import itertools

from django.db.models import Count, Min

from symposion.schedule.models import Room, Slot, SlotRoom

class TimeTable(object):

    def __init__(self, day):

        self.day = day

    def slots_qs(self):

        qs = Slot.objects.all()

        qs = qs.filter(day=self.day)

        return qs

    def rooms(self):

        qs = Room.objects.all()

        qs = qs.filter(schedule=self.day.schedule)

        qs = qs.filter(

            pk__in=SlotRoom.objects.filter(slot__in=self.slots_qs().values("pk")).values("room"))

        qs = qs.order_by("order")

        return qs

    def __iter__(self):

        times = sorted(set(itertools.chain(*self.slots_qs().values_list("start", "end"))))

        slots = Slot.objects.filter(pk__in=self.slots_qs().values("pk"))

        slots = slots.annotate(room_count=Count("slotroom"), order=Min("slotroom__room__order"))

        slots = slots.order_by("start", "order")

        row = []

        for time, next_time in pairwise(times):

            row = {"time": time, "slots": []}

            for slot in slots:

                if slot.start == time:

                    slot.rowspan = TimeTable.rowspan(times, slot.start, slot.end)

                    slot.colspan = slot.room_count

                    row["slots"].append(slot)

            if row["slots"] or next_time is None:

                yield row

    @staticmethod

    def rowspan(times, start, end):

        return times.index(end) - times.index(start)

def pairwise(iterable):

    a, b = itertools.tee(iterable)