#
# NodeManager plugin - first step of handling reservable nodes
# Thierry Parmentelat <thierry.parmentelat@inria.fr>
#

"""
Manages running slices when reservation_policy is 'lease_or_idle' or 'lease_or_shared'
"""

import time
import threading

import logger
import account
import database

# there is an implicit assumption that this triggers after slicemanager
priority = 45

# this instructs nodemanager that we want to use the latest known data in case the plc link is down
persistent_data = True

# of course things would be simpler if node manager was to create one instance of the plugins
# instead of blindly caling functions in the module...

##############################
# rough implementation for a singleton class
def Singleton (klass, *args, **kwds):
    if not hasattr(klass, '_instance'):
        klass._instance=klass(*args, **kwds)
    return klass._instance

def start():
    return Singleton(reservation).start()

def GetSlivers(data, conf = None, plc = None):
    return Singleton(reservation).GetSlivers(data, conf, plc)

##############################
class reservation:

    debug=False
    debug=True

    def __init__ (self):
        # the last snapshot of data exposed by GetSlivers
        self.data = None
        # this is a dict mapping a raounded timestamp to the corr. Timer object
        self.timers = {}

    ####################
    def start(self):
        logger.log("reservation: plugin performing dummy start...")

    # this method is entirely about making sure that we have events scheduled
    # at the <granularity> intervals where there is a lease that starts or ends
    def GetSlivers (self, data, conf=None, plc=None):

        # check we're using a compliant GetSlivers
        if 'reservation_policy' not in data:
            logger.log_missing_data("reservation.GetSlivers", 'reservation_policy')
            return
        self.reservation_policy=data['reservation_policy']
        if 'leases' not in data:
            logger.log_missing_data("reservation.GetSlivers", 'leases')
            return

        # store data locally
        # since we've asked for persistent_data, we should not get an empty data here
        if data: self.data = data

        # regular nodes are not affected
        if self.reservation_policy == 'none':
            return
        elif self.reservation_policy not in ['lease_or_idle', 'lease_or_shared']:
            logger.log("reservation: ignoring -- unexpected value for reservation_policy %r"%self.reservation_policy)
            return
        # at this point we have reservation_policy in ['lease_or_idle', 'lease_or_shared']
        # we make no difference for now
        logger.log("reservation.GetSlivers: reservable node -- policy=%s"%self.reservation_policy)
        self.sync_timers_from_leases()
        logger.log("reservation.GetSlivers: listing timers")
        if reservation.debug:
            self.list_timers()

    ####################
    # the granularity is set in the API (initial value is 15 minutes)
    # and it used to round all leases start/until times
    # changing this dynamically can have some weird effects of course..
    def granularity (self):
        try:
            return self.data['lease_granularity']
        # in case we'd try to access this before it's populated..
        except:
            return 60*60

    # round to granularity
    def round_time (self, time):
        granularity=self.granularity()
        return ((int(time)+granularity/2)/granularity)*granularity

    def clear_timers (self):
        for timer in list(self.timers.values()):
            timer.cancel()
        self.timers={}

    def sync_timers_from_leases (self):
        self.clear_timers()
        for lease in self.data['leases']:
            self.ensure_timer_from_until(lease['t_from'], lease['t_until'])

    # assuming t1<t2
    def ensure_timer_from_until (self, t1, t2):
        now=int(time.time())
        # both times are in the past: forget about it
        if t2 < now : return
        # we're in the middle of the lease: make sure to arm a callback in the near future for checking
        # this mostly is for starting the slice if nodemanager gets started in the middle of a lease
        if t1 < now : 
            self.ensure_timer (now, now+10)
        # both are in the future : arm them
        else :
            self.ensure_timer (now, self.round_time(t1))
            self.ensure_timer (now, self.round_time(t2))

    def ensure_timer(self, now, timestamp):
        if timestamp in self.timers: return
        def this_closure ():
            import time
            logger.log("TIMER trigering at %s (was armed at %s, expected to trigger at %s)"%\
                           (reservation.time_printable(time.time()),
                            reservation.time_printable(now),
                            reservation.time_printable(timestamp)))
            self.granularity_callback (now)
        timer=threading.Timer(timestamp-now, this_closure)
        self.timers[timestamp]=timer
        timer.start()

    def list_timers(self):
        timestamps=list(self.timers.keys())
        timestamps.sort()
        for timestamp in timestamps:
            logger.log('reservation: TIMER armed for %s'%reservation.time_printable(timestamp))
        logger.log('reservation.GetSlivers : end listing timers')


    @staticmethod
    def time_printable (timestamp):
        return time.strftime ("%Y-%m-%d %H:%M UTC", time.gmtime(timestamp))

    @staticmethod
    def lease_printable (lease):
        d=dict ( iter(lease.items()))
        d['from']=reservation.time_printable(lease['t_from'])
        d['until']=reservation.time_printable(lease['t_from'])
        s=[]
        s.append("slice=%(name)s (%(slice_id)d)"%d)
        s.append("from %(from)s"%d)
        s.append("until %(until)s"%d)
        return " ".join(s)

    # this is invoked at the granularity boundaries where something happens (a lease ends or/and a lease starts)
    def granularity_callback (self, time_arg):
        now=int(time.time())
        round_now=self.round_time(now)
        leases=self.data['leases']
        ###
        if reservation.debug:
            logger.log('reservation.granularity_callback now=%f round_now=%d arg=%d...'%(now, round_now, time_arg))
        if leases and reservation.debug:
            logger.log('reservation: Listing leases beg')
            for lease in leases:
                logger.log("reservation: lease="+reservation.lease_printable(lease))
            logger.log('reservation: Listing leases end')

        ### what do we have to do at this point in time?
        ending_lease=None
        for lease in leases:
            if lease['t_until']==round_now:
                logger.log('reservation: end of lease for slice %s - (lease=%s)'%(lease['name'], reservation.lease_printable(lease)))
                ending_lease=lease
        starting_lease=None
        for lease in leases:
            if lease['t_from']==round_now:
                logger.log('reservation: start of lease for slice %s - (lease=%s)'%(lease['name'], reservation.lease_printable(lease)))
                starting_lease=lease

        ########## nothing is starting nor ending
        if not ending_lease and not starting_lease:
            ### this might be useful for robustness - not sure what to do now though
            logger.log("reservation.granularity_callback: xxx todo - should make sure to start the running lease if relevant")
        ########## something to start - something to end
        elif ending_lease and starting_lease:
            ## yes, but that's the same sliver
            if ending_lease['name']==starting_lease['name']:
                slicename=ending_lease['name']
                if self.is_running(slicename):
                    logger.log("reservation.granularity_callback: end/start of same sliver %s -- ignored"%ending_lease['name'])
                else:
                    logger.log("reservation.granularity_callback: mmh, the sliver is unexpectedly not running, starting it...")
                    self.restart_slice(slicename)
            ## two different slivers
            else:
                self.restart_slice(starting_lease['name'])
                self.suspend_slice(ending_lease['name'])
        ########## something to start, nothing to end
        elif starting_lease and not ending_lease:
            self.restart_slice(starting_lease['name'])
            # with the lease_or_shared policy, this is mandatory
            # otherwise it's just safe
            self.suspend_all_slices(exclude=starting_lease['name'])
        ########## so now, something to end, nothing to start
        else:
            self.suspend_slice (ending_lease['name'])
            if self.reservation_policy=='lease_or_shared':
                logger.log("reservation.granularity_callback: 'lease_or_shared' not implemented - using 'lease_or_idle'")
            # only lease_or_idle policy available for now: we freeze the box
            logger.log("reservation.granularity_callback: suspending all slices")
            self.suspend_all_slices()

    def debug_box(self, message, slicename=None):
        if reservation.debug:
            logger.log ('reservation: '+message)
            logger.log_call( ['/usr/sbin/vserver-stat', ] )
            if slicename:
                logger.log_call ( ['/usr/sbin/vserver', slicename, 'status', ])

    def is_running (self, slicename):
        try:
            return account.get(slicename).is_running()
        except:
            return False

    # quick an d dirty - this does not obey the account/sliver_vs/controller hierarchy
    def suspend_slice(self, slicename):
        logger.log('reservation: Suspending slice %s'%(slicename))
        self.debug_box('before suspending', slicename)
        worker=account.get(slicename)
        try:
            logger.log("reservation: Located worker object %r"%worker)
            worker.stop()
        except AttributeError:
            # when the underlying worker is not entirely initialized yet
            pass
        except:
            logger.log_exc("reservation.suspend_slice: Could not stop slice through its worker", name=slicename)
        # we hope the status line won't return anything
        self.debug_box('after suspending', slicename)

    # exclude can be a slicename or a list
    # this probably should run in parallel
    def suspend_all_slices (self, exclude=[]):
        if isinstance(exclude, str): exclude=[exclude,]
        for sliver in self.data['slivers']:
            # skip excluded
            if sliver['name'] in exclude: continue
            # is this a system sliver ?
            system_slice=False
            for d in sliver['attributes']:
                if d['tagname']=='system' and d['value'] : system_slice=True
            if system_slice: continue
            self.suspend_slice(sliver['name'])

    def restart_slice(self, slicename):
        logger.log('reservation: Restarting slice %s'%(slicename))
        self.debug_box('before restarting', slicename)
        worker=account.get(slicename)
        try:
            # dig in self.data to retrieve corresponding rec
            slivers = [ sliver for sliver in self.data['slivers'] if sliver['name']==slicename ]
            sliver=slivers[0]
            record=database.db.get(slicename)
            record['enabled']=True
            #
            logger.log("reservation: Located worker object %r"%worker)
            logger.log("reservation: Located record at the db %r"%record)
            worker.start(record)
        except:
            logger.log_exc("reservation.restart_slice: Could not start slice through its worker", name=slicename)
        # we hope the status line won't return anything
        self.debug_box('after restarting', slicename)