Monstrous one-size-fits-all Lua table copy

osfacopy.lua

return function (t,o)
  local refs = {}
  local rk, rv
  if type(o.recurse) == "string" then
    if string.find(o.recurse,'k') then
      rk = true end
    if string.find(o.recurse,'v') then
      rv = true end
  elseif o.recurse then
    rk=true; rv=true
  end
  local mt = o.metatables
  local getmetatable = o.getmetatable or getmetatable
  local setmetatable = o.setmetatable or setmetatable
  
  local copy
  function copy(t)
    if type(t)~="table" then
      return t
    elseif refs[t] then
      return refs[t]
    else
      local c = {}
      refs[t] = c
      for k, v in next, t do
        if rk then
          k = copy(k)
        end
        if rv then
          c[k] = copy(v)
        else
          c[k] = v
        end
      end
      if mt == "reuse" then
        setmetatable(c,getmetatable(t))
      elseif mt == "copy" then
        setmetatable(c,copy(getmetatable(t)))
      end
      return c
    end
  end
end