Caesar lib - OpenComputers

local caesar = {}

function caesar.convert(Text,Action,Shift)
 local function Check(C) --Checker For Check If Current Letters Is A-Z or a-z .
 if string.byte(C) >= 65 and string.byte(C) <= 90 then
   return "U" --string.upper
 elseif string.byte(C) >= 97 and string.byte(C) <= 122 then
  return "L" --string.lower
 end
end
Shift = Shift%26
if Shift == 0 then Shift = 26 end
local Enc = function (a,b)
  local Byte = (string.byte(a)-b+Shift)%26
    if Byte == 0 then Byte = 26 end
  return string.char(Byte+b)
end
local Dec = function (a,b)
    local Byte = (string.byte(a)-b-Shift)%26
    if Byte == 0 then Byte = 26 end
  return string.char(Byte+b)
end
local E , Activity = ""
if tostring(Action) == "Enc" then
Activity = Enc
elseif tostring(Action) == "Dec" then
Activity = Dec
else
print("Error : Action Not Selected")
os.exit()
end
for I = 1,#Text do
  local C = string.sub(Text,I,I)
  local Checked = Check(C)
  if Checked == "U" then
     E = E..Activity(C,64)
 elseif Checked == "L" then
           E = E..Activity(C,96)
 else
 E = E..C
  end
 end
  return E
end



return caesar