Added function to fetch url from image id

Fixes #84

fbchat/client.py

@@ -771,6 +771,23 @@ class Client(object):
             "unseen_threads": j['payload']['unseen_thread_ids']
         }
 
+    def fetchImageUrl(self, image_id):
+        """Fetches the url to the original image from an image attachment ID
+
+        :param image_id: The image you want to fethc
+        :type image_id: str
+        :return: An url where you can download the original image
+        :rtype: str
+        :raises: Exception if request failed
+        """
+        image_id = str(image_id)
+        j = checkRequest(self._get(ReqUrl.ATTACHMENT_PHOTO, query={'photo_id': str(image_id)}))
+
+        url = get_jsmods_require(j, 3)
+        if url is None:
+            raise Exception('Could not fetch image url from: {}'.format(j))
+        return url
+
     """
     END FETCH METHODS
     """
@@ -833,12 +850,10 @@ class Client(object):
         except (KeyError, IndexError) as e:
             raise Exception('Error when sending message: No message IDs could be found: {}'.format(j))
 
-        # update JS token if receive from response
+        # update JS token if received in response
-        if ('jsmods' in j) and ('require' in j['jsmods']):
+        fb_dtsg = get_jsmods_require(j, 2)
-            try:
+        if fb_dtsg is not None:
-                self.payloadDefault['fb_dtsg'] = j['jsmods']['require'][0][3][0]
+            self.payloadDefault['fb_dtsg'] = fb_dtsg
-            except (KeyError, IndexError) as e:
-                log.warning("Error when update fb_dtsg. Facebook might have changed protocol.")
 
         return message_id
 

fbchat/models.py

@@ -220,7 +220,11 @@ class ImageAttachment(Attachment):
     animated_preview_height = int
 
     def __init__(self, original_extension=None, width=None, height=None, is_animated=None, thumbnail_url=None, preview=None, large_preview=None, animated_preview=None, **kwargs):
-        """Represents an image that has been sent as a Facebook attachment"""
+        """
+        Represents an image that has been sent as a Facebook attachment
+        To retrieve the full image url, use: :func:`fbchat.Client.fetchImageUrl`,
+        and pass it the uid of the image attachment
+        """
         super(ImageAttachment, self).__init__(**kwargs)
         self.original_extension = original_extension
         self.width = width

fbchat/utils.py

@@ -112,6 +112,7 @@ class ReqUrl(object):
     MESSAGE_REACTION = "https://www.facebook.com/webgraphql/mutation"
     TYPING = "https://www.facebook.com/ajax/messaging/typ.php"
     GRAPHQL = "https://www.facebook.com/api/graphqlbatch/"
+    ATTACHMENT_PHOTO = "https://www.facebook.com/mercury/attachments/photo/"
 
 
 facebookEncoding = 'UTF-8'
@@ -191,3 +192,11 @@ def checkRequest(r, do_json_check=True):
         return j
     else:
         return content
+
+def get_jsmods_require(j, index):
+    if j.get('jsmods') and j['jsmods'].get('require'):
+        try:
+            return j['jsmods']['require'][0][index][0]
+        except (KeyError, IndexError) as e:
+            log.warning('Error when getting jsmods_require: {}. Facebook might have changed protocol'.format(j))
+    return None