module Validator

  attr_accessor :errors, :exception

  def validate_rules y=nil
    definition.rules.each do |rule|
      _y, x = position rule.fetch(:position)
      begin
        validate_cell (_y||y), x, rule
      rescue => e
        errors << { y: (_y||y), x: x, message: e.message, key: rule.fetch(:key) }
        raise if exception
      end
    end
  end

  def valid?() errors.empty?; end

  protected

  def validate_cell y, x, rule

    value = data_source[y][x] rescue nil

    begin
      raise unless value unless rule.fetch :allow_blank
      if value && (values = rule.fetch :values)
        raise unless values.include?(value)
      end
    rescue => e
      raise message(rule, y, x)
    end
  end

  def message rule, y, x
    msg = rule.fetch(:message).tap do |msg|
      rule.each { |key, value| msg.gsub!(":#{key.to_s}", value.to_s) unless key == :position }
    end
    msg.gsub ':position', "[#{y}, #{x}]"
  end

end