basic waiter support; needs polishing

[wolnelektury.git] / apps / waiter / models.py

diff --git a/apps/waiter/models.py b/apps/waiter/models.py
new file mode 100644 (file)
index 0000000..fd97301
--- /dev/null
+++ b/apps/waiter/models.py
@@ -0,0 +1,53 @@
+from os.path import join, abspath, exists
+from django.db import models
+from waiter.settings import WAITER_ROOT, WAITER_URL
+from django.core.urlresolvers import reverse
+
+class WaitedFile(models.Model):
+    path = models.CharField(max_length=255, unique=True, db_index=True)
+    task = models.CharField(max_length=64, null=True, editable=False)
+    description = models.CharField(max_length=255, null=True, blank=True)
+
+    @staticmethod
+    def abspath(path):
+        abs_path = abspath(join(WAITER_ROOT, path))
+        if not abs_path.startswith(WAITER_ROOT):
+            raise ValueError('Path not inside WAITER_ROOT.')
+        return abs_path
+
+    @classmethod
+    def exists(cls, path):
+        """Returns opened file or None.
+        
+        `path` is relative to WAITER_ROOT.
+        Won't open a path leading outside of WAITER_ROOT.
+        """
+        abs_path = cls.abspath(path)
+        # Pre-fetch objects to avoid minor race condition
+        relevant = [o.id for o in cls.objects.filter(path=path)]
+        print abs_path
+        if exists(abs_path):
+            cls.objects.filter(id__in=relevant).delete()
+            return True
+        else:
+            return False
+
+    @classmethod
+    def order(cls, path, task_creator, description=None):
+        """
+        Returns an URL for the user to follow.
+        If the file is ready, returns download URL.
+        If not, starts preparing it and returns waiting URL.
+        """
+        already = cls.exists(path)
+        if not already:
+            waited, created = cls.objects.get_or_create(path=path)
+            if created:
+                # TODO: makedirs
+                waited.task = task_creator(cls.abspath(path))
+                print waited.task
+                waited.description = description
+                waited.save()
+            # TODO: it the task exists, if stale delete, send some mail and restart
+            return reverse("waiter", args=[path])
+        return join(WAITER_URL, path)