zulip/docs/bots-guide.md

# Writing bots
**This feature is still experimental.**

The contrib_bots system is a new part of Zulip that allows bot
developers to write a large class of interactive bots that react to
messages.

With the contrib_bots API, you *can* easily

* intercept, view, and process messages sent by users on Zulip
* send out new messages as replies to the processed messages

With this API, you *cannot*

* modify an intercepted message (you have to send a new message)
* send messages on behalf of or impersonate other users
* intercept private messages (except for PMs that with the bot as an
explicit recipient)

On this page you'll find:

* A step-by-step [tutorial](#how-to-deploy-a-bot) on how to deploy a bot.
* A step-by-step [tutorial](#how-to-develop-a-bot) on how to develop a bot.
* A [documentation](#bot-api) of the bot API.
* Common [problems](#common-problems) when developing/deploying bots and their solutions.

Contributions to this guide are very welcome, so if you run into any
issues following these instructions or come up with any tips or tools
that help with writing bots, please visit
[#bots](https://chat.zulip.org/#narrow/stream/bots) on the
[Zulip development community server](https://chat.zulip.org), open an
issue, or submit a pull request to share your ideas!

## How to deploy a bot

This guide will show you how to deploy a bot on a running Zulip
server.  It assumes you want to use one of the existing `contrib_bots`
bots in your Zulip organization.  If you want to write a new one, you
just need to write the `<my-bot>.py` script.

You need:

* An account in an organization on a Zulip server
  (e.g. [chat.zulip.org](https://chat.zulip.org) or
  yourSubdomain.zulipchat.com, or your own development server).
  Within that Zulip organization, users will be able to interact with
  your bot.
* A computer where you're running the bot from, with a clone of the
  [Zulip repository](https://github.com/zulip/zulip), which contains
  the bot library code in its `contrib_bots` subdirectory. This is
  required to run your bot. The following instructions assume this
  repository to be located in `~/zulip/`.

**Note: Please be considerate when testing experimental bots on
  public servers such as chat.zulip.org.**

1. Register a new bot user on the Zulip server's web interface.

    * Log in to the Zulip server.
    * Navigate to *Settings* -> *Your bots* -> *Add a new bot*, fill
      out the form and click on *Create bot*.
    * A new bot user should appear in the *Your bots* panel.

2. Download the bot's `.zuliprc` configuration file to your computer.

    * In the *Your bots* panel, click on the green icon to download
      its configuration file *.zuliprc* (the structure of this file is
      explained [here](#configuration-file).
    * Copy the file to a destination of your choice, e.g. to `~/.zuliprc` or `~/zuliprc-test`.

3. Subscribe the bot to the streams that the bot needs to interact with.

    * To subscribe your bot to streams, navigate to *Manage
      Streams*. Select a stream and add your bot by its email address
      (the address you assigned in step 3).
    * Now, the bot do its job on the streams you subscribed it to.
    * (In future versions of the API, this step may not be required).

4. Run the bot.

    * In your Zulip repository, navigate to `~/zulip/contrib_bots/`
    * Run
      ```
      python run.py ~/zulip/contrib_bots/bots/<my-bot>/<my-bot>.py --config-file ~/.zuliprc`
      ```
      (using the path to the `.zuliprc` file from step 2).
    * Check the output of the command. It should start with the text
      the `usage` function returns, followed by logging output similar
      to this:

      ```
      INFO:root:starting message handling...
      INFO:requests.packages.urllib3.connectionpool:Starting new HTTP connection (1): localhost
      ```

    * Congrats! Now, your bot should be ready to test on the streams you've subscribed it to.

### Test the `followup.py` bot

1. Do the previous steps for the `followup.py` bot.
2. Create the *followup* stream.
3. Subscribe the bot to the newly created *followup* stream and a
   stream you want to use it from, e.g. *social*.
4. Send a message mentioning your new bot to the stream you've
   subscribed the bot to (other than *followup*). If everything works,
   a copy of the message should now pop up in the *followup* stream.

## How to develop a bot

The tutorial below explains the structure of a bot `<my-bot>.py`,
which is the only file you need to create to develop a new bot. You
can use this as boilerplate code for developing your own bot.

Every bot is built upon this structure:

```
class MyBotHandler(object):
    '''
    A docstring documenting this bot.
    '''

    def usage(self):
        return '''Your description of the bot'''

    def handle_message(self, message, client, state_handler):
        # add your code here

handler_class = MyBotHandler
```

* The class name (in this case *MyBotHandler*) can be defined by you
  and should match the name of your bot. To register your bot's class,
  adjust the last line `handler_class = MyBotHandler` to match your
  class name.

* Every bot needs to implement the functions
    * `usage(self)`
    * `handle_message(self, message, client)`

* These functions are documented in the [next section](#bot-api).

## Bot API

This section documents the functions every bot needs to implement and
the structure of the bot's config file.

### usage
*usage(self)*

is called to retrieve information about the bot.

#### Arguments
* self - the instance the method is called on.

#### Return values
* A string describing the bot's functionality

#### Example implementation
```
def usage(self):
    return '''
        This plugin will allow users to flag messages
        as being follow-up items.  Users should preface
        messages with "@followup".
        Before running this, make sure to create a stream
        called "followup" that your API user can send to.
        '''
```

### handle_message
*handle_message(self, message, client)*

handles user message.

#### Arguments
* self - the instance the method is called on.

* message - a dictionary describing a Zulip message

* client - used to interact with the server, e.g. to send a message
    * use client.send_message(message) to send a message

* state_handler - used to save states/information of the bot **beta**
    * use `state_handler.set_state(state)` to set a state (any object)
    * use `state_handler.get_state()` to retrieve the state set; returns a `NoneType` object if no state is set

#### Return values
None.

#### Example implementation

 ```
  def handle_message(self, message, client, state_handler):
     original_content = message['content']
     original_sender = message['sender_email']
     new_content = original_content.replace('@followup',
                                            'from %s:' % (original_sender,))

     client.send_message(dict(
         type='stream',
         to='followup',
         subject=message['sender_email'],
         content=new_content,
     ))
 ```

### Configuration file

 ```
 [api]
 key=<api-key>
 email=<email>
 site=<dev-url>
 ```

* key - the API key you created for the bot; this is how Zulip knows
  the request is from an authorized user.

* email - the email address of the bot, e.g. `some-bot@zulip.com`

* site - your development environment URL; if you are working on a
  development environment hosted on your computer, use
  `localhost:9991`

## Common problems

* I modified my bot's code, yet the changes don't seem to have an effect.
    * Ensure that you restarted the `run.py` script.

* My bot won't start
    * Ensure that your API config file is correct (download the config file from the server).
    * Ensure that you bot script is located in zulip/contrib_bots/bots/<my-bot>/
    * Are you using your own Zulip development server? Ensure that you run your bot outside
      the Vagrant environment.

* My bot works only on some streams.
    * Subscribe your bot to other streams, as described [here](#how-to-deploy-a-bot).

## Future direction

The long-term plan for this bot system is to allow the same
`BotHandler` code to eventually be usable in several contexts:

* Run directly using the Zulip `call_on_each_message` API, which is
  how the implementation above works.  This is great for quick
  development with minimal setup.
* Run in a simple Python webserver server, processing messages
  received from Zulip's outgoing webhooks integration.
* For bots merged into the mainline Zulip codebase, enabled via a
  button in the Zulip web UI, with no code deployment effort required.