Hideous first iteration of an algorithm I wrote

header_row_of_doom.rb

def header_rows(labeller = Labeller.new)
  # This won't handle mismatched sizes yet
  # Also hack the null case for now
  number_of_rows = @fragments.map(&:number_of_dimensions).max || 0

  bottom_up_header_rows = [ ]

  number_of_rows.times do |row_index|
    current_row = bottom_up_header_rows[row_index] = [ ]

    @fragments.each do |fragment|
      if fragment.number_of_dimensions <= row_index
        current_row << HeaderColumn.new
      else
        index_from_end = -(row_index + 1)

        columns_for_row = fragment.dimension_value_labels[index_from_end].map { |label|
          HeaderColumn.new(
            label: labeller.label_for(label),
            number_of_encompassed_dimension_values: fragment.number_of_encompassed_dimension_values_at_level(index_from_end)
          )
        }

        current_row.concat(columns_for_row)
      end
    end
  end

  bottom_up_header_rows.reverse
end