class Eco::API::UseCases::DefaultCases::CsvToTree
  module Helper
    extend NodesCleaner
    extend Treeify

    class << self
      def csv_from(filename)
        raise "Missing #{filename}" unless File.exists?(filename)
        result = csv_from_file(filename)
        if result.is_a?(Integer)
          puts "An encoding problem was found on line #{result}"
          result = csv_from_content(filename)
        end
        result
      end

      def nodes_from_csv(csv)
        i = 1; prev_level = nil; prev_node = nil; prev_nodes = Array(1..11).zip(Array.new(11, nil)).to_h
        nodes = csv.each_with_object([]) do |row, out|
          values = row.fields.map do |value|
            value = value.to_s.strip
            value.empty?? nil : value
          end
          i += 1
          node = Node.new(i, *values)
          prev_node ||= node

          # If node is nested in prev_node or is a sibling thereof
          if prev_node.raw_level <= node.raw_level
            # Make sure parent is among upper level tags
            node.set_high_levels(prev_node)
          else
            if parent_node = prev_nodes[node.raw_level - 1]
              node.set_high_levels(parent_node)
            elsif node.raw_level == 1
              # It is expected not to have parent
              #puts "Node '#{node.raw_tag}' doesn't have parent, but it's top level tag"
            else
              raise "Node '#{node.raw_tag}' (#{node.row_num} row) doesn't have parent"
            end
          end
          out << node
          prev_nodes[node.raw_level] = node
          prev_node = node
        end
        tidy_nodes(nodes)
      end

      def csv_nodes(filename)
        nodes_from_csv(csv_from(filename))
      end

      private

      def csv_from_content(filename)
        CSV.parse(file_content(filename), headers: true)
      end

      def file_content(filename)
        coding = encoding(filename)
        coding = (coding != "utf-8")? "#{coding}|utf-8": coding
        if content = File.read(filename, encoding: coding)
          content.scrub do |bytes|
            '<' + bytes.unpack('H*')[0] + '>'
          end
        end
      end

      def csv_from_file(filename)
        coding = encoding(filename)
        coding = (coding != "utf-8")? "#{coding}|utf-8": coding
        CSV.read(filename, headers: true, encoding: coding)
      rescue CSV::MalformedCSVError => e
        if line = e.message.match(/line (?<line>\d+)/i)[:line]
          return line.to_i
        else
          raise
        end
      end

      def has_bom?(path)
        return false if !path || file_empty?(path)
        File.open(path, "rb") do |f|
          bytes = f.read(3)
          return bytes.unpack("C*") == [239, 187, 191]
        end
      end

      def encoding(path)
        has_bom?(path) ? "bom" : "utf-8"
      end

      def file_empty?(path)
        return true if !File.file?(path)
        File.zero?(path)
      end
    end
  end
end