#Login method
def login
    session[:user_id] = nil
    if request.post?
      user = User.authenticate(params[:email], params[:password])
      if user
        session[:user_id] = user.id
        User.last_login = Time.now()
        redirect_to(:action => "index")
      else
        flash[:notice] = "Invalid user/password combination"
      end
    end
end

#which calls authenticate method in User class
def self.authenticate(email, password)
    user = self.find_by_email(email)
    if user
      expected_password = encrypted_password(password, user.salt)
      if user.password != expected_password
        user = nil
      end
    end
    user
  end

#Which uses encrypted_password() function
def self.encrypted_password(password, salt)
    string_to_hash = password + "junk" + salt
    Digest::SHA1.hexdigest(string_to_hash)
  end