Group uploaded letters by day of printing

Some teams have started uploading quite a lot of letters (in the
hundreds per week). They’re also uploading CSVs of emails. This means
the uploads page ends up quite jumbled.

This is because:
- there’s just a lot of items to scan through
- conceptually it’s a bit odd to have batches of things displayed
  alongside individual things on the same page

So instead we’re going to start grouping together uploaded letters. This
will be by the date on which we ‘start’ printing them, or in other
words the time at which they can no longer be cancelled.

This feels like a natural grouping, and it matches what we know about
people’s mental models of ‘batches’ and ‘runs’ when talking about
printing.

This grouping will be done in the API, so all this commit need to do is:
- be ready to display this new type of pseudo-job
- link to the page that displays all the uploaded letters for a given
  print day

app/utils.py

@@ -2,7 +2,7 @@ import csv
 import os
 import re
 import unicodedata
-from datetime import datetime, time, timedelta, timezone
+from datetime import datetime, timedelta, timezone
 from functools import wraps
 from io import BytesIO, StringIO
 from itertools import chain
@@ -14,6 +14,7 @@ import ago
 import dateutil
 import pyexcel
 import pyexcel_xlsx
+import pytz
 from dateutil import parser
 from flask import abort, current_app, redirect, request, session, url_for
 from flask_login import current_user, login_required
@@ -33,6 +34,7 @@ from notifications_utils.template import (
     SMSPreviewTemplate,
 )
 from notifications_utils.timezones import (
+    convert_bst_to_utc,
     convert_utc_to_bst,
     utc_string_to_aware_gmt_datetime,
 )
@@ -550,11 +552,13 @@ def get_default_sms_sender(sms_senders):
     ), "None"))
 
 
-def printing_today_or_tomorrow():
-    now_utc = datetime.utcnow()
-    now_bst = convert_utc_to_bst(now_utc)
+def printing_today_or_tomorrow(created_at):
+    print_cutoff = convert_bst_to_utc(
+        convert_utc_to_bst(datetime.utcnow()).replace(hour=17, minute=30)
+    ).replace(tzinfo=pytz.utc)
+    created_at = utc_string_to_aware_gmt_datetime(created_at)
 
-    if now_bst.time() < time(17, 30):
+    if created_at < print_cutoff:
         return 'today'
     else:
         return 'tomorrow'
@@ -569,10 +573,11 @@ def redact_mobile_number(mobile_number, spacing=""):
     return "".join(mobile_number_list)
 
 
-def get_letter_printing_statement(status, created_at):
+def get_letter_printing_statement(status, created_at, long_form=True):
     created_at_dt = parser.parse(created_at).replace(tzinfo=None)
     if letter_can_be_cancelled(status, created_at_dt):
-        return 'Printing starts {} at 5:30pm'.format(printing_today_or_tomorrow())
+        decription = 'Printing starts' if long_form else 'Printing'
+        return f'{decription} {printing_today_or_tomorrow(created_at)} at 5:30pm'
     else:
         printed_datetime = utc_string_to_aware_gmt_datetime(created_at) + timedelta(hours=6, minutes=30)
         if printed_datetime.date() == datetime.now().date():
@@ -581,8 +586,9 @@ def get_letter_printing_statement(status, created_at):
             return 'Printed yesterday at 5:30pm'
 
         printed_date = printed_datetime.strftime('%d %B').lstrip('0')
+        description = 'Printed on' if long_form else 'Printed'
 
-        return 'Printed on {} at 5:30pm'.format(printed_date)
+        return f'{description} {printed_date} at 5:30pm'
 
 
 LETTER_VALIDATION_MESSAGES = {