Excel Cell Names

excel_names.rb

class CellRange

  LETTERS = ('A'..'ZZ').to_a

  attr_reader :max_col, :min_col, :max_row, :min_row

  def initialize(cells)
    @cells = cells

    @min_row = @min_col = @cells.size
    @max_col = @max_row = 0

    @sorted_cells = cells.sort_by do|cell| 
      alpha = column(cell)
      numeric = row(cell)
      [LETTERS.index(alpha), numeric]
    end

  end

  def valid?
    @sorted_cells.size == width * height
  end

  def width
    LETTERS.index(column(@sorted_cells.last)) - LETTERS.index(column(@sorted_cells.first))
  end

  def height
    row(@sorted_cells.last) - row(@sorted_cells.first)
  end

  def dimensions
    "#{row_dimension(@min_col)}#{@min_row}:#{row_dimension(@max_col)}#{@max_row}"
  end

  def row_dimension(val)
    LETTERS[val -1]
  end

  private

  def row(cell_address)
    r = cell_address.match(/[0-9]{1,}$/).to_s.to_i

    @min_row = r if r < @min_row
    @max_row = r if r > @max_row

    r
  end

  def column(cell_address)
    alpha = cell_address.match(/^[A-Z]{1,}/).to_s

    c = LETTERS.index(alpha) + 1
    @min_col = c if c < @min_col
    @max_col = c if c > @max_col

    alpha
  end
  
end


r = CellRange.new(["A1","A11","A9","AB2","AA1","A10","B1"])

puts r.width
puts r.height
puts r.valid?
puts r.dimensions