class TOML::Keygroup

def accept_visitor(parser)
  parser.visit_keygroup self
end

def ensure_key_not_defined(visited_keys)
  fail ValueOverwriteError.new(full_key) if visited_keys.include?(full_key)
  visited_keys << full_key
end

def full_key
  @nested_keys.join('.')
end

def initialize(nested_keys)
  @nested_keys = nested_keys
end

def navigate_keys(hash, visited_keys, symbolize_keys = false)
  ensure_key_not_defined(visited_keys)
  @nested_keys.each do |key|
    key = symbolize_keys ? key.to_sym : key
    hash[key] = {} unless hash.key?(key)
    element = hash[key]
    hash = element.is_a?(Array) ? element.last : element
    # check that key has not been defined before as a scalar value
    fail ValueOverwriteError.new(key) unless hash.is_a?(Hash)
  end
  hash
end