Count recently-returned letters on the dashboard

Currently you have no way of getting to the returned letter page. This
commit adds a link to it from the dashboard, following the pattern of
the new received text messages banner.

app/__init__.py

@@ -356,6 +356,22 @@ def format_delta(date):
     )
 
 
+def format_delta_days(date):
+    now = datetime.now(timezone.utc)
+    date = utc_string_to_aware_gmt_datetime(date)
+    delta = now - date
+    if date.strftime('%Y-%M-%D') == now.strftime('%Y-%M-%D'):
+        return "today"
+    if date.strftime('%Y-%M-%D') == (now - timedelta(days=1)).strftime('%Y-%M-%D'):
+        return "yesterday"
+    return ago.human(
+        delta,
+        precision=1,
+        future_tense='{} from now',
+        past_tense='{} ago',
+    )
+
+
 def valid_phone_number(phone_number):
     try:
         validate_phone_number(phone_number)
@@ -744,6 +760,7 @@ def add_template_filters(application):
         format_date_short,
         format_datetime_relative,
         format_delta,
+        format_delta_days,
         format_notification_status,
         format_notification_type,
         format_notification_status_as_time,

app/models/service.py

@@ -1,4 +1,8 @@
+from datetime import datetime, timedelta
+
+from dateutil.parser import parse
 from flask import abort, current_app
+from notifications_utils.timezones import local_timezone
 from werkzeug.utils import cached_property
 
 from app.models import JSONModel
@@ -670,3 +674,24 @@ class Service(JSONModel):
     @cached_property
     def returned_letter_summary(self):
         return service_api_client.get_returned_letter_summary(self.id)
+
+    @property
+    def most_recent_returned_letter_report(self):
+        if not self.returned_letter_summary:
+            return None
+        return parse(
+            self.returned_letter_summary[0]['reported_at'] + " 00:00:00"
+        ).replace(tzinfo=local_timezone)
+
+    @property
+    def count_of_returned_letters_in_last_7_days(self):
+        seven_days_ago = (
+            datetime.now() - timedelta(days=7)
+        ).replace(
+            hour=0, minute=0, second=0
+        )
+        return sum(
+            report['returned_letter_count']
+            for report in self.returned_letter_summary
+            if parse(report['reported_at'] + " 00:00:00") >= seven_days_ago
+        )

app/templates/views/dashboard/_inbox.html

@@ -17,4 +17,17 @@
       {% endif %}
     </a>
   {% endif %}
+  {% if current_service.returned_letter_summary %}
+    <a id="total-returned-letters" class="banner-dashboard" href="{{ url_for('main.returned_letter_summary', service_id=current_service.id) }}">
+      <span class="banner-dashboard-count">
+        {{ current_service.count_of_returned_letters_in_last_7_days|format_thousands }}
+      </span>
+      <span class="banner-dashboard-count-label">
+        returned {{ message_count_label(current_service.count_of_returned_letters_in_last_7_days, 'letter', suffix='') }}
+      </span>
+      <span class="banner-dashboard-meta">
+        latest report {{ current_service.most_recent_returned_letter_report|format_delta_days }}
+      </span>
+    </a>
+  {% endif %}
 </div>