Move computing of start of semester to core/utils

Signed-off-by: Skia <skia@libskia.so>

core/utils.py

@@ -27,11 +27,38 @@ import re
 # Image utils
 
 from io import BytesIO
+from datetime import datetime, timezone, date
+
 from PIL import Image, ExifTags
-# from exceptions import IOError
 import PIL
+
+from django.conf import settings
 from django.core.files.base import ContentFile
 
+
+def get_start_of_semester(d=date.today()):
+    """
+    This function computes the start date of the semester with respect to the given date (default is today),
+    and the start date given in settings.SITH_START_DATE.
+    It takes the nearest past start date.
+    Exemples: with SITH_START_DATE = (8, 15)
+        Today      -> Start date
+        2015-03-17 -> 2015-02-15
+        2015-01-11 -> 2014-08-15
+    """
+    today = d
+    year = today.year
+    start = date(year, settings.SITH_START_DATE[0], settings.SITH_START_DATE[1])
+    start2 = start.replace(month=(start.month+6)%12)
+    if start > start2:
+        start, start2 = start2, start
+    if today < start:
+        return start2.replace(year=year-1)
+    elif today < start2:
+        return start
+    else:
+        return start2
+
 def scale_dimension(width, height, long_edge):
     if width > height:
         ratio = long_edge * 1. / width

subscription/models.py

@@ -32,6 +32,7 @@ from django.core.urlresolvers import reverse
 from django.contrib.auth.forms import PasswordResetForm
 
 from core.models import User
+from core.utils import get_start_of_semester
 
 
 
@@ -147,18 +148,7 @@ class Subscription(models.Model):
         """
         if duration <= 2: # Sliding subscriptions for 1 or 2 semesters
             return d
-        today = d
-        year = today.year
-        start = date(year, settings.SITH_START_DATE[0], settings.SITH_START_DATE[1])
-        start2 = start.replace(month=(start.month+6)%12)
-        if start > start2:
-            start, start2 = start2, start
-        if today < start:
-            return start2.replace(year=year-1)
-        elif today < start2:
-            return start
-        else:
-            return start2
+        return get_start_of_semester(d)
 
     @staticmethod
     def compute_end(duration, start=None):