class Sinatra::RespondWith::Format

def finish
  yield self if block_given?
  mime_type = @app.content_type ||
              @app.request.preferred_type(@map.keys)  ||
              @app.request.preferred_type             ||
              'text/html'
  type = mime_type.split(/\s*;\s*/, 2).first
  handlers = [@map[type], @generic[type[%r{^[^/]+}]], @default].compact
  handlers.each do |block|
    if (result = block.call(type))
      @app.content_type mime_type
      @app.halt result
    end
  end
  @app.halt 500, 'Unknown template engine'
end

def initialize(app)
  @app = app
  @map = {}
  @generic = {}
  @default = nil
end

def method_missing(method, *args, &block)
  return super if args.any? || block.nil? || !@app.mime_type(method)
  on(method, &block)
end

def on(type, &block)
  @app.settings.mime_types(type).each do |mime|
    case mime
    when '*/*'            then @default     = block
    when %r{^([^/]+)/\*$} then @generic[$1] = block
    else                       @map[mime]   = block
    end
  end
end