forked from cadey/xesite
114 lines
3.4 KiB
Markdown
114 lines
3.4 KiB
Markdown
---
|
|
title: Pursuit of a DSL
|
|
date: 2014-08-16
|
|
---
|
|
|
|
A project we have been working on is [Tetra](http://github.com/Xe/Tetra). It is
|
|
an extended services package in Go with Lua and Moonscript extensions. While
|
|
writing Tetra, I have found out how to create a Domain Specific Language, and
|
|
I would like to recommend Moonscript as a toolkit for creating DSL's.
|
|
|
|
[Moonscript](http://moonscript.org) is a high level wrapper around Lua designed
|
|
to make programming easier. We have used Moonscript heavily in Tetra because of
|
|
how easy it is to make very idiomatic code in it.
|
|
|
|
Here is some example code from the Tetra codebase for making a command:
|
|
|
|
```moonscript
|
|
require "lib/elfs"
|
|
|
|
Command "NAMEGEN", ->
|
|
"> #{elfs.GenName!\upper!}"
|
|
```
|
|
|
|
That's it. That creates a command named `NAMEGEN` that uses `lib/elfs` to
|
|
generate goofy heroku-like application names based on names from [Pokemon Vietnamese Crystal](http://tvtropes.org/pmwiki/pmwiki.php/JustForFun/PokemonVietnameseCrystal).
|
|
|
|
In fact, because this is so simple and elegant, you can document code like this
|
|
inline.
|
|
|
|
## Command Tutorial
|
|
|
|
In this file we describe an example command `TEST`. `TEST` will return some
|
|
information about the place the command is used as well as explain the
|
|
arguments involved.
|
|
|
|
Because Tetra is a polyglot of Lua, Moonscript and Go, the relevant Go objects
|
|
will have their type definitions linked to on [godoc](http://godoc.org)
|
|
|
|
Declaring commands is done with the `Command` macro. It takes in two arguments.
|
|
|
|
1. The command verb
|
|
2. The command function
|
|
|
|
It also can take in 3 arguments if the command needs to be restricted to IRCops
|
|
only.
|
|
|
|
1. The command verb
|
|
2. `true`
|
|
3. The command function
|
|
|
|
The command function can have up to 3 arguments set when it is called. These
|
|
are:
|
|
|
|
1. The [Client](https://godoc.org/github.com/Xe/Tetra/bot#Client) that
|
|
originated the command call.
|
|
2. The [Destination](https://godoc.org/github.com/Xe/Tetra/bot#Targeter) or
|
|
where the command was sent to. This will be a Client if the target is an
|
|
internal client or
|
|
a [Channel](https://godoc.org/github.com/Xe/Tetra/bot#Channel) if the target
|
|
is a channel.
|
|
3. The command arguments as a string array.
|
|
|
|
```moonscript
|
|
Command "TEST", (source, destination, args) ->
|
|
```
|
|
|
|
All scripts have `client` pointing to the pseudoclient that the script is
|
|
spawned in. If the script name is `chatbot/8ball`, the value of `client` will
|
|
point to the `chatbot` pseudoclient.
|
|
|
|
```moonscript
|
|
client.Notice source, "Hello there!"
|
|
```
|
|
|
|
This will send a `NOTICE` to the source of the command saying "Hello there!".
|
|
|
|
```moonscript
|
|
client.Notice source, "You are #{source.Nick} sending this to #{destination.Target!} with #{#args} arguments"
|
|
```
|
|
|
|
All command must return a string with a message to the user. This is a good
|
|
place to do things like summarize the output of the command or if it worked or
|
|
not. If the command is oper-only, this will be the message logged to the
|
|
services snoop channel.
|
|
|
|
```moonscript
|
|
"End of TEST output"
|
|
```
|
|
|
|
See? That easy.
|
|
|
|
```moonscript
|
|
Command "TEST", ->
|
|
"Hello!"
|
|
```
|
|
|
|
This is much better than Cod's
|
|
|
|
```python
|
|
#All modules have a name and description
|
|
NAME="Test module"
|
|
DESC="Small example to help you get started"
|
|
|
|
def initModule(cod):
|
|
cod.addBotCommand("TEST", testbotCommand)
|
|
|
|
def destroyModule(cod):
|
|
cod.delBotCommand("TEST")
|
|
|
|
def testbotCommand(cod, line, splitline, source, destination):
|
|
"A simple test command"
|
|
return "Hello!"
|
|
```
|