validate_salesforce_ids.rb

# https://stackoverflow.com/a/29299786/512507
def self.valid_id?(id)
  case id
  when /^[a-zA-Z0-9]{15}$/
    return true
  when /^[a-zA-Z0-9]{18}$/
    id[15..17] == [
      id[0..4],
      id[5..9],
      id[10..14]
    ].map(&:reverse).
      map do |p|
        (('A'..'Z').to_a + ('0'..'9').to_a)[
          p.chars.map { |c| c =~ /[A-Z]/ ? '1' : '0' }.join.to_i(2)
        ]
      end.join
  else
    return false
  end
end