module Datagrid
  module ColumnNamesAttribute
    extend ActiveSupport::Concern

    included do
      datagrid_attribute :column_names do |names|
        names = Array(names).reject(&:blank?)
        if names.reject(&:blank?).blank?
          []
        else
          names
        end
      end
    end

    module ClassMethods
      # Adds a filter that acts like a column selection
      # All defined columns will be available to select/deselect
      # as a multi-select enum filter.
      # Columns with <tt>mandatory: true</tt> option
      # will always present in the grid table and won't be listed
      # in column names selection
      # Accepts same options as <tt>:enum</tt> filter
      # @example
      #   column_names_filter(header: "Choose columns")
      # @see Datagrid::Filters::ClassMethods#filter
      def column_names_filter(**options)
        filter(
          :column_names, :enum,
          select: :optional_columns_select,
          multiple: true,
          dummy: true,
          **options,
        )
      end
    end

    # @!visibility private
    def columns(*args, **options)
      super(*selected_column_names(*args), **options)
    end

    # Returns a list of enabled columns with <tt>mandatory: true</tt> option
    # If no mandatory columns specified than all of them considered mandatory
    # @return [Array<Datagrid::Columns::Column>]
    def mandatory_columns
      available_columns.select {|c| c.mandatory? }
    end

    # Returns a list of enabled columns without <tt>mandatory: true</tt> option
    # If no mandatory columns specified than all of them considered mandatory but not optional
    # @return [Array<Datagrid::Columns::Column>]
    def optional_columns
      available_columns - mandatory_columns
    end

    protected

    def optional_columns_select
      optional_columns.map {|c| [c.header, c.name] }
    end

    def selected_column_names(*args)
      if args.any?
        args.compact!
        args.map! do |column|
          column.is_a?(Datagrid::Columns::Column) ? column.name : column.to_sym
        end
        args
      else
        if column_names && column_names.any?
          column_names + mandatory_columns.map(&:name)
        else
          columns_enabled_by_default.map(&:name)
        end
      end
    end

    def columns_visibility_enabled?
      columns_array.any? do |column|
        column.mandatory_explicitly_set?
      end
    end

    def columns_enabled_by_default
      columns_visibility_enabled? ? mandatory_columns : []
    end
  end
end