module Volt
  module Buffer
    # Save saves the contents of a buffer to the save_to location.  If the buffer is new, it will create a new
    # model to save to.  Otherwise it will be an existing model.  Save returns a promise that may fail with
    # validation errors from the server (or the client).  You can also pass a block as a shortcut to calling
    # ```.save!.then do```
    def save!(&block)
      # TODO: this shouldn't need to be run, but if no attributes are assigned, then
      # if needs to be run.  Maybe there's a better way to handle it.
      validate!

      # Get errors from validate
      errors = self.errors.to_h

      result = nil

      if errors.size == 0
        save_to = options[:save_to]
        if save_to
          if save_to.is_a?(ArrayModel)
            # Add to the collection
            promise = save_to.append(attributes)
          else
            # We have a saved model
            promise = save_to.assign_attributes(attributes)
          end

          result = promise.then do |new_model|
            # The main model saved, so mark the buffer as not new
            @new = false

            if new_model
              # Set the buffer's id to track the main model's id
              attributes[:_id] = new_model._id
              options[:save_to]     = new_model
            end

            nil
          end.fail do |errors|
            if errors.is_a?(Hash)
              server_errors.replace(errors)
            end

            promise_for_errors(errors)
          end
        else
          fail 'Model is not a buffer, can not be saved, modifications should be persisted as they are made.'
        end
      else
        # Some errors, mark all fields
        result = promise_for_errors(errors)
      end

      # If passed a block, call then on it with the block.
      result = result.then(&block) if block

      return result
    end

    # When errors come in, we mark all fields and return a rejected promise.
    def promise_for_errors(errors)
      mark_all_fields!

      Promise.new.reject(errors)
    end

    def buffer?
      options[:buffer]
    end

    def save_to
      options[:save_to]
    end

    # Returns a buffered version of the model
    def buffer
      model_path = options[:path]

      model_klass = self.class

      new_options = options.merge(path: model_path, save_to: self, buffer: true).reject { |k, _| k.to_sym == :persistor }

      model = nil
      Volt::Model.no_validate do
        model = model_klass.new(attributes, new_options, :loaded)

        model.instance_variable_set('@new', @new)
      end

      model
    end
  end
end