tg_server_name = "tg_server"

local args = {...}

local function split(str, divider)
    local t = {}
    for part in string.gmatch(str, "([^" .. divider .. "]+)") do
        table.insert(t, part)
    end
    return t
end

local function establish_connection()
    local peripherals = peripheral.getNames()
    for _, side in ipairs(peripherals) do
        if peripheral.getType(side) == "modem" then
            rednet.open(side)
            return true
        end
    end
    return false
end

function validate_clearance(computer_id, clearance_level)
    if establish_connection() then
        tg_server_id = rednet.lookup('tg', tg_server_name)
        rednet.send(tg_server_id, "validate_clearance,"..computer_id..","..clearance_level,"tg")
        local id, msg, proto = rednet.receive("tg")
        if msg == "granted" then
            return true
        else
            return false, "authentication failed"
        end
    else
        return false, "modem not found"
    end
end

function validate_key(minimum_clearance)
    if establish_connection() then
        if fs.exists("/disk/key") then
            local key_file = fs.open("/disk/key","r")
            local key = key_file.readLine()
            tg_server_id = rednet.lookup('tg', tg_server_name)
            rednet.send(tg_server_id, "validate_key,"..key..","..minimum_clearance, "tg")
            local id, msg, _ = rednet.receive("tg")
            if msg == "authentication successful" then
                return true
            else
                return false, "authentication error: "..msg
            end
        else
            return false, "key file not found"
        end
    else
        return false, "modem not found"
    end
end

function authenticate()
    if fs.exists('/disk/key') then
        local key_file = fs.open('/disk/key', 'r')
        local key = key_file.readLine()
        if establish_connection() then
            tg_server_id = rednet.lookup("tg", tg_server_name)
            rednet.send(tg_server_id, "authenticate,"..key,"tg")
            local id, msg, proto = rednet.receive("tg")

            if msg == "authentication successful" then
                local key_parts = split(key,',')
                local card_holder = key_parts[1]
                local card_clearance = key_parts[2]
                return true, _, card_holder, card_clearance
            else
                print("Authentication failed.")
                return false, "authentication failed"
            end
        else
            return false, "modem not found"
        end
        key_file.close()
    else
        print("Key file not found. Aborting.")
        return false, "key file not found"
    end
end

if args[1] == "auth" or args[1] == "authenticate" then
    local success, error, card_holder, card_clearance = authenticate()
    if success then
        print("Authentication was successful.")
        print("Hello "..card_holder..", you were granted clearance level "..card_clearance.." for this computer.")
    else
        print("Authentication failed: "..error)
    end
end