#  _________________________________________________________________________
#
#  Pyomo: Python Optimization Modeling Objects
#  Copyright (c) 2014 Sandia Corporation.
#  Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
#  the U.S. Government retains certain rights in this software.
#  This software is distributed under the BSD License.
#  _________________________________________________________________________


__all__ = ['ActionManagerError', 'ActionHandle', 'AsynchronousActionManager', 'ActionStatus', 'FailedActionHandle', 'solve_all_instances']

from pyutilib.enum import Enum

ActionStatus = Enum('done', 'error', 'queued', 'executing', 'unknown')


def solve_all_instances(solver_manager, solver, instances, **kwds):
    """
    A simple utility to apply a solver to a list of problem instances.
    """
    solver_manager.solve_all(solver, instances, **kwds)


class ActionManagerError(Exception):
    """
    An exception used when an error occurs within an ActionManager.
    """

    def __init__(self,*args,**kargs):
        Exception.__init__(self,*args,**kargs)      #pragma:nocover


class ActionHandle(object):

    id_counter = 0

    def __init__(self, error=False, explanation=""):
        """Constructor"""
        if error:
            self.id = -1
        else:
            self.id = ActionHandle.id_counter
            ActionHandle.id_counter += 1
            self.status = ActionStatus.error
        self.explanation = explanation

    def update(self, ah):
        """ Update the contents of the provided ActionHandle """
        self.id = ah.id
        self.status = ah.status

    def __lt__(self, other):
        return self.id < other.id

    def __hash__(self):
        return self.id.__hash__()

    def __eq__(self, other):
        return (self.__class__ is other.__class__) and (self.id.__hash__() == other.__hash__()) and (self.id == other.id)

    def __ne__(self, other):
        return not self.__eq__(other)

    def __str__(self):
        return str(self.id)


FailedActionHandle = ActionHandle(error=True)


class AsynchronousActionManager(object):

    def __init__(self):
        """Constructor"""
        self.clear()

    def clear(self):
        """
        Clear manager state
        """
        self.event_handle = {}
        self.results = {}
        self.queued_action_counter = 0

    def execute(self, *args, **kwds):
        """
        Synchronously execute an action.
        """
        ah = self.queue(*args, **kwds)
        results = self.wait_for(ah)
        if results is None:
            raise ActionManagerError("Problem executing an event.  No results are available.")
        return results

    def queue(self, *args, **kwds):
        """
        Queue an action, returning an ActionHandle object.
        """
        ah = ActionHandle()
        self.event_handle[ah.id] = ah
        ah.status = ActionStatus.queued
        self.queued_action_counter += 1
        return self._perform_queue(ah, *args, **kwds)

    def wait_all(self, *args):
        """
        Wait for all actions to complete.  The arguments to this method
        are expected to be ActionHandle objects or iterators that return
        ActionHandle objects.  If no arguments are provided, then this
        method will terminate after all queued actions are
        """
        #
        # Collect event handlers from the arguments
        #
        ahs = set()
        if len(args) == 0:
            for key in self.event_handle:
                ahs.add( self.event_handle[key] )
        else:
            for item in args:
                if type(item) is ActionHandle:
                    ahs.add(item)
                elif type(item) in [list, tuple]:
                    for ah in item:
                        if type(ah) is not ActionHandle:     #pragma:nocover
                            raise ActionManagerError("Bad argument type %s" % str(ah))
                        ahs.add(ah)
                else:                       #pragma:nocover
                    raise ActionManagerError("Bad argument type %s" % str(ah))
        #
        # Iterate until all ah's have completed
        #
        while len(ahs) > 0:
            ah = self.wait_any()
            ahs.discard(ah)

    def wait_any(self):
        """
        Wait for any action to complete, and return the
        corresponding ActionHandle.
        """
        ah = None
        while ah is None:
            ah = self._perform_wait_any()
        if ah == FailedActionHandle:
            return ah
        self.queued_action_counter -= 1
        self.event_handle[ah.id].update(ah)
        return self.event_handle[ah.id]

    def wait_for(self, ah):
        """
        Wait for the specified action to complete.
        """
        tmp = self.wait_any()
        while tmp != ah:
            tmp = self.wait_any()
            if tmp == FailedActionHandle:
                raise ActionManagerError("Action %s failed: %s" % (ah, tmp.explanation))
        return self.get_results(ah)

    def num_queued(self):
        """
        Return the number of queued actions
        """
        return self.queued_action_counter

    def get_status(self, ah):
        """
        Return the status of the ActionHandle.
        """
        return ah.status

    def get_results(self, ah):
        """
        Return solver results.  If solver results are not available,
        return None.
        """
        if ah.id in self.results:
            # extremely important - clean up the map before returning the result.
            # otherwise, it will be around forever, acting as a memory leak (because
            # the solver manager will always retain a reference).
            result = self.results[ah.id]
            del self.results[ah.id]
            return result
        return None

    def _perform_queue(self, ah, *args, **kwds):
        """
        Perform the queue operation.  This method returns the ActionHandle,
        and the ActionHandle status indicates whether the queue was successful.
        """
        raise ActionManagerError("The _perform_queue method is not defined")     #pragma:nocover

    def _perform_wait_any(self):
        """
        Perform the wait_any operation.  This method returns an
        ActionHandle with the results of waiting.  If None is returned
        then the ActionManager assumes that it can call this method again.
        Note that an ActionHandle can be returned with a dummy value,
        to indicate an error.
        """
        raise ActionManagerError("The _perform_wait_any method is not defined")      #pragma:nocover
