P7_crypt

verze = "23.0401.R1"
local args = {...}

if #args < 2 then
  print("Usage: lua encrypt.lua <key> <file> [remove_original]")
  return
end

local key = args[1]
local input_file = args[2]
local remove_original = args[3] == "true"

-- check if file is encrypted
local is_encrypted = input_file:sub(-4) == ".pcr"

-- read input file
local file = io.open(input_file, "rb")
if not file then
  print("Error: Input file not found")
  return
end
local input_data = file:read("*all")
file:close()

-- encryption function
local function encrypt(text, key)
  local result = ""
  for i = 1, #text do
    local byte = text:byte(i)
    local key_byte = key:byte((i - 1) % #key + 1)
    result = result .. string.char(bit.bxor(byte, key_byte))
  end
  return result
end

-- decryption function
local function decrypt(ciphertext, key)
  return encrypt(ciphertext, key) -- decryption is just encryption with the same key
end

-- encrypt or decrypt data
local output_data
local output_file
if is_encrypted then
  -- decrypt data
  output_data = decrypt(input_data, key)
  output_file = input_file:sub(1, -5)
else
  -- encrypt data
  output_data = encrypt(input_data, key)
  output_file = input_file .. ".pcr"
end

-- write output file
local file = io.open(output_file, "wb")
if not file then
  return
end
file:write(output_data)
file:close()

-- check if output file was created
if not fs.exists(output_file) then
  return
end

-- remove original file if specified
if remove_original then
  local success, message = fs.delete(input_file)
  if not success then
    return
  end

  -- rename new file
  success, message = fs.move(output_file, input_file)
  if not success then
    return
  end
else
  -- rename new file
  success, message = fs.move(output_file, input_file .. ".new")
  if not success then
    return
  end
end

-- output success message
if is_encrypted then
  print("File decrypted and saved as " .. output_file)
else
  print("File encrypted and saved as " .. output_file)
end