from django.db import models
from pyrosapp.models import Schedule, Sequence
from operator import attrgetter
from decimal import *

DEFAULT_PLAN_START = Decimal(2457485.250000) # April 6th 2016, 18:00:00.0 UT
DEFAULT_PLAN_END = Decimal(2457485.916667) # April 7th 2016, 10:00:00.0 UT

PRECISION = Decimal(0.0000000001)

SIMULATION = False

'''
    Note : the following functions are necessary due to a too-high precision of Decimal objects
'''
def is_nearby_equal(a : Decimal, b : Decimal, precision : Decimal = PRECISION):
    '''
        Compare the two decimal, according to the given precision
    '''
    return (True if abs(b - a) < PRECISION else False)


def is_nearby_sup_or_equal(a : Decimal, b : Decimal, precision : Decimal = PRECISION):
    '''
        Compare the two decimal, according to the given precision
    '''
    if (a > b):
        return True
    return (True if abs(b - a) < PRECISION else False)


def is_nearby_less_or_equal(a : Decimal, b : Decimal, precision : Decimal = PRECISION):
    '''
        Compare the two decimal, according to the given precision
    '''
    if (a < b):
        return True
    return (True if abs(b - a) < PRECISION else False)


    
class Interval:
    """
    Simple class that represents an interval of time
    Julian days should be used
    """
    
    def __init__(self, start, end):
        self._start = Decimal(start)
        self._end = Decimal(end)
        self.duration = Decimal(end - start)

        
    def __str__(self):
        print("["+str(self.start)+" - "+str(self.end)+"]")

    def _get_start(self):
        return self._start

    def _set_start(self, start):
        if start > self._end:
            raise ValueError("Cannot set start (%d): must be lower than end (%d)" % (start, self._end))
        self._start = start
        self.duration = self._end - self._start
        
    def _get_end(self):
        return self._end

    def _set_end(self, end):
        if end < self._start:
            raise ValueError("Cannot set end (%d): must be bigger than start (%d)" % (end, self._start))
        self._end = end
        self.duration = self._end - self._start
        
    start = property(fget=_get_start, fset=_set_start)
    end = property(fget=_get_end, fset=_set_end)


class Scheduler():
    """
   Role : create a planning for the following/current night
   
   Read in DB : Sequence, PyrosUser, ScheduleHistory and parents
   Create in DB : Schedule, ScheduleHistory ? (not sure)
   Update in DB : Schedule, Sequence
   Delete in DB : None
   
   Entry point(s) :
           - make_schedule
           - re_schedule
           - simulate_schedule
    """

    """
    TODO:
        - définition de plan_start et plan_end
        - calcul de la priorité
        - calcul des quotas
        - définir l'attribut 'flag' de Schedule
        - gestion du re-scheduling (en cas de nouvelle requete)
        - remplissage des espaces libres
        - gestion de l'historique (je sais pas si c'est ce module qui va s'en charger au final mais bon ...)

    """

    def __init__(self):
        self.schedule = Schedule.objects.create()
        # TODO: quel est le "flag" dans le schedule ??
        self.get_night_limits() # TODO
        self.intervals = []
    
        
    def get_night_limits(self):
        '''
        determines and set plan_start and plan_end (beginning & end of the observation night)        
        '''
        
        # TODO: définir comment on calcule plan_start et plan_end (via quels moyens)
        self.schedule.plan_start = DEFAULT_PLAN_START # default value
        self.schedule.plan_end = DEFAULT_PLAN_END # default value
  
    
    def set_night_limits(self, plan_start, plan_end):
        '''
        Sets given schedule start & end (in julian day)
        '''
        self.schedule.plan_start = Decimal(plan_start)
        self.schedule.plan_end = Decimal(plan_end)
        
    def make_schedule(self):
        '''
        ENTRY POINT

        Check all 'OBSERVABLE' sequences to create the most optimized planning for the following/current night
        
        It is assumed that all sequences that MUST and CAN be analyse have the OBSERVABLE status (e.g. : there must not be any PLANNED sequence at this point)        
        
        :side-effect :
            - modify sequences status and dates in DB
        '''
        
        global SIMULATION
        SIMULATION = False
        
        self.sequences = list(Sequence.objects.filter(status=Sequence.OBSERVABLE))
        self.compute_schedule()
        self.save_sequences()


    def re_schedule(self):
        '''
        ENTRY POINT
        
        Creates a brand new schedule for the current night.
        Takes all the PLANNED sequences to make them OBSERVABLE
        Saves all the EXECUTED sequences of the current planning to put them in the new one, then delete the current
        
        Calls make_schedule to create the new one
        '''
        
        # voir comment on gère la sauvegarde des plannings, si on fait le coup des EXECUTED qui rentrent dans le nouveau, on n'aura
        # plus la correspondance des dates. Ce serait peut-être bien de garder le même objet schedule au cours de la nuit,
        # avec le même plan_start et plan_end, mais quand on fait un scheduling on le fait à partir d'un start déterminé en interne
        # mais ça va être chiant si le plan_start et plan_end peuvent changer au cours de la journée
        # TODO: cette méthode
        pass



    def simulate_schedule(self, sequences):
        '''
        ENTRY POINT - SIMULATION
        
        Do the same as make_schedule but do not touch the DB
        
        :type sequences : list of Sequence
        :param sequences : sequences to plan

        :returns : a tuple (Schedule, list of sequences)
        '''
        
        global SIMULATION
        SIMULATION = True
        
        self.sequences = sequences
        self.compute_schedule()
        return (self.schedule, self.sequences)
    

    def compute_schedule(self):
        self.intervals.append(Interval(self.schedule.plan_start, self.schedule.plan_end))
        self.check_sequences_validity()
        self.determine_priorities()
        self.remove_not_eligible_sequences()
        self.sort_by_jd2_and_priorities()
        self.organize_sequences()

    
    def check_sequences_validity(self):
        '''
        Checks come sequence attributes to validate their integrity
        
        :side-effect :
            - remove invalid sequences from self.sequences
            - set INVALID status for invalid sequences in DB
        '''
        
        ''' Note(1) '''
        for sequence in list(self.sequences):
            if sequence.jd1 < 0 or sequence.jd2 < 0 or is_nearby_less_or_equal(sequence.duration, 0) or sequence.jd2 - sequence.jd1 < sequence.duration:
                self.sequences.remove(sequence)
                sequence.status = Sequence.INVALID
                if SIMULATION == False:
                    sequence.save()
            
            
    def determine_priorities(self):
        '''
        Computes sequences priority according to the user, the scientific program, ...        
        '''
        
        # TODO: définir comment on calcule la priorité
        pass
    
    
    def remove_not_eligible_sequences(self):
        '''
        Computes overlap between [jd1; jd2] and [plan_start; plan_end]
        Removes from self.sequences all the sequences that cannot be observed between plan_start and plan_end
        Set UNPLANNABLE sequences if jd2 < plan_start
        
        :side-effect :
            - remove unwanted sequences from self.sequences
        '''
        
        ''' Note (1) '''
        for sequence in list(self.sequences):
            overlap = min(self.schedule.plan_end, sequence.jd2) - max(self.schedule.plan_start, sequence.jd1)
            if overlap < sequence.duration:
                if sequence.jd1 < self.schedule.plan_start:
                    """ Note (2) """
                    sequence.status = Sequence.UNPLANNABLE
                    if SIMULATION == False:
                        sequence.save()
                self.sequences.remove(sequence)

        
    def sort_by_jd2_and_priorities(self):
        '''
        Sort by priority and jd2, priority being the main sorting parameter        
        '''
        
        self.sequences.sort(key=attrgetter('priority', 'jd2'))
        

    def organize_sequences(self):
        '''
        Main function of the Scheduler
        Arrange a maximum of observable sequences in the planning

        Algorithm (for each sequence) :
            - check quota (remove sequence from list if quota is too low)
            - select matching intervals
            - IF matching intervals => place sequence according to tPrefered
            - IF NO matching intervals => try to move other sequences to place this one
        
        :side-effect :
            - remove unwanted sequences from self.sequences
            - change status and dates of sequences in self.sequences (but not in DB yet)
        '''
   
        ''' Note (1) '''     
        for sequence in list(self.sequences):
            quota = self.determine_quota(sequence)
            if quota < sequence.duration:
                self.sequences.remove(sequence)
                continue

            matching_intervals = self.get_matching_intervals(sequence)
            if len(matching_intervals) > 0:
                self.place_sequence(sequence, matching_intervals)
                sequence_placed = True
            else:
                sequence_placed = self.try_shifting_sequences(sequence)
                
            if sequence_placed == True:
                sequence.status = Sequence.PLANNED
                self.update_quota(sequence)
    
    def determine_quota(self, sequence:Sequence) -> float:
        '''
        Determines the quota (in minutes) according to the current planning duration and the quota of the user and scientific program associated

        :returns : The quota (float)
        '''
        # TODO: définir comment on calcule le quota
        
        return sequence.request.pyros_user.quota # default value
        
    
    def get_matching_intervals(self, sequence:Sequence):
        '''
        Find the intervals where the sequence could be inserted
        
        :returns : list of matching Intervals
        '''
        
        matching_intervals = []
        
        for interval in self.intervals:
            overlap = min(sequence.jd2, interval.end) - max(sequence.jd1, interval.start)
            if overlap > sequence.duration or is_nearby_equal(overlap, sequence.duration):
                matching_intervals.append(interval)
        
        return matching_intervals
        
        
    def place_sequence(self, sequence:Sequence, matching_intervals) :
        '''
        Place the sequence in the better interval, according to the t_prefered
        
        :type matching_intervals: list [Interval]
        :param matching_intervals: Intervals in which the sequence can be placed

        :side-effect :
            - changes self.intervals
            - change the sequence if it it placed
        '''
        
        if len(matching_intervals) == 0:
            raise ValueError("matching_intervals shall not be empty")

        prefered_interval = self.get_prefered_interval(sequence, matching_intervals)
        sequence_position_in_interval = self.get_sequence_position_in_interval(sequence, prefered_interval)        
        self.insert_sequence_in_interval(sequence, prefered_interval, sequence_position_in_interval)
        self.cut_interval(sequence, prefered_interval)
        self.update_other_deltas(sequence, prefered_interval)

            
    def get_prefered_interval(self, sequence:Sequence, matching_intervals) -> Interval:
        '''
        Find the better interval, according to the t_prefered (get the nearest)
        
        :type matching_intervals: list [Interval]
        :param matching_intervals: Intervals in which the sequence can be placed
        
        :returns : An Interval that fits sequence.t_prefered at most
        '''

        if len(matching_intervals) == 0:
            raise ValueError("matching_intervals shall not be empty")

        if sequence.t_prefered == 0 or len(matching_intervals) == 1:
            prefered_interval = matching_intervals[0]
        else:
            for index, interval in enumerate(matching_intervals):
                if is_nearby_less_or_equal(interval.start, sequence.t_prefered) and is_nearby_less_or_equal(sequence.t_prefered, interval.end):
                    prefered_interval = interval
                    break
                elif sequence.t_prefered < interval.start:
                    if index == 0:
                        prefered_interval = interval
                    else:
                        prefered_interval = matching_intervals[index - 1]
                    break
        return prefered_interval
        
    
    def get_sequence_position_in_interval(self, sequence:Sequence, interval:Interval) -> str:
        '''
        Determines where the sequence will be inserted in the interval, regarding sequence.t_prefered

        :returns : A string in ["START", "END", "PREFERED"] describing where the sequence will be inserted in the interval
        '''

        if is_nearby_less_or_equal(interval.start, sequence.t_prefered) and is_nearby_less_or_equal(sequence.t_prefered, interval.end):
            if is_nearby_less_or_equal(sequence.t_prefered - Decimal(0.5) * sequence.duration, interval.start):
                position_in_interval = "START"
            elif is_nearby_sup_or_equal(sequence.t_prefered + Decimal(0.5) * sequence.duration, interval.end):
                position_in_interval = "END"
            else:
                position_in_interval = "PREFERED"  
        else:
            if sequence.t_prefered < interval.start:
                position_in_interval = "START"
            else:
                position_in_interval = "END"
        return position_in_interval
    

    def insert_sequence_in_interval(self, sequence:Sequence, interval:Interval, position:str):
        '''
        Inserts the sequence in the interval:
            - sets sequence.tsp and sequence.tep
            - sets sequence.deltaTL and sequence.deltaTR
            
        :param interval: Interval in which the sequence will be inserted
        :param position: String describing where the sequence will be inserted in the interval
        
        :side-effect :
            - modify sequence attributes (tsp, tep, deltaTL, deltaTR)
        '''
        
        if position not in ["START", "END", "PREFERED"]:
            raise ValueError("position must be either 'START', 'END' or 'PREFERED'")
        
        if position == "START":
            sequence.tsp = max(interval.start, sequence.jd1)
            sequence.tep = sequence.tsp + sequence.duration
            sequence.deltaTL = 0
            sequence.deltaTR = min(interval.end, sequence.jd2) - sequence.tep
        elif position == "END":
            sequence.tep = min(interval.end, sequence.jd2)
            sequence.tsp = sequence.tep - sequence.duration
            sequence.deltaTL = sequence.tsp - max(interval.start, sequence.jd1)
            sequence.deltaTR = 0
        else:
            sequence.tsp = max(sequence.jd1, sequence.t_prefered - Decimal(0.5) * sequence.duration)
            sequence.tep = sequence.tsp + sequence.duration
            sequence.deltaTL = sequence.tsp - max(interval.start, sequence.jd1)
            sequence.deltaTR = min(interval.end, sequence.jd2) - sequence.tep

        
    def cut_interval(self, sequence:Sequence, interval:Interval):
        '''
        Separates the interval in two parts regarding to the sequence position
        Sorts the interval list in time order
        
        :param interval : the interval in which the sequence was added
        
        :side-effect :
            - removes interval from self.intervals
            - add created intervals to self.intervals
            - sorts self.intervals
        '''
        
        interval_before_sequence = Interval(interval.start, sequence.tsp)
        interval_after_sequence = Interval(sequence.tep, interval.end)
        
        self.intervals.remove(interval)
        if interval_before_sequence.duration > 0:
            self.intervals.append(interval_before_sequence)
        if interval_after_sequence.duration > 0:
            self.intervals.append(interval_after_sequence)
        self.intervals.sort(key=lambda interval: interval.start, reverse=False)


    def update_other_deltas(self, sequence:Sequence, interval:Interval):
        '''
        Update deltaTL and deltaTR of sequences planned near this sequence
        
        :param interval: Interval in which the sequence was added
        
        :side-effect :
            - modify deltaTL and deltaTR of sequences before and after the interval
        '''
        
        for sequence_ in self.sequences:
            if sequence_.status == Sequence.PLANNED:
                if is_nearby_equal(sequence_.tep, interval.start):
                    sequence_before_interval = sequence_
                elif is_nearby_equal(sequence_.tsp, interval.end):
                    sequence_after_interval = sequence_
        
        if 'sequence_before_interval' in locals():
            sequence_before_interval.deltaTR = min(sequence.tsp, sequence_before_interval.jd2) - sequence_before_interval.tep                    
        if 'sequence_after_interval' in locals():
            sequence_after_interval.deltaTL = sequence_after_interval.tsp - max(sequence.tep, sequence_after_interval.jd1)
        
    
    def try_shifting_sequences(self, sequence:Sequence) -> bool:
        '''
        Tries to find a place in the planning for the sequence, moving the other sequences
        
        :returns : A boolean -> True if the sequence was placed, False otherwise
        
        :side-effect:
            - might change some sequences' deltaTL and/or deltaTR
        '''
        
        
        potential_intervals = self.get_potential_intervals(sequence)
        potential_intervals.sort(key=attrgetter("duration"), reverse=True)
        for interval in potential_intervals:
            ''' we get the adjacent sequences '''
            for sequence_ in self.sequences:
                if sequence_.status == Sequence.PLANNED:
                    if is_nearby_equal(sequence_.tep, interval.start):
                        sequence_before_interval = sequence_
                    elif is_nearby_equal(sequence_.tsp, interval.end):
                        sequence_after_interval = sequence_

            available_duration = min(interval.end, sequence.jd2) - max(interval.start, sequence.jd1)
            missing_duration = sequence.duration - available_duration
            if 'sequence_before_interval' in locals():
                possible_move_to_left = min(sequence_before_interval.deltaTL, interval.start - sequence.jd1)
            else:
                possible_move_to_left = 0
                
            if 'sequence_after_interval' in locals():
                possible_move_to_right =  min(sequence_after_interval.deltaTR, sequence.jd2 - interval.end)
            else:
                possible_move_to_right = 0

            if is_nearby_sup_or_equal(possible_move_to_left, missing_duration):
                self.move_sequence(sequence_before_interval, missing_duration, "LEFT")
            elif is_nearby_sup_or_equal(possible_move_to_right, missing_duration):
                self.move_sequence(sequence_after_interval, missing_duration, "RIGHT")
            elif is_nearby_sup_or_equal(possible_move_to_left + possible_move_to_right, missing_duration):
                self.move_sequence(sequence_before_interval, possible_move_to_left, "LEFT")
                self.move_sequence(sequence_after_interval, missing_duration - possible_move_to_left, "RIGHT")
            else:
                continue

            matching_intervals = self.get_matching_intervals(sequence)
            
            if len(matching_intervals) != 1:
                raise ValueError("There should be one and only one matching interval after shifting")
            self.place_sequence(sequence, matching_intervals)

            return True
            
        return False
        
        
    def get_potential_intervals(self, sequence:Sequence):
        '''
        Find the intervals where a part of the sequence could be inserted
        
        :returns : list of partially-matching Intervals
        '''
        
        potential_intervals = []
        
        for interval in self.intervals:
            overlap = min(sequence.jd2, interval.end) - max(sequence.jd1, interval.start)
            if overlap > 0:
                potential_intervals.append(interval)
        
        return potential_intervals

        
    def move_sequence(self, sequence:Sequence, time_shift:Decimal, direction:str):
        '''
        Moves the sequence in the wanted direction, decreasing its deltaTL or deltaTR.
        
        :param sequence: sequence to be moved
        :param time_shift: amplitude of the shift
        :param direction: "LEFT" or "RIGHT"
        
        :side-effect :
            - modify the sequence in self.sequences
            - changes the interval before and the interval after the sequence
        '''
         
        if direction not in ["LEFT", "RIGHT"]:
            raise ValueError("direction must be 'LEFT' or 'RIGHT'")
        if time_shift > (sequence.deltaTL if direction == "LEFT" else sequence.deltaTR):
            raise ValueError("Shift value is bigger than deltaT(R/L)")
        
        for interval in self.intervals:
            if is_nearby_equal(interval.end, sequence.tsp):
                interval_before = interval
            elif is_nearby_equal(interval.start, sequence.tep):
                interval_after = interval
                
        if direction == "LEFT":
            interval_before.end -= time_shift
            if "interval_after" in locals():
                interval_after.start -= time_shift
            sequence.tsp -= time_shift
            sequence.tep -= time_shift
            sequence.deltaTL -= time_shift
            sequence.deltaTR += time_shift
        else:
            if "interval_before" in locals():
                interval_before.end += time_shift
            interval_after.start += time_shift
            sequence.tsp += time_shift
            sequence.tep += time_shift
            sequence.deltaTL += time_shift
            sequence.deltaTR -= time_shift
        if "interval_before" in locals() and is_nearby_equal(interval_before.duration, 0):
            self.intervals.remove(interval_before)
        if "interval_after" in locals() and is_nearby_equal(interval_after.duration, 0):
            self.intervals.remove(interval_after)

        
    def update_quota(self, sequence:Sequence):
        '''
        Update the quota of the user / scientific program / whatever by substracting the sequence duration to the quotas
        
        :side-effect:
            - Modify User quota in DB
        '''
        
        # TODO: faire les vrais calculs de quota
        user = sequence.request.pyros_user
        user.quota -= float(sequence.duration) # action par défaut qui correspond au code de self.determine_quota
        
        if SIMULATION == False:
            user.save()
        
    def save_sequences(self):
        '''
        Final function : save in the db all modifications done to sequences, and the schedule
        
        :side-effect :
            - change sequences status and dates in DB
            - add a schedule in the DB
        '''
        
        self.schedule.save()
        for sequence in self.sequences:
            sequence.schedule = self.schedule
            sequence.save()

    
    def print_schedule(self):
        '''
        ONLY FOR DEBUG
        
        Prints the planned sequences
        '''

        sequences = Sequence.objects.filter(status=Sequence.PLANNED).order_by('tsp')
        
        print("---- There are %d sequence(s) planned ----" % len(sequences))
        
        for sequence in sequences:
            print("name: %r\t, start: %d\t, end: %d\t, duration: %d\t, deltaTL: %d\t, deltaTR: %d\t"
                  % (sequence.name, sequence.tsp, sequence.tep, sequence.duration, sequence.deltaTL, sequence.deltaTR))

        print("---- There are %d free interval(s) ----" % len(self.intervals))
        
        for interval in self.intervals:
            print("start: %d\t, end: %d\t" % (interval.start, interval.end))

''' Notes

(1) list(self.sequences) creates a copy in order to modify self.sequences and still iterate on it without unexpected behavior
(2) UNPLANNABLE is a definitive status meaning that the sequence will never be able to be scheduled

'''