OC Logistics Robot MK1 Updater

-- Logistics Robot Update
-- Program to be run first on a wireless-capable computer with an updated "/home/LRobot.lua" file, then on a wireless-capable robot within range to receive that file.

local component = require("component")
local event = require("event")
local m = component.modem -- get primary modem component
local fs = require("filesystem")
local term = require("term")

local PORT = 10

local argv = {...}

local mode = "receive" -- "send" or "receive"
if argv[1] == "send" then
    mode = "send"
end

local signal_strength = tonumber(argv[2])

local function writeFile(path, data_string)
    local f_h = fs.open(path, "w")
    f_h:write(data_string)
    f_h:close()
end

local function getMessage()
    local _, _, from, port, _, message = event.pull("modem_message")
    return message
end

m.open(PORT)
m.setStrength(signal_strength)

if mode == "send" then
    print("Preparing to send file...")
    local max_send_length = 250
    if not fs.exists("/home/LRobot.lua") then
        print("ERROR: No such file '/home/LRobot.lua!'")
        os.exit()
    end
    local send_h = fs.open("/home/LRobot.lua", "r")

    local send_total_length = fs.size("/home/LRobot.lua")
    local total_sent = 0

    local next_send_length = 0
    local next_send_string = ""
    local function getNextSendString()
        next_send_length = math.min(max_send_length, send_total_length - total_sent)
        next_send_string = send_h:read(next_send_length)
    end

    getNextSendString()
    while total_sent < send_total_length do
        term.clear()
        local broadcast_status = m.broadcast(PORT, next_send_string)
        if not broadcast_status then
            print("ERROR: Couldn't broadcast!")
            os.exit()
        end
        local msg = getMessage()
        if msg == "next" then
            total_sent = total_sent + next_send_length
            getNextSendString()
        end
        if total_sent == 0 then
            print("Waiting for receiver to accept data...")
        else
            print("Sending File. (" .. tostring(math.floor(((total_sent / send_total_length) * 100) * 100) / 100) .. "%)")
        end
        os.sleep(1)
    end
    term.clear()

    m.broadcast(PORT, "DOWNLOAD_END")

    print("File sent successfully!")

    send_h:close()
elseif mode == "receive" then
    local received_data = ""

    local data_end = false
    while not data_end do
        term.clear()
        print("Listening...")
        local msg = getMessage()
        if msg then
            if msg == "DOWNLOAD_END" then
                data_end = true
            else
                received_data = received_data .. msg
                print("Packet Received!")
                m.broadcast(PORT, "next")
            end
        else
            print("Waiting for next packet...")
        end
        os.sleep(1)
    end

    writeFile("/home/LRobot.lua", received_data)
    print("Download Complete!")
end

m.close(PORT)