Add warning messages for badly configured refund patterns

For refund patterns to work well, there should be no gaps (a day in
between two defined patterns where there are suddenly no refunds would
be strange) and it should have something open-ended at the beginning.

1 files changed, 30 insertions, 1 deletions

diff --git a/postgresqleu/confreg/backendforms.py b/postgresqleu/confreg/backendforms.py
index a094836f..8a05714c 100644
--- a/postgresqleu/confreg/backendforms.py
+++ b/postgresqleu/confreg/backendforms.py
@@ -19,7 +19,7 @@ from urllib.parse import urlparse
 from psycopg2.extras import DateTimeTZRange
 import zoneinfo
 
-from postgresqleu.util.db import exec_to_single_list, exec_to_scalar
+from postgresqleu.util.db import exec_to_single_list, exec_to_scalar, exec_to_list
 from postgresqleu.util.crypto import generate_rsa_keypair
 from postgresqleu.util.forms import SelectSetValueField
 from postgresqleu.util.widgets import StaticTextWidget, EmailTextWidget, MonospaceTextarea
@@ -769,6 +769,35 @@ class BackendRefundPatternForm(BackendForm):
             p.todate + xform if p.todate else '<empty>',
         ) for p in patterns]
 
+    @classmethod
+    def get_warning_text(cls, conference):
+        patterns = list(RefundPattern.objects.filter(conference=conference))
+        if not patterns:
+            return None
+
+        issues = []
+        if not next((r for r in patterns if r.todate and not r.fromdate), None):
+            issues.append('There is no refund pattern with an open-ended start')
+
+        for fromdate, todate, lagdate, lagdays in exec_to_list("""WITH t AS (
+  SELECT fromdate, todate, lag(todate) OVER (w) AS prevdate, fromdate - lag(todate) OVER (w) as lag
+  FROM confreg_refundpattern
+  WHERE conference_id=%(confid)s AND (fromdate IS NOT NULL OR todate IS NOT NULL)
+  WINDOW w AS (ORDER BY fromdate NULLS FIRST)
+) SELECT * FROM t WHERE lag > 1""", {'confid': conference.id}):
+            issues.append('There is a gap of {} days between {} and {}'.format(lagdays, lagdate, fromdate))
+
+        for r1, r2 in exec_to_list("""WITH t AS (
+  SELECT daterange(fromdate, todate, '[]') AS dr
+  FROM confreg_refundpattern
+  WHERE conference_id=%(confid)s AND (fromdate IS NOT NULL OR todate IS NOT NULL)
+) SELECT a.dr, b.dr FROM t a INNER JOIN t b ON a.dr && b.dr AND a.dr != b.dr ORDER BY 1""", {'confid': conference.id}):
+            issues.append('Date range {} overlaps with {}'.format(r1, r2))
+
+        if issues:
+            return "<ul>{}</ul>".format("".join("<li>{}</li>".format(i) for i in issues))
+        return None
+
 
 class ConferenceSessionSlideForm(BackendForm):
     helplink = 'callforpapers#slides'