# Single responsibility
# Creates a DB connection
class UserRegistration
  EMAIL_REGEXP = /some regexp/

  def initialize
    @connection = Database.new(username: 'root', password: '123', database: 'my_app')
  end

  def perform(params)
    validate(params)
    register_user(params[:email], password[:password])
    send_welcome_email(params)
  end

  private

  def validate(params)
    email = params[:email]
    password = params[:password]

    unless REGEXP.match(email)
      raise ValidationError.new('Invalid email')
    end

    rows = @connection.fetch('SELECT * FROM users WHERE email = :email LIMIT 1', email: email)

    if rows.length == 1
      raise ValidationError.new('Email taken')
    end

    unless password.length > 6
      raise ValidationError.new('Invalid password')
    end
  end

  def register_user(username, password)
    @connection.execute(
      'INSERT INTO users name, password VALUES (:name, :password)',
      name: name,
      password: password
    )
  end

  def send_welcome_email(params)
    smtp = Smtp.new('username:password@some_server')
    contents = File.contents('app/templates/welcome_email.html')
    contents = Template.new(contents).replace_vars(parmas)
    smtp.send(params[:email], body: body)
  end
end


registration = UserRegistration.new
registration.perform(email: 'foo@bar.com', password: '1235abcd')