Implementation of ExtendedURLField type field for django models

oscar/apps/promotions/abstract_models.py

@@ -4,6 +4,8 @@ from django.utils.translation import ugettext as _
 from django.core.urlresolvers import reverse
 from django.core.exceptions import ValidationError
 
+from oscar.core.fields import ExtendedURLField
+
 BANNER_FOLDER = settings.OSCAR_BANNER_FOLDER
 POD_FOLDER = settings.OSCAR_POD_FOLDER
 
@@ -15,6 +17,7 @@ POSITION_CHOICES = (
     (RAW_HTML, _("Raw HTML"))
 )
 
+
 class AbstractPromotion(models.Model):
     u"""
     A promotion model.
@@ -24,7 +27,7 @@ class AbstractPromotion(models.Model):
 
     """
     name = models.CharField(_("Name"), max_length=128)
-    link_url = models.URLField(blank=True, null=True, help_text="""This is 
+    link_url = ExtendedURLField(blank=True, null=True, help_text="""This is 
         where this promotion links to""")
 
     # Three ways of supplying the content

oscar/core/fields.py

@@ -0,0 +1,56 @@
+from django.core.exceptions import ValidationError
+from django.core.validators import URLValidator
+from django.core.urlresolvers import resolve
+from django.db import models
+from django.http import Http404
+
+class ExtendedURLField(models.CharField):
+    u"""
+    Custom field similar to URLField type field, however also accepting 
+    and validating local relative URLs, ie. '/product/'
+    """
+    description = "Extended URL"
+
+    def __init__(self, verbose_name=None, name=None, verify_exists=True, **kwargs):
+        kwargs['max_length'] = kwargs.get('max_length', 200)
+        models.CharField.__init__(self, verbose_name, name, **kwargs)
+        self.is_local_url = False
+        self.verify_exists = verify_exists
+        
+    def get_prep_value(self, value):
+        u"""
+        Make sure local URLs have preceding and trailing slashes 
+        """
+        if self.is_local_url == True:
+            value = self.fix_local_url(value)
+        return value
+
+    def validate(self, value, model_instance):
+        u"""
+        Overrides global vaidate method to check whether URL is valid
+        """
+        v = URLValidator(verify_exists=self.verify_exists)
+        try:
+            v(value)
+        except ValidationError, e:
+            if (e.code == 'invalid_link'):
+                raise ValidationError('This link appears to be broken')
+            self.validate_local_url(value)
+
+    def validate_local_url(self, value):
+        u"""
+        Validate local URL name
+        """
+        try:
+            value = self.fix_local_url(value)
+            resolve(value)
+            self.is_local_url = True
+        except Http404:
+            raise ValidationError('Specified page does not exist')
+
+    def fix_local_url(self, value):
+        u"""
+        Puts preceding and trailing slashes to local URL name 
+        """
+        return '/' + value.strip('/') + '/'
+