add initial code

Author: freenoth

.gitignore

@@ -1,2 +1,6 @@
 # Created by .ignore support plugin (hsz.mobi)
 .idea
+manage.py
+django-auto-rollback
+__pycache__
+db.sqlite3

django_auto_rollback/__init__.py

@@ -0,0 +1 @@
+name = 'django_rollback'

django_auto_rollback/management/commands/freeze_migrations_state.py

@@ -0,0 +1,5 @@
+from django.apps import AppConfig
+
+
+class StatusConfig(AppConfig):
+    name = 'django_rollback'

django_auto_rollback/management/commands/rollback_migrations.py

@@ -0,0 +1,132 @@
+import json
+from collections import namedtuple
+
+import git
+from django.core.management import call_command
+from django.core.management.base import BaseCommand, CommandError
+
+from django_rollback.models import AppsState
+
+COMMIT_MAX_LENGTH = 40
+MIGRATE_COMMAND = 'migrate'
+
+MigrationRecord = namedtuple('MigrationRecord', ['id', 'app', 'name'])
+
+
+class Command(BaseCommand):
+    help = 'Rollback migrations state of all django apps to chosen tag or commit if previously stored.'
+
+    def add_arguments(self, parser):
+        parser.add_argument('-t', '--tag', type=str, help='Git tag in witch needs to rollback migrations.')
+        parser.add_argument('-c', '--commit', type=str, help='Git commit hash in witch needs to rollback migrations.')
+        parser.add_argument('--fake', action='store_true',
+                            help='Used to block migrate commands execution, so it allow to only print info '
+                                 'about processed actions without execution.')
+
+    def handle(self, *args, **options):
+        other_commit = self.get_commit_from_options(options)
+        current_commit = self.get_current_commit()
+
+        current_data = self.get_migrations_data_from_commit(current_commit)
+        other_data = self.get_migrations_data_from_commit(other_commit)
+
+        diff = self.get_migrations_diff(current=current_data, other=other_data)
+
+        self.run_rollback(diff, fake=options['fake'])
+
+        self.stdout.write(self.style.SUCCESS('Rollback successfully finished.'))
+
+    def get_commit_from_options(self, options):
+        if not options['tag'] and not options['commit']:
+            raise CommandError('Tag or commit should be described by -t or -c arguments.')
+
+        if options['tag'] and options['commit']:
+            raise CommandError('Tag and commit arguments should not be described together.')
+
+        if options['commit']:
+            return options['commit']
+
+        tag = options['tag']
+        try:
+            repo = git.Repo('.')
+            if tag not in repo.tags:
+                raise CommandError(f'Can not find tag `{tag}` in git repository.')
+
+            return repo.tags[tag].commit.hexsha
+
+        except CommandError as err:
+            raise err
+
+        except Exception as err:
+            self.stdout.write(self.style.ERROR(f'WARNING: an error occurred while working with git repo!'))
+            raise CommandError(err)
+
+    def get_current_commit(self):
+        try:
+            repo = git.Repo('.')
+            return repo.head.commit.hexsha
+
+        except ValueError as err:
+            self.stdout.write(self.style.ERROR(f'WARNING: an error occurred while working with git repo!'))
+            raise CommandError(err)
+
+    def get_migrations_data_from_commit(self, commit):
+        queryset = AppsState.objects.filter(commit__istartswith=commit)
+
+        count = queryset.count()
+
+        if count == 0:
+            raise CommandError(f'Can not find stored data of migrations state for commit `{commit}`.')
+
+        if count > 1:
+            is_short_commit = len(commit) < COMMIT_MAX_LENGTH
+            raise CommandError(f'Found more than 1 ({count}) records for selected commit {commit}.'
+                               f'{" Please clarify commit hash for more identity." if is_short_commit else ""}')
+
+        instance = queryset.first()
+        return json.loads(instance.migrations)
+
+    def get_migrations_diff(self, current, other):
+        """
+        current and other is type of list of tuples in format:
+        [(<id> : int, <app> : str, <name> : str), ...]
+
+        :return dict that indicates what migrations should be executed
+        migration_id is useful to detect migration order (from higher to lower)
+        {
+            <migration_id>: <migrate command args>
+        }
+        """
+        result = []
+
+        current = [MigrationRecord(*rec) for rec in current]
+        other = [MigrationRecord(*rec) for rec in other]
+        other_apps = {migration.app for migration in other}
+
+        # find what is changed in current relative to other
+        diff = set(current) - set(other)
+        for migration in diff:
+            is_new_app = migration.app not in other_apps
+            result.append(MigrationRecord(
+                migration.id,
+                migration.app,
+                'zero' if is_new_app else list(filter(lambda x: x.app == migration.app, other))[0].name,
+            ))
+
+        return result
+
+    def run_rollback(self, migrations_diff_records, fake=False):
+        """
+        sort all migrations by migration.id order from higher to lower and execute migrate command for them
+        """
+
+        if not migrations_diff_records:
+            self.stdout.write(f'>>> There is no migrations to rollback.')
+            return
+
+        for migration in sorted(migrations_diff_records, key=lambda r: int(r.id), reverse=True):
+            execute_args = (MIGRATE_COMMAND, migration.app, migration.name)
+            self.stdout.write(f'>>> Executing command: {" ".join(execute_args)}')
+
+            if not fake:
+                call_command(*execute_args)