http: add logger for debugging purposes.

Usage: Danbooru::Http.new.use(:logger).get(url).

app/logical/danbooru/http.rb

@@ -1,6 +1,7 @@
 require "danbooru/http/html_adapter"
 require "danbooru/http/xml_adapter"
 require "danbooru/http/cache"
+require "danbooru/http/logger"
 require "danbooru/http/redirector"
 require "danbooru/http/retriable"
 require "danbooru/http/session"

app/logical/danbooru/http/logger.rb

@@ -0,0 +1,35 @@
+module Danbooru
+  class Http
+    class Logger < HTTP::Feature
+      HTTP::Options.register_feature :logger, self
+
+      attr_reader :logger
+
+      def initialize(logger: ::Logger.new(STDOUT))
+        @logger = logger
+      end
+
+      def perform(request, &block)
+        log_request(request)
+        response = yield request
+        log_response(request, response)
+        response
+      end
+
+      def log_request(request)
+        logger.info do
+          verb = request.verb.to_s.upcase
+          headers = request.headers.map { |name, value| "#{name}: #{value}" }.join("\n")
+          "> #{verb} #{request.uri}\n#{headers}\n"
+        end
+      end
+
+      def log_response(request, response)
+        logger.info do
+          headers = response.headers.map { |name, value| "#{name}: #{value}" }.join("\n")
+          "< #{response.status.to_i} | #{request.uri}\n#{headers}\n"
+        end
+      end
+    end
+  end
+end