Creating a Validator
====================

To create a custom validator, you can define a class that specifies the validation rules for each field. This is done
using the `Validator` class from the `libmercury` library. Below is an example of how to create a `SigninValidator` 
for validating user sign-in data.

Example Validator Class
-----------------------

.. code-block:: python

	from libmercury import Validator 

	class SigninValidator:
		username = Validator.String(min=3, max=20)
		password = Validator.String(min=8, max=50)
		isActive = Validator.Boolean()
		age = Validator.Integer(min=13, max=101)
		pets = Validator.Array(min=0, max=3)

		@Validator.Object()
		class cars:
			name = Validator.String
			horsepower = Validator.Integer(min=0, max=3000)

This `SigninValidator` class defines several fields, each with its own validation criteria:

- **username**: A string with a minimum length of 3 characters and a maximum of 20.
- **password**: A string with a minimum length of 8 characters and a maximum of 50.
- **isActive**: A boolean value indicating whether the user is active.
- **age**: An integer between 13 and 101.
- **pets**: An array with a minimum of 0 and a maximum of 3 elements.
- **cars**: An embedded object containing two fields:
  - **name**: A string for the car's name.
  - **horsepower**: An integer between 0 and 3000 representing the car's horsepower.

This structure ensures that incoming data adheres to the specified rules before processing.

We can integrate these validators in our controller logic using the useValidator decorator. Here is an example of
how to use the `SigninValidator` class in a controller:

.. code-block:: python3

	from libmercury import GETRoute, POSTRoute, Request, Response, useValidator
	from src.validators.SigninValidator import SigninValidator
	class AuthFlowController:
		@staticmethod
		@useValidator(SigninValidator)
		@POSTRoute("/api/example")
		def example(request: Request) -> Response:
			response = Response("<h1>You passed the validator</h1>")
			return response

The decorator also has a custom option called "error" which allows us to use a custom error message if the validation
fails.

.. code-block:: python3

	from libmercury import GETRoute, POSTRoute, Request, Response, useValidator
	from src.validators.SigninValidator import SigninValidator
	class AuthFlowController:
		@staticmethod
		@useValidator(SigninValidator, error=lambda: Response("Invalid data"))
		@POSTRoute("/api/example")
		def example(request: Request) -> Response:
			response = Response("<h1>You passed the validator</h1>")
			return response

Using the anonomous function syntax, we can have custom error messages for validation failures. These can also be
redirects.