Class for dealing with ranges of cells (2-dimensional) in spreadsheet gem

spreadsheet_range.rb

class SpreadSheetRange
  BORDER_EDGES=[:bottom, :top, :right, :left]

  def initialize(worksheet, row_range, col_range)
    @worksheet = worksheet
    @row_range = row_range
    @col_range = col_range
  end

  def draw_border(where = :all, color = nil)
    if where == :all
      border_top(color)
      border_bottom(color)
      border_left(color)
      border_right(color)
    else
      send("draw_border_#{where.to_s}", color)
    end
  end

  private

  def draw_border_top(color)
    format_cell_border(@row_range.first..@row_range.first, @col_range, :top, color)
  end

  def draw_border_bottom(color)
    format_cell_border(@row_range.last..@row_range.last, @col_range, :bottom, color)
  end
  
  def draw_border_left(color)
    format_cell_border(@row_range, @col_range.first..@col_range.first, :left, color)
  end
  
  def draw_border_right(color)
    format_cell_border(@row_range, @col_range.last..@col_range.last, :right, color)
  end

  def format_cell_border(row_range, col_range, border, color)
    border_array = Array.new 4, false

    border_array[BORDER_EDGES.index border] = true

    row_range.each do |row|
      col_range.each do |col|
        old_format = @worksheet.rows[row].format(col)
        old_border_array = old_format.border
        new_border_array = merge_border_arrays(old_border_array, border_array)
        format = Spreadsheet::Format.new

        if color
          format.border_color=color
        end

        BORDER_EDGES.each do |edge|
          border_boolean = new_border_array.shift

          format.send("#{edge}=", border_boolean)
        end

        @worksheet.rows[row].set_format(col, format)
      end
    end
  end

  def merge_border_arrays(old_border, new_border)
    new_border_copy = new_border.dup

    merged_border = old_border.collect do |entry|
      new_border_copy.shift || entry
    end

    merged_border
  end
end


# create a new book and sheet
book = Spreadsheet::Workbook.new
sheet = book.create_worksheet 

range = SpreadSheetRange.new(sheet, 1..5, 1..5)
range.draw_border(:bottom, :blue)