keyword_curry.rb

module KeywordCurry
  def initialize
    @vars = {}
  end

  def with_argument(name, val)
    d = self.dup
    d.bind_argument(name.to_sym, val)
    d
  end

  protected

  def bound_argument_sig(param)
    if @vars[param[1]]
      case param[0]
      when :keyreq
        param[0] = :key
      when :key
      else
        raise("Unable to set value #{name} for type #{param[0]}")
      end
    end

    case param[0]
    when :key
      "#{param[1]}: @vars.fetch(:#{param[1]})"
    when :keyreq
      "#{param[1]}:"
    when :rest
      "*#{param[1]}"
    when :keyrest
      "**#{param[1]}"
    when :block
      "&#{param[1]}"
    else
      raise("Unsupported arg type: #{param[0]}")
    end
  end

  def bind_argument(name, val)
    @vars[name] = val

    public_methods(false).each do |m|
      params = method(m).parameters
      next unless params.any? { |p| p[1] == name }

      sig = params.map(&method(:bound_argument_sig))
      instance_eval(<<~RUBY)
        def #{m}(#{sig.join(', ')})
          super
        end
      RUBY
    end
  end
end

class Paths
  include KeywordCurry

  def root(root:)
    root
  end

  def projects_root(root:)
    File.join(root(root: root), 'projects')
  end

  def project_path(root:, project:)
    File.join(projects_root(root: root), project)
  end
end

paths = Paths.new
puts paths.project_path(root: '/root', project: 'myproject')

root = paths.with_argument(:root, '/root')
puts root.project_path(project: 'myproject')

project = root.with_argument(:project, 'myproject')
puts project.project_path