    """This is the TaskManager 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 TaskHandler import TaskHandler
    from time import time
    from exceptions import IOError

    try: # for Python < 2.3
        True, False
    except NameError:
        True, False = 1, 0

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

        The Scheduler is a thread that handles organizing and running tasks.
        The Scheduler class should be instantiated to start a TaskManager sessions.
        Its start method should be called to start the TaskManager.
        Its stop method should be called to end the TaskManager 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 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 self._running.has_key(name)

        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 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 self._scheduled.has_key(name)

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

        def onDemandTasks(self):
            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 onDemand list?"""
            return self._onDemand.has_key(name)

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

        def delOnDemand(self, name):
            """Delete a task with the given name from the onDemand list."""
            try:
                handle = self._onDemand[name]
                del self._onDemand[name]
                return handle
            except Exception:
                return None

        def nextTime(self):
            return self._nextTime

        def setNextTime(self, time):
            self._nextTime = time

        def isRunning(self):
            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 not handle:
                handle = TaskHandler(self, time, 0, task, name)
            else:
                handle.reset(time, 0, task, True)
            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 not handle:
                handle = TaskHandler(self, time(), 0, task, name)
            else:
                handle.reset(time(), 0, task, True)
            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.

            """
            import time
            current = time.localtime(time.time())
            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.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 not handle:
                handle = TaskHandler(self, start, period, task, name)
            else:
                handle.reset(start, period, task, True)
            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 = None
            if self.hasScheduled(name):
                handle = self.delScheduled(name)
            if self.hasOnDemand(name):
                handle = 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 not self.hasRunning(name) and not self.hasOnDemand(name):
                return False
            else:
                handle = self.running(name)
                if handle:
                    handle.runOnCompletion()
                    return True
                handle = self.onDemand(name)
                if not handle:
                    return False
                self.runTask(handle)
                return True

        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.keys():
                print "Stopping ", i
                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 not handle.startTime():
                        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):
            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):
            """Run task in 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()