module TOML
  class ValueOverwriteError < StandardError; end

  class Keyvalue
    attr_reader :key, :value

    def initialize(key, value)
      @key, @value = key, value
    end

    def assign(hash, symbolize_keys = false)
      key = symbolize_keys ? @key.to_sym : @key
      fail ValueOverwriteError if hash[key]
      hash[key] = @value
    end

    def accept_visitor(parser)
      parser.visit_keyvalue self
    end
  end
end

# Used in document.citrus
module Keyvalue
  def value
    TOML::Keyvalue.new(capture(:key).value, capture(:v).value)
  end
end