTIVE = 1
    _STATUS_INACTIVE = 2

    def __init__(self, conn, backend, key, parseclass):
        vmmGObject.__init__(self)
        self._conn = conn
        self._backend = backend
        self._key = key
        self._parseclass = parseclass

        self.__initialized = False
        self.__status = None
        self._support_isactive = None

        self._xmlobj = None
        self._xmlobj_to_define = None
        self._is_xml_valid = False

        # These should be set by the child classes if necessary
        self._inactive_xml_flags = 0
        self._active_xml_flags = 0

        # Cache object name. We may need to do this even
        # before init_libvirt_state since it might be needed ahead of time.
        self._name = None
        self.get_name()

    @staticmethod
    def log_redefine_xml_diff(obj, origxml, newxml):
        objname = "<%s name=%s>" % (obj.__class__.__name__, obj.get_name())
        if origxml == newxml:
            logging.debug("Redefine requested for %s, but XML didn't change!",
                          objname)
            return

        import difflib
        diff = "".join(difflib.unified_diff(origxml.splitlines(1),
                                            newxml.splitlines(1),
                                            fromfile="Original XML",
                                            tofile="New XML"))
        logging.debug("Redefining %s with XML diff:\n%s", objname, diff)

    @staticmethod
    def lifecycle_action(fn):
        """
        Decorator for object lifecycle actions like start, stop, delete.
        Will make sure any necessary state is updated accordingly.
        """
        def newfn(self, *args, **kwargs):
            ret = fn(self, *args, **kwargs)

            # If events are supported, this is a no-op, but the event loop
            # will trigger force_status_update, which will refresh_xml as well.
            #
            # If events aren't supported, the priority tick will call
            # self.tick(), which will call force_status_update
            poll_param = self._conn_tick_poll_param()  # pylint: disable=protected-access
            tick_kwargs = {poll_param: True}
            self.conn.schedule_priority_tick(**tick_kwargs)

            return ret
        return newfn

    def _cleanup(self):
        pass

    def _get_conn(self):
        return self._conn
    conn = property(_get_conn)

    def get_backend(self):
        return self._backend
    def get_connkey(self):
        return self._key

    def change_name_backend(self, newbackend):
        # Used for changing the backing object after a rename
        self._backend = newbackend

    def define_name(self, newname):
        oldconnkey = self.get_connkey()
        oldname = self.get_xmlobj().name

        self.ensure_latest_xml()
        xmlobj = self._make_xmlobj_to_define()
        if xmlobj.name == newname:
            return

        logging.debug("Changing %s name from %s to %s",
                      self.__class__, oldname, newname)
        origxml = xmlobj.get_xml_config()
        xmlobj.name = newname
        newxml = xmlobj.get_xml_config()

        try:
            self._key = newname
            self.conn.rename_object(self, origxml, newxml, oldconnkey)
        except:
            self._key = oldname
            raise
        finally:
            self.__force_refresh_xml()


    #############################################################
    # Functions that should probably be overridden in sub class #
    #############################################################

    def _XMLDesc(self, flags):
        raise NotImplementedError()
    def class_name(self):
        raise NotImplementedError()
    def _conn_tick_poll_param(self):
        # The parameter name for conn.tick() object polling. So
        # for vmmDomain == "pollvm"
        raise NotImplementedError()

    def reports_stats(self):
        return False
    def _using_events(self):
        return False
    def _check_supports_isactive(self):
        return False
    def _get_backend_status(self):
        raise NotImplementedError()

    def _define(self, xml):
        ignore = xml
        return

    def delete(self, force=True):
        ignore = force

    def get_name(self):
        if self._name is None:
            self._name = self._backend_get_name()
        return self._name

    def _backend_get_name(self):
        return self._backend.name()

    def tick(self, stats_update=True):
        raise NotImplementedError()

    def _init_libvirt_state(self):
        raise NotImplementedError()

    def init_libvirt_state(self):
        """
        Function called by vmmConnection to populate initial state when
        a new object appears.
        """
        if self.__initialized:
            return

        initialize_failed = False
        try:
            self._init_libvirt_state()
        except:
            logging.debug("Error initializing libvirt state for %s", self,
                exc_info=True)
            initialize_failed = True

        self.__initialized = True
        self.idle_emit("initialized", initialize_failed)


    ###################
    # Status handling #
    ###################

    def _get_status(self):
        return self.__status

    def is_active(self):
        # vmmDomain overwrites this since it has more fine grained statuses
        return self._get_status() == self._STATUS_ACTIVE

    def run_status(self):
        if self.is_active():
            return _("Active")
        return _("Inactive")

    def _refresh_status(self, newstatus=None, cansignal=True):
        """
        Grab the object status/active state from libvirt, and if the
        status has changed, update the XML cache. Typically called from
        object tick functions for manually updating the object state.

        :param newstatus: Used by vmmDomain as a small optimization to
            avoid polling info() twice
        :param cansignal: If True, this function will signal state-changed
            if required.
        :returns: True if status changed, false otherwise
        """
        if (self._using_events() and
            self.__status is not None):
            return False

        if newstatus is None:
            newstatus = self._get_backend_status()
        status = newstatus
        if status == self.__status:
            return False
        self.__status = status

        self.ensure_latest_xml(nosignal=True)
        if cansignal:
            self.idle_emit("state-changed")
        return True

    def _backend_get_active(self):
        if self._support_isactive is None:
            self._support_isactive = self._check_supports_isactive()

        if not self._support_isactive:
            return self._STATUS_ACTIVE
        return (bool(self._backend.isActive()) and
                self._STATUS_ACTIVE or
                self._STATUS_INACTIVE)


    ##################
    # Public XML API #
    ##################

    def refresh_from_event_loop(self):
        """
        Updates the VM status and XML, because we received an event from
        libvirt's event implementations. That's the only time this should
        be used.

        We refresh status and XML because they are tied together in subtle
        ways, like runtime XML changing when a VM is started.
        """
        try:
            self.__force_refresh_xml(nosignal=True)
            # status = None forces a signal to be emitted
            self.__status = None
            self._refresh_status()
        except Exception, e:
            # If we hit an exception here, it's often that the object
            # disappeared, so request the poll loop to be updated
            logging.debug("Error refreshing %s from events: %s", self, e)
            poll_param = self._conn_tick_poll_param()
            if poll_param:
                kwargs = {"force": True, poll_param: True}
                logging.debug("Scheduling priority tick with: %s", kwargs)
                self.conn.schedule_priority_tick(**kwargs)

    def ensure_latest_xml(self, nosignal=False):
        """
        Refresh XML if it isn't up to date, basically if we aren't using
        events.
        """
        if (self._using_events() and
            self._xmlobj and
            self._is_xml_valid):
            return
        self.__force_refresh_xml(nosignal=nosignal)

    def __force_refresh_xml(self, nosignal=False):
        """
        Force an xml update. Signal 'state-changed' if domain xml has
        changed since last refresh

        :param nosignal: If true, don't send state-changed. Used by
            callers that are going to send it anyways.
        """
        origxml = None
        if self._xmlobj:
            origxml = self._xmlobj.get_xml_config()

        self._invalidate_xml()
        active_xml = self._XMLDesc(self._active_xml_flags)
        self._xmlobj = self._parseclass(self.conn.get_backend(),
            parsexml=active_xml)
        self._is_xml_valid = True

        if not nosignal and origxml != active_xml:
            self.idle_emit("state-changed")

    def get_xmlobj(self, inactive=False, refresh_if_nec=True):
        """
        Get object xml, return it wrapped in a virtinst object.
        If cached xml is invalid, update.

        :param inactive: Return persistent XML, not the running config.
            No effect if domain is not running. Use this flag
            if the XML will be used for redefining a guest
        :param refresh_if_nec: Check if XML is out of date, and if so,
            refresh it (default behavior). Skipping a refresh is
            useful to prevent updating xml in the tick loop when
            it's not that important (disk/net stats)
        """
        if inactive:
            # If inactive XML requested, always return a fresh object even if
            # the current object is inactive XML (like when the domain is
            # stopped). Callers that request inactive are basically expecting
            # a new copy.
            inactive_xml = self._XMLDesc(self._inactive_xml_flags)
            return self._parseclass(self.conn.get_backend(),
                parsexml=inactive_xml)

        if (self._xmlobj is None or
            (refresh_if_nec and not self._is_xml_valid)):
            self.ensure_latest_xml()

        return self._xmlobj

    @property
    def xmlobj(self):
        return self.get_xmlobj()


    #########################
    # Internal XML routines #
    #########################

    def _invalidate_xml(self):
        """
        Mark cached XML as invalid. Subclasses may extend this
        to invalidate any specific caches of their own
        """
        self._name = None

        # While for events we do want to clear cached XML values like
        # _name, the XML is never invalid.
        self._is_xml_valid = self._using_events()

    def _make_xmlobj_to_define(self):
        """
        Build an xmlobj that should be used for defining new XML.

        Most subclasses shouldn't touch this, but vmmDomainVirtinst needs to.
        """
        return self.get_xmlobj(inactive=True)

    def _redefine_xmlobj(self, xmlobj, origxml=None):
        """
        Redefine the passed xmlobj, which should be generated with
        self._make_xmlobj_to_define()

        Most subclasses shouldn't touch this, but vmmDomainVirtinst needs to.

        :param origxml: vmmDomainVirtinst uses that field to make sure
            we detect the actual XML change and log it correctly.
        """
        if not origxml:
            origxml = self._make_xmlobj_to_define().get_xml_config()

        newxml = xmlobj.get_xml_config()
        self.log_redefine_xml_diff(self, origxml, newxml)

        if origxml != newxml:
            self._define(newxml)

        if self._using_events():
            return

        # Make sure we have latest XML.
        self.ensure_latest_xml(nosignal=True)

        # We force a signal even if XML didn't change, so the details
        # window is correctly refreshed.
        self.idle_emit("state-changed")
