class Login
  attr_reader :sessions, :users

  # Receives a array with hash with usernames and passwords
  def initialize(db = {})
    @sessions = []
    @users    = db
  end

  # check if user exists
  def find_user(username, password)
    @users.select{ |user| user if (user[:username] == username && user[:password] == password) }
  end

  # new user registration, username and password are required
  def user_registration(username, password)
    users << { username: username, password: password }
  end

  # check that there is a username and password, before deleting a user.
  def destroy(username, password)
    results = find_user(username, password)
    @users.delete_if { |u| u[:username] == username && u[:password] == password } if results.present?
  end

  # We can update password
  def update_password(username, old_password, new_password)
    results = find_user(username, old_password)
    results[0][:password] = new_password

  end

  # We check if there is a username and password in our hash
  def authentication(username, password)
    return false if username.nil? || password.nil?
    auth = find_user(username, password)
    @sessions << auth[0] if auth.present?
  end

  # We eliminate session in case it exists.
  def logout(username)
    sessions.delete_if { |u| u[:username] == username } if username.present?
  end

end

registered_users = { username: 'Felipe', password: '123'},
                   { username: 'Lisandro', password: '123'}

login            = Login.new(registered_users)
login.user_registration('Amit', '123');
login.authentication('Felipe', '123');
login.update_password('Felipe', '123', '456');
login.authentication('Felipe', '123');
login.logout('Felipe');
login.destroy('Felipe', '123');