module Dry::Initializer::Builders
  # @private
  class Signature
    def self.[](config)
      new(config).call
    end

    def call
      [*required_params, *optional_params, "*", options].compact.join(", ")
    end

    private

    def initialize(config)
      @config  = config
      @options = config.options.any?
      @null    = config.null ? "Dry::Initializer::UNDEFINED" : "nil"
    end

    def required_params
      @config.params.reject(&:optional).map(&:source)
    end

    def optional_params
      @config.params.select(&:optional).map { |rec| "#{rec.source} = #{@null}" }
    end

    def options
      "**__dry_initializer_options__" if @options
    end
  end
end