Stargate_shield

local component = require("component")
local radar = component.radar

local ShieldStatus = true
local whitelist = {"pandorrama","kat3nemar"}
local distance = 5

local function detectPlayer()
  local scan = radar.getPlayers()
  if not scan[1] then
    return("nobodyThere")
  else
    if scan[1].distance < distance then
      return(scan[1].name)
    else
      return("toFarAway")
    end
  end
  os.sleep(1)
end

local function checkAuthority(player)
  if player == "toFarAway" or player == "nobodyThere" then
--    print("no player in range")
  else
--    print("checking authorisation")
    for index, value in pairs(whitelist) do
      if value == player then
        return("GRANTED")
      end
    end
  end
end

local function shieldControl()
  if ShieldStatus == true then
    ShieldStatus = false
    robot.useUp()
    return("deactivating")
  else
    ShieldStatus = true
    robot.useUp()
    return("activating")
  end
end

while true do
  local player = detectPlayer()
  local authorized = checkAuthority(player)
  if authorized == "GRANTED" and ShieldStatus == true then
    shieldControl()
    print("Grant access to player "..player)
  elseif player == "nobodyThere" and ShieldStatus == false then
    shieldControl()
    print("There is currently no player in range")
  elseif player == "toFarAway" and ShieldStatus == false then
    shieldControl()
    print("Player is to far away")
  elseif authorized == nil and ShieldStatus == false then
    shieldControl()
    print("Player "..player.." is not allowed to pass")
  end

  os.sleep(.5)
end