[nhentai] select random file servers for download URLs (#6620)

i1, i2, i3, i4 instead of just i.nhentai.net

gallery_dl/extractor/nhentai.py

@@ -11,6 +11,7 @@
 from .common import GalleryExtractor, Extractor, Message
 from .. import text, util
 import collections
+import random
 
 
 class NhentaiGalleryExtractor(GalleryExtractor):
@@ -59,15 +60,18 @@ class NhentaiGalleryExtractor(GalleryExtractor):
         }
 
     def images(self, _):
-        ufmt = ("https://i.nhentai.net/galleries/" +
-                self.data["media_id"] + "/{}.{}")
-        extdict = {"j": "jpg", "p": "png", "g": "gif", "w": "webp"}
+        exts = {"j": "jpg", "p": "png", "g": "gif", "w": "webp", "a": "avif"}
+
+        data = self.data
+        ufmt = ("https://i{}.nhentai.net/galleries/" +
+                data["media_id"] + "/{}.{}").format
 
         return [
-            (ufmt.format(num, extdict.get(img["t"], "jpg")), {
-                "width": img["w"], "height": img["h"],
+            (ufmt(random.randint(1, 4), num, exts.get(img["t"], "jpg")), {
+                "width" : img["w"],
+                "height": img["h"],
             })
-            for num, img in enumerate(self.data["images"]["pages"], 1)
+            for num, img in enumerate(data["images"]["pages"], 1)
         ]