rougail/docs/tutorial/dynfam.rst

.. _dynfam:

A dynamic family
================

.. objectives:: Objectives

   In this section we will learn how to create a dynamically created family.

.. prerequisites:: Reminder

   We handled the HTTPS mode in the previous section. But there's more.
   Let's have a look at the firefox's configuration page:

.. image:: images/soksv5.png

We see that we need to handle the SOCKS configuration in addition to the HTTPs configuration.
Moreover, we can see that these two group of variables are very similar: 
they both have a host and a port.

Creating a generic family
----------------------------


There are two proxies that are to be configured : 

- the HTTP proxy
- the SOCKS proxy

It's not the place here to describe what the HTTP and SOCKS protocols are. 
The interesting point here is that they are very similar in our firefox's configuration.

With Rougail, we can create some kind of a model of family. 
we can use a generic family declaration mode in this use case. 
We call this genericity family a "dynamic creation" because as we will see below, 
these families exist at the very moment we define their identifiers.

what we could do with our current knowledge: 

.. code-block:: yaml

   https_proxy:
     description: HTTPS Proxy
     ...

     address:
       description: HTTPS address
       ...

     port:
       description: HTTPS Port
       ...

   sock_proxy:
     description: SOCKS Proxy
     ...

     address:
       description: SOCKS address
       ...

     port:
       description: SOCKS Port
       ...

With Rougail we have the ability to declare our families this way:

.. extinclude:: https://forge.cloud.silique.fr/stove/rougail-tutorials/raw/tag/v1.1_037/firefox/20-manual.yml
   :language: yaml
   :caption: firefox/20-proxy.yml

What is an identifier?
-------------------------

If you know a YAML declaration tool named Ansible, 
the variable used to iterate over multiple values in a task is called an **`item`**.

It is used in the context of a loop. For example:

.. code-block:: yaml

   - name: Loop example with 'item'
     ansible.builtin.debug:
       msg: "The current value is {{ item }}"
     loop:
       - value1
       - value2
       - value3

This code will output: 

.. code-block:: text

   The current value is value1
   The current value is value2
   The current value is value3

In the Rougail context, we name this item an identifier because it is an item 
that allow us to define dynamically family names.

.. glossary::

   identifier

      In the :ref:`dynamic family creation field <dynfam>` we call an identifier
      an item that defines a family name. An item is a variable on which an iteration 
      on keywords will be carried out. 

      An :term:`identifier` is a local variable, used only for creating multiple 
      iterations, used for creating multiple families in only one declaration.

      It allows us to declare very similar families in a more generic way.

Here is the syntax we are using that allows the declaration of multiple families at one time:

.. code-block:: yaml

  "{{ identifier }}_proxy":
    description: "{{ identifier }} Proxy"
    dynamic:
      - HTTPS
      - SOCKS

This identifier is a parameter that enables us to create two families named `https_proxy` and `socks_proxy`:



.. code-block:: yaml

  https_proxy:
    description: "HTTPS Proxy"

  socks_proxy:
    description: "SOCKS Proxy"

.. note:: The declaration syntax used is the :term:`Jinja <jinja>` templating syntax, 
          Jinja which is widely used in python.

.. attention:: Be careful when choosing your identifiers items: the family 
               that will be dynamically created shall not exist already.

               If you define a dynamic family with the `https` item that will 
               build a `https_proxy` family and if this familiy already exist,
               then rougail will raise a warning.


Besides, when we launch the rougail command line, we can have a look at the concrete variables here:

.. code-block:: text

    rougail -m structfile/proxy.yml -u yaml --yaml.filename userdata/proxy.yml
    ╭─────────────────── Caption ────────────────────╮
    │ Variable              Default value            │
    │ Unmodifiable variable Modified value           │
    │                       (Original default value) │
    ╰────────────────────────────────────────────────╯
    Variables:
    ┗━━ 📂 Manual proxy configuration
        ┣━━ 📂 HTTP Proxy
        ┃   ┣━━ 📓 HTTP address: ... (loaded from the YAML file "userdata/proxy.yml")
        ┃   ┗━━ 📓 HTTP Port: ... (8080 - loaded from the YAML file "userdata/proxy.yml")
        ┣━━ 📓 Also use this proxy for HTTPS: true
        ┣━━ 📂 HTTPS Proxy
        ┃   ┣━━ 📓 HTTPS address: ...
        ┃   ┗━━ 📓 HTTPS port: ...
        ┗━━ 📂 SOCKS Proxy
            ┣━━ 📓 SOCKS address: ...
            ┗━━ 📓 SOCKS port: ...

We can see that the dynamic family has created: 

- an `HTTPS Proxy` family
- a `SOCKS Proxy` family

as we wanted.


A conditional hidden familiy
--------------------------------

Yes we have gained in genericity but we have lost in readability, you would say.
But we haven't just been generic. We now have the ability to create conditional hidden family
(and not only conditionnal hidden variables like we did earlier).