EStack

local event_stack = {}
local output = ""
local ticks = 0
local block = false

local function getLines(dir)
    if fs.exists(dir) then
        local file = fs.open(dir, "r")
        local lines = {}
        local line = file.readLine()
        while line ~= nil do
            lines[#lines + 1] = line
            line = file.readLine()
        end
        file.close()
        return lines
    else
        return {}
    end
end

local function writeLines(dir, lines)
    if #lines > 0 then
        if fs.exists(dir) then fs.delete(dir) end
        local file = fs.open(dir, "a")
        local tick = 0
        for i=1,#lines do
            file.writeLine(lines[i])
            tick = tick + 1
            if tick > 100 then
                tick = 0
                sleep(0)
            end
        end
        file.close()
        return true
    else
        return false
    end
end

local function getFirst(line, char)
    local index = -1
    for i=1,string.len(line) do
        local c = line:sub(i, i)
        if c == char and index == -1 then index = i end
    end
    return index
end

local function flushStack()
    local lines = getLines(output)
    for i=1,#event_stack do
        local event = event_stack[i]
        local ev = ""
        for i=2,#event do
            if ev == "" then ev = type(event[i])..","..event[i] else ev = ev..";"..type(event[i])..","..event[i] end
        end
        local nln = event[1]..";"..ev
        if #lines > 0 then
            local index = getFirst(lines[#lines], "@")
            if index ~= -1 then
                if (lines[#lines]:sub(index+1, -1) == nln) then
                    lines[#lines] = (tonumber(lines[#lines]:sub(1, index-1))+1).."@"..lines[#lines]:sub(index+1, -1)
                else
                    lines[#lines + 1] = "1@"..nln
                end
            else
                lines[#lines + 1] = "1@"..nln
            end
        else
            lines[#lines + 1] = "1@"..nln
        end
    end
    if writeLines(output, lines) then
        event_stack = {}
    end
end


old_eventPull = os.pullEvent
new_eventPull = function(args)
    local event, p1, p2, p3 = old_eventPull(args)
    detectToggle(event, p1)
    event_stack[#event_stack + 1] = {event, p1, p2, p3}
    ticks = ticks + 1
    if ticks > 100 then
        ticks = 0
        flushStack()
    end
    return event, p1, p2, p3
end

old_eventRawPull = os.pullEventRaw
new_eventRawPull = function()
    local event, p1, p2, p3 = old_eventRawPull()
    detectToggle(event, p1)
    event_stack[#event_stack + 1] = {event, p1, p2, p3}
    ticks = ticks + 1
    if ticks > 100 then
        ticks = 0
        flushStack()
    end
    return event, p1, p2, p3
end

local function revert()
    flushStack()
    os.pullEvent = old_eventPull
    os.pullEventRaw = old_eventRawPull
    event_stack = {}
    ticks = 0
    block = true
    print("Ended recording, flushed to: "..output)
    output = ""
end

local function start()
    if not block then
        print("Output?")
        output = read()
        print("Target program?")
        local pname = read()
        print("F12 to toggle, loading program...")
        sleep(1)
        os.pullEvent = new_eventPull
        os.pullEventRaw = new_eventRawPull
        os.run({}, pname)
    end
end

function detectToggle(event, p1)
    if event == "key" and p1 == 88 then
        if output ~= "" then revert() else start() end
    end
end

start()