class EacRubyUtils::Immutable::HashAccessor

def apply(klass)
  apply_get(klass)
  apply_set(klass)
end

def apply_get(klass)
  accessor = self
  klass.send(:define_method, ::ActiveSupport::Inflector.pluralize(name)) do
    accessor.immutable_value_get(self)
  end
end

def apply_set(klass)
  accessor = self
  klass.send(:define_method, name) do |*args|
    case args.count
    when 1 then next accessor.immutable_value_get(self, args[0])
    when 2 then next accessor.immutable_value_set(self, *args[0..1])
    else
      raise ::ArgumentError, "wrong number of arguments (given #{args.count}, expected 1..2)"
    end
  end
end

def immutable_value_get(object)
  super || {}
end

def immutable_value_set(object, key, value)
  duplicate_object(object) do |old_value|
    (old_value || {}).merge(key => value)
  end
end