module Parliament
  module Utils
    module Helpers
      module GroupingHelper
        # Groups objects by category where possible
        #
        # @param data [Array] Array of Grom::Nodes to be grouped
        # @param grouping_methods [Symbol] One or more methods that should be called on Grom::Node to find suitable nodes for grouping
        # @return [Array] Single array of grouped, ungrouped and unknown objects
        def group(data, *grouping_methods)
          grouped_data = group_data(data, grouping_methods)
          create_sorted_array(grouped_data)
        end

        # Where grouping methods can be called (e.g. #category and #id), this method groups by the result of calling each of those methods in succession on each Grom::Node
        # If a grouping cannot be found, adds 'UNKNOWN' as key of the hash
        #
        # @param data [Array] Array of Grom::Nodes to be grouped
        # @param grouping_methods [Array] One or more methods that should be called on Grom::Node to find suitable nodes for grouping
        # @return [Hash] Keys identify grouping (grouped by category.property), with each value being an array of grouped, ungrouped and unknown Grom::Nodes
        #
        # e.g. { 12345678 => [...], 23456789 => [...], "UNKNOWN" => [...] }
        def group_data(data, grouping_methods)
          data.group_by do |data_point|
            grouping_methods.inject(data_point) { |point, method| point.try(method) } || 'UNKNOWN'
          end
        end

        # Places unknown and ungrouped Grom::Nodes into sorted_array without calling any further methods on them
        # For Grom::Nodes that need to be grouped, calls create_grouped_objects method and places result into sorted_array
        #
        # @param data_hash [Hash] Keys identify grouping, with each value being an array of grouped, ungrouped and unknown Grom::Nodes
        # @return [Array] Array of unknown and ungrouped Grom::Nodes, and sorted and grouped instances of GroupingHelper::GroupedObject
        def create_sorted_array(data_hash)
          sorted_array = []
          data_hash.each do |key, value|
            # Identify Grom::Nodes that don't need to be grouped (either UNKNOWN or singular values)
            sorted_array << if key == 'UNKNOWN' || value.length == 1
              value
            else
              create_grouped_objects(data_hash, key)
            end
          end
          sorted_array.flatten
        end
      end
    end
  end
end