conneg.rb in rack-linkeddata-3.0.0

- old
+ new

@@ -15,10 +15,11 @@
   #     use Rack::LinkedData::ContentNegotation, :format => :ttl
   #     use Rack::LinkedData::ContentNegotiation, :format => RDF::NTriples::Format
   #     use Rack::LinkedData::ContentNegotiation, :default => 'application/rdf+xml'
   #
   # @see http://www4.wiwiss.fu-berlin.de/bizer/pub/LinkedDataTutorial/
+  # @see https://www.rubydoc.info/github/rack/rack/master/file/SPEC
   class ContentNegotiation
     DEFAULT_CONTENT_TYPE = "application/n-triples" # N-Triples
     VARY = {'Vary' => 'Accept'}.freeze
 
     # @return [#call]
@@ -43,11 +44,11 @@
     # Parses Accept header to find appropriate mime-type and sets content_type accordingly.
     #
     # Inserts ordered content types into the environment as `ORDERED_CONTENT_TYPES` if an Accept header is present
     #
     # @param  [Hash{String => String}] env
-    # @return [Array(Integer, Hash, #each)]
+    # @return [Array(Integer, Hash, #each)] Status, Headers and Body
     # @see    http://rack.rubyforge.org/doc/SPEC.html
     def call(env)
       env['ORDERED_CONTENT_TYPES'] = parse_accept_header(env['HTTP_ACCEPT']) if env.has_key?('HTTP_ACCEPT')
       response = app.call(env)
       body = response[2].respond_to?(:body) ? response[2].body : response[2]
@@ -65,86 +66,114 @@
     #
     # @param  [Hash{String => String}] env
     # @param  [Integer]                status
     # @param  [Hash{String => Object}] headers
     # @param  [RDF::Enumerable]        body
-    # @return [Array(Integer, Hash, #each)]
+    # @return [Array(Integer, Hash, #each)] Status, Headers and Body
     def serialize(env, status, headers, body)
-      begin
-        writer, content_type = find_writer(env, headers)
-        if writer
-          # FIXME: don't overwrite existing Vary headers
-          headers = headers.merge(VARY).merge('Content-Type' => content_type)
-          [status, headers, [writer.dump(body, nil, @options)]]
-        else
-          not_acceptable
+      result, content_type = nil, nil
+      find_writer(env, headers) do |writer, ct, accept_params = {}|
+        begin
+          # Passes content_type as writer option to allow parameters to be extracted.
+          result, content_type = writer.dump(body, nil, @options.merge(accept_params: accept_params)), ct.split(';').first
+          break
+        rescue RDF::WriterError
+          # Continue to next writer
+          ct
+        rescue
+          ct
         end
-      rescue RDF::WriterError => e
+      end
+
+      if result
+        headers = headers.merge(VARY).merge('Content-Type' => content_type)
+        [status, headers, [result]]
+      else
         not_acceptable
       end
     end
 
+    protected
     ##
-    # Returns an `RDF::Writer` class for the given `env`.
+    # Yields an `RDF::Writer` class for the given `env`.
     #
     # If options contain a `:format` key, it identifies the specific format to use;
     # otherwise, if the environment has an HTTP_ACCEPT header, use it to find a writer;
     # otherwise, use the default content type
     #
     # @param  [Hash{String => String}] env
     # @param  [Hash{String => Object}] headers
-    # @return [Array(Class, String)]
+    # @yield |writer, content_type|
+    # @yield_param [RDF::Writer] writer
+    # @yield_param [String] content_type from accept media-range without parameters
+    # @yield_param [Hash{Symbol => String}] accept_params from accept media-range
     # @see    http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
     def find_writer(env, headers)
       if @options[:format]
         format = @options[:format]
-        writer = RDF::Writer.for(format.to_sym) unless format.is_a?(RDF::Format)
-        return [writer, writer.format.content_type.first] if writer
+        writer = RDF::Writer.for(format.to_sym)
+        yield(writer, writer.format.content_type.first) if writer
       elsif env.has_key?('HTTP_ACCEPT')
         content_types = parse_accept_header(env['HTTP_ACCEPT'])
         content_types.each do |content_type|
-          writer, content_type = find_writer_for_content_type(content_type)
-          return [writer, content_type] if writer
+          find_writer_for_content_type(content_type) do |writer, ct, accept_params|
+            # Yields content type with parameters
+            yield(writer, ct, accept_params)
+          end
         end
-        return nil
       else
         # HTTP/1.1 §14.1: "If no Accept header field is present, then it is
         # assumed that the client accepts all media types"
-        find_writer_for_content_type(options[:default])
+        find_writer_for_content_type(options[:default]) do |writer, ct|
+          # Yields content type with parameters
+          yield(writer, ct)
+        end
       end
     end
 
     ##
-    # Returns an `RDF::Writer` class for the given `content_type`.
+    # Yields an `RDF::Writer` class for the given `content_type`.
     #
+    # Calls `Writer#accept?(content_type)` for matched content type to allow writers to further discriminate on how if to accept content-type with specified parameters.
+    #
     # @param  [String, #to_s] content_type
-    # @return [Array(Class, String)]
+    # @yield |writer, content_type|
+    # @yield_param [RDF::Writer] writer
+    # @yield_param [String] content_type (including media-type parameters)
     def find_writer_for_content_type(content_type)
-      writer = RDF::Writer.for(content_type: content_type) if content_type
-      writer ? [writer, content_type] : nil
+      ct, *params = content_type.split(';').map(&:strip)
+      accept_params = params.inject({}) do |memo, pv|
+        p, v = pv.split('=').map(&:strip)
+        memo.merge(p.downcase.to_sym => v.sub(/^["']?([^"']*)["']?$/, '\1'))
+      end
+      formats = RDF::Format.each(content_type: ct, has_writer: true).to_a.reverse
+      formats.each do |format|
+        yield format.writer, (ct || format.content_type.first), accept_params if
+          format.writer.accept?(accept_params)
+      end
     end
 
-    protected
-
     ##
     # Parses an HTTP `Accept` header, returning an array of MIME content
     # types ordered by the precedence rules defined in HTTP/1.1 §14.1.
     #
     # @param  [String, #to_s] header
     # @return [Array<String>]
     # @see    http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.1
     def parse_accept_header(header)
       entries = header.to_s.split(',')
       entries = entries.map { |e| accept_entry(e) }.sort_by(&:last).map(&:first)
-      entries.map { |e| find_content_type_for_media_range(e) }
+      entries.map { |e| find_content_type_for_media_range(e) }.flatten
     end
 
+    # Returns pair of content_type (including non-'q' parameters)
+    # and array of quality, number of '*' in content-type, and number of non-'q' parameters
     def accept_entry(entry)
-      type, *options = entry.delete(' ').split(';')
+      type, *options = entry.split(';').map(&:strip)
       quality = 0 # we sort smallest first
       options.delete_if { |e| quality = 1 - e[2..-1].to_f if e.start_with? 'q=' }
-      [type, [quality, type.count('*'), 1 - options.size]]
+      [options.unshift(type).join(';'), [quality, type.count('*'), 1 - options.size]]
     end
 
     ##
     # Returns a content type appropriate for the given `media_range`,
     # returns `nil` if `media_range` contains a wildcard subtype
@@ -187,10 +216,10 @@
     # @param  [String, #to_s]          message
     # @param  [Hash{String => String}] headers
     # @return [Array(Integer, Hash, #each)]
     def http_error(code, message = nil, headers = {})
       message = http_status(code) + (message.nil? ? "\n" : " (#{message})\n")
-      [code, {'Content-Type' => "#{DEFAULT_CONTENT_TYPE}; charset=utf-8"}.merge(headers), [message]]
+      [code, {'Content-Type' => "text/plain"}.merge(headers), [message]]
     end
 
     ##
     # Returns the standard HTTP status message for the given status `code`.
     #