Lua - String/Comment Parser

local rules = {
    {"%-%-%[(=*)%[.-%]%1%]","COMMENT"};
    {"%-%-.-\n","COMMENT"};
    {"['\"]","START"};
    {"%[(=*)%[.-%]%1%]","LONGSTRING"};
    {"[^%[-'\"]+","OTHER"};
}

local function parse(source)
    local result,i = {},1
    local function parser()
        if i == #source + 1 then return end
        for k,v in pairs(rules) do
            local a,b = source:find(v[1],i)
            if a == i then i = b+1
                return v[2],source:sub(a,b),a
            end
        end error("No rule found at pos "..i,0)
    end
    for typ,part,start in parser do
        --print(typ,part,start)
        if typ == "START" then local st = start+1
            local a,b = source:find("\\*"..part,st)
            while a do st = b + 1
                if (b-a)%2==0 then a=nil break end
                a,b = source:find("\\*"..part,st)
            end
            if b and not a then i = b+1
                local str = source:sub(start,b)
                -- print"hi" will make 'str' be "hi" (including quotes)
                table.insert(result,"(sandboxstring"..str..")")
            else
                error("Couldn't find closing quote thingy starting at pos "..start,0)
            end
        elseif typ == "LONGSTRING" then
            table.insert(result,"(sandboxstring"..part..")")
        elseif typ == "COMMENT" then
            -- ignore? idk. Could parse javadocs or whatever for fun
        else
            table.insert(result,part)
        end
    end
    return table.concat(result)
end

local code = parse[==========[
print"pls"
print'hi'
-- comment that'll get ignored
print[==[
    long
    bananas
]==]
--[[
    This one gets ignored too, yeuy!
--]]
print[[not-so-long bananas with " and ' quotes and [=[this thing]=] ]]
print("Ah putting ' in here works fine")
print("Putting \" with backslash works fine too")
]==========]

print(code)
assert(loadstring(code))






--[[ START OF RESULT
print(sandboxstring"pls")
print(sandboxstring'hi')
print(sandboxstring[==[
    long
    bananas
]==])

print(sandboxstring[[not-so-long bananas with " and ' quotes and [=[this thing]=] ]])
print((sandboxstring"Ah putting ' in here works fine"))
print((sandboxstring"Putting \" with backslash works fine too"))
--]] END OF RESULT