#1866: Add nico seiga support and fix various seiga bugs

* Support rewriting source when user uploads from a thumbnail url or
html page url
* Fix bug where site did not log in correctly
* Fix bug where the image url couldn't be extracted from the page if the
image was rated as adults only on seiga
* Normalize direct image url to html page url so tags, etc., can be
extracted

app/logical/downloads/strategies/base.rb

@@ -2,7 +2,7 @@ module Downloads
   module Strategies
     class Base
       def self.strategies
-        [Pixiv, Twitpic, DeviantArt, Tumblr]
+        [Pixiv, NicoSeiga, Twitpic, DeviantArt, Tumblr]
       end
 
       def rewrite(url, headers)

app/logical/downloads/strategies/nico_seiga.rb

@@ -0,0 +1,42 @@
+module Downloads
+  module Strategies
+    class NicoSeiga < Base
+      def rewrite(url, headers)
+        if url =~ %r{https?://lohas\.nicoseiga\.jp} || url =~ %r{https?://seiga\.nicovideo\.jp}
+          url, headers = rewrite_headers(url, headers)
+          url, headers = rewrite_html_pages(url, headers)
+          url, headers = rewrite_thumbnails(url, headers)
+        end
+
+        return [url, headers]
+      end
+
+    protected
+      def rewrite_headers(url, headers)
+        headers["Referer"] = "http://seiga.nicovideo.jp"
+        return [url, headers]
+      end
+
+      def rewrite_html_pages(url, headers)
+        # example: http://seiga.nicovideo.jp/seiga/im1389842
+
+        if url =~ %r{https?://seiga\.nicovideo\.jp/seiga/im\d+}
+          source = ::Sources::Strategies::NicoSeiga.new(url)
+          source.get
+          return [source.image_url, headers]
+        else
+          return [url, headers]
+        end
+      end
+
+      def rewrite_thumbnails(url, headers)
+        if url =~ %r{/thumb/(\d+)}
+          id = $1
+          url = "http://seiga.nicovideo.jp/image/source?id=" + id
+        end
+
+        return [url, headers]
+      end
+    end
+  end
+end