[furaffinity:favorite] support URLs with custom start position

gallery_dl/extractor/furaffinity.py

@@ -168,8 +168,10 @@ class FuraffinityExtractor(Extractor):
                 return
             num += 1
 
-    def _pagination_favorites(self):
+    def _pagination_favorites(self, start=None):
         path = f"/favorites/{self.user}/"
+        if start is not None:
+            path += start
 
         while path:
             page = self.request(self.root + path).text
@@ -271,11 +273,11 @@ class FuraffinityFavoriteExtractor(FuraffinityExtractor):
     """Extractor for a furaffinity user's favorites"""
     subcategory = "favorite"
     directory_fmt = ("{category}", "{user!l}", "Favorites")
-    pattern = BASE_PATTERN + r"/favorites/([^/?#]+)"
+    pattern = BASE_PATTERN + r"/favorites/([^/?#]+)(/\d+/(?:next|prev))?"
     example = "https://www.furaffinity.net/favorites/USER/"
 
     def posts(self):
-        return self._pagination_favorites()
+        return self._pagination_favorites(self.groups[1])
 
     def _parse_post(self, post_id):
         if post := FuraffinityExtractor._parse_post(self, post_id):

test/results/furaffinity.py

@@ -53,6 +53,19 @@ __tests__ = (
     "favorite_id": int,
 },
 
+{
+    "#url"     : "https://www.furaffinity.net/favorites/mirlinthloth/46682246/next?",
+    "#comment" : "custom start location",
+    "#class"   : furaffinity.FuraffinityFavoriteExtractor,
+    "#auth"    : False,
+    "#range"   : "1-3",
+    "#results" : (
+        "https://d.furaffinity.net/art/kacey/1263424668/1263424668.kacey_mine.jpg",
+        "https://d.furaffinity.net/art/leomon32/1254250660/1254250660.leomon32_high_in_the_sky.jpg",
+        "https://d.furaffinity.net/art/firefoxzero/1262442028/1262442028.firefoxzero_resolute_model_4.png",
+    ),
+},
+
 {
     "#url"     : "https://www.furaffinity.net/search/?q=cute",
     "#category": ("", "furaffinity", "search"),