class Nenv::Environment

def _create_env_accessor(klass, meth, &block)
  _fail_if_accessor_exists(klass, meth)
  if meth.to_s.end_with? '='
    _create_env_writer(klass, meth, &block)
  else
    _create_env_reader(klass, meth, &block)
  end
end

def _create_env_reader(klass, meth, &block)
  env_name = nil
  loader = nil
  klass.send(:define_method, meth) do
    env_name ||= _namespaced_sanitize(meth)
    loader ||= Loader.setup(meth, &block)
    loader.(ENV[env_name])
  end
end

def _create_env_writer(klass, meth, &block)
  env_name = nil
  dumper = nil
  klass.send(:define_method, meth) do |raw_value|
    env_name ||= _namespaced_sanitize(meth)
    dumper ||= Dumper.setup(&block)
    ENV[env_name] = dumper.(raw_value)
  end
end

def _fail_if_accessor_exists(klass, meth)
  fail(AlreadyExistsError, meth) if klass.method_defined?(meth)
end

def _namespaced_sanitize(meth)
  [@namespace, _sanitize(meth)].compact.join('_')
end

def _sanitize(meth)
  meth.to_s[/^([^=?]*)[=?]?$/, 1].upcase
end

def create_method(meth, &block)
  self.class._create_env_accessor(singleton_class, meth, &block)
end

def create_method(meth, &block)
  _create_env_accessor(self, meth, &block)
end

def initialize(namespace = nil)
  @namespace = (namespace ? namespace.upcase : nil)
end