module ActionDispatch
  class RequestEncoder # :nodoc:
    @encoders = {}

    attr_reader :response_parser

    def initialize(mime_name, param_encoder, response_parser, url_encoded_form = false)
      @mime = Mime[mime_name]

      unless @mime
        raise ArgumentError, "Can't register a request encoder for " \
          "unregistered MIME Type: #{mime_name}. See `Mime::Type.register`."
      end

      @url_encoded_form = url_encoded_form
      @path_format      = ".#{@mime.symbol}" unless @url_encoded_form
      @response_parser  = response_parser || -> body { body }
      @param_encoder    = param_encoder   || :"to_#{@mime.symbol}".to_proc
    end

    def append_format_to(path)
      if @url_encoded_form
        path
      else
        path + @path_format
      end
    end

    def content_type
      @mime.to_s
    end

    def encode_params(params)
      @param_encoder.call(params)
    end

    def self.parser(content_type)
      mime = Mime::Type.lookup(content_type)
      encoder(mime ? mime.ref : nil).response_parser
    end

    def self.encoder(name)
      @encoders[name] || WWWFormEncoder
    end

    def self.register_encoder(mime_name, param_encoder: nil, response_parser: nil)
      @encoders[mime_name] = new(mime_name, param_encoder, response_parser)
    end

    register_encoder :json, response_parser: -> body { JSON.parse(body) }

    WWWFormEncoder = new(:url_encoded_form, -> params { params }, nil, true)
  end
end