Triggers
========

The package provides ability to write custom extensions which will be run on (the most) actions, e.g. after updates. By default ahriman provides two types of extensions - reporting and files uploading. Each extension must derive from the ``ahriman.core.triggers.Trigger`` class and implement ``run`` method

Trigger example
---------------

Lets consider example of reporting trigger (e.g. `slack <https://slack.com/>`_, which provides easy HTTP API for integration triggers).

In order to post message to slack we will need a specific trigger url (something like ``https://hooks.slack.com/services/company_id/trigger_id``), channel (e.g. ``#archrepo``) and username (``repo-bot``).

As it has been mentioned, our trigger must derive from specific class:

.. code-block:: python

   from ahriman.core.triggers import Trigger

   class SlackReporter(Trigger):

       def __init__(self, architecture, configuration):
           Trigger.__init__(self, architecture, configuration)
           self.slack_url = configuration.get("slack", "url")
           self.channel = configuration.get("slack", "channel")
           self.username = configuration.get("slack", "username")

By now we have class with all required variables. Lets implement run method. Slack API requires positing data with specific payload by HTTP, thus:

.. code-block:: python

   import json
   import requests

   def notify(result, slack_url, channel, username):
       text = f"""Build has been completed with packages: {", ".join([package.name for package in result.success])}"""
       payload = {"channel": channel, "username": username, "text": text}
       response = requests.post(slack_url, data={"payload": json.dumps(payload)})
       response.raise_for_status()

Obviously you can implement the specified method in class, but for guide purpose it has been done as separated method. Now we can merge this method into the class:

.. code-block:: python

   class SlackReporter(Trigger):

       def __init__(self, architecture, configuration):
           Trigger.__init__(self, architecture, configuration)
           self.slack_url = configuration.get("slack", "url")
           self.channel = configuration.get("slack", "channel")
           self.username = configuration.get("slack", "username")

       def run(self, result, packages):
           notify(result, self.slack_url, self.channel, self.username)

Setup the trigger
-----------------

First, put the trigger in any path it can be exported, e.g. by packing the resource into python package (which will lead to import path as ``package.slack_reporter.SlackReporter``) or just put file somewhere it can be accessed by application (e.g. ``/usr/local/lib/slack_reporter.py.SlackReporter``.

After that run application as usual and receive notification in your slack channel.
