$chars = [*(0..9).to_a, *('a'..'z').to_a, *('A'..'Z').to_a]
$lengths = {
  username: 14,
  password: 26,
  db_name: 14
}

def random_chars length
  length.times.map do
    $chars.sample
  end.join
end

chars = $lengths.map { |_, v| random_chars(v) }

url = 'postgres://%s:%s@host:5432/%s' % chars
puts url