[fantia] add 'content_count' and 'content_num' metadata fields (#4627)

gallery_dl/extractor/fantia.py

@@ -42,7 +42,11 @@ class FantiaExtractor(Extractor):
             post = self._get_post_data(post_id)
             post["num"] = 0
 
-            for content in self._get_post_contents(post):
+            contents = self._get_post_contents(post)
+            post["content_count"] = len(contents)
+            post["content_num"] = 0
+
+            for content in contents:
                 files = self._process_content(post, content)
                 yield Message.Directory, post
 
@@ -131,6 +135,7 @@ class FantiaExtractor(Extractor):
         post["content_filename"] = content.get("filename") or ""
         post["content_id"] = content["id"]
         post["content_comment"] = content.get("comment") or ""
+        post["content_num"] += 1
         post["plan"] = content["plan"] or self._empty_plan
 
         files = []