Royalnet Commands¶

A Royalnet Command is a small script that is run whenever a specific message is sent to a Royalnet interface.

A Command code looks like this:

from royalnet.commands import Command

class PingCommand(Command):
    name = "ping"

    description = "Play ping-pong with the bot."

    def __init__(self, interface):
        # This code is run just once, while the bot is starting
        super().__init__()

    async def run(self, args, data):
        # This code is run every time the command is called
        await data.reply("Pong!")

Creating a new Command¶

First, think of a name for your command. It’s the name your command will be called with: for example, the “spaghetti” command will be called by typing /spaghetti in chat. Try to keep the name as short as possible, while staying specific enough so no other command will have the same name.

Next, create a new Python file with the name you have thought of. The previously mentioned “spaghetti” command should have a file called spaghetti.py.

Then, in the first row of the file, import the Command class from royalnet, and create a new class inheriting from it:

from royalnet.commands import Command

class SpaghettiCommand(Command):
    ...

Inside the class, override the attributes name and description with respectively the name of the command and a small description of what the command will do:

from royalnet.commands import Command

class SpaghettiCommand(Command):
    name = "spaghetti"

    description = "Send a spaghetti emoji in the chat."

Now override the Command.run() method, adding the code you want the bot to run when the command is called.

To send a message in the chat the command was called in, you can use the CommandData.reply() method:

from royalnet.commands import Command

class SpaghettiCommand(Command):
    name = "spaghetti"

    description = "Send a spaghetti emoji in the chat."

    async def run(self, args, data):
        await data.reply("🍝")

And… it’s done! The command is ready to be added to a bot!

Command arguments¶

A command can have some arguments passed by the user: for example, on Telegram an user may type /spaghetti carbonara al-dente to pass the str “carbonara al-dente” to the command code.

These arguments can be accessed in multiple ways through the args parameter passed to the Command.run() method.

Direct access¶

You can consider arguments as if they were separated by spaces.

You can then access command arguments directly by number as if the args object was a list of str.

If you request an argument with a certain number, but the argument does not exist, an royalnet.error.InvalidInputError is raised, making the arguments accessed in this way required.

args[0]
# "carbonara"

args[1]
# "al-dente"

args[2]
# InvalidInputError() is raised

Optional access¶

If you don’t want arguments to be required, you can access them through the CommandArgs.optional() method: it will return None if the argument wasn’t passed, making it optional.

args.optional(0)
# "carbonara"

args.optional(1)
# "al-dente"

args.optional(2)
# None

You can specify a default result too, so that the method will return it instead of returning None:

args.optional(2, default="banana")
# "banana"

Full string¶

If you want the full argument string, you can use the CommandArgs.joined() method.

args.joined()
# "carbonara al-dente"

You can specify a minimum number of arguments too, so that an royalnet.error.InvalidInputError will be raised if not enough arguments are present:

args.joined(require_at_least=3)
# InvalidInputError() is raised

Regular expressions¶

For more complex commands, you may want to get arguments through regular expressions.

You can then use the CommandArgs.match() method, which tries to match a pattern to the command argument string, which returns a tuple of the matched groups and raises an royalnet.error.InvalidInputError if there is no match.

To match a pattern, re.match() is used, meaning that Python will try to match only at the beginning of the string.

args.match(r"(carb\w+)")
# ("carbonara",)

args.match(r"(al-\w+)")
# InvalidInputError() is raised

args.match(r"\s*(al-\w+)")
# ("al-dente",)

args.match(r"\s*(carb\w+)\s*(al-\w+)")
# ("carbonara", "al-dente")

Coroutines and slow operations¶

You may have noticed that in the previous example I wrote await data.reply("🍝") instead of just data.reply("🍝").

This is because CommandData.reply() isn’t a simple method: it is a coroutine, a special kind of function that can be executed separately from the rest of the code, allowing the bot to do other things in the meantime.

By adding the await keyword before the data.reply("🍝"), we tell the bot that it can do other things, like receiving new messages, while the message is being sent.

You should avoid running slow normal functions inside bot commands, as they will stop the bot from working until they are finished and may cause bugs in other parts of the code!

async def run(self, args, data):
    # Don't do this!
    image = download_1_terabyte_of_spaghetti("right_now", from="italy")
    ...

If the slow function you want does not cause any side effect, you can wrap it with the royalnet.utils.asyncify() function:

async def run(self, args, data):
    # If the called function has no side effect, you can do this!
    image = await asyncify(download_1_terabyte_of_spaghetti, "right_now", from="italy")
    ...

Avoid using time.sleep() function, as it is considered a slow operation: use instead asyncio.sleep(), a coroutine that does the same exact thing.