.. _intro:

Introduction
============

``fbchat`` uses your email and password to communicate with the Facebook server.
That means that you should always store your password in a separate file, in case e.g. someone looks over your shoulder while you're writing code.
You should also make sure that the file's access control is appropriately restrictive


.. _intro_logging_in:

Logging In
----------

Simply create an instance of `Client`. If you have two factor authentication enabled, type the code in the terminal prompt
(If you want to supply the code in another fashion, overwrite `Client.on_2fa_code`)::

    from fbchat import Client
    from fbchat.models import *
    client = Client('<email>', '<password>')

Replace ``<email>`` and ``<password>`` with your email and password respectively

.. note::
    For ease of use then most of the code snippets in this document will assume you've already completed the login process
    Though the second line, ``from fbchat.models import *``, is not strictly necessary here, later code snippets will assume you've done this

If you want to change how verbose ``fbchat`` is, change the logging level (in `Client`)

Throughout your code, if you want to check whether you are still logged in, use `Client.is_logged_in`.
An example would be to login again if you've been logged out, using `Client.login`::

    if not client.is_logged_in():
        client.login('<email>', '<password>')

When you're done using the client, and want to securely logout, use `Client.logout`::

    client.logout()


.. _intro_threads:

Threads
-------

A thread can refer to two things: A Messenger group chat (`Group`) or a single Facebook user (`User`).

Searching for group chats and finding their ID can be done via. `Client.search_for_groups`,
and searching for users is possible via. `Client.search_for_users`. See :ref:`intro_fetching`

You can get your own user ID by using `Session.user_id`

Getting the ID of a group chat is fairly trivial otherwise, since you only need to navigate to `<https://www.facebook.com/messages/>`_,
click on the group you want to find the ID of, and then read the id from the address bar.
The URL will look something like this: ``https://www.facebook.com/messages/t/1234567890``, where ``1234567890`` would be the ID of the group.
An image to illustrate this is shown below:

.. image:: /_static/find-group-id.png
    :alt: An image illustrating how to find the ID of a group

The same method can be applied to some user accounts, though if they've set a custom URL, then you'll just see that URL instead

Here's an snippet showing the usage of thread IDs and thread types, where ``<user id>`` and ``<group id>``
corresponds to the ID of a single user, and the ID of a group respectively::

    user.send(Message(text='<message>'))
    group.send(Message(text='<message>'))

Some functions don't require a thread type, so in these cases you just provide the thread ID::

    thread = fbchat.Thread(session=session, id="<user-or-group-id>")
    thread.set_color("#a695c7")
    thread.set_color("#67b868")


.. _intro_message_ids:

Message IDs
-----------

Every message you send on Facebook has a unique ID, and every action you do in a thread,
like changing a nickname or adding a person, has a unique ID too.

This snippet shows how to send a message, and then use the returned ID to react to that message with a 😍 emoji::

    message = thread.send_text("A message!")
    message.react("😍")


.. _intro_interacting:

Interacting with Threads
------------------------

``fbchat`` provides multiple functions for interacting with threads

Most functionality works on all threads, though some things,
like adding users to and removing users from a group chat, logically only works on group chats

The simplest way of using ``fbchat`` is to send a message.
The following snippet will, as you've probably already figured out, send the message ``test message`` to your account::

    user = User(session=session, id=session.user_id)
    message_id = user.send(Message(text='test message'))

You can see a full example showing all the possible thread interactions with ``fbchat`` by going to :ref:`examples`


.. _intro_fetching:

Fetching Information
--------------------

You can use ``fbchat`` to fetch basic information like user names, profile pictures, thread names and user IDs

You can retrieve a user's ID with `Client.search_for_users`.
The following snippet will search for users by their name, take the first (and most likely) user, and then get their user ID from the result::

    users = client.search_for_users('<name of user>')
    user = users[0]
    print("User's ID: {}".format(user.id))
    print("User's name: {}".format(user.name))
    print("User's profile picture URL: {}".format(user.photo))
    print("User's main URL: {}".format(user.url))

Since this uses Facebook's search functions, you don't have to specify the whole name, first names will usually be enough

You can see a full example showing all the possible ways to fetch information with ``fbchat`` by going to :ref:`examples`


.. _intro_sessions:

Sessions
--------

``fbchat`` provides functions to retrieve and set the session cookies.
This will enable you to store the session cookies in a separate file, so that you don't have to login each time you start your script.
Use `Client.get_gession` to retrieve the cookies::

    session_cookies = client.get_gession()

Then you can use `Client.set_gession`::

    client.set_gession(session_cookies)

Or you can set the ``session_cookies`` on your initial login.
(If the session cookies are invalid, your email and password will be used to login instead)::

    client = Client('<email>', '<password>', session_cookies=session_cookies)

.. warning::
    You session cookies can be just as valuable as you password, so store them with equal care


.. _intro_events:

Listening & Events
------------------

To use the listening functions ``fbchat`` offers (like `Client.listen`),
you have to define what should be executed when certain events happen.
By default, (most) events will just be a `logging.info` statement,
meaning it will simply print information to the console when an event happens

.. note::
    You can identify the event methods by their ``on`` prefix, e.g. ``on_message``

The event actions can be changed by subclassing the `Client`, and then overwriting the event methods::

    class CustomClient(Client):
        def on_message(self, mid, author_id, message_object, thread, ts, metadata, msg, **kwargs):
            # Do something with message_object here
            pass

    client = CustomClient('<email>', '<password>')

**Notice:** The following snippet is as equally valid as the previous one::

    class CustomClient(Client):
        def on_message(self, message_object, author_id, thread, **kwargs):
            # Do something with message_object here
            pass

    client = CustomClient('<email>', '<password>')

The change was in the parameters that our ``on_message`` method took: ``message_object`` and ``author_id`` got swapped,
and ``mid``, ``ts``, ``metadata`` and ``msg`` got removed, but the function still works, since we included ``**kwargs``

.. note::
    Therefore, for both backwards and forwards compatibility,
    the API actually requires that you include ``**kwargs`` as your final argument.

View the :ref:`examples` to see some more examples illustrating the event system
