Migrate document source transformation validation solution to document page transformation

apps/documents/models.py

@@ -1,6 +1,7 @@
 import os
 import tempfile
 import hashlib
+from ast import literal_eval
 
 from django.db import models
 from django.utils.translation import ugettext_lazy as _
@@ -8,6 +9,7 @@ from django.contrib.auth.models import User
 from django.contrib.contenttypes import generic
 from django.contrib.comments.models import Comment
 from django.conf import settings
+from django.core.exceptions import ValidationError
 
 from taggit.managers import TaggableManager
 from dynamic_search.api import register
@@ -295,6 +297,27 @@ class DocumentPage(models.Model):
         return ('document_page_view', [self.pk])
 
 
+class ArgumentsValidator(object):
+    message = _(u'Enter a valid value.')
+    code = 'invalid'
+
+    def __init__(self, message=None, code=None):
+        if message is not None:
+            self.message = message
+        if code is not None:
+            self.code = code
+
+    def __call__(self, value):
+        """
+        Validates that the input evaluates correctly.
+        """
+        value = value.strip()
+        try:
+            literal_eval(value)
+        except (ValueError, SyntaxError):
+            raise ValidationError(self.message, code=self.code)
+
+
 class DocumentPageTransformation(models.Model):
     """
     Model that stores the transformation and transformation arguments
@@ -303,7 +326,7 @@ class DocumentPageTransformation(models.Model):
     document_page = models.ForeignKey(DocumentPage, verbose_name=_(u'document page'))
     order = models.PositiveIntegerField(default=0, blank=True, null=True, verbose_name=_(u'order'), db_index=True)
     transformation = models.CharField(choices=get_available_transformations_choices(), max_length=128, verbose_name=_(u'transformation'))
-    arguments = models.TextField(blank=True, null=True, verbose_name=_(u'arguments'), help_text=_(u'Use dictionaries to indentify arguments, example: {\'degrees\':90}'))
+    arguments = models.TextField(blank=True, null=True, verbose_name=_(u'arguments'), help_text=_(u'Use dictionaries to indentify arguments, example: {\'degrees\':90}'), validators=[ArgumentsValidator()])
 
     objects = DocumentPageTransformationManager()