Add HyperlinkField for serializers

This field allow adding URLs to ModelSerializers.

Signed-off-by: Roberto Rosario <Roberto.Rosario@mayan-edms.com>

mayan/apps/rest_api/fields.py

@@ -5,6 +5,7 @@ from django.utils.six import string_types
 from django.utils.translation import ugettext_lazy as _
 
 from rest_framework import serializers
+from rest_framework.reverse import reverse
 
 
 class DynamicSerializerField(serializers.ReadOnlyField):
@@ -31,3 +32,33 @@ class DynamicSerializerField(serializers.ReadOnlyField):
                 ).to_representation(instance=value)
 
         return _('Unable to find serializer class for: %s') % value
+
+
+class HyperlinkField(serializers.Field):
+    lookup_field = 'pk'
+    view_name = None
+
+    def __init__(self, view_name=None, **kwargs):
+        kwargs['read_only'] = True
+
+        if view_name is not None:
+            self.view_name = view_name
+        assert self.view_name is not None, 'The `view_name` argument is required.'
+        self.lookup_field = kwargs.pop('lookup_field', self.lookup_field)
+        self.lookup_url_kwarg = kwargs.pop('lookup_url_kwarg', self.lookup_field)
+        self.format = kwargs.pop('format', None)
+        super(HyperlinkField, self).__init__(**kwargs)
+
+    def get_attribute(self, instance):
+        # We pass the object instance onto `to_representation`,
+        # not just the field attribute.
+        return instance
+
+    def to_representation(self, value):
+        kwargs = {}
+        kwargs[self.lookup_url_kwarg] = getattr(value, self.lookup_field)
+
+        return reverse(
+            kwargs=kwargs, request=self.context.get('request'),
+            viewname=self.view_name
+        )