[furaffinity] Adding a FuraffinityFolderExtractor, which extracts a single folder

- Ensure FuraffinityGalleryExtractor doesn't detect folder links
- Fix example URL for folder extractor
- Reordering classes a bit
- Another tweak of the regex
- One more go at the regex..
- cleanup

docs/supportedsites.md

@@ -286,7 +286,7 @@ Consider all listed sites to potentially be NSFW.
 <tr>
     <td>Fur Affinity</td>
     <td>https://www.furaffinity.net/</td>
-    <td>Favorites, Followed Users, Galleries, Posts, Scraps, Search Results, New Submissions, User Profiles</td>
+    <td>Favorites, Folders, Followed Users, Galleries, Posts, Scraps, Search Results, New Submissions, User Profiles</td>
     <td><a href="https://github.com/mikf/gallery-dl#cookies">Cookies</a></td>
 </tr>
 <tr>

gallery_dl/extractor/furaffinity.py

@@ -153,12 +153,13 @@ class FuraffinityExtractor(Extractor):
     def _process_description(description):
         return text.unescape(text.remove_html(description, "", ""))
 
-    def _pagination(self, path):
+    def _pagination(self, path, folder=None):
         num = 1
+        folder = "" if folder is None else "/folder/{}/a".format(folder)
 
         while True:
-            url = "{}/{}/{}/{}/".format(
+            url = "{}/{}/{}{}/{}/".format(
-                self.root, path, self.user, num)
+                self.root, path, self.user, folder, num)
             page = self.request(url).text
             post_id = None
 
@@ -232,13 +233,31 @@ class FuraffinityExtractor(Extractor):
 class FuraffinityGalleryExtractor(FuraffinityExtractor):
     """Extractor for a furaffinity user's gallery"""
     subcategory = "gallery"
-    pattern = BASE_PATTERN + r"/gallery/([^/?#]+)"
+    pattern = BASE_PATTERN + r"/gallery/([^/?#]+)(?:$|/(?!folder/))"
     example = "https://www.furaffinity.net/gallery/USER/"
 
     def posts(self):
         return self._pagination("gallery")
 
 
+class FuraffinityFolderExtractor(FuraffinityExtractor):
+    """Extractor for a FurAffinity folder"""
+    subcategory = "folder"
+    directory_fmt = ("{category}", "{user!l}",
+                     "Folders", "{folder_id}{folder_name:? //}")
+    pattern = BASE_PATTERN + r"/gallery/([^/?#]+)/folder/(\d+)(?:/([^/?#]+))?"
+    example = "https://www.furaffinity.net/gallery/USER/folder/12345/FOLDER"
+
+    def metadata(self):
+        return {
+            "folder_id"  : self.groups[1],
+            "folder_name": self.groups[2] or "",
+        }
+
+    def posts(self):
+        return self._pagination("gallery", self.groups[1])
+
+
 class FuraffinityScrapsExtractor(FuraffinityExtractor):
     """Extractor for a furaffinity user's scraps"""
     subcategory = "scraps"

test/results/furaffinity.py

@@ -17,6 +17,23 @@ __tests__ = (
     "#count"   : 6,
 },
 
+{
+    "#url"     : "https://www.furaffinity.net/gallery/markrun15/folder/173240/Inanimate/?",
+    "#category": ("", "furaffinity", "folder"),
+    "#class"   : furaffinity.FuraffinityFolderExtractor,
+    "#range"   : "46-50",
+    "#urla"    : (
+        "https://d.furaffinity.net/art/markrun15/1598704240/1598704240.markrun15_20200829_dusknoir_flat3.jpg",
+        "https://d.furaffinity.net/art/markrun15/1598704109/1598704109.markrun15_20200829_dusknoir_flat1.jpg",
+        "https://d.furaffinity.net/art/markrun15/1588674514/1588674514.markrun15_20200504_cubemorgana.jpg",
+        "https://d.furaffinity.net/art/markrun15/1588501280/1588501280.markrun15_20200427_inanimate_animal3.jpg",
+        "https://d.furaffinity.net/art/markrun15/1588501161/1588501161.markrun15_20200427_inanimate_animal.jpg",
+    ),
+
+    "folder_id"  : "173240",
+    "folder_name": "Inanimate",
+},
+
 {
     "#url"     : "https://www.furaffinity.net/scraps/mirlinthloth/",
     "#category": ("", "furaffinity", "scraps"),