module Pruning
  module Processing
    class Pruner

      def initialize(tree)
        @tree = tree
      end

      def prune_tree(indicator_ids)
        pruned_tree = @tree.dup
        prune_subtree(pruned_tree, indicator_ids)
        pruned_tree
      end

      private
      def prune_subtree(nodes, indicator_ids)
        nodes_to_examine = nodes.dup
        nodes_to_examine.each do |node|
          if indicator_node?(node) 
            unwanted_indicator = !indicator_ids.include?(node['id'])  
            nodes.delete(node) if unwanted_indicator 
          else 
            has_no_wanted_indicators_in_children = prune_subtree(children(node), indicator_ids)
            nodes.delete(node) if has_no_wanted_indicators_in_children   
          end
        end
        nodes.empty?
      end

      def children(node)
        node.fetch('sub_themes', false) ||
        node.fetch('categories', false) || 
        node.fetch('indicators', false) ||
        []
      end
      
      def indicator_node?(node)
        children(node).empty?
      end
    end
  end
end