constraint to verify reverseEntryUuid with other asset transaction entry

src/main/resources/db/changelog/5-hs-office/512-coopassets/5120-hs-office-coopassets.sql

@@ -27,6 +27,31 @@ create table if not exists hs_office_coopassetstransaction
     reverseEntryUuid    uuid references hs_office_coopassetstransaction (uuid) deferrable ,
     comment             varchar(512)
 );
+
+alter table hs_office_coopassetstransaction
+    add constraint hs_office_coopassetstransaction_reverse_entry_missing
+        check ( transactionType != 'ADJUSTMENT' or reverseEntryUuid is not null);
+
+CREATE OR REPLACE FUNCTION hs_office_coopassetstransaction_reverse_entry_is_reciprocal_tf()
+    RETURNS TRIGGER
+    LANGUAGE plpgsql AS $$
+BEGIN
+    IF NEW.reverseEntryUuid IS NULL
+        OR NEW.uuid IN (SELECT other.reverseEntryUuid
+                      FROM hs_office_coopassetstransaction other
+                      WHERE other.uuid = NEW.reverseEntryUuid
+                        AND NEW.membershipUuid = other.membershipUuid)
+    THEN
+        RETURN NEW;
+    END IF;
+
+    RAISE EXCEPTION 'reverseEntryUuid must refer to a row that has a reference back to this row and belongs to the same membership';
+END; $$;
+
+-- FIXME: why does this not work?
+-- CREATE TRIGGER hs_office_coopassetstransaction_reverse_entry_is_reciprocal_tg
+--     AFTER INSERT OR UPDATE ON hs_office_coopassetstransaction
+--     FOR EACH ROW EXECUTE FUNCTION hs_office_coopassetstransaction_reverse_entry_is_reciprocal_tf();
 --//
 
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