[box] allow subdomain for box without file id in url

youtube_dl/extractor/box.py

@@ -14,7 +14,7 @@ from ..utils import (
 
 
 class BoxIE(InfoExtractor):
-    _VALID_URL = r'https?://(?:[^.]+\.)?app\.box\.com/s/(?P<shared_name>[^/]+)/file/(?P<id>\d+)'
+    _VALID_URL = r'https?://(?P<prefix>(?:[^.]+\.)?)app\.box\.com/s/(?P<shared_name>[^/]+)(?:/file/(?P<id>\d+))?'
     _TEST = {
         'url': 'https://mlssoccer.app.box.com/s/0evd2o3e08l60lr4ygukepvnkord1o1x/file/510727257538',
         'md5': '1f81b2fd3960f38a40a3b8823e5fcd43',
@@ -30,20 +30,22 @@ class BoxIE(InfoExtractor):
     }
 
     def _real_extract(self, url):
-        shared_name, file_id = re.match(self._VALID_URL, url).groups()
+        prefix, shared_name, file_id = re.match(self._VALID_URL, url).groups()
         webpage = self._download_webpage(url, file_id)
+        if not file_id:
+            file_id = re.search(r'"typedID":\s*"f_(\d+)"', webpage).group(1)
         request_token = self._parse_json(self._search_regex(
             r'Box\.config\s*=\s*({.+?});', webpage,
             'Box config'), file_id)['requestToken']
         access_token = self._download_json(
-            'https://app.box.com/app-api/enduserapp/elements/tokens', file_id,
+            'https://' + prefix + 'app.box.com/app-api/enduserapp/elements/tokens', file_id,
             'Downloading token JSON metadata',
             data=json.dumps({'fileIDs': [file_id]}).encode(), headers={
                 'Content-Type': 'application/json',
                 'X-Request-Token': request_token,
                 'X-Box-EndUser-API': 'sharedName=' + shared_name,
             })[file_id]['read']
-        shared_link = 'https://app.box.com/s/' + shared_name
+        shared_link = 'https://' + prefix + 'app.box.com/s/' + shared_name
         f = self._download_json(
             'https://api.box.com/2.0/files/' + file_id, file_id,
             'Downloading file JSON metadata', headers={