Move prev/next functions to TimePeriod model

Close #65 (closed)

aleksis/apps/chronos/util/prev_next.py

-from datetime import timedelta, date, time
-from typing import Optional, Tuple
-
-from calendarweek import CalendarWeek
-from django.urls import reverse
-from django.utils import timezone
-
-from ..models import TimePeriod
-
-
-def get_next_relevant_day(day: Optional[date] = None, time: Optional[time] = None, prev: bool = False) -> date:
-    """ Returns next (previous) day with lessons depending on date and time """
-
-    if day is None:
-        day = timezone.now().date()
-
-    if time is not None and not prev:
-        if time > TimePeriod.time_max:
-            day += timedelta(days=1)
-
-    cw = CalendarWeek.from_date(day)
-
-    if day.weekday() > TimePeriod.weekday_max:
-        if prev:
-            day = cw[TimePeriod.weekday_max]
-        else:
-            cw += 1
-            day = cw[TimePeriod.weekday_min]
-    elif day.weekday() < TimePeriod.weekday_min:
-        if prev:
-            cw -= 1
-            day = cw[TimePeriod.weekday_max]
-        else:
-            day = cw[TimePeriod.weekday_min]
-
-    return day
-
-
-def get_prev_next_by_day(day: date, url: str) -> Tuple[str, str]:
-    """ Build URLs for previous/next day """
-
-    day_prev = get_next_relevant_day(day - timedelta(days=1), prev=True)
-    day_next = get_next_relevant_day(day + timedelta(days=1))
-
-    url_prev = reverse(url, args=[day_prev.year, day_prev.month, day_prev.day])
-    url_next = reverse(url, args=[day_next.year, day_next.month, day_next.day])
-
-    return url_prev, url_next