class PrintingDepartment
  attr_reader :rows, :removed_rolls
  def initialize(rows)
    @rows = rows
    @removed_rolls = []
  end

  def self.for(string)
    new string.split("\n").map{ |row| row.split("") }
  end

  def rolls
    rows.each_with_index.map do |row, row_index|
      row.each_with_index.map do |char, column_index|
        [row_index, column_index] if char == "@"
      end.compact
    end.flatten(1)
  end

  def char_at(row, column)
    rows[row][column]
  end

  def width
    rows[0].length
  end

  def height
    rows.length
  end

  def neighbor_indices(row, column)
    [0, row - 1].max.upto([width - 1, row + 1].min).map do |r|
      [0, column - 1].max.upto([height - 1, column + 1].min).map do |c|
        [r, c]
      end
    end.flatten(1).reject{ |r, c| r == row && c == column }
  end

  def neighbors(row, column)
    neighbor_indices(row, column).map { |nr, nc| char_at nr, nc }
  end

  def adjacent_roll_count(row, column)
    neighbors(row, column).select { |char| char == "@" }.count
  end

  def accessible_rolls
    rolls.select{ |r, c| adjacent_roll_count(r, c) < 4 }
  end

  def remove_roll!(row, col)
    removed_rolls << [row, col]
    rows[row][col] = "."
  end

  def remove_accessible_rolls!
    accessible_rolls.each { |r, c| remove_roll! r, c }
  end

  def remove_all_accessible_rolls!
    remove_accessible_rolls! until accessible_rolls.empty?
  end
end