Question

I’m trying to program an addon for WoW (in lua). It’s a chat filter based on specific words. I can’t figure out how to get the array of these words to be case insensitive, so that any upper/lower case combination of the word matches the array. Any ideas would be greatly appreciated. Thanks!

local function wordFilter(self,event,msg)
local keyWords = {"word","test","blah","here","code","woot"}
local matchCount = 0;
    for _, word in ipairs(keyWords) do
            if (string.match(msg, word,)) then
            matchCount = matchCount + 1;
        end
    end
    if (matchCount > 1) then
            return false;
    else
        return true;
    end
end

Answer 1

1. Define keyWords outside of function. Otherwise you’re recreating
   table every time just to thorw it away moments latter, wasting time
   on both creation and GC.
2. Convert keyWords to patter that match
   both upper and lower case letters.
3. You don’t need captured data
   from string, so use string.find for speed.
4. According to your
   logic, if you’ve got more than one match you signal ‘false’. Since
   you need only 1 match, you don’t need to count them. Just return
   false as soon as you hit it. Saves you time for checking all
   remaining words too. If later you decide you want more than one
   match, you still better check it inside loop and return as soon as
   you’ve reached desired count.

5. Don’t use ipairs. It’s slower than simple for loop from 1 to array length and ipairs is deprecated in Lua 5.2 anyway.

   local keyWords = {"word","test","blah","here","code","woot"}
   local caselessKeyWordsPatterns = {}
   
   local function letter_to_pattern(c)
       return string.format("[%s%s]", string.lower(c), string.upper(c))
   end
   
   for idx = 1, #keyWords do
       caselessKeyWordsPatterns[idx] = string.gsub(keyWords[idx], "%a", letter_to_pattern)
   end
   
   local function wordFilter(self, event, msg)
       for idx = 1, #caselessKeyWordsPatterns  do
           if (string.find(msg, caselessKeyWordsPatterns[idx])) then
               return false
           end
       end
       return true
   end
   
   local _
   print(wordFilter(_, _, 'omg wtf lol'))
   print(wordFilter(_, _, 'word man'))
   print(wordFilter(_, _, 'this is a tEsT'))
   print(wordFilter(_, _, 'BlAh bLAH Blah'))
   print(wordFilter(_, _, 'let me go'))
   

Result is:

true
false
false
false
true