suffix_accept.rb

# prepend the mime type suggested by the path_info extname to the Accept: header,
# and pass on the request with suffix removed

module Rack
  class SuffixAccept
    def initialize(app)
      @app = app
    end

    def call(env)
      req = Rack::Request.new(env)
      extname = ::File.extname(req.path_info)

      if !extname.empty? && !(mime_type = Rack::Mime.mime_type(extname)).empty?
        env['HTTP_ACCEPT'] = mime_type + ',' + env['HTTP_ACCEPT']
        env['PATH_INFO'] = ::File.join(::File.dirname(req.path_info), ::File.basename(req.path_info, extname))
      end

      @app.call(env)
    end
  end
end