Add filtering support for Accept HTTP header.

Adds an "provides"-option to a route definition, which can either be
a string specifying a MIME type, a symbol that Rack can resolve to
a MIME type, or an array of either.

CHANGES

@@ -1,5 +1,9 @@
 = 0.9.0 (unreleased)
 
+ * New ":provides" route condition takes an array of mime types and
+   matches only when an Accept request header is present with a
+   corresponding type. [cypher]
+
  * Work with and require Rack >= 0.9
 
  * Regular expressions may now be used in route pattens; captures are

lib/sinatra/base.rb

@@ -10,6 +10,10 @@ class Request < Rack::Request
     def user_agent
       @env['HTTP_USER_AGENT']
     end
+
+    def accept
+      @env['HTTP_ACCEPT'].split(',').map { |a| a.strip }
+    end
   end
 
   class Response < Rack::Response
@@ -88,9 +92,7 @@ def session
 
     # Look up a media type by file extension in Rack's mime registry.
     def media_type(type)
-      return type if type.nil? || type.to_s.include?('/')
-      type = ".#{type}" unless type.to_s[0] == ?.
-      Rack::Mime.mime_type(type, nil)
+      Base.media_type(type)
     end
 
     # Set the Content-Type of the response body given a media type or file
@@ -479,6 +481,13 @@ def use_in_file_templates!
         end
       end
 
+      # Look up a media type by file extension in Rack's mime registry.
+      def media_type(type)
+        return type if type.nil? || type.to_s.include?('/')
+        type = ".#{type}" unless type.to_s[0] == ?.
+        Rack::Mime.mime_type(type, nil)
+      end
+
       def before(&block)
         @filters << block
       end
@@ -502,6 +511,21 @@ def user_agent(pattern)
         }
       end
 
+      def accept_mime_types(types)
+        types = [types] unless types.kind_of? Array
+        types.map!{|t| media_type(t)}
+
+        condition {
+          matching_types = (request.accept & types)
+          unless matching_types.empty?
+            response.headers['Content-Type'] = matching_types.first
+            true
+          else
+            false
+          end
+        }
+      end
+
       def get(path, opts={}, &block)
         conditions = @conditions.dup
         route 'GET', path, opts, &block
@@ -519,6 +543,7 @@ def head(path, opts={}, &bk); route 'HEAD', path, opts, &bk; end
       def route(method, path, opts={}, &block)
         host_name  opts[:host]  if opts.key?(:host)
         user_agent opts[:agent] if opts.key?(:agent)
+        accept_mime_types opts[:provides] if opts.key?(:provides)
 
         pattern, keys = compile(path)
         conditions, @conditions = @conditions, []

test/routing_test.rb

@@ -302,4 +302,37 @@
     status.should.equal 200
     body.should.equal 'Hello Bar'
   end
+
+  it "filters by accept header" do
+    mock_app {
+      get '/', :provides => :xml do
+        request.env['HTTP_ACCEPT']
+      end
+    }
+
+    get '/', :env => { :accept => 'application/xml' }
+    should.be.ok
+    body.should.equal 'application/xml'
+    response.headers['Content-Type'].should.equal 'application/xml'
+
+    get '/', :env => { :accept => 'text/html' }
+    should.not.be.ok
+  end
+
+  it "allows multiple mime types for accept header" do
+    types = ['image/jpeg', 'image/pjpeg']
+
+    mock_app {
+      get '/', :provides => types do
+        request.env['HTTP_ACCEPT']
+      end
+    }
+
+    types.each do |type|
+      get '/', :env => { :accept => type }
+      should.be.ok
+      body.should.equal type
+      response.headers['Content-Type'].should.equal type
+    end
+  end
 end