Resolve "Provide infrastructure for live documents"

Closes #3 (closed)

aleksis/apps/resint/models.py

 from datetime import datetime
 from typing import Optional
 
+from django.core.files import File
 from django.core.validators import FileExtensionValidator, MaxValueValidator, MinValueValidator
 from django.db import models
 from django.utils import timezone
 from django.utils.translation import gettext_lazy as _
 
+import reversion
 from calendarweek import CalendarWeek
 from calendarweek.django import i18n_day_name_choices_lazy
+from reversion.models import Revision, Version
 
-from aleksis.core.mixins import ExtensibleModel
+from aleksis.core.mixins import ExtensibleModel, ExtensiblePolymorphicModel
 
 
 class PosterGroup(ExtensibleModel):
@@ -141,3 +144,69 @@ class Poster(ExtensibleModel):
         cw = CalendarWeek(week=self.week, year=self.year)
         day = cw[self.group.publishing_day]
         return timezone.datetime.combine(day, self.group.publishing_time)
+
+
+class LiveDocument(ExtensiblePolymorphicModel):
+    """Model for periodically/automatically updated files."""
+
+    slug = models.SlugField(
+        verbose_name=_("Slug"),
+        help_text=_("This will be used for the name of the current PDF file."),
+    )
+    name = models.CharField(max_length=255, verbose_name=_("Name"))
+
+    current_file = models.FileField(
+        upload_to="live_documents/",
+        null=True,
+        blank=True,
+        verbose_name=_("Current file"),
+        editable=False,
+    )
+    last_update_triggered_manually = models.BooleanField(
+        default=False, verbose_name=_("Was the last update triggered manually?"), editable=False
+    )
+
+    @property
+    def last_version(self) -> Optional[Revision]:
+        """Get django-reversion version of last file update."""
+        versions = Version.objects.get_for_object(self).order_by("revision__date_created")
+        if versions.exists():
+            return versions.last()
+        return None
+
+    @property
+    def last_update(self) -> Optional[datetime]:
+        """Get datetime of last file update."""
+        last_version = self.last_version
+        if last_version:
+            return last_version.revision.date_created
+        return None
+
+    def get_current_file(self) -> Optional[File]:
+        """Get current file."""
+        if not self.current_file:
+            self.update()
+        return self.current_file
+
+    @property
+    def filename(self) -> str:
+        """Get the filename without path of the PDF file."""
+        return f"{self.slug}.pdf"
+
+    def save(self, *args, **kwargs):
+        with reversion.create_revision():
+            super().save(*args, **kwargs)
+
+    def update(self, triggered_manually: bool = True):
+        """Update the file with a new version.
+
+        Has to be implemented by subclasses.
+        """
+        raise NotImplementedError("Subclasses of LiveDocument must implement update()")
+
+    def __str__(self) -> str:
+        return self.name
+
+    class Meta:
+        verbose_name = _("Live document")
+        verbose_name_plural = _("Live documents")