How can I remove multi-line (Lua) comments in a bash script?

I'm writing a bash script where I need to strip comments from Lua files, which are formatted:

--like this

foo="bar" --or like this

--[[ or like this ]]

--[[
    or
    like
    this
]]

I know I can use sed 's/--.*$//' ${my_file} to remove the single-line comments, but how can I address the multi-line one? Thanks!