Add an endpoint for stats about scheduled jobs

At the moment we display the count of scheduled jobs on the dashboard
by sending all the scheduled jobs to the admin app and letting it work
out the stats.

This is inefficient and, because the get jobs response has a page size
of 50, becomes incorrect if a service schedules more than 50 jobs.

This commit adds a separate endpoint which gives the admin app the stats
it needs directly and correctly.

app/dao/jobs_dao.py

@@ -84,6 +84,18 @@ def dao_get_jobs_by_service_id(
         .paginate(page=page, per_page=page_size)
 
 
+def dao_get_scheduled_job_stats(
+    service_id,
+):
+    return db.session.query(
+        func.count(Job.id),
+        func.min(Job.scheduled_for),
+    ).filter(
+        Job.service_id == service_id,
+        Job.job_status == JOB_STATUS_SCHEDULED,
+    ).one()
+
+
 def dao_get_job_by_id(job_id):
     return Job.query.filter_by(id=job_id).one()
 

app/job/rest.py

@@ -1,4 +1,5 @@
 import dateutil
+import pytz
 from flask import (
     Blueprint,
     jsonify,
@@ -14,6 +15,7 @@ from app.dao.jobs_dao import (
     dao_get_jobs_by_service_id,
     dao_get_future_scheduled_job_by_id_and_service_id,
     dao_get_notification_outcomes_for_job,
+    dao_get_scheduled_job_stats,
     dao_cancel_letter_job,
     can_letter_job_be_cancelled
 )
@@ -188,6 +190,18 @@ def create_job(service_id):
     return jsonify(data=job_json), 201
 
 
+@job_blueprint.route('/scheduled-job-stats', methods=['GET'])
+def get_scheduled_job_stats(service_id):
+    count, soonest_scheduled_for = dao_get_scheduled_job_stats(service_id)
+    return jsonify(
+        count=count,
+        soonest_scheduled_for=(
+            soonest_scheduled_for.replace(tzinfo=pytz.UTC).isoformat()
+            if soonest_scheduled_for else None
+        ),
+    ), 200
+
+
 def get_paginated_jobs(
     service_id,
     *,

tests/app/job/test_rest.py

@@ -910,3 +910,36 @@ def test_get_jobs_should_retrieve_from_ft_notification_status_for_old_jobs(admin
     assert resp_json['data'][1]['statistics'] == [{'status': 'created', 'count': 1}]
     assert resp_json['data'][2]['id'] == str(job_1.id)
     assert resp_json['data'][2]['statistics'] == [{'status': 'delivered', 'count': 6}]
+
+
+@freeze_time('2017-07-17 07:17')
+def test_get_scheduled_job_stats_when_no_scheduled_jobs(admin_request, sample_template):
+
+    # This sets up a bunch of regular, non-scheduled jobs
+    _setup_jobs(sample_template)
+
+    service_id = sample_template.service.id
+
+    resp_json = admin_request.get('job.get_scheduled_job_stats', service_id=service_id)
+    assert resp_json == {
+        'count': 0,
+        'soonest_scheduled_for': None,
+    }
+
+
+@freeze_time('2017-07-17 07:17')
+def test_get_scheduled_job_stats(admin_request, sample_template):
+    create_job(sample_template, job_status='scheduled', scheduled_for='2017-07-17 09:00')
+    create_job(sample_template, job_status='scheduled', scheduled_for='2017-07-17 10:00')
+    create_job(sample_template, job_status='scheduled', scheduled_for='2017-07-17 11:00')
+
+    service_id = sample_template.service.id
+
+    resp_json = admin_request.get(
+        'job.get_scheduled_job_stats',
+        service_id=service_id,
+    )
+    assert resp_json == {
+        'count': 3,
+        'soonest_scheduled_for': '2017-07-17T09:00:00+00:00',
+    }