Generate a new nickname when it is in use or erroneous and check the

provided nickname for validity

handlers.lua

@@ -79,6 +79,17 @@ handlers["NICK"] = function(o, prefix, newnick)
 	end
 end
 
+local function needNewNick(o, prefix, target, badnick)
+	local newnick = o.nickGenerator(badnick)
+	o:send("NICK %s", newnick)
+end
+
+-- ERR_ERRONEUSNICKNAME (Misspelt but remains for historical reasons)
+handlers["432"] = needNewNick
+
+-- ERR_NICKNAMEINUSE
+handlers["433"] = needNewNick
+
 --NAMES list
 handlers["353"] = function(o, prefix, me, chanType, channel, names)
 	if o.track_users then

init.lua

@@ -31,14 +31,16 @@ function meta_preconnect.__index(o, k)
 	return v
 end
 
-function new(user)
+function new(data)
 	local o = {
-		nick = assert(user.nick, "Field 'nick' is required");
+		nick = assert(data.nick, "Field 'nick' is required");
-		username = user.username or "lua";
+		username = data.username or "lua";
-		realname = user.realname or "Lua owns";
+		realname = data.realname or "Lua owns";
+		nickGenerator = data.nickGenerator or defaultNickGenerator;
 		hooks = {};
 		track_users = true;
 	}
+	assert(checkNick(o.nick), "Erroneous nickname passed to irc.new")
 	return setmetatable(o, meta_preconnect)
 end
 

util.lua

@@ -1,9 +1,12 @@
 local setmetatable = setmetatable
+local sub = string.sub
+local byte = string.byte
 local char = string.char
 local table = table
 local assert = assert
 local tostring = tostring
 local type = type
+local random = math.random
 
 module "irc"
 
@@ -107,3 +110,27 @@ local underlineByte = char(31)
 function underline(text)
 	return underlineByte..text..underlineByte
 end
+
+function checkNick(nick)
+	return nick:find("^[a-zA-Z_%-%[|%]%^{|}`][a-zA-Z0-9_%-%[|%]%^{|}`]*$") ~= nil
+end
+
+function defaultNickGenerator(nick)
+	-- LuaBot -> LuaCot -> LuaCou -> ...
+	-- We change a random charachter rather than appending to the
+	-- nickname as otherwise the new nick could exceed the ircd's
+	-- maximum nickname length.
+	local randindex = random(1, #nick)
+	local randchar = sub(nick, randindex, randindex)
+	local b = byte(randchar)
+	b = b + 1
+	if b < 65 or b > 125 then
+		b = 65
+	end
+	-- Get the halves before and after the changed character
+	local first = sub(nick, 1, randindex - 1)
+	local last = sub(nick, randindex + 1, #nick)
+	nick = first..char(b)..last  -- Insert the new charachter
+	return nick
+end
+