add logger adapter

lib/faraday/adapter.rb

@@ -13,7 +13,8 @@ class Adapter < Middleware
       :EMSynchrony    => 'em_synchrony',
       :Patron         => 'patron',
       :Excon          => 'excon',
-      :Test           => 'test'
+      :Test           => 'test',
+      :Logger         => 'logger'
 
     register_lookup_modules \
       :action_dispatch => :ActionDispatch,
@@ -22,7 +23,8 @@ class Adapter < Middleware
       :typhoeus        => :Typhoeus,
       :patron          => :Patron,
       :em_synchrony    => :EMSynchrony,
-      :excon           => :Excon
+      :excon           => :Excon,
+      :logger          => :Logger
 
     def call(env)
       process_body_for_request(env)

lib/faraday/adapter/logger.rb

@@ -0,0 +1,30 @@
+module Faraday
+  class Adapter
+    class Logger < Faraday::Adapter
+      def initialize(app = nil, logger = nil)
+        super(app)
+        @logger = logger || begin
+          require 'logger'
+          Logger.new(STDOUT)
+        end
+      end
+
+      def call(env)
+        super
+        @logger.info "#{env[:method]} #{env[:url].to_s}"
+        @logger.debug("request") do
+          env[:request_headers].map { |(k, v)| "#{k}: #{v.inspect}" }.join("\n")
+        end
+
+        env[:response].on_complete do |resp_env|
+          @logger.info("Status") { env[:status].to_s }
+          @logger.debug("response") do
+            resp_env[:response_headers].map { |(k, v)| "#{k}: #{v.inspect}" }.join("\n")
+          end
+        end
+
+        @app.call(env)
+      end
+    end
+  end
+end

test/adapters/logger_test.rb

@@ -0,0 +1,37 @@
+require File.expand_path(File.join(File.dirname(__FILE__), '..', 'helper'))
+require 'stringio'
+require 'logger'
+
+module Adapters
+  class LoggerTest < Faraday::TestCase
+    def setup
+      @io     = StringIO.new
+      @logger = Logger.new(@io)
+      @logger.level = Logger::DEBUG
+
+      @conn = Faraday::Connection.new do |b|
+        b.adapter :logger, @logger
+        b.adapter :test do |stubs|
+          stubs.get('/hello') { [200, {'Content-Type' => 'text/html'}, 'hello'] }
+        end
+      end
+      @resp = @conn.get '/hello', :accept => 'text/html'
+    end
+
+    def test_still_returns_output
+      assert_equal 'hello', @resp.body
+    end
+
+    def test_logs_method_and_url
+      assert_match "get /hello", @io.string
+    end
+
+    def test_logs_request_headers
+      assert_match %(Accept: "text/html), @io.string
+    end
+
+    def test_logs_response_headers
+      assert_match %(Content-Type: "text/html), @io.string
+    end
+  end
+end