.. _your_first_dirac_code:

=====================
Your first DIRAC code
=====================

We will now code some very simple exercises, based on what we have seen in the previous section.
Before going through the exercise, you should verify in which GIT branch you are, so go to the directory where you cloned DIRAC and issue::

  > git branch

this will show all your local branches. Now,
remember that you have to base your development on a *remote* branch.
This is clearly explained in :ref:`contributing_code`,
so be careful on what you choose: checkout a new branch from a remote one before proceeding.


Exercise 1:
-----------

Code a python module in DIRAC.Core.Utilities.checkCAOfUser where there is only the following function:

.. code-block:: python

   def checkCAOfUser( user, CA ):
     """ user, and CA are string
     """

This function should:

* Get from the CS the registered Certification Authority for the user
* if the CA is the expected one return S_OK, else return S_ERROR

To code this exercise, albeit very simple, we will use TDD (Test Driven Development),
and we will use the *unittest* and *mock* python packages, as explained in :ref:`testing_environment`.
What we will code here will be a real *unit test*, in the sense that we will test only this function, in isolation.
In general, it is always an excellent idea to code a unit test for every development you do.
We will put the unit test in DIRAC.Core.Utilities.test. The unit test has been fully coded already:


.. code-block:: python

   # imports
   import unittest, mock, importlib
   # sut
   from DIRAC.Core.Utilities.checkCAOfUser import checkCAOfUser

   class TestcheckCAOfUser( unittest.TestCase ):

     def setUp( self ):
       self.gConfigMock = mock.Mock()
       self.checkCAOfUser = importlib.import_module( 'DIRAC.Core.Utilities.checkCAOfUser' )
       self.checkCAOfUser.gConfig = self.gConfigMock

     def tearDown( self ):
       pass

   class TestcheckCAOfUserSuccess(TestcheckCAOfUser):

     def test_success( self ):
       self.gConfigMock.getValue.return_value = 'attendedValue'
       res = checkCAOfUser( 'aUser', 'attendedValue' )
       self.assertTrue(res['OK'])

     def test_failure( self ):
       self.gConfigMock.getValue.return_value = 'unAttendedValue'
       res = checkCAOfUser( 'aUser', 'attendedValue' )
       self.assertFalse( res['OK'] )


   if __name__ == '__main__':
     suite = unittest.defaultTestLoader.loadTestsFromTestCase( TestcheckCAOfUser )
     suite.addTest( unittest.defaultTestLoader.loadTestsFromTestCase( TestcheckCAOfUserSuccess ) )
     testResult = unittest.TextTestRunner( verbosity = 2 ).run( suite )


Now, try to run it. In case you are using Eclipse, it's time to try to run this test within Eclipse itself (run as: Python unit-test): it shows a graphical interface that you can find convenient. If you won't manage to run, it's probably because there is a missing configuration of the PYTHONPATH within Eclipse.

Then, code ``checkCAOfUser`` and run the test again.


Exercise 2:
-----------

As a continuation of the previous exercise, code a python script that will:

* call DIRAC.Core.Utilities.checkCAOfUser.checkCAOfUser
* log wih info or error mode depending on the result

Remember to start the script with:

.. code-block:: python

   #!/usr/bin/env python
   """ Some doc: what does this script should do?
   """
   from DIRAC.Core.Base import Script
   Script.parseCommandLine()


Then run it.