module CSVImporter
  # A Row from the CSV file.
  #
  # Using the header, the model_klass and the identifier it builds the model
  # to be persisted.
  class Row
    include Virtus.model

    attribute :header, Header
    attribute :row_array, Array[String]
    attribute :model_klass
    attribute :identifier

    # The model to be persisted
    def model
      @model ||= begin
        model = if identifier
          find_or_build_model
        else
          build_model
        end

        set_attributes(model)
      end
    end

    # A hash with this row's attributes
    def csv_attributes
      @csv_attributes ||= Hash[header.column_names.zip(row_array)]
    end

    # Set attributes
    def set_attributes(model)
      header.columns.each do |column|
        value = csv_attributes[column.name]
        column_definition = column.definition

        next if column_definition.nil?

        set_attribute(model, column_definition, value)
      end

      model
    end

    # Set the attribute using the column_definition and the csv_value
    def set_attribute(model, column_definition, csv_value)
      if column_definition.to && column_definition.to.is_a?(Proc)
        to_proc = column_definition.to

        case to_proc.arity
        when 1 # to: ->(email) { email.downcase }
          model.public_send("#{column_definition.name}=", to_proc.call(csv_value))
        when 2 # to: ->(published, post) { post.published_at = Time.now if published == "true" }
          to_proc.call(csv_value, model)
        else
          raise ArgumentError, "`to` proc can only have 1 or 2 arguments"
        end
      else
        attribute = column_definition.attribute
        model.public_send("#{attribute}=", csv_value)
      end

      model
    end

    # Error from the model mapped back to the CSV header if we can
    def errors
      Hash[
        model.errors.map do |attribute, errors|
          if column_name = header.column_name_for_model_attribute(attribute)
            [column_name, errors]
          else
            [attribute, errors]
          end
        end
      ]
    end

    def find_or_build_model
      model = build_model
      set_attributes(model)
      value = model.public_send(identifier)
      model_klass.public_send("find_by_#{identifier}", value) || build_model
    end

    def build_model
      model_klass.new
    end
  end
end