Chat Command Builder

Introduction

This chapter will show you how to make complex chat commands with ChatCmdBuilder, such as /msg <name> <message>, /team join <teamname> or /team leave <teamname>.

Note that ChatCmdBuilder is a library created by the author of this book, and most modders tend to use the method outlined in the chat commnds chapter.

  • Why ChatCmdBuilder?
  • Routes.
  • Subcommand functions.
  • Installing ChatCmdBuilder.
  • Admin complex command.

Why ChatCmdBuilder?

Traditionally mods implemented these complex commands using Lua patterns.

local name = string.match(param, "^join ([%a%d_-]+)")

I however find Lua patterns annoying to write and unreadable. Because of this, I created a library to do this for you.

ChatCmdBuilder.new("sethp", function(cmd)
    cmd:sub(":target :hp:int", function(name, target, hp)
        local player = minetest.get_player_by_name(target)        
        if player then
            player:set_hp(hp)
            return true, "Killed " .. target
        else
            return false, "Unable to find " .. target
        end
    end)
end, {
    description = "Set hp of player",
    privs = {
        kick = true
        -- ^ probably better to register a custom priv
    }
})

ChatCmdBuilder.new(name, setup_func, def) creates a new chat command called name. It then calls the function passed to it (setup_func), which then creates sub commands. Each cmd:sub(route, func) is a sub command.

A sub command is a particular response to an input param. When a player runs the chat command, the first sub command that matches their input will be run, and no others. If no subcommands match, then the user will be told of the invalid syntax. For example, in the above code snippet if a player types something of the form /sethp username 12 then the function passed to cmd:sub will be called. If they type /sethp 12 bleh, then a wrong input message will appear.

:name :hp:int is a route. It describes the format of the param passed to /teleport.

Routes

A route is made up of terminals and variables. Terminals must always be there. For example, join in /team join :username :teamname. The spaces also count as terminals.

Variables can change value depending on what the user types. For example, :username and :teamname.

Variables are defined as :name:type. The name is used in the help documentation. The type is used to match the input. If the type is not given, then the type is word.

Valid types are:

  • word - default. Any string without spaces.
  • int - Any integer/whole number, no decimals.
  • number - Any number, including ints and decimals.
  • pos - 1,2,3 or 1.1,2,3.4567 or (1,2,3) or 1.2, 2 ,3.2
  • text - Any string. There can only ever be one text variable, no variables or terminals can come afterwards.

In :name :hp:int, there are two variables there:

  • name - type of word as no type is specified. Accepts any string without spaces.
  • hp - type of int

Subcommand functions

The first argument is the caller’s name. The variables are then passed to the function in order.

cmd:sub(":target :hp:int", function(name, target, hp)
    -- subcommand function
end)

Installing ChatCmdBuilder

The source code can be found and downloaded on Github.

There are two ways to install:

  1. Install ChatCmdBuilder as a mod and depend on it.
  2. Include the init.lua file in ChatCmdBuilder as chatcmdbuilder.lua in your mod, and dofile it.

Admin complex command

Here is an example that creates a chat command that allows us to do this:

  • /admin kill <username> - kill user
  • /admin move <username> to <pos> - teleport user
  • /admin log <username> - show report log
  • /admin log <username> <message> - log to report log
local admin_log
local function load()
    admin_log = {}
end
local function save()
    -- todo
end
load()

ChatCmdBuilder.new("admin", function(cmd)
    cmd:sub("kill :name", function(name, target)
        local player = minetest.get_player_by_name(target)
        if player then
            player:set_hp(0)
            return true, "Killed " .. target
        else
            return false, "Unable to find " .. target
        end
    end)

    cmd:sub("move :name to :pos:pos", function(name, target, pos)
        local player = minetest.get_player_by_name(target)
        if player then
            player:setpos(pos)
            return true, "Moved " .. target .. " to " ..
                    minetest.pos_to_string(pos)
        else
            return false, "Unable to find " .. target
        end
    end)

    cmd:sub("log :username", function(name, target)
        local log = admin_log[target]
        if log then
            return true, table.concat(log, "\n")
        else
            return false, "No entries for " .. target
        end
    end)

    cmd:sub("log :username :message", function(name, target, message)
        local log = admin_log[target] or {}
        table.insert(log, message)
        admin_log[target] = log
        save()
        return true, "Logged"
    end)
end, {
    description = "Admin tools",
    privs = {
        kick = true,
        ban = true
    }
})
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