#93: reorganise Rerun, Diffusion, Schedule module (#95)

#93

Co-authored-by: bkfox <thomas bkfox net>
Reviewed-on: rc/aircox#95

aircox/models/rerun.py

@@ -0,0 +1,106 @@
+from django.core.exceptions import ValidationError
+from django.db import models
+from django.utils.translation import gettext_lazy as _
+
+from .program import Program
+
+
+__all__ = (
+    "Rerun",
+    "RerunQuerySet",
+)
+
+
+class RerunQuerySet(models.QuerySet):
+    """Queryset for Rerun (sub)classes."""
+
+    def station(self, station=None, id=None):
+        return (
+            self.filter(program__station=station)
+            if id is None
+            else self.filter(program__station__id=id)
+        )
+
+    def program(self, program=None, id=None):
+        return (
+            self.filter(program=program)
+            if id is None
+            else self.filter(program__id=id)
+        )
+
+    def rerun(self):
+        return self.filter(initial__isnull=False)
+
+    def initial(self):
+        return self.filter(initial__isnull=True)
+
+
+class Rerun(models.Model):
+    """Abstract model offering rerun facilities.
+
+    Assume `start` is a datetime field or attribute implemented by
+    subclass.
+    """
+
+    program = models.ForeignKey(
+        Program,
+        models.CASCADE,
+        db_index=True,
+        verbose_name=_("related program"),
+    )
+    initial = models.ForeignKey(
+        "self",
+        models.SET_NULL,
+        related_name="rerun_set",
+        verbose_name=_("rerun of"),
+        limit_choices_to={"initial__isnull": True},
+        blank=True,
+        null=True,
+        db_index=True,
+    )
+
+    objects = RerunQuerySet.as_manager()
+
+    class Meta:
+        abstract = True
+
+    @property
+    def is_initial(self):
+        return self.initial is None
+
+    @property
+    def is_rerun(self):
+        return self.initial is not None
+
+    def get_initial(self):
+        """Return the initial schedule (self or initial)"""
+        return self if self.initial is None else self.initial.get_initial()
+
+    def clean(self):
+        super().clean()
+        if (
+            hasattr(self, "start")
+            and self.initial is not None
+            and self.initial.start >= self.start
+        ):
+            raise ValidationError(
+                {"initial": _("rerun must happen after original")}
+            )
+
+    def save_rerun(self):
+        self.program = self.initial.program
+
+    def save_initial(self):
+        pass
+
+    def save(self, *args, **kwargs):
+        if self.initial is not None:
+            self.initial = self.initial.get_initial()
+        if self.initial == self:
+            self.initial = None
+
+        if self.is_rerun:
+            self.save_rerun()
+        else:
+            self.save_initial()
+        super().save(*args, **kwargs)