
"""This is the task manager Python package.

It provides a system for running any number of predefined tasks in separate
threads in an organized and controlled manner.

A task in this package is a class derived from the Task class. The task
should have a run method that, when called, performs some task.

The Scheduler class is the organizing object. It manages the addition,
execution, deletion, and well being of a number of tasks. Once you have
created your task class, you call the Scheduler to get it added to the
tasks to be run.

"""


from threading import Thread, Event
from time import localtime, time

from TaskHandler import TaskHandler


class Scheduler(Thread):
    """The top level class of the task manager system.

    The Scheduler is a thread that handles organizing and running tasks.
    The Scheduler class should be instantiated to start a task manager session.
    Its start method should be called to start the task manager.
    Its stop method should be called to end the task manager session.

    """


    ## Init ##

    def __init__(self, daemon=True, exceptionHandler=None):
        Thread.__init__(self)
        self._notifyEvent = Event()
        self._nextTime = None
        self._scheduled = {}
        self._running = {}
        self._onDemand = {}
        self._isRunning = False
        self._exceptionHandler = exceptionHandler
        if daemon:
            self.setDaemon(True)


    ## Event Methods ##

    def wait(self, seconds=None):
        """Our own version of wait().

        When called, it waits for the specified number of seconds, or until
        it is notified that it needs to wake up, through the notify event.

        """
        try:
            self._notifyEvent.wait(seconds)
        except IOError:
            pass
        self._notifyEvent.clear()


    ## Attributes ##

    def runningTasks(self):
        """Return all running tasks."""
        return self._running

    def running(self, name, default=None):
        """Return running task with given name.

        Returns a task with the given name from the "running" list,
        if it is present there.

        """
        return self._running.get(name, default)

    def hasRunning(self, name):
        """Check to see if a task with the given name is currently running."""
        return name in self._running

    def setRunning(self, handle):
        """Add a task to the running dictionary.

        Used internally only.

        """
        self._running[handle.name()] = handle

    def delRunning(self, name):
        """Delete a task from the running list.

        Used internally.

        """
        try:
            handle = self._running[name]
            del self._running[name]
            return handle
        except Exception:
            return None

    def scheduledTasks(self):
        """Return all scheduled tasks."""
        return self._scheduled

    def scheduled(self, name, default=None):
        """Return a task from the scheduled list."""
        return self._scheduled.get(name, default)

    def hasScheduled(self, name):
        """Checks whether task with given name is in the scheduled list."""
        return name in self._scheduled

    def setScheduled(self, handle):
        """Add the given task to the scheduled list."""
        self._scheduled[handle.name()] = handle

    def delScheduled(self, name):
        """Delete a task with the given name from the scheduled list."""
        return self._scheduled.pop(name, None)

    def onDemandTasks(self):
        """Return all on demand tasks."""
        return self._onDemand

    def onDemand(self, name, default=None):
        """Return a task from the onDemand list."""
        return self._onDemand.get(name, default)

    def hasOnDemand(self, name):
        """Checks whether task with given name is in the on demand list."""
        return name in self._onDemand

    def setOnDemand(self, handle):
        """Add the given task to the on demand list."""
        self._onDemand[handle.name()] = handle

    def delOnDemand(self, name):
        """Delete a task with the given name from the on demand list."""
        return self._onDemand.pop(name, None)

    def nextTime(self):
        """Get next execution time."""
        return self._nextTime

    def setNextTime(self, time):
        """Set next execution time."""
        self._nextTime = time

    def isRunning(self):
        """Check whether thread is running."""
        return self._isRunning


    ## Adding Tasks ##

    def addTimedAction(self, time, task, name):
        """Add a task to be run once, at a specific time."""
        handle = self.unregisterTask(name)
        if handle:
            handle.reset(time, 0, task, True)
        else:
            handle = TaskHandler(self, time, 0, task, name)
        self.scheduleTask(handle)

    def addActionOnDemand(self, task, name):
        """Add a task to be run only on demand.

        Adds a task to the scheduler that will not be scheduled
        until specifically requested.

        """
        handle = self.unregisterTask(name)
        if handle:
            handle.reset(time(), 0, task, True)
        else:
            handle = TaskHandler(self, time(), 0, task, name)
        self.setOnDemand(handle)

    def addDailyAction(self, hour, minute, task, name):
        """Add an action to be run every day at a specific time.

        If a task with the given name is already registered with the
        scheduler, that task will be removed from the scheduling queue
        and registered anew as a periodic task.

        Can we make this addCalendarAction? What if we want to run
        something once a week? We probably don't need that for Webware,
        but this is a more generally useful module. This could be a
        difficult function, though. Particularly without mxDateTime.

        """
        current = localtime()
        currHour = current[3]
        currMin = current[4]

        if hour > currHour:
            hourDifference = hour - currHour
            if minute > currMin:
                minuteDifference = minute - currMin
            elif minute < currMin:
                minuteDifference = 60 - currMin + minute
                hourDifference -= 1
            else:
                minuteDifference = 0
        elif hour < currHour:
            hourDifference = 24 - currHour + hour
            if minute > currMin:
                minuteDifference = minute - currMin
            elif minute < currMin:
                minuteDifference = 60 - currMin + minute
                hourDifference -= 1
            else:
                minuteDifference = 0
        else:
            if minute > currMin:
                hourDifference = 0
                minuteDifference = minute - currMin
            elif minute < currMin:
                minuteDifference = 60 - currMin + minute
                hourDifference = 23
            else:
                hourDifference = 0
                minuteDifference = 0

        delay = (minuteDifference + (hourDifference * 60)) * 60
        self.addPeriodicAction(time()+delay, 24*60*60, task, name)

    def addPeriodicAction(self, start, period, task, name):
        """Add a task to be run periodically.

        Adds an action to be run at a specific initial time,
        and every period thereafter.

        The scheduler will not reschedule a task until the last
        scheduled instance of the task has completed.

        If a task with the given name is already registered with
        the scheduler, that task will be removed from the scheduling
        queue and registered anew as a periodic task.

        """
        handle = self.unregisterTask(name)
        if handle:
            handle.reset(start, period, task, True)
        else:
            handle = TaskHandler(self, start, period, task, name)
        self.scheduleTask(handle)


    ## Task methods ##

    def unregisterTask(self, name):
        """Unregisters the named task.

        After that it can be rescheduled with different parameters,
        or simply removed.

        """

        handle = (self.delRunning(name)
            or self.delScheduled(name) or self.delOnDemand(name))
        if handle:
            handle.unregister()
        return handle

    def runTaskNow(self, name):
        """Allow a registered task to be immediately executed.

        Returns True if the task is either currently running or was started,
        or False if the task could not be found in the list of currently
        registered tasks.

        """
        if self.hasRunning(name):
            return True
        handle = self.scheduled(name)
        if not handle:
            handle = self.onDemand(name)
        if not handle:
            return False
        self.runTask(handle)
        return True

    def demandTask(self, name):
        """Demand execution of a task.

        Allow the server to request that a task listed as being registered
        on-demand be run as soon as possible.

        If the task is currently running, it will be flagged to run again
        as soon as the current run completes.

        Returns False if the task name could not be found on the on-demand
        or currently running lists.

        """
        if self.hasRunning(name) or self.hasOnDemand(name):
            handle = self.running(name)
            if handle:
                handle.runOnCompletion()
                return True
            handle = self.onDemand(name)
            if not handle:
                return False
            self.runTask(handle)
            return True
        else:
            return False

    def stopTask(self, name):
        """Put an immediate halt to a running background task.

        Returns True if the task was either not running, or was
        running and was told to stop.

        """
        handle = self.running(name)
        if not handle:
            return False
        handle.stop()
        return True

    def stopAllTasks(self):
        """Terminate all running tasks."""
        for i in self._running:
            self.stopTask(i)

    def disableTask(self, name):
        """Specify that a task be suspended.

        Suspended tasks will not be scheduled until later enabled.
        If the task is currently running, it will not be interfered
        with, but the task will not be scheduled for execution in
        future until re-enabled.

        Returns True if the task was found and disabled.

        """
        handle = self.running(name)
        if not handle:
            handle = self.scheduled(name)
        if not handle:
            return False
        handle.disable()
        return True

    def enableTask(self, name):
        """Enable a task again.

        This method is provided to specify that a task be re-enabled
        after a suspension. A re-enabled task will be scheduled for
        execution according to its original schedule, with any runtimes
        that would have been issued during the time the task was suspended
        simply skipped.

        Returns True if the task was found and enabled.

        """
        handle = self.running(name)
        if not handle:
            handle = self.scheduled(name)
        if not handle:
            return False
        handle.enable()
        return True

    def runTask(self, handle):
        """Run a task.

        Used by the Scheduler thread's main loop to put a task in
        the scheduled hash onto the run hash.

        """
        name = handle.name()
        if self.delScheduled(name) or self.delOnDemand(name):
            self.setRunning(handle)
            handle.runTask()

    def scheduleTask(self, handle):
        """Schedule a task.

        This method takes a task that needs to be scheduled and adds it
        to the scheduler. All scheduling additions or changes are handled
        by this method. This is the only Scheduler method that can notify
        the run() method that it may need to wake up early to handle a
        newly registered task.

        """
        self.setScheduled(handle)
        if not self.nextTime() or handle.startTime() < self.nextTime():
            self.setNextTime(handle.startTime())
            self.notify()


    ## Misc Methods ##

    def notifyCompletion(self, handle):
        """Notify completion of a task.

        Used by instances of TaskHandler to let the Scheduler thread know
        when their tasks have run to completion. This method is responsible
        for rescheduling the task if it is a periodic task.

        """
        name = handle.name()
        if self.hasRunning(name):
            self.delRunning(name)
            if handle.startTime() and handle.startTime() > time():
                self.scheduleTask(handle)
            else:
                if handle.reschedule():
                    self.scheduleTask(handle)
                elif handle.isOnDemand():
                    self.setOnDemand(handle)
                    if handle.runAgain():
                        self.runTask(handle)

    def notifyFailure(self, handle):
        """Notify failure of a task.

        Used by instances of TaskHandler to let the Scheduler thread know
        if an exception has occurred within the task thread.

        """
        self.notifyCompletion(handle)
        if self._exceptionHandler is not None:
            self._exceptionHandler()

    def notify(self):
        """Wake up scheduler by sending a notify even."""
        self._notifyEvent.set()

    def start(self):
        """Start the scheduler's activity."""
        self._isRunning = True
        Thread.start(self)

    def stop(self):
        """Terminate the scheduler and its associated tasks."""
        self._isRunning = False
        self.notify()
        self.stopAllTasks()
        # jdh: wait until the scheduler thread exits; otherwise
        # it's possible for the interpreter to exit before this thread
        # has a chance to shut down completely, which causes a traceback
        # cz: but use a timeout of 3 seconds, this should suffice
        self.join(3)


    ## Main Method ##

    def run(self):
        """The main method of the scheduler running as a background thread.

        This method is responsible for carrying out the scheduling work of
        this class on a background thread. The basic logic is to wait until
        the next action is due to run, move the task from our scheduled
        list to our running list, and run it. Other synchronized methods
        such as runTask(), scheduleTask(), and notifyCompletion(), may
        be called while this method is waiting for something to happen.
        These methods modify the data structures that run() uses to
        determine its scheduling needs.

        """
        while self._isRunning:
            if self.nextTime():
                nextTime = self.nextTime()
                currentTime = time()
                if currentTime < nextTime:
                    sleepTime = nextTime - currentTime
                    self.wait(sleepTime)
                if not self._isRunning:
                    return
                currentTime = time()
                if currentTime >= nextTime:
                    toRun = []
                    nextRun = None
                    for handle in self._scheduled.values():
                        startTime = handle.startTime()
                        if startTime <= currentTime:
                            toRun.append(handle)
                        else:
                            if not nextRun:
                                nextRun = startTime
                            elif startTime < nextRun:
                                nextRun = startTime
                    self.setNextTime(nextRun)
                    for handle in toRun:
                        self.runTask(handle)
            else:
                self.wait()
