Validate HSN
============

This section explains how to validate HSN (Harmonized System of Nomenclature) codes.

What is HSN Validation?
-----------------------

HSN validation ensures that the provided HSN code:
- Exists in the official GST database
- Is properly formatted (6-8 digits)
- Is currently active and applicable

Validation Process
-----------------

1. **Input Validation**
   - Check if HSN code is numeric
   - Verify length (6, 7, or 8 digits)
   - Validate format pattern

2. **Database Lookup**
   - Search in official GST HSN database
   - Check if code is active
   - Verify description matches

3. **Response Generation**
   - Return validation status
   - Provide error details if invalid
   - Include HSN information if valid

API Endpoint
-----------

.. code-block:: bash

   POST /api/v1/validate/hsn
   
   {
     "hsn_code": "123456"
   }

Response Format
--------------

.. code-block:: json

   {
     "status": "success",
     "valid": true,
     "hsn_code": "123456",
     "description": "Valid HSN code",
     "gst_rate": "18%"
   }

Error Response
-------------

.. code-block:: json

   {
     "status": "error",
     "valid": false,
     "error": "Invalid HSN code format",
     "message": "HSN code must be 6-8 digits"
   }