better exception handling

lib/fb_graph2/app_link_host.rb

@@ -25,8 +25,6 @@ module FbGraph2
           Struct::AppLink::Native::Android
         when :windows_phone
           Struct::AppLink::Native::WindowsPhone
-        else
-          raise 'Unknown AppLink Type'
         end
         klass.new link
       end

lib/fb_graph2/exception.rb

@@ -0,0 +1,81 @@
+module FbGraph2
+  class Exception < StandardError
+    attr_accessor :status, :type, :code
+
+    class << self
+      def detect(status, body = {}, headers = {})
+        error = body[:error]
+        message = error.try(:[], :message)
+        klass = detect_from_header(headers, error) || detect_from_status(status)
+        if klass
+          klass.new message, error
+        else
+          new status, message, error
+        end
+      end
+
+      def detect_from_status(status)
+        case status
+        when 400
+          BadRequest
+        when 401
+          Unauthorized
+        when 404
+          NotFound
+        when 500
+          InternalServerError
+        end
+      end
+
+      def detect_from_header(headers, error)
+        key, value = headers.detect do |name, value|
+          name.upcase == "WWW-Authenticate".upcase
+        end || return
+        matched, klass = ERROR_HEADER_MATCHERS.detect do |matcher, klass_name|
+          matcher =~ value
+        end || return
+        klass
+      end
+    end
+
+    def initialize(status, message, error = {})
+      super message
+      self.status = status
+      self.type = error[:type]
+      self.code = error[:code]
+    end
+
+    class BadRequest < Exception
+      def initialize(message, details = {})
+        super 400, message, details
+      end
+    end
+
+    class Unauthorized < Exception
+      def initialize(message, details = {})
+        super 401, message, details
+      end
+    end
+
+    class NotFound < Exception
+      def initialize(message, details = {})
+        super 404, message, details
+      end
+    end
+
+    class InternalServerError < Exception
+      def initialize(message, details = {})
+        super 500, message, details
+      end
+    end
+
+    class InvalidToken < Unauthorized; end
+    class InvalidRequest < BadRequest; end
+
+    ERROR_HEADER_MATCHERS = {
+      /not_found/       => NotFound,
+      /invalid_token/   => InvalidToken,
+      /invalid_request/ => InvalidRequest
+    }
+  end
+end

lib/fb_graph2/node.rb

@@ -107,12 +107,10 @@ module FbGraph2
       when 200...300
         _response_
       else
-        # TODO: better exception structure
-        raise response.body
+        raise Exception.detect(response.status, _response_, response.headers)
       end
     rescue MultiJson::DecodeError
-      # TODO: better exception structure
-      raise response.body
+      raise Exception.new(response.status, "Unparsable Response: #{response.body}")
     end
   end
 end

spec/fb_graph2/node_spec.rb

@@ -103,8 +103,8 @@ describe FbGraph2::Node do
                 instance.fetch
               end
             end.to raise_error { |e|
-              e.should be_instance_of RuntimeError
-              e.message.should == mock_json('error/400/2500')
+              e.should be_instance_of FbGraph2::Exception::BadRequest
+              e.message.should == mock_json('error/400/2500')[:error][:message]
             }
           end
         end
@@ -116,8 +116,8 @@ describe FbGraph2::Node do
                 instance.fetch
               end
             end.to raise_error { |e|
-              e.should be_instance_of RuntimeError
-              e.message.should == mock_json('error/invalid_format')
+              e.should be_instance_of FbGraph2::Exception
+              e.message.should == "Unparsable Response: #{mock_json('error/invalid_format')}"
             }
           end
         end

spec/spec_helper/mock_graph.rb

@@ -23,7 +23,10 @@ module MockGraph
   end
 
   def mock_json(response_path)
-    response_for(response_path)[:body].read
+    content = response_for(response_path)[:body].read
+    MultiJson.load(content).with_indifferent_access
+  rescue MultiJson::DecodeError
+    content
   end
 
   def request_to(path, method = :get, options = {})