-- Run this on a separate computer to display a log on an attached monitor.

-- This program expects a 6x6 monitor to be connected at the back,
-- a bell at the bottom and an ender modem at the right.

local monitor = peripheral.wrap("back")
local modem = peripheral.wrap("right")
local bell_side = "bottom"
local port = 12345

local height = 38

local messages = {}
local totalMsgs = 0

modem.open(port)

function bell()
  redstone.setOutput(bell_side, true)
  sleep(0.1)
  redstone.setOutput(bell_side, false)
end

function clear()
  monitor.clear()
  monitor.setCursorPos(1, 1)
  monitor.setTextScale(1)
end

function writeLine(text)
  local x, y = monitor.getCursorPos()
  monitor.setCursorPos(1, y + 1)
  monitor.write(text)
end

function refresh()
  clear()
  
  monitor.setCursorPos(27, 1)
  monitor.setTextColor(colors.blue)
  monitor.write("Event log")
  monitor.setTextColor(colors.white)
  
  monitor.setCursorPos(1, 2)

  if table.getn(messages) == 0 then
    monitor.setCursorPos(22, height / 2)
    monitor.setTextColor(colors.lightGray)
    monitor.write("Nothing here yet ...")
    monitor.setTextColor(colors.white)
  else    
    for k,v in pairs(messages) do
      writeLine(v)
    end
    monitor.setCursorPos(1, 1)
    monitor.setTextColor(colors.lightGray)
    monitor.write(totalMsgs.." total")
    monitor.setTextColor(colors.white)
  end
end

refresh()

while true do
  local event, side, channel, replyChannel, message,
    distance = os.pullEvent("modem_message")
  
  table.insert(messages, message)
  totalMsgs = totalMsgs + 1

  while table.getn(messages) > height do
    table.remove(messages, 1)
  end
  
  bell()
  refresh()
end