Use jsonpatch to provide a JSON patch document

The attribute "patch" of a model now returns a string
representing all of the operations that have occurred
on the model since it was created in JSON patch form.

3 files changed, 52 insertions, 0 deletions

diff --git a/requirements.txt b/requirements.txt
index 35c7022..bd9b4f7 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1 +1,2 @@
 jsonschema>=0.7,<1
+jsonpatch==0.10
diff --git a/test/test_core.py b/test/test_core.py
index b4e1627..5226794 100644
--- a/test/test_core.py
+++ b/test/test_core.py
@@ -142,3 +142,47 @@ class TestCore(unittest.TestCase):
         self.assertEqual(sweden.changes, {'name': 'Finland'})
         sweden['name'] = 'Norway'
         self.assertEqual(sweden.changes, {'name': 'Norway'})
+
+    def test_patch_no_changes(self):
+        Country = warlock.model_factory(fixture)
+        sweden = Country(name='Sweden', population=9379116)
+        self.assertEqual(sweden.patch, '[]')
+
+    def test_patch_alter_value(self):
+        Country = warlock.model_factory(fixture)
+        sweden = Country(name='Sweden', population=9379116)
+        sweden['name'] = 'Finland'
+        self.assertEqual(
+            sweden.patch,
+            '[{"path": "/name", "value": "Finland", "op": "replace"}]')
+
+    def test_patch_drop_attribute(self):
+        Country = warlock.model_factory(fixture)
+        sweden = Country(name='Sweden', population=9379116)
+        del sweden['name']
+        self.assertEqual(sweden.patch, '[{"path": "/name", "op": "remove"}]')
+
+    def test_patch_reduce_operations(self):
+        Country = warlock.model_factory(fixture)
+        sweden = Country(name='Sweden', population=9379116)
+
+        sweden['name'] = 'Finland'
+        self.assertEqual(
+            sweden.patch,
+            '[{"path": "/name", "value": "Finland", "op": "replace"}]')
+
+        sweden['name'] = 'Norway'
+        self.assertEqual(
+            sweden.patch,
+            '[{"path": "/name", "value": "Norway", "op": "replace"}]')
+
+    def test_patch_multiple_operations(self):
+        Country = warlock.model_factory(fixture)
+        sweden = Country(name='Sweden', population=9379116)
+
+        sweden['name'] = 'Finland'
+        sweden['population'] = 5387000
+        self.assertEqual(
+            sweden.patch,
+            '[{"path": "/name", "value": "Finland", "op": "replace"}, '
+            '{"path": "/population", "value": 5387000, "op": "replace"}]')
diff --git a/warlock/core.py b/warlock/core.py
index 38cb854..9c3cdf7 100644
--- a/warlock/core.py
+++ b/warlock/core.py
@@ -3,6 +3,7 @@
 import copy
 
 import jsonschema
+import jsonpatch
 
 
 class InvalidOperation(RuntimeError):
@@ -43,6 +44,7 @@ def model_factory(schema):
                 dict.__init__(self, d)
 
             self.__dict__['changes'] = {}
+            self.__dict__['__original__'] = copy.deepcopy(d)
 
         def __getattr__(self, key):
             try:
@@ -118,5 +120,10 @@ def model_factory(schema):
         def changes(self):
             return copy.deepcopy(self.__dict__['changes'])
 
+        @property
+        def patch(self):
+            original = self.__dict__['__original__']
+            return jsonpatch.make_patch(original, dict(self)).to_string()
+
     Model.__name__ = str(schema['name'])
     return Model