Update Caravan Magazine

Add support for optional login

recipes/caravan_magazine.recipe

@@ -1,4 +1,11 @@
-# coding: utf-8
+#!/usr/bin/env python2
+# vim:fileencoding=utf-8
+# License: GPLv3 Copyright: 2015, Kovid Goyal <kovid at kovidgoyal.net>
+
+import json
+
+from mechanize import Request
+
 from calibre.web.feeds.recipes import BasicNewsRecipe
 
 
@@ -16,6 +23,7 @@ class CaravanMagazine(BasicNewsRecipe):
     language = 'en_IN'
     timefmt = ' [%b, %Y]'
     encoding = 'utf-8'
+    needs_subscription = 'optional'
 
     no_stylesheets = True
 
@@ -29,6 +37,32 @@ class CaravanMagazine(BasicNewsRecipe):
         dict(attrs={'class': ['share-with']}),
     ]
 
+    def get_browser(self, *args, **kw):
+        br = BasicNewsRecipe.get_browser(self, *args, **kw)
+        if not self.username or not self.password:
+            return br
+        data = json.dumps({'email': self.username, 'name': '', 'password': self.password})
+        if not isinstance(data, bytes):
+            data = data.encode('utf-8')
+        rq = Request(
+            url='https://caravanmagazine.in/api/users/login',
+            data=data,
+            headers={
+                'Accept': 'application/json, text/plain, */*',
+                'Origin': 'https://caravanmagazine.in',
+                'Referer': 'https://caravanmagazine.in/',
+                'Content-type': 'application/json;charset=UTF-8',
+            },
+            method='POST'
+        )
+        res = br.open(rq).read()
+        res = res.decode('utf-8')
+        self.log('Login request response: {}'.format(res))
+        res = json.loads(res)
+        if res['code'] != 200 or res['message'] != "Login success":
+            raise ValueError('Login failed, check your username and password')
+        return br
+
     # To parse artice toc
     def parse_index(self):
         base_url = 'https://www.caravanmagazine.in/'