.. default-role:: literal

===============================
Options handling basics
===============================

Tiramisu is made of almost three main objects :

- :class:`tiramisu.config.Config` witch is the whole configuration entry point
- :class:`tiramisu.option.Option` stands for the option types
- :class:`tiramisu.option.OptionDescription` is the shema, the option's structure

Accessing the `Option`'s
-------------------------

The `Config` object attribute access notation stands for the value of the
configuration's `Option`. That is, the `Config`'s object attribute is the name
of the `Option`, and the value is the value accessed by the `__getattr__`
attribute access mechanism.

If the attribute of the `Config` called by `__getattr__` has not been set before
(by the classic `__setattr__` mechanism), the default value of the `Option`
object is returned, and if no `Option` has been declared in the
`OptionDescription` (that is the schema of the configuration), an
`AttributeError` is raised.

::

    >>> gcdummy = BoolOption('dummy', 'dummy', default=False)
    >>> gcdummy._name
    'dummy'
    >>> gcdummy.getdefault()
    False
    >>> descr = OptionDescription('tiramisu', '', [gcdummy])
    >>> cfg = Config(descr)
    >>> cfg.dummy
    False
    >>> cfg.dummy = True
    >>> cfg.dummy
    True
    >>> cfg.idontexist
    AttributeError: 'OptionDescription' object has no attribute 'idontexist'

The `Option` objects (in this case the `BoolOption`), are organized into a tree
into nested `OptionDescription` objects. Every option has a name, as does every
option group. The parts of the full name of the option are separated by dots:
e.g. ``cfg.optgroup.optname``.

Let's make the protocol of accessing a config's attribute explicit
(because explicit is better than implicit):

1. If the option has not been declared, an `AttributeError` is raised,

2. If an option is declared, but neither a value nor a default value has
   been set, the returned value is `None`,

3. If an option is declared and a default value has been set, but no value
   has been set, the returned value is the default value of the option,

4. If an option is declared, and a value has been set, the returned value is
   the value of the option.

But there are special exceptions. We will see later on that an option can be a
:term:`mandatory option`. A mandatory option is an option that must have a defined value.
If no value have been set yet, the value is `None`.
When the option is called to retrieve a value, an exception is raised.

What if a value has been set and `None` is to be returned again ? Don't
worry, an option value can be "reseted" with the help of the `option.Option.reset()`
method.

If you know the path:

::

    >>> config.gc.dummy
    False

Setting the values of the options
----------------------------------------

An important part of the setting of the configuration consists of setting the
values of the configuration options. There are different ways of setting values,
the first one is of course the `__setattr__` method

::

    cfg.name = value

And if you wanna come back to a default value, use the builtin `del()` function::

    del(cfg.name)

.. module:: tiramisu.config

.. _`tree`:

The handling of options
~~~~~~~~~~~~~~~~~~~~~~~~~~

The handling of options is split into two parts: the description of
which options are available, what their possible values and defaults are
and how they are organized into a tree. A specific choice of options is
bundled into a configuration object which has a reference to its option
description (and therefore makes sure that the configuration values
adhere to the option description).


Common manipulations
------------------------

Let's perform some common manipulation on some options:

>>> from tiramisu.config import Config
>>> from tiramisu.option import UnicodeOption, OptionDescription
>>>
>>> var1 = UnicodeOption('var1', 'first variable')
>>> var2 = UnicodeOption('var2', '', u'value')
>>>
>>> od1 = OptionDescription('od1', 'first OD', [var1, var2])
>>> rootod = OptionDescription('rootod', '', [od1])

let's set somme access rules on the main namespace

>>> c = Config(rootod)
>>> c.read_write()

let's travel the namespaces

>>> print c
[od1]
>>> print c.od1
var1 = None
var2 = value
>>> print c.od1.var1
None
>>> print c.od1.var2
value

let's modify a value (careful to the value's type...)

>>> c.od1.var1 = 'value'
Traceback (most recent call last):
[...]
ValueError: invalid value value for option var1
>>> c.od1.var1 = u'value'
>>> print c.od1.var1
value
>>> c.od1.var2 = u'value2'
>>> print c.od1.var2
value2

let's come back to the default value

>>> del(c.od1.var2)
>>> print c.od1.var2
value

The value is saved in a :class:`~tiramisu.value.Value` object. It is on this 
object that we have to trigger the `reset`, wich take the option itself 
(`var2`) as a parameter.

On the other side, in the `read_only` mode, it is not possible to modify the value::

    >>> c.read_only()
    >>> c.od1.var2 = u'value2'
    Traceback (most recent call last):
    [...]
    tiramisu.error.PropertiesOptionError: 
    cannot change the value to var2 
    for option ['frozen'] this option is frozen
    
let's retrieve the option `var1` description

>>> var1.impl_get_information('doc')
'first variable'

And if the option has been lost, it is possible to retrieve it again:

>>> c.unwrap_from_path('od1.var1').impl_get_information('doc')
'first variable'

Searching for an option
~~~~~~~~~~~~~~~~~~~~~~~~~~

In an application, knowing the path of an option is not always feasible. 
That's why a tree of options can easily be searched. First, let's build such a tree::

>>> var1 = UnicodeOption('var1', '')
>>> var2 = UnicodeOption('var2', '')
>>> var3 = UnicodeOption('var3', '')
>>> od1 = OptionDescription('od1', '', [var1, var2, var3])
>>> var4 = UnicodeOption('var4', '')
>>> var5 = UnicodeOption('var5', '')
>>> var6 = UnicodeOption('var6', '')
>>> var7 = UnicodeOption('var1', '', u'value')
>>> od2 = OptionDescription('od2', '', [var4, var5, var6, var7])
>>> rootod = OptionDescription('rootod', '', [od1, od2])
>>> c = Config(rootod)
>>> c.read_write()

Second, let's find an option by his name::

    >>> print c.find(byname='var1')
    [<tiramisu.option.UnicodeOption object at 0x7ff1bf7d6ef0>, 
    <tiramisu.option.UnicodeOption object at 0x7ff1b90c7290>] 
    
If the option name is unique, the search can be stopped once one matched option 
has been found:

    >>> print c.find_first(byname='var1')
    <tiramisu.option.UnicodeOption object at 0x7ff1bf7d6ef0>

Instead of the option's object, the value or path can be retrieved:

    >>> print c.find(byname='var1', type_='value')
    [None, u'value']
    >>> print c.find(byname='var1', type_='path')
    ['od1.var1', 'od2.var1']
    
Finaly, a search can be performed on the values, the type or even a combination 
of all these criteria:


    >>> print c.find(byvalue=u'value', type_='path')
    ['od2.var1']
    >>> print c.find(bytype=UnicodeOption, type_='path')
    ['od1.var1', 'od1.var2', 'od1.var3', 'od2.var4', 'od2.var5', 'od2.var6', 'od2.var1']
    >>> print c.find(byvalue=u'value', byname='var1', bytype=UnicodeOption, type_='path')
    ['od2.var1']
    
The search can be performed in a subtree:

>>> print c.od1.find(byname='var1', type_='path')
['od1.var1']

In a root tree or in a subtree, all option can be retrieved in a dict container:

    >>> print c.make_dict()
    {'od2.var4': None, 'od2.var5': None, 'od2.var6': None, 'od2.var1': u'value', 
    'od1.var1': None, 'od1.var3': None, 'od1.var2': None}
    
If the organisation in a tree is not important, 
:meth:`~config.SubConfig.make_dict()` results can be flattened

>>> print c.make_dict(flatten=True)
{'var5': None, 'var4': None, 'var6': None, 'var1': u'value', 'var3': None, 
'var2': None}

.. note:: carefull with this `flatten` parameter, here we have just lost 
               two options named `var1`

One can export only interesting parts of a tree of options into a dict, for 
example the options that are in the same group that a given `var1` option::

    >>> print c.make_dict(withoption='var1')
    {'od2.var4': None, 'od2.var5': None, 'od2.var6': None, 'od2.var1': u'value', 
    'od1.var1': None, 'od1.var3': None, 'od1.var2': None}
    >>> print c.make_dict(withoption='var1', withvalue=u'value')
    {'od2.var4': None, 'od2.var5': None, 'od2.var6': None, 'od2.var1': u'value'}
    
and of course, :meth:`~config.SubConfig.make_dict()` can be called in a subtree:

>>> print c.od1.make_dict(withoption='var1')
{'var1': None, 'var3': None, 'var2': None}

the owners
~~~~~~~~~~~

When a value is set on an option, an owner is set too, that's why one can know 
at any time if a value is a default value or not. Let's create a tree::

    >>> var1 = UnicodeOption('var1', '', u'oui')
    >>> od1 = OptionDescription('od1', '', [var1])
    >>> rootod = OptionDescription('rootod', '', [od1])
    >>> c = Config(rootod)
    >>> c.read_write()
    
Then let's retrieve the owner associated to an option::

    >>> print c.getowner('var1')
    default
    >>> c.od1.var1 = u'non'
    >>> print c.getowner('var1')
    user
    >>> del(c.var1)
    >>> print c.getowner('var1')
    default
    
the properties
~~~~~~~~~~~~~~~~

A property is an information on an option's state. 
Let's create options with properties::

    >>> var1 = UnicodeOption('var1', '', u'value', properties=('hidden',))
    >>> var2 = UnicodeOption('var2', '', properties=('mandatory',))
    >>> var3 = UnicodeOption('var3', '', u'value', properties=('frozen', 'inconnu'))
    >>> var4 = UnicodeOption('var4', '', u'value')
    >>> od1 = OptionDescription('od1', '', [var1, var2, var3])
    >>> od2 = OptionDescription('od2', '', [var4], properties=('hidden',))
    >>> rootod = OptionDescription('rootod', '', [od1, od2])
    >>> c = Config(rootod)
    >>> c.read_write()
    
A hidden value is a value that cannot be accessed in read/write mode. This 
option cannot be modified any more. Let's try to access to an option's value 
with a hidden option::

    >>> print c.od1.var1
    Traceback (most recent call last):
    [...]
    tiramisu.error.PropertiesOptionError: trying to access to an option named: var1 
    with properties ['hidden']
    >>> c.read_only()
    >>> print c.od1.var1
    value
    
A mandatory option is an option with a value that shall not be `None`. The 
value has to be defined. Accessing to such an option is easy in read/write 
mode. But in read only mode, an error is raised if no value has been defined:: 

    >>> c.read_write()
    >>> print c.od1.var2
    None
    >>> c.read_only()
    >>> print c.od1.var2
    Traceback (most recent call last):
    [...]
    tiramisu.error.PropertiesOptionError: trying to access to an option named: var2 
    with properties ['mandatory']
    >>> c.read_write()
    >>> c.od1.var2 = u'value'
    >>> c.read_only()
    >>> print c.od1.var2
    value
    
A frozen option, is an option that cannot be modified by a user. 
Let's try to modify a frozen option::

    >>> c.read_write()
    >>> print c.od1.var3
    value
    >>> c.od1.var3 = u'value2'
    Traceback (most recent call last):
    [...]
    tiramisu.error.PropertiesOptionError: cannot change the value for option var3 this option is frozen
    >>> c.read_only()
    >>> print c.od1.var3
    value
    
Tiramisu allows us to use user defined properties. Let's define and use one in 
read/write or read only mode::

    >>> c.cfgimpl_get_settings().append('inconnu')
    >>> print c.od1.var3
    Traceback (most recent call last):
    [...]
    tiramisu.error.PropertiesOptionError: trying to access to an option named: 
    var3 with properties ['inconnu']
    >>> c.cfgimpl_get_settings().remove('inconnu')
    >>> print c.od1.var3
    value 
    
Properties can also be defined on option groups, 
(that is, on :ref:`option description`s), let's hide a group and try to access to it::

    >>> c.read_write()
    >>> print c.od2.var4
    Traceback (most recent call last):
    [...]
    tiramisu.error.PropertiesOptionError: trying to access to an option named: od2 
    with properties ['hidden']
    >>> c.read_only()
    >>> print c.od2.var4
    value
    
Furthermore, let's retrieve the properties, delete and add the `hidden` property::

    >>> c.read_write()
    >>> c.cfgimpl_get_settings()[rootod.od1.var1]
    ['hidden']
    >>> print c.od1.var1
    Traceback (most recent call last):
    [...]
    tiramisu.error.PropertiesOptionError: trying to access to an option named: 
    var1 with properties ['hidden']
    >>> c.cfgimpl_get_settings()[rootod.od1.var1].remove('hidden')
    >>> c.cfgimpl_get_settings()[rootod.od1.var1]
    []
    >>> print c.od1.var1
    value
    >>> c.cfgimpl_get_settings()[rootod.od1.var1].append('hidden')
    >>> c.cfgimpl_get_settings()[rootod.od1.var1]
    ['hidden']
    >>> print c.od1.var1
    Traceback (most recent call last):
    [...]
    tiramisu.error.PropertiesOptionError: trying to access to an option named: 
    var1 with properties ['hidden']

The requirements
~~~~~~~~~~~~~~~~~~

Let's create an option wich has requirements::

    >>> var1 = UnicodeOption('var1', '', u'value', requires=(('od1.var2', 
       'non', 'hidden'),))
    >>> var2 = UnicodeOption('var2', '', u'oui')
    >>> var3 = UnicodeOption('var3', '', u'value', requires=(('od1.var2', 
        'non', 'hidden'), ('od1.var2', 'non', 'disabled')))
    >>> var4 = UnicodeOption('var4', '', u'oui')
    >>>
    >>> od1 = OptionDescription('od1', '', [var1, var2, var3])
    >>> od2 = OptionDescription('od2', '', [var4], requires=(('od1.var2', 
        'oui', 'hidden', True),))
    >>> rootod = OptionDescription('rootod', '', [od1, od2])
    >>> c = Config(rootod)
    >>> c.read_write()    

The requirement here is the tuple `('od1.var2' , 'non', 'hidden')` wich means 
that is the option `'od1.var2'` is set to `'non'`, the option `'od1.var1'` is 
gonna be hidden. On the other hand, if the option `'od1.var2'` is different 
from `'non'`, the option `'od1.var1'` is not hidden any more::

    >>> print c.cfgimpl_get_settings()[rootod.od1.var1]
    []
    >>> print c.od1.var1
    value
    >>> print c.od1.var2
    oui
    >>> c.od1.var2 = u'non'
    >>> print c.cfgimpl_get_settings()[rootod.od1.var1]
    ['hidden']
    >>> print c.od1.var1
    Traceback (most recent call last):
    [...]
    tiramisu.error.PropertiesOptionError: trying to access to an option named: 
    var1 with properties ['hidden']
    >>> c.od1.var2 = u'oui'
    >>> print c.cfgimpl_get_settings()[rootod.od1.var1]
    []
    >>> print c.od1.var1
    value
    
The requirement on `od2` is `('od1.var2', 'oui', 'hidden', True)`, which means 
that if the option `od1.var2` is set to `oui`, the option is not hidden 
(because of the `True` at the end of the tuple wich means 'inverted', take a 
look at the :doc:`consistency` document.):: 

    >>> print c.od2.var4
    oui
    >>> c.od1.var2 = u'non'
    >>> print c.od2.var4
    Traceback (most recent call last):
    [...]
    tiramisu.error.PropertiesOptionError: trying to access to an option named: od2 with properties ['hidden']
    >>> c.od1.var2 = u'oui'
    >>> print c.od2.var4
    oui
    
Requirements can be accumulated 

    >>> print c.cfgimpl_get_settings()[rootod.od1.var3]
    []
    >>> c.od1.var2 = u'non'
    >>> print c.cfgimpl_get_settings()[rootod.od1.var3]
    ['disabled', 'hidden']
    >>> c.od1.var2 = u'oui'
    >>> print c.cfgimpl_get_settings()[rootod.od1.var3]
    []

Requirements can be accumulated for different or identical properties (inverted 
or not)::

    >>> a = UnicodeOption('var3', '', u'value', requires=(('od1.var2', 'non', 
        'hidden'), ('od1.var1', 'oui', 'hidden')))
    >>> a = UnicodeOption('var3', '', u'value', requires=(('od1.var2', 'non', 
        'hidden'), ('od1.var1', 'oui', 'disabled', True)))

But it is not possible to have inverted requirements on the same property. 
Here is an impossible situation::

    >>> a = UnicodeOption('var3', '', u'value', requires=(('od1.var2', 'non', 
        'hidden'), ('od1.var1', 'oui', 'hidden', True)))
    Traceback (most recent call last):
    [...]
    ValueError: inconsistency in action types for option: var3 action: hidden

        
Configuration's interesting methods 
------------------------------------------

A `Config` object is informed by an `option.OptionDescription`
instance. The attributes of the ``Config`` objects are the names of the
children of the ``OptionDescription``.

Here are the (useful) methods on ``Config`` (or `SubConfig`).

.. currentmodule:: tiramisu.config

.. class:: Config

.. autoclass:: SubConfig
    :members: find, find_first, __iter__, iter_groups, iter_all, make_dict

    .. automethod:: __init__

    .. rubric:: Summary

    .. autosummary::

       find
       find_first

       __iter__
       iter_groups
       iter_all

       make_dict

    .. rubric:: Methods


A :class:`~config.CommonConfig` is a abstract base class. A
:class:`~config.SubConfig` is an just in time created objects that wraps an
::class:`~option.OptionDescription`. A SubConfig differs from a Config in the
::fact that a config is a root object and has an environnement, a context wich
::defines the different properties, access rules, vs... There is generally only
::one Config, and many SubConfigs.