local monitor = peripheral.wrap("right")
local sFile = "MessageBoardLog.txt"
local w, h = monitor.getSize()
local sLog = {}


function writeCenter(sString, yPos)
   x = math.floor((w / 2) - (#sString / 2))
   monitor.setCursorPos(x, yPos)
   monitor.write(sString)
end

function saveLog()
   local sFile = "MessageBoardLog.txt"
   if fs.exists(sFile) then
           local hRead = assert(fs.open(sFile, "r")) -- assert will error for us if we can't open the file.
           hRead.close() -- Close the handle! This is extremely important, as not doing so can cause errors when writin/opening the file.
   end

   hWrite = fs.open(sFile, "w") -- w for write! Note that this will also clear the file.
   hWrite.write(textutils.serialize(sLog))
   hWrite.close()

   return
end

function loadLog()
   if fs.exists(sFile) == true then
      local file = fs.open(sFile,"r")
      local data = file.readAll()
      file.close()
      sLog = textutils.unserialize(data)
      for i=1,#sLog do
         print(sLog[i])
         writeLine( sLog[i] )
      end
   else
      print("file does not exist, check path..")
   end
end

function addMessage()
   shell.run("clear")
   print ("Enter Message")
   local input = read()
   table.insert(sLog, input)
   writeLine(input)
   saveLog()
end

function writeLine(text)
  local _,row=monitor.getCursorPos()
  local _,height=monitor.getSize()

   --write the line
   monitor.write(text)
   --move to next row
   row=row+1
   --if this went off the screen, scroll

   --set to start of next line
   monitor.setCursorPos(1,row)
end

monitor.clear()
loadLog()
while true do
   addMessage()
end