[WEI] Add dry mode in WEI algorithm command, output generated data

Signed-off-by: Yohann D'ANELLO <ynerant@crans.org>

apps/wei/management/commands/wei_algorithm.py

@@ -1,15 +1,44 @@
 # Copyright (C) 2018-2021 by BDE ENS Paris-Saclay
 # SPDX-License-Identifier: GPL-3.0-or-later
+from argparse import ArgumentParser, FileType
 
 from django.core.management import BaseCommand
+from django.db import transaction
+
 from wei.forms import CurrentSurvey
 
 
 class Command(BaseCommand):
     help = "Attribute to each first year member a bus for the WEI"
 
+    def add_arguments(self, parser: ArgumentParser):
+        parser.add_argument('--doit', '-d', action='store_true', help='Finally run the algorithm in non-dry mode.')
+        parser.add_argument('--output', '-o', nargs='?', type=FileType('w'), default=self.stdout,
+                            help='Output file for the algorithm result. Default is standard output.')
+
+    @transaction.atomic
     def handle(self, *args, **options):
         """
         Run the WEI algorithm to attribute a bus to each first year member.
         """
-        CurrentSurvey.get_algorithm_class()().run_algorithm()
+        sid = transaction.savepoint()
+
+        algorithm = CurrentSurvey.get_algorithm_class()()
+        algorithm.run_algorithm()
+
+        output = options['output']
+        registrations = algorithm.get_registrations()
+        per_bus = {bus: [r for r in registrations if r.information['selected_bus_pk'] == bus.pk]
+                   for bus in algorithm.get_buses()}
+        for bus, members in per_bus.items():
+            output.write(bus.name + "\n")
+            output.write("=" * len(bus.name) + "\n")
+            for r in members:
+                output.write(r.user.username + "\n")
+            output.write("\n")
+
+        if not options['doit']:
+            self.stderr.write(self.style.WARNING("Running in dry mode. "
+                                                 "Use --doit option to really execute the algorithm."))
+            transaction.savepoint_rollback(sid)
+            return