class Scrivener
  module Validations
    # Validates that minimum size of the specified attribute.
    #
    #   class SignUp < Scrivener
    #     attr_accessor :password
    #
    #     def validate
    #       assert_minimum_length(:password, 8)
    #     end
    #   end
    #
    #   signup = Signup.new(password: "short")
    #   signup.valid? # => false
    #   signup.errors[:password] # => [:too_short]
    #
    def assert_minimum_length(att, val, error = [att, :too_short])
      assert(send(att).to_s.length >= val, error)
    end

    # Validates that maximum size of the specified attribute.
    #
    #   class SignUp < Scrivener
    #     attr_accessor :password
    #
    #     def validate
    #       assert_minimum_length(:password, 72)
    #     end
    #   end
    #
    #   signup = Signup.new(password: _very_long_password)
    #   signup.valid? # => false
    #   signup.errors[:password] # => [:too_long]
    #
    def assert_maximum_length(att, val, error = [att, :too_long])
      assert(send(att).to_s.length <= val, error)
    end

    # Validates that the specified attribute matches exactly the
    # length restriction supplied.
    #
    #   class SignUp < Scrivener
    #     attr_accessor :status
    #
    #     def validate
    #       assert_exact_length(:status, 1)
    #     end
    #   end
    #
    #   signup = Signup.new(status: "10")
    #   signup.valid? # => false
    #   signup.errors[:status] # => [:wrong_length]
    #
    def assert_exact_length(att, val, error = [att, :wrong_length])
      assert(send(att).to_s.length == val, error)
    end

    # Encapsulates the pattern of wanting to validate a password or
    # email address field with a confirmation.
    #
    #   class SignUp < Scrivener
    #     attr_accessor :password, :password_confirmation
    #
    #     def validate
    #       assert_present(:password)
    #       assert_confirmation(:password)
    #     end
    #   end
    #
    #   signup = SignUp.new
    #   signup.password = "123456"
    #   signup.password_confirmation = "nonsense"
    #   signup.valid? # => false
    #   signup.errors[:password] # => [:not_confirmed]
    #
    def assert_confirmation(att, error = [att, :not_confirmed])
      assert(send(:"#{att}_confirmation") == send(att), error)
    end
  end
end