class User < ActiveRecord::Base 
  # Max & min lengths for all fields 
  SCREEN_NAME_MIN_LENGTH = 4 
  SCREEN_NAME_MAX_LENGTH = 20 
  PASSWORD_MIN_LENGTH = 4 
  PASSWORD_MAX_LENGTH = 40 
  EMAIL_MAX_LENGTH = 50 
  SCREEN_NAME_RANGE = SCREEN_NAME_MIN_LENGTH..SCREEN_NAME_MAX_LENGTH 
  PASSWORD_RANGE = PASSWORD_MIN_LENGTH..PASSWORD_MAX_LENGTH 

  # Text box sizes for display in the views 
  SCREEN_NAME_SIZE = 20 
  PASSWORD_SIZE = 10 
  EMAIL_SIZE = 30 

  validates_uniqueness_of :screen_name, :email 
  validates_length_of :screen_name, :within => SCREEN_NAME_RANGE
  validates_length_of :password, :within => PASSWORD_RANGE 
  validates_length_of :email, :maximum => EMAIL_MAX_LENGTH 

  validates_format_of :screen_name, 
                      :with => /^[A-Z0-9_]*$/i, 
                      :message => "must contain only letters, " + 
                                  "numbers, and underscores" 
  validates_format_of :email, 
                      :with => /^[A-Z0-9._%-]+@([A-Z0-9-]+\.)+[A-Z]{2,4}$/i, 
                      :message => "must be a valid email address"
  
  # Log a user in.
  def login!(session)
    session[:user_id] = id
  end
  
  # Log a user out.
  def self.logout!(session)
    session[:user_id] = nil
  end
  
  # Clear the password (typically to suppress its display in a view).
  def clear_password!
    self.password = nil
  end
end