[*chan] code cleanup

gallery_dl/extractor/chan.py

@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-# Copyright 2015 Mike Fährmann
+# Copyright 2015, 2016 Mike Fährmann
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 as
@@ -11,34 +11,37 @@
 from .common import Extractor, Message
 from .. import text
 
-class ChanExtractor(Extractor):
+class ChanThreadExtractor(Extractor):
     """Base class for extractors for Futaba Channel boards"""
+    category = "chan"
+    subcategory = "thread"
     directory_fmt = ["{category}", "{board}-{thread}"]
     filename_fmt = "{tim}-{filename}{ext}"
     api_url = ""
     file_url = ""
 
-    def __init__(self, board, thread):
+    def __init__(self, match):
         Extractor.__init__(self)
         self.metadata = {
-            "board": board,
-            "thread": thread,
+            "board": match.group(1),
+            "thread": match.group(2),
         }
 
     def items(self):
         yield Message.Version, 1
-        posts = self.request(self.api_url.format(**self.metadata)).json()["posts"]
+        url = self.api_url.format_map(self.metadata)
+        posts = self.request(url).json()["posts"]
         self.metadata["title"] = self.get_thread_title(posts[0])
         yield Message.Directory, self.metadata
         for post in posts:
             if "filename" not in post:
                 continue
             post.update(self.metadata)
-            yield Message.Url, self.file_url.format(**post), post
+            yield Message.Url, self.file_url.format_map(post), post
             if "extra_files" in post:
                 for file in post["extra_files"]:
                     post.update(file)
-                    yield Message.Url, self.file_url.format(**post), post
+                    yield Message.Url, self.file_url.format_map(post), post
 
     @staticmethod
     def get_thread_title(post):