rougail/docs/tutorial/dynfam.rst

.. _dynfam:

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

.. objectives:: Objectives

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

   In a dynamically built family, instead of duplicating the definition of 
   identical variables in several families, they can be generated automatically.

.. prerequisites:: Reminder

   We handled the HTTPS mode in the previous section. But there's more modes to handle.
   Let's turn back to 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 groups of variables are similar in the structure: 
they both have a host and a port.

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

There are two proxies that are to be configured : 

- the HTTPS proxy
- the SOCKS proxy

As they have the same structure, would it be possible to define the two of them 
in one shot?

.. note:: 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 and that we can do batch processing.

With Rougail, it is possible to create some kind of a model of family. 
Kind of a generic family declaration. 
We call this generic family creation process a "dynamic creation" because as we will see below, 
these families exist at the very moment we define their **identifiers**.

First, here is what we need to make (without identifiers):

.. 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
       ...

Now with identifiers, we have the ability to declare our families this way:

.. code-block:: yaml

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

    address:
      description: "{{ identifier }} address"

    port:
      description: "{{ identifier }} port"

What is exactly 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"

.. attention:: Be careful when choosing your identifiers items: pay attention that the family 
               that will be dynamically created has not been declared before in some other 
               YAML structure file.

               If you define a dynamic family with the `https` item that will 
               build a `https_proxy` family and if this familiy already exists,
               then rougail will raise a family/variable override warning.
               
               When choosing a name, 
               
               - rougail will put it in lowercase
               - only ASCII and `_` characters are allowed.
               
When we launch the rougail command line, we can have a look at the concrete families and variables that have appear:

.. 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, containing an address and a port.


.. todo:: déplacer ce hidden dans une autre page

.. _conditional_hidden_family:

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

Here is the final YAML version of the HTTPS and SOCKS proxy families: 


We have added:

- a conditional hidden family property
- a default value

.. 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

.. 
    ---
    manual:

      use_for_https:
        description: Also use this proxy for HTTPS
        default: true

      "{{ identifier }}_proxy":
        description: "{{ identifier }} Proxy"
        dynamic:
          - HTTPS
          - SOCKS
        hidden:
          variable: manual.use_for_https

        address:
          description: "{{ identifier }} address"
          default:
            variable: manual.http_proxy.address

        port:
          description: "{{ identifier }} port"
          default:
            variable: manual.http_proxy.port


The conditional property is this one: 

.. code-block:: yaml

    hidden:
      variable: manual.use_for_https
      
it uses `use_for_https` variable:

.. code-block:: yaml


  use_for_https:
    description: Also use this proxy for HTTPS
    default: true

.. keypoints:: Key points

   - We now know what a dynamic family is, with its identifier.
   - we now how to create default values for a variable that is calculated
     because it retrieves the value of another variable. 
   - we know how to hide conditionaly a family with the same mechanism, 
     that is a calculated value. It is calculated because there is a dependancy
     over another variable. 
     
   We will see other types of calculation in the next section.