OC Remote Control

-- Remote Control
-- When installed on a computer, that computer can have files transfered to/from it and commands executed.
-- Note that after this program is installed, keyboard input can only be given after a certain command is send to the computer.

-- This program is generally useful as a "boot-loader" kind of program, something to allow the updating and execution of a main program without the need of internet cards or monitor/keyboards.

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

local PORT_FILE = "/home/port.txt"
local PORT = 17

local function readFile(path)
    if not fs.exists(path) then
        return false
    else
        local f_h = fs.open(path, "r")
        local rtn = f_h:read(fs.size(path))
        f_h:close()
        return rtn
    end
end
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
local function sendMessage(msg)
    m.broadcast(PORT, msg)
end

local function sendFile(fileName, fileRaw) -- Copy this function to programs that will communicate with this one. Also copy the getMessage and sendMessage functions.
    local file_length = fileRaw:len()
    local sent_amount = 0

    sendMessage("download:start")
    getMessage()
    sendMessage(fileName)
    getMessage()
    while sent_amount < file_length do
        local send_length = math.min(file_length, sent_amount + 500)
        local send_string = fileRaw:sub(sent_amount + 1, send_length)
        sent_amount = send_length
        sendMessage(send_string)
        print("Sending File (" .. tostring(file_length - sent_amount) .. " bytes remaining)")
        getMessage()
    end
    print("File sent!")
    sendMessage("download:end")
end
local function downloadFile()
    sendMessage("download:name")
    local file_name = getMessage()
    local file_raw = ""
    sendMessage("download:next")
    while true do
        local msg = getMessage()
        if msg == "download:end" then
            break
        else
            file_raw = file_raw .. msg
        end
        sendMessage("download:next")
    end
    writeFile("/home/" .. file_name, file_raw)
end

local argv = {...}

local function init_rc()
    local rc_path = shell.resolve(process.info().path)
    if not string.find(rc_path, ".lua") then
        rc_path = rc_path .. ".lua"
    end
    writeFile("/home/.shrc", rc_path)
    writeFile(PORT_FILE, argv[2])
end

if argv[1] == "init" then
    PORT = tonumber(argv[2])
    init_rc()
else
    if fs.exists(PORT_FILE) then
        PORT = tonumber(readFile(PORT_FILE))
    end
end

m.open(PORT)
m.setStrength(64)

while true do
    local msg = getMessage()
    if msg == "download:start" then
        downloadFile()
    elseif msg == "execute" then
        sendMessage("execute:command")
        shell.execute(getMessage())
    elseif msg == "exit" then
        break
    end
end
print("Remote Control Terminated.")