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Adding Commands

===============

Kamaki commands are implemented as python classes, decorated with a special

decorator called *command*. This decorator is a method of kamaki.cli that adds

a new command in a CommandTree structure (kamaki.cli.commant_tree). The later

is used by interfaces to manage kamaki commands.

In the following, a set of kamaki commands will be implemented::

    mygrp1 list all                         //show a list

    mygrp1 list details [--match=<>]        //show list of details

    mygrp2 list all [regular expression] [-l]       //list all subjects

    mygrp2 info <id> [name]      //get information for subject with id

There are two command sets to implement, namely mygrp1 and mygrp2. The first

will contain two commands, namely list-all and list-details. The second one

will also contain two commands, list-all and info. To avoid ambiguities,

command names should rather be prefixed with the group they belong to, e.g.

mygrp1-list-all and mygrp2-list-all.

The first command has the simplest possible syntax: no parameters, no runtime

arguments. The second accepts an optional runtime argument with a value. The

third features an optional argument and an optional runtime flag argument. The

last is an example of a command with an obligatory and an optional argument.

Samples of the expected behavior in one-command mode are following:

.. code-block:: console

    $kamaki mygrp1

        mygrp1 description

        Options

         - - - -

        list

    $ kamaki mygrp1 list

        Syntax Error

        Options

         - - - -

        all        show a list

        details     show a list of details

    $ kamaki mygrp1 list all

        ... (mygrp1 client method is called) ...

    $ kamaki mygrp2 list all 'Z[.]' -l

        ... (mygrp2 client method is called) ...

    $

The above example will be used throughout the present guide.

The CommandTree structure

-------------------------

CommandTree manages a command by its path. Each command is stored in multiple

nodes on the tree, so that the last term is a leaf and the route from root to

that leaf represents the command path. For example the commands *file upload*,

*file list* and *file info* are stored together as shown bellow::

    - file

    ''''''''|- info

            |- list

            |- upload

The example used in the present, should result to the creation of two trees::

    - mygrp1

    ''''''''|- list

            '''''''|- all

                   |- details

    - mygrp2

    ''''''''|- list

            '''''''|- all

            |- info

Each command group should be stored on a different CommandTree. For that

reason, command specification modules should contain a list of CommandTree

objects, named *_commands*

A command group information (name, description) is provided at CommandTree

structure initialization:

.. code-block:: python

    _mygrp1_commands = CommandTree('mygrp', 'mygrp1 description')

    _mygrp2_commands = CommandTree('mygrp', 'mygrp2 description')

    _commands = [_mygrp1_commands, _mygrp2_commands]

The command decorator

---------------------

The *command* decorator mines all the information necessary to build a command

specification which is then inserted in a CommanTree instance::

    class code  --->  command()  -->  updated CommandTree structure

Kamaki interfaces make use of this CommandTree structure. Optimizations are

possible by using special parameters on the command decorator method.

.. code-block:: python

    def command(cmd_tree, prefix='', descedants_depth=None):

    """Load a class as a command

        :param cmd_tree: is the CommandTree to be updated with a new command

        :param prefix: of the commands allowed to be inserted ('' for all)

        :param descedants_depth: is the depth of the tree descedants of the

            prefix command.

    """

Creating a new command specification set

----------------------------------------

A command specification developer should create a new module (python file) with as many classes as the command specifications to be offered. Each class should be decorated with *command*.

.. code-block:: python

    ...

    _commands = [_mygrp1_commands, _mygrp2_commands]

    @command(_mygrp1_commands)

    class mygrp1_list_all():

        ...

    ...

A list of CommandTree structures must exist in the module scope, with the name

_commands, as shown above. Different CommandTree objects correspond to

different command groups.

Get command description

-----------------------

The description of each command is the first line of the class commend. The

following declaration of *mygrp2-info* command has a "*get information for

subject with id*" description.

.. code-block:: python

    ...

    @command(_mygrp2_commands)

    class mygrp2_info()

        """get information for subject with id"""

        ...

Declare run-time argument

-------------------------

The argument mechanism allows the definition of run-time arguments. Some basic

argument types are defined at the

`argument module <code.html#module-kamaki.cli.argument>`_, but it is not

uncommon to extent these classes in order to achieve specialized type checking

and syntax control (e.g. at

`pithos cli module <code.html#module-kamaki.cli.commands.pithos>`_).

To declare a run-time argument on a specific command, the object class should

initialize a dict called *arguments* , where Argument objects are stored. Each

argument object is a possible run-time argument. Syntax checking happens at

client level, while the type checking is implemented in the Argument code

(thus, many different Argument types might be needed).`

.. code-block:: python

    from kamaki.cli.argument import ValueArgument

    ...

    @command(_mygrp1_commands)

    class mygrp1_list_details():

        """list of details"""

        def __init__(self, global_args={}):

            global_args['match'] = ValueArgument(

                'Filter results to match string',

                ('-m', '--match'))

            self.arguments = global_args

or more usually and elegantly:

.. code-block:: python

    from kamaki.cli.argument import ValueArgument

    @command(_mygrp1_commands)

    class mygrp1_list_details():

    """List of details"""

        arguments = dict(

            match=ValueArgument(

            'Filter output to match string', ('-m', --match'))

        )

Accessing run-time arguments

----------------------------

To access run-time arguments, users can use the _command_init interface, which

implements __item__ accessors to handle run-time argument values. In specific,

an instance of _command_init can use brackets to set or read <argument>.value .

.. code-block:: python

    from kamaki.cli.argument import ValueArgument

    from kamaki.cli.commands import _command_init

    @command(_mygrp1_commands)

    class mygrp1_list_details(_command_init):

        """List of details"""

        arguments = dict(

            match=ValueArgument(

                'Filter output to match string', ('-m', --match'))

        )

        def check_runtime_arguments(self):

            ...

            assert self['match'] == self.arguments['match'].value

            ...

The main method and command parameters

--------------------------------------

The command behavior for each command / class is coded in *main*. The

parameters of *main* method defines the command parameters part of the syntax.

In specific::

    main(self, param)                   - obligatory parameter <param>

    main(self, param=None)              - optional parameter [param]

    main(self, param1, param2=42)       - <param1> [param2]

    main(self, param1____param2)        - <param1:param2>

    main(self, param1____param2=[])     - [param1:param2]

    main(self, param1____param2__)      - <param1[:param2]>

    main(self, param1____param2__='')   - [param1[:param2]]

    main(self, *args)                   - arbitary number of params [...]

    main(self, param1____param2, *args) - <param1:param2> [...]

The information that can be mined by *command* for each individual command is

presented in the following:

.. code-block:: python

    :linenos:

    from kamaki.cli.argument import FlagArgument

    ...

    _commands = [_mygrp1_commands, _mygrp2=commands]

    ...

    @command(_mygrp2_commands)

    class mygrp2_list_all():

        """List all subjects"""

        arguments = dict(FlagArgument('detailed list', '-l'))

        def main(self, reg_exp=None):

            ...

This will load the following information on the CommandTree:

* Syntax (from lines 8,12,19): mygrp list all [reg exp] [-l]

* Description (form line 9): List all subjects

* Arguments help (from line 13,14): -l: detailed list

Letting kamaki know

-------------------

Kamaki will load a command specification *only* if it is set as a configurable

option. To demonstrate this, let the command specifications coded above be

stored in a file named *grps.py*.

The developer should move file *grps.py* to kamaki/cli/commands, the default

place for command specifications, although running a command specification from

a different path is also a kamaki feature.

The user has to use a configuration file where the following is added:

::

    [global]

    mygrp1_cli = grps

    mygrp2_cli = grps

or equivalently:

.. code-block:: console

    $ kamaki config set mygrp1_cli grps

    $ kamaki config set mygrp2_cli grps

Command specification modules don't need to live in kamaki/cli/commands,

although this is suggested for uniformity. If a command module exist in another

path::

    [global]

    mygrp_cli = /another/path/grps.py

Summary: create a command set

-----------------------------

.. code-block:: python

    #  File: grps.py

    from kamaki.cli.commands import _command_init

    from kamaki.cli.command_tree import CommandTree

    from kamaki.cli.argument import ValueArgument, FlagArgument

    ...

    #  Initiallize command trees

    _mygrp1_commands = CommandTree('mygrp', 'mygrp1 description')

    _mygrp2_commands = CommandTree('mygrp', 'mygrp2 description')

    _commands = [_mygrp1_commands, _mygrp2_commands]

    #  Define command specifications

    @command(_mygrp1_commands)

    class mygrp1_list_all(_command_init):

        """show a list"""

        def main(self):

            ...

    @command(_mygrp1_commands)

    class mygrp1_list_details(_command_init):

        """show list of details"""

        arguments = dict(

            match=ValueArgument(

                'Filter output to match string', ('-m', --match'))

        )

        def main(self):

            ...

            match_value = self['match']

            ...

    @command(_mygrp2_commands)

    class mygrp2_list_all(_command_init):

        """list all subjects"""

        arguments = dict(

            list=FlagArgument('detailed listing', '-l')

        )

        def main(self, regular_expression=None):

            ...

            detail_flag = self['list']

            ...

            if detail_flag:

                ...

            ...

            if regular_expression:

                ...

            ...

    @command(_mygrp2_commands)

    class mygrp2_info(_command_init):

        """get information for subject with id"""

        def main(self, id, name=''):

            ...