Minesweeper

minesweeper.rb

class Board
  
  def self.transform(input)
    output = []
    fail ValueError unless valid_game?(input)
    input.each_with_index do |row, row_index|
      if row_index == 0 || row_index == (input.size - 1)
        output << row
      else
        output_row = ''
        row.split('').each_with_index do |tile, tile_index|
          if %w(| *).include? tile
            output_row += tile
          else
            output_row += bomb_count(input, row_index, tile_index)
          end
        end
        output << output_row
      end
    end
    output
  end
  
  private
  
    def self.bomb_count(input, row_index, tile_index)
      count = 0
      touching_tiles = []
      touching_tiles << row_above(input, row_index, tile_index)
      touching_tiles << row_current(input, row_index, tile_index)
      touching_tiles << row_below(input, row_index, tile_index)
      touching_tiles.flatten.each { |value| count += 1 if value == '*' }
      if count > 0
        count.to_s
      else
        ' '
      end
    end
        
    def self.row_above(input, row_index, tile_index)
      row = input[row_index - 1].split('')
      touching_tiles = [row[tile_index - 1], row[tile_index], row[tile_index + 1]]
    end
    
    def self.row_current(input, row_index, tile_index)
      row = input[row_index].split('')
      touching_tiles = [row[tile_index - 1], row[tile_index + 1]]
    end
    
    def self.row_below(input, row_index, tile_index)
      row = input[row_index + 1].split('')
      touching_tiles = [row[tile_index - 1], row[tile_index], row[tile_index + 1]]
    end
    
    def self.valid_game?(input)
      valid_length?(input) && valid_border?(input) && valid_char?(input)
    end
    
    def self.valid_length?(input)
      lengths = input.map { |row| row.length }
      lengths.uniq.size == 1
    end
    
    def self.valid_border?(input)
      [input[0], input[-1]].each do |row|
        invalid_border = row.split('').any? do |char|
          !['+', '-', '|'].include? char
        end
        return nil if invalid_border
      end
    end
    
    def self.valid_char?(input)
      input.each do |row|
        invalid_chars = row.split('').any? do |char|
          !['+', '-', ' ', '|', '*'].include? char
        end
        return nil if invalid_chars
      end
    end
end

ValueError = Class.new(StandardError)