This adds new endpoints to retrieve billing data from the new table:

1. Create a separate billing blueprint to house these endpoints

2. Return monthly breakdown in same format as we did before

3. Return yearly breakdown but only return {billing units, rate,
notification_type}. Admin only makes use of these.

app/billing/rest.py

@@ -0,0 +1,73 @@
+from datetime import datetime
+import json
+
+from flask import Blueprint, jsonify, request
+
+from app.dao.notification_usage_dao import get_billing_data_for_month
+from app.dao.monthly_billing_dao import get_billing_data_for_financial_year
+from app.dao.date_util import get_financial_year
+from app.errors import register_errors
+from app.models import SMS_TYPE, EMAIL_TYPE
+
+
+billing_blueprint = Blueprint(
+    'billing',
+    __name__,
+    url_prefix='/service/<uuid:service_id>/billing'
+)
+
+
+register_errors(billing_blueprint)
+
+
+@billing_blueprint.route('/monthly-usage')
+def get_yearly_usage_by_month(service_id):
+    try:
+        year = int(request.args.get('year'))
+        start_date, end_date = get_financial_year(year)
+        results = get_billing_data_for_month(service_id, start_date, end_date, SMS_TYPE)
+        json_results = [{
+            "month": datetime.strftime(x[0], "%B"),
+            "billing_units": x[1],
+            "rate_multiplier": x[2],
+            "international": x[3],
+            "notification_type": x[4],
+            "rate": x[5]
+        } for x in results]
+        return json.dumps(json_results)
+    except TypeError:
+        return jsonify(result='error', message='No valid year provided'), 400
+
+
+@billing_blueprint.route('/yearly-usage-summary')
+def get_yearly_billing_usage_summary(service_id):
+    try:
+        year = int(request.args.get('year'))
+        billing_data = get_billing_data_for_financial_year(service_id, year)
+        notification_types = [SMS_TYPE, EMAIL_TYPE]
+        response = [
+            _get_total_billable_units_and_rate_for_notification_type(billing_data, notification_type)
+            for notification_type in notification_types
+        ]
+
+        return json.dumps(response)
+
+    except TypeError:
+        return jsonify(result='error', message='No valid year provided'), 400
+
+
+def _get_total_billable_units_and_rate_for_notification_type(billing_data, noti_type):
+    total_sent = 0
+    rate = 0
+    for entry in billing_data:
+        for monthly_total in entry.monthly_totals:
+            if entry.notification_type == noti_type:
+                total_sent += monthly_total['billing_units'] \
+                    if noti_type == EMAIL_TYPE else (monthly_total['billing_units'] * monthly_total['rate_multiplier'])
+                rate = monthly_total['rate']
+
+    return {
+        "notification_type": noti_type,
+        "billing_units": total_sent,
+        "rate": rate
+    }