require "pwm/version"

module Pwm

  # Internal: The exception raised when a requested password length is
  # too short.
  class TooShortException < Exception; end

  # Internal: The set of characters from which passwords will be assembled.
  # This could be overridden if you don't like the default.
  #
  # Returns the set of characters as an Array.
  def self.characters
    (('A'..'Z').to_a  + ('a'..'z').to_a +
     ('2'..'9').to_a) - ['I', 'O', 'l']
  end

  # Public: Generate a password.
  #
  # length - The length of the password. Minimum is 8. Default is 16.
  #
  # Examples
  #
  #   Pwm.password
  #   # => 'SPdHeZnn9rut4AUz'
  #
  #   Pwm.password(8)
  #   # => 'oUX4fmqr'
  #
  # Returns the generated password as a String if length >= 8,
  # or raises exception if length < 8.
  def self.password(length = 16)
    if length < 8
      raise Pwm::TooShortException,
            "Requested length #{length} is too short."
    else
      password = ''
      until (password.match(/[A-Z]/) &&
             password.match(/[a-z]/) &&
             password.match(/[0-9]/))
        password = (0..length - 1).inject('') do |pw, n|
          pw + characters[rand(characters.length)]
        end
      end
      password
    end
  end
end