Add print timings to letter timings

It will also be useful to know (especially for the API):
- when a letter was printed
- if it’s been printed or not

This commit:
- adds code to calculate these two pieces of information
- refactors the function to return a `namedtuple` – a tuple of two items
  was manageable, but with four items it was getting hard to know what
  each one meant – this lets us label each piece of information that is
  being returned

tests/app/test_utils.py

@@ -5,6 +5,7 @@ from csv import DictReader
 import pytest
 
 from collections import OrderedDict
+from freezegun import freeze_time
 
 from app.utils import (
     email_safe,
@@ -12,7 +13,7 @@ from app.utils import (
     generate_previous_dict,
     generate_next_dict,
     Spreadsheet,
-    get_estimated_delivery_date_for_letters,
+    get_letter_timings,
 )
 
 from tests import notification_json, single_notification_json
@@ -157,43 +158,135 @@ def test_generate_notifications_csv_calls_twice_if_next_link(mocker):
     assert mock_get_notifications.mock_calls[1][2]['page'] == 2
 
 
-@pytest.mark.parametrize('upload_time, expected_estimate', [
+@freeze_time('2017-07-14 14:59:59')  # Friday, before print deadline
+@pytest.mark.parametrize('upload_time, expected_print_time, is_printed, expected_earliest, expected_latest', [
 
     # BST
     # ==================================================================
     #  First thing Monday
-    ('2017-07-10 00:00:01', ('Thursday', 'Friday')),
+    (
+        '2017-07-10 00:00:01',
+        'Tuesday 15:00',
+        True,
+        'Thursday 2017-07-13',
+        'Friday 2017-07-14'
+    ),
     #  Monday at 16:59 BST
-    ('2017-07-10 15:59:59', ('Thursday', 'Friday')),
+    (
+        '2017-07-10 15:59:59',
+        'Tuesday 15:00',
+        True,
+        'Thursday 2017-07-13',
+        'Friday 2017-07-14'
+    ),
     #  Monday at 17:00 BST
-    ('2017-07-10 16:00:01', ('Friday', 'Saturday')),
+    (
+        '2017-07-10 16:00:01',
+        'Wednesday 15:00',
+        True,
+        'Friday 2017-07-14',
+        'Saturday 2017-07-15'
+    ),
     #  Tuesday before 17:00 BST
-    ('2017-07-11 12:00:00', ('Friday', 'Saturday')),
+    (
+        '2017-07-11 12:00:00',
+        'Wednesday 15:00',
+        True,
+        'Friday 2017-07-14',
+        'Saturday 2017-07-15'
+    ),
     #  Wednesday before 17:00 BST
-    ('2017-07-12 12:00:00', ('Saturday', 'Monday')),
+    (
+        '2017-07-12 12:00:00',
+        'Thursday 15:00',
+        True,
+        'Saturday 2017-07-15',
+        'Monday 2017-07-17'
+    ),
     #  Thursday before 17:00 BST
-    ('2017-07-13 12:00:00', ('Monday', 'Tuesday')),
+    (
+        '2017-07-13 12:00:00',
+        'Friday 15:00',
+        True,  # WRONG
+        'Monday 2017-07-17',
+        'Tuesday 2017-07-18'
+    ),
     #  Friday anytime
-    ('2017-07-14 00:00:00', ('Wednesday', 'Thursday')),
-    ('2017-07-14 12:00:00', ('Wednesday', 'Thursday')),
-    ('2017-07-14 22:00:00', ('Wednesday', 'Thursday')),
+    (
+        '2017-07-14 00:00:00',
+        'Monday 15:00',
+        False,
+        'Wednesday 2017-07-19',
+        'Thursday 2017-07-20'
+    ),
+    (
+        '2017-07-14 12:00:00',
+        'Monday 15:00',
+        False,
+        'Wednesday 2017-07-19',
+        'Thursday 2017-07-20'
+    ),
+    (
+        '2017-07-14 22:00:00',
+        'Monday 15:00',
+        False,
+        'Wednesday 2017-07-19',
+        'Thursday 2017-07-20'
+    ),
     #  Saturday anytime
-    ('2017-07-14 12:00:00', ('Wednesday', 'Thursday')),
+    (
+        '2017-07-14 12:00:00',
+        'Monday 15:00',
+        False,
+        'Wednesday 2017-07-19',
+        'Thursday 2017-07-20'
+    ),
     #  Sunday before 1700 BST
-    ('2017-07-15 15:59:59', ('Wednesday', 'Thursday')),
+    (
+        '2017-07-15 15:59:59',
+        'Monday 15:00',
+        False,
+        'Wednesday 2017-07-19',
+        'Thursday 2017-07-20'
+    ),
     #  Sunday after 17:00 BST
-    ('2017-07-16 16:00:01', ('Thursday', 'Friday')),
+    (
+        '2017-07-16 16:00:01',
+        'Tuesday 15:00',
+        False,
+        'Thursday 2017-07-20',
+        'Friday 2017-07-21'
+    ),
 
     # GMT
     # ==================================================================
     #  Monday at 16:59 GMT
-    ('2017-01-02 16:59:59', ('Thursday', 'Friday')),
+    (
+        '2017-01-02 16:59:59',
+        'Tuesday 15:00',
+        True,
+        'Thursday 2017-01-05',
+        'Friday 2017-01-06',
+    ),
     #  Monday at 17:00 GMT
-    ('2017-01-02 17:00:01', ('Friday', 'Saturday')),
+    (
+        '2017-01-02 17:00:01',
+        'Wednesday 15:00',
+        True,
+        'Friday 2017-01-06',
+        'Saturday 2017-01-07',
+    ),
 
 ])
-def test_get_estimated_delivery_date_for_letter(upload_time, expected_estimate):
-    assert tuple(
-        day.strftime('%A')
-        for day in get_estimated_delivery_date_for_letters(upload_time)
-    ) == expected_estimate
+def test_get_estimated_delivery_date_for_letter(
+    upload_time,
+    expected_print_time,
+    is_printed,
+    expected_earliest,
+    expected_latest,
+):
+    timings = get_letter_timings(upload_time)
+    assert timings.printed_by.strftime('%A %H:%M') == expected_print_time
+    assert timings.is_printed == is_printed
+    assert timings.earliest_delivery.strftime('%A %Y-%m-%d') == expected_earliest
+    assert timings.latest_delivery.strftime('%A %Y-%m-%d') == expected_latest