clean up usage of dates/datetimes in performance platform tasks

* call variables unambiguous things like `start_time` or `bst_date` to
  reduce risk of passing in the wrong thing
* simplify the count_dict object - remove nested dict and start_date
  fields as superfluous
* use static datetime objects in tests rather than calculating them
  each time

app/celery/nightly_tasks.py

@@ -37,6 +37,7 @@ from app.models import (
 )
 from app.performance_platform import total_sent_notifications, processing_time
 from app.cronitor import cronitor
+from app.utils import get_london_midnight_in_utc
 
 
 @notify_celery.task(name="remove_sms_email_jobs")
@@ -152,36 +153,37 @@ def timeout_notifications():
 def send_daily_performance_platform_stats():
     if performance_platform_client.active:
         yesterday = datetime.utcnow() - timedelta(days=1)
-        send_total_sent_notifications_to_performance_platform(yesterday)
+        send_total_sent_notifications_to_performance_platform(bst_date=yesterday.date())
         processing_time.send_processing_time_to_performance_platform()
 
 
-def send_total_sent_notifications_to_performance_platform(day):
-    count_dict = total_sent_notifications.get_total_sent_notifications_for_day(day.date())
-    email_sent_count = count_dict.get('email').get('count')
-    sms_sent_count = count_dict.get('sms').get('count')
-    letter_sent_count = count_dict.get('letter').get('count')
-    start_date = count_dict.get('start_date')
+def send_total_sent_notifications_to_performance_platform(bst_date):
+    count_dict = total_sent_notifications.get_total_sent_notifications_for_day(bst_date)
+    start_time = get_london_midnight_in_utc(bst_date)
+
+    email_sent_count = count_dict['email']
+    sms_sent_count = count_dict['sms']
+    letter_sent_count = count_dict['letter']
 
     current_app.logger.info(
         "Attempting to update Performance Platform for {} with {} emails, {} text messages and {} letters"
-        .format(start_date, email_sent_count, sms_sent_count, letter_sent_count)
+        .format(bst_date, email_sent_count, sms_sent_count, letter_sent_count)
     )
 
     total_sent_notifications.send_total_notifications_sent_for_day_stats(
-        start_date,
+        start_time,
         'sms',
         sms_sent_count
     )
 
     total_sent_notifications.send_total_notifications_sent_for_day_stats(
-        start_date,
+        start_time,
         'email',
         email_sent_count
     )
 
     total_sent_notifications.send_total_notifications_sent_for_day_stats(
-        start_date,
+        start_time,
         'letter',
         letter_sent_count
     )

app/clients/performance_platform/performance_platform_client.py

@@ -46,17 +46,17 @@ class PerformancePlatformClient:
                 resp.raise_for_status()
 
     @staticmethod
-    def format_payload(*, dataset, date, group_name, group_value, count, period='day'):
+    def format_payload(*, dataset, start_time, group_name, group_value, count, period='day'):
         """
         :param dataset - the name of the overall graph, as referred to in the endpoint.
-        :param date - the date we're sending stats for
+        :param start_time - UTC midnight of the day we're sending stats for
         :param group_name - the name of the individual groups of data, eg "channel" or "status"
         :param group_value - the value of the group, eg "sms" or "email" for group_name=channel
         :param count - the actual numeric value to send
         :param period - the period that this data covers - "day", "week", "month", "quarter".
         """
         payload = {
-            '_timestamp': convert_utc_to_bst(date).isoformat(),
+            '_timestamp': convert_utc_to_bst(start_time).isoformat(),
             'service': 'govuk-notify',
             'dataType': dataset,
             'period': period,

app/performance_platform/processing_time.py

@@ -9,29 +9,29 @@ from app import performance_platform_client
 
 def send_processing_time_to_performance_platform():
     today = datetime.utcnow()
-    start_date = get_midnight_for_day_before(today)
-    end_date = get_london_midnight_in_utc(today)
+    start_time = get_midnight_for_day_before(today)
+    end_time = get_london_midnight_in_utc(today)
 
-    send_processing_time_for_start_and_end(start_date, end_date)
+    send_processing_time_for_start_and_end(start_time, end_time)
 
 
-def send_processing_time_for_start_and_end(start_date, end_date):
-    result = dao_get_total_notifications_sent_per_day_for_performance_platform(start_date, end_date)
+def send_processing_time_for_start_and_end(start_time, end_time):
+    result = dao_get_total_notifications_sent_per_day_for_performance_platform(start_time, end_time)
 
     current_app.logger.info(
         'Sending processing-time to performance platform for date {}. Total: {}, under 10 secs {}'.format(
-            start_date, result.messages_total, result.messages_within_10_secs
+            start_time, result.messages_total, result.messages_within_10_secs
         )
     )
 
-    send_processing_time_data(start_date, 'messages-total', result.messages_total)
-    send_processing_time_data(start_date, 'messages-within-10-secs', result.messages_within_10_secs)
+    send_processing_time_data(start_time, 'messages-total', result.messages_total)
+    send_processing_time_data(start_time, 'messages-within-10-secs', result.messages_within_10_secs)
 
 
-def send_processing_time_data(date, status, count):
+def send_processing_time_data(start_time, status, count):
     payload = performance_platform_client.format_payload(
         dataset='processing-time',
-        date=date,
+        start_time=start_time,
         group_name='status',
         group_value=status,
         count=count

app/performance_platform/total_sent_notifications.py

@@ -1,12 +1,11 @@
 from app import performance_platform_client
 from app.dao.fact_notification_status_dao import get_total_sent_notifications_for_day_and_type
-from app.utils import get_london_midnight_in_utc
 
 
-def send_total_notifications_sent_for_day_stats(date, notification_type, count):
+def send_total_notifications_sent_for_day_stats(start_time, notification_type, count):
     payload = performance_platform_client.format_payload(
         dataset='notifications',
-        date=date,
+        start_time=start_time,
         group_name='channel',
         group_value=notification_type,
         count=count
@@ -20,17 +19,8 @@ def get_total_sent_notifications_for_day(day):
     sms_count = get_total_sent_notifications_for_day_and_type(day, 'sms')
     letter_count = get_total_sent_notifications_for_day_and_type(day, 'letter')
 
-    start_date = get_london_midnight_in_utc(day)
-
     return {
-        "start_date": start_date,
-        "email": {
-            "count": email_count
-        },
-        "sms": {
-            "count": sms_count
-        },
-        "letter": {
-            "count": letter_count
-        },
+        "email": email_count,
+        "sms": sms_count,
+        "letter": letter_count,
     }