Realtime file viewer (ComputerCraft)

--[[
 pastebin get uKMMLFYX artie
 std PB uKMMLFYX artie
--]]

local tArg = {...}
local filename = tArg[1]

if not fs.exists(filename) then
    return printError("That doesn't exist")
elseif fs.isDir(filename) then
    return printError("That's a folder, smartass")
end

local scrollX = 1
local scrollY = 1

local scr_x, scr_y = term.getSize()

local fileToTable = function(name)
    if not fs.exists(name) then
        return false, {}
    end
    local output = {}
    local file = fs.open(name,"r")
    local line = ""
    repeat
        line = file.readLine()
        if line then
            output[#output+1] = line
        end
    until not line
    file.close()
    return true, output
end

local zom = function(num)
    return num > 0 and num or 0
end

local t = term.current().setVisible

local render = function(scrollX,scrollY,tbl)
    if t then t(false) end
    for y = 1, scr_y do
        term.setCursorPos(1,y)
        term.clearLine()
        if tbl[y+scrollY] then
            term.write((" "):rep(zom(-(scrollX-1))) ..tbl[y+scrollY]:sub(zom(scrollX)))
        end
    end
    if t then t(true) end
end

local _,contbl

local doIt = function()
    while true do
        _,contbl = fileToTable(filename)
        render(scrollX,scrollY,contbl)
        sleep(0)
    end
end

local scrolling = function()
    while true do
        local evt, key = os.pullEvent("key")
        if key == keys.left then
            scrollX = scrollX - 1
        elseif key == keys.right then
            scrollX = scrollX + 1
        elseif key == keys.up then
            scrollY = scrollY - 1
        elseif key == keys.down then
            scrollY = scrollY + 1
        elseif key == keys.q then
            return
        end
    end
end

parallel.waitForAny(scrolling,doIt)
term.setCursorPos(1,scr_y)
print("")
sleep(0)