Preliminaries
================

.. objectives:: Objectives

   We will learn how to:

   - create a Rougail :term:`structure description file <structure file>`
   - define a Rougail :term:`structure description file <structure file>` format version
   - define a Rougail :term:`variable` and set its :term:`value`

.. prerequisites:: Prerequisites

    We assume that Rougail's library is :ref:`already installed <installation>` on your computer (or in a virtual environment).

.. type-along:: an empty structure file

    An empty structure description file

.. exercise:: The folder structure

    Here is the tree structure we want to have::

        workplace
        ├── firefox
        │   └── struct.yml

- Let's make a :file:`workplace` directory, with a :file:`firefox` subfolder.
- First, we wil make a :term:`structure file <structure file>`, so let's create a :file:`struct.yml` file
  located in the :file:`firefox` subfolder.

The structure file 
--------------------

This is an empty Rougail dictionnary

.. extinclude:: https://forge.cloud.silique.fr/stove/rougail-tutorials/raw/tag/v1.1_000/firefox/00-proxy.yml
   :language: yaml
   :caption: An empty rougail dictionnary file with the version number only
   :name: RougailStructVersion

.. 
    ---
    version: 1.1

.. type-along:: a first variable

    Let's put a variable in the Rougail :term:`structure description file <structure file>`

Defining a variable and its default value
----------------------------------------------

This is a first Rougail variable in a Rougail dictionnary.

.. extinclude:: https://forge.cloud.silique.fr/stove/rougail-tutorials/raw/tag/v1.1_010/firefox/00-proxy.yml
   :language: yaml
   :caption: A Rougail dictionnary file with only one variable
   :name: RougailDictionaryFirstVariableName

.. 
    ---
    proxy_mode:

- Then if we run the Rougail CLI utility command 

.. code-block:: text
   :class: terminal
   
    rougail -v 1.1 -m firefox/

we will actually have an error: 

.. raw:: html
   :url: https://forge.cloud.silique.fr/stove/rougail-tutorials/raw/tag/v1.1_010/config/01/output_ro.html
   :class: error-box

..
    🛑 ERRORS
    ┣━━ The following variables are mandatory but have no value:
    ┗━━   - proxy_mode

Because this variable is :term:`mandatory` and needs to be set **but** there's no value yet.

So we can therefore see this consequence:

.. important:: Once defined, an option configuration :term:`value` is :term:`mandatory`.

Rougail waits for the `proxy_mode` configuration option's value to be set.

.. seealso:: To go further, have a look at the :tiramisu:`mandatory option <glossary.html#term-mandatory-option>` Tiramisu's definition.

.. glossary::

    mandatory

        A variable is mandatory when a value is required, that is, `None` is not an option.

Then we just add a variable's description, which is a good practice.

.. extinclude:: https://forge.cloud.silique.fr/stove/rougail-tutorials/raw/tag/v1.1_011/firefox/00-proxy.yml
   :language: yaml
   :caption: A Rougail dictionnary file with a variable and a description
   :name: RougailStructFirstVariableDescription

.. 
    ---
    proxy_mode:
      description: Configure Proxy Access to the Internet

We need a **default value**. 

.. glossary::

    default values
        
        A default value is a variable value that is predefined, that is, this value is placed 
        right in the structure file.

So let's define a variable with a description -- **and a default value**

.. extinclude:: https://forge.cloud.silique.fr/stove/rougail-tutorials/raw/commit/a1969abccd5e10872d4eb901a26fa16007c9fb1d/firefox/00-proxy.yml
    :language: yaml
    :caption: A rougail dictionnary file with a default value for the variable
    :name: RougailDictionaryVariableDefault

..
    ---
    proxy_mode:
      description: Configure Proxy Access to the Internet
      default: No proxy


.. type-along:: how to set a value

    A default value has been set, great. Now how do I assign a value to a variable?

How to set a value
----------------------

So far we have only talked about the one that writes the structure files. It is called the integrator. 

.. glossary::

    integrator

        An integrator in the Rougail logic is the person who writes the :term:`structure files <structure file>`\ .
        He has the responsibilité of the integration process, that is,
        defines the variables and the relationship between them, the variables that are allowed
        (or not) to be set, and so on. His responsabilites are the **structuration** and the **consistency**
        of the variables.

Now we will talk about the one that defines the values. It is called the operator.

.. glossary::

    operator

        An operator ih the Rougail logic is the person who gives :term:`value`\ s to the pre-defined variables,
        his responsabilities are to set variable values correctly.

        The user :term:`value`\ s, that is the values that have been set by the operator, are of course type validated by the :term:`structure file definition <structure file>`.

Values are mandatory
-------------------------

It is the operator's responsibility to set configuration options values.
He does not work with the structure file, 
he is responsible for other files, called the configuration files. 

.. glossary::

    configuration file
    
        A configuration file is a file where only the values ​​of the configuration options are assigned. The structure, the consistency of the variables between them is not the responsibility of these files (but of the structure files).

.. exercise:: Folder structure update

    Now we add a :file:`config/config.yml` file in our project::

        workplace
        ├── firefox
        │   ├── struct.yml
        └── config
            └── config.yml

.. type-along:: how to set a default value in a configuration file

So for example if the integrator has not set any default value in his structure file, 
the operator can do it like this:

.. extinclude:: https://forge.cloud.silique.fr/stove/rougail-tutorials/raw/tag/v1.1_011/config/02/config.yaml
   :language: yaml
   :caption: The Rougail configuration file :file:`config/config.yml`, with a default value set.
   :name: RougailConfigDefaultValue

.. 
    ---
    proxy_mode: No proxy

With the rougail CLI the operator has to add the `-u file -ff config/config.yml` options: 

.. code-block:: text
   :class: terminal
   :caption: A rougail Command Line Utility call with the :file:`config/config.yml` Rougail configuration file

   rougail -v 1.1 -m firefox -u file -ff config/01/config.yaml

Let us clarify this essential point:

- the integrator works on dictionaries
- the operator works on configuration files
    
.. note:: Most of the time, the integrator and the operator are one and the same person, here we are talking about roles and not necessarily about people.    

Variable's type
-----------------

If the `type` attribute is not set, Rougail infers a `string` type for the `proxy_mode` configuration option variable type as defined in the structure file.

If the operator sets an option value for example with the `number` type, like this:

.. code-block:: yaml

    ---
    example_var:
      description: Configure Proxy Access to the Internet
      type: number

Then Rougail will expect a `int` or a `float` as a value for the `example_var` variable.
In our firefox use case, the real type of the `proxy_mode` variable will be now set as a  `choice` type:

.. type-along:: Defining a choice type

    A choice type variable is a variable where the content is constrained by a list

.. extinclude:: https://forge.cloud.silique.fr/stove/rougail-tutorials/raw/tag/v1.1_013/firefox/00-proxy.yml
   :linenos:
   :language: yaml
   :caption: The real :file:`firefox/proxy.yml` Rougail dictionnary file with a choice type
   :name: RougailDictionaryChoiceType

..
    ---
    proxy_mode:
      description: Configure Proxy Access to the Internet
      type: choice
      choices:
        - No proxy
        - Auto-detect proxy settings for this network
        - Use system proxy settings
        - Manual proxy configuration
        - Automatic proxy configuration URL
      default: No proxy

- Then if we run the Rougail CLI 

.. code-block:: text
   :class: terminal
   
    rougail -v 1.1 -m firefox/

We will have an output like this: 

.. raw:: html
   :url: https://forge.cloud.silique.fr/stove/rougail-tutorials/raw/commit/v1.1_013/config/01/output_ro.html
   :class: output
   
..
    <pre>╭────────────────────────── Caption ──────────────────────────╮
    │ Variable                           <span style="color: #ffd700">Default value</span>            │
    │ <span style="color: #5c5cff">Undocumented variable</span>              Modified value           │
    │ <span style="color: #ff0000">Undocumented but modified variable</span> (<span style="color: #00aa00">Original default value</span>) │
    │ <span style="color: #ffaf00">Unmodifiable variable</span>                                       │
    ╰─────────────────────────────────────────────────────────────╯
    Variables:
    <span style="color: #5c5cff">┗━━ </span>📓 proxy_mode: <span style="color: #ffd700">No proxy</span>
    </pre>

The `proxy_mode` variable here, implicitely requires a value. It is a :term:`mandatory` variable.

As we set the `proxy_mode` variable as `No proxy` by default, we actually have specified a value, and the value appears in yellow, which means : "set by default". 

Container type
-----------------

We say that the `proxy_mode` variable is *constrained* (by the `choice` type).

We have the list of the possible (authorized) values:

- `No proxy`
- `Auto-detect proxy settings for this network`
- `Use system proxy settings`
- `Manual proxy configuration`
- `Automatic proxy configuration URL`

.. glossary::

    choice type

        The `proxy_mode` setting is "choice" (`type: choice`) means that
        there is a list of available values that can be selected.

.. keypoints:: Key points progress

    Indeed, in the Firefox configuration, it is possible to define several configuration modes, from no proxy at all (`no proxy`) to a kind of automatic configuration mode from a file (`set up proxy configuration from a file`).


    **Keywords**

    - :term:`structure file <structure file>`: structure description file
    - :term:`variable`: an option's name which has a value
    - a variable's description
    - a variable's type
    - a variable's default value
    - the :term:`integrator` and :term:`operator` roles
    - a mandatory value
    - a choice type

    **Progress**

    To sum up, we have arrived at this point in writing a structure file like this:

    **Structure description file**

    .. extinclude:: https://forge.cloud.silique.fr/stove/rougail-tutorials/raw/tag/v1.1_013/firefox/00-proxy.yml
       :linenos:
       :language: yaml
       :caption: A Rougail dictionnary file with a variable named `proxy_mode`, with a default value.

..

   .. raw:: text

    ---
    proxy_mode:
      description: Configure Proxy Access to the Internet
      type: choice
      choices:
        - No proxy
        - Auto-detect proxy settings for this network
        - Use system proxy settings
        - Manual proxy configuration
        - Automatic proxy configuration URL
      default: No proxy

