PyLink plugins are modules that extend its functionality by giving it something to do. Without any plugins loaded, PyLink can only sit on a server and do absolutely nothing.
Plugins have three main ways of communicating with IRC: hooks, WHOIS handlers, and commands sent in PM to the main PyLink client. A simple plugin can use one, or any mixture of these.
Hooks are probably the most versatile form of communication. The data in each hook payload is formatted as a Python `dict`, with different data keys depending on the command.
For example, a `PRIVMSG` payload would give you the fields `target` and `text`, while a `PART` payload would only give you `channels` and `reason` fields.
There are many hook types available (one for each supported IRC command), and you can read more about them in the [PyLink hooks reference](hooks-reference.md).
Plugins can bind to hooks using the `utils.add_hook()` function like so: `utils.add_hook(function_name, 'PRIVMSG')`, where `function_name` is your function definition, and `PRIVMSG` is whatever hook name you want to bind to. Once set up, `function_name` will be called whenever the protocol module receives a `PRIVMSG` command.
Each hook-bound function takes 4 arguments: `irc, source, command, args`.
- **irc**: The IRC object where the hook was called. Plugins are globally loaded, so there will be one of these per network.
- **source**: The numeric of the sender. This will usually be a UID (for users) or a SID (for server).
- **command**: The true command name where the hook originates. This may or may not be the same as the name of the hook, depending on context.
- **args**: The hook data (a `dict`) associated with the command. Again, the available data keys differ by hook name
(see the [hooks reference](hooks-reference.md) for a list of which can be used).
Hook functions do not return anything, and can raise exceptions to be caught by the core.
Commands are bound to using the `utils.add_cmd()` function: `utils.add_cmd(testcommand, "hello")`. Here, `testcommand` is the name of your function, and `hello` is the (optional) name of the command to bind to; if it is not specified, it'll use the same name as the function.
Now, your command function will be called whenever someone PMs the PyLink client with the command (e.g. `/msg PyLink hello`, case-insensitive).
Each command function takes 3 arguments: `irc, source, args`.
- **irc**: The IRC object where the command was called.
- **source**: The numeric of the sender. This will usually be a UID (for users) or a SID (for server).
- **args**: A `list` of space-separated command args (excluding the command name) that the command was called with. For example, `/msg PyLink hello world 1234` would give an `args` list of `['world', '1234']`
The third option, `WHOIS` handlers, are a lot more limited compared to the other options. They are solely used for `WHOIS` replies, **and only work on IRCds where WHOIS commands are sent to remote servers!** This includes Charybdis and UnrealIRCd, but **not** InspIRCd, which handles all `WHOIS` requests locally (the only thing sent between servers is an IDLE time query).
WHOIS replies are special in that any plugins wishing to add lines to a WHOIS reply must do so after the regular WHOIS lines (handled by the core), but before a special "End of WHOIS" line. This means that the regular hooks mechanism, which are only called after core handling, doesn't work here.
An example of a plugin WHOIS handler is in the [relay plugin](../../plugins/relay.py) (search for `relayWhoisHandler`. WHOIS handler functions are added to the `world.whois_handlers` list using a simple `append()`. They should return either nothing or a list of two-length tuples: the first item being the WHOIS numeric, and the second the raw whois text.
Plugins receive data from the underlying protocol module, and communicate back using outgoing [command functions](pmodule-spec.md) implemented by the protocol module. They should *never* send raw data directly back to IRC, because that wouldn't be portable across different IRCds.
These functions are usually called in this fashion: `irc.proto.abcdClient(arg1, arg2)`. For example, the command `irc.proto.join('10XAAAAAB', '#bots')` would join a PyLink client with UID `10XAAAAAB` to channel `#bots`.
For sending messages (e.g. replies to commands), simpler forms of:
-`irc.reply(text, notice=False, source=None)`
- and `irc.msg(targetUID, text, notice=False, source=None)`
are also used.
`irc.reply()` is a special form of `irc.msg` in that it automatically finds the target to reply to. If the command was called in a channel using fantasy, it will send the reply in that channel. Otherwise, the reply will be sent in a PM to the caller.
The sender UID for both can be set using the `source` argument, and defaults to the main PyLink client.
