Add proper email notifications

apps/submissions/management/commands/process_submissions.py

@@ -0,0 +1,80 @@
+"""`python manage.py process_submissions` -- implements plan.md §7.5.
+
+Drains one batch of submissions stuck in `processing`: validates each row's
+STL (uploads) or URL (printables / makerworld / thingiverse) and transitions
+to `verifying` on success or `rejected` on failure. Runs on a 30-second
+loop from the `web` container's entrypoint (plan.md §10) -- one invocation
+of this command per tick.
+
+Concurrency: `select_for_update(skip_locked=True)` keeps replicas / stray
+cron ticks / a re-entrant restart from grabbing the same row. On SQLite the
+locks are no-ops (dev only); Postgres in prod gets the non-blocking lock
+semantics the design assumes.
+"""
+
+from __future__ import annotations
+
+from django.core.management.base import BaseCommand
+from django.db import transaction
+from django.utils import timezone
+
+from apps.submissions.emails import send_status_update_email, send_verifying_email
+from apps.submissions.models import Submission
+from apps.submissions.validation import (
+    ValidationError,
+    validate_external_url,
+    validate_stl_file,
+)
+
+BATCH = 50
+
+
+class Command(BaseCommand):
+    help = (
+        "Drain submissions stuck in `processing` -- one batch per invocation. "
+        "Designed to be called on a loop from the web container entrypoint; "
+        "safe to also call ad-hoc for debugging."
+    )
+
+    def add_arguments(self, parser) -> None:
+        parser.add_argument(
+            "--batch",
+            type=int,
+            default=BATCH,
+            help=f"Max rows to process per invocation (default: {BATCH}).",
+        )
+
+    def handle(self, *args, batch: int, **opts) -> None:
+        with transaction.atomic():
+            # `list(...)` materialises the slice inside the transaction so
+            # subsequent `.save()` calls don't invalidate the queryset.
+            queue = list(
+                Submission.objects
+                .select_for_update(skip_locked=True)
+                .filter(status=Submission.Status.PROCESSING)
+                .order_by("updated_at")[:batch]
+            )
+
+            if not queue:
+                return
+
+            for sub in queue:
+                try:
+                    if sub.source_type == Submission.SourceType.UPLOAD:
+                        validate_stl_file(sub.stl_file.path)
+                    else:
+                        validate_external_url(sub.source_url, sub.source_type)
+                except ValidationError as exc:
+                    sub.status = Submission.Status.REJECTED
+                    sub.operator_notes = f"Automatic rejection: {exc}"
+                    sub.closed_at = timezone.now()
+                    # closed_by stays NULL -- the validator did the rejecting,
+                    # not an operator (plan.md §5 / §7.3).
+                    sub.save()
+                    send_status_update_email(sub, previous_status="processing")
+                    self.stdout.write(f"rejected  {sub.slug}: {exc}")
+                else:
+                    sub.status = Submission.Status.VERIFYING
+                    sub.save()
+                    send_verifying_email(sub)
+                    self.stdout.write(f"verifying {sub.slug}")