module Dry::Configurable

def self.extended(base)
  base.class_eval do
    @_config_mutex = Mutex.new
    @_settings = Concurrent::Map.new
  end
end

def _config_for(&block)
  config_klass = Class.new { extend Dry::Configurable }
  config_klass.instance_eval(&block)
  config_klass.config
end

def _settings
  @_settings
end

def config
  @_config_mutex.synchronize do
    return @_config if defined?(@_config)
    @_config = Config.new(*_settings.keys).new(*_settings.values) unless _settings.empty?
  end
end

def configure
  yield(config) if block_given?
end

def inherited(subclass)
  subclass.instance_variable_set(:@_config_mutex, Mutex.new)
  subclass.instance_variable_set(:@_settings, @_settings.clone)
  subclass.instance_variable_set(:@_config, @_config.clone) if defined?(@_config)
  super
end

def setting(key, default = nil, &block)
  default = _config_for(&block) if block_given?
  _settings[key] = default
end