TurtleDigitServerUserCount

local td = require "turtledigit"

local function main()
  local link = require "link"

  local tPast = {toggle = 3}
  local iWaitTime = 60
  local iWaitInMins = iWaitTime / 60
  local iNum = "0"
  local iFails = 0

  local function loadData(sFilename)
    local h = io.open(sFilename, 'r')
    if not h then
      return {toggle = 3}
    else
      local sTmp = textutils.unserialize(h:read("*a"))
      h:close()
      return sTmp
    end
  end

  local function saveData(sFilename, sData)
    local h = io.open(sFilename, 'w')
    if not h then
      error("Failed to open file for writing.")
    else
      h:write(textutils.serialize(sData)):close()
    end
  end

  local function wait(iSeconds)
    iSeconds = math.floor(iSeconds)
    local x, y = term.getCursorPos()
    local mx, _ = term.getSize()
    local sClearLine = string.rep(' ', mx - x)
    local function wrt(sData, bClear)
      if not bClear then
        wrt(sClearLine, true)
      end
      term.setCursorPos(x, y)
      term.write(tostring(sData))
    end

    for i = iSeconds, 1, -1 do
      wrt(i)
      os.sleep(1)
    end
    wrt(0)
    print()
  end

  -- main control loop
  tPast = loadData("/PAST.dat")
  while true do
    if tPast.toggle >= 3 then
      -- get the invite
      local h = http.get(link)
      if h then
        -- read the invite if we acquired it.
        local sData = h.readAll()
        h.close()

        -- get the number of users from the invite data
        local sNewNum = table.concat({sData:match("with (%d+),?(%d+)")})

        -- if it was valid
        if sNewNum ~= nil then
          -- check which digits changed (if any)
          local sOld = string.rep(' ', 4 - #iNum) .. iNum
          local sNew = string.rep(' ', 4 - #sNewNum) .. sNewNum
          local sDiff = ""
          local bChanged = false
          for i = 1, 4 do
            local c1 = sOld:sub(i, i)
            local c2 = sNew:sub(i, i)
            sDiff = sDiff .. (c1 == c2 and " " or "^")
            bChanged = bChanged or c1 ~= c2

            -- send the new digit, even if unchanged.  The turtles will know if they changed or not.
            td.send(i, sNew:sub(i, i))
          end

          -- send info
          print()
          print(string.format("Current: %s", sOld))
          print(string.format("New    : %s", sNew))
          print(string.format("Diff   : %s", sDiff))

          -- set the old value to the current value if changed
          if bChanged then
            iNum = sNewNum
          end

          -- save the value recieved
          table.insert(tPast, 1, tonumber(sNewNum))
          if #tPast > iWaitInMins * 720 then -- if there is more records than one day, delete the extra record.
            table.remove(tPast) -- pop
          end
          saveData("/PAST.dat", tPast)

          -- reset the fail counter
          iFails = 0
        elseif sNewNum == nil then
          -- if it is invalid, increase failures
          iFails = iFails + 1
        end
      else
        -- if we failed to acquire the invite link, increase failures
        iFails = iFails + 1
        print("Failed to get count")
      end

      -- error if we failed 10 times
      if iFails > 10 then
        error("Failed over ten times to update.", 0)
      end
      print("Waiting...")
      wait(iWaitTime)
    elseif tPast.toggle == 2 then
      print("Show Dif")
      local iLast  = tPast[#tPast]
      local iFirst = tPast[1]
      print(string.format("%d (old) vs %d (new)", iLast, iFirst))
      local iColor = 5 -- if first == last, color is blue
      local sDif   = tostring(math.abs(iFirst - iLast))
      local sRep   = string.rep(' ', 4 - (#sDif + 1))
      local sOp    = iFirst == iLast and "=" or iFirst < iLast and "DN" or "UP"
      local sOut   = sRep .. "%" .. sDif
      if iFirst > iLast then
        iColor = 4 -- if first is greater, color is green
      elseif iFirst < iLast then
        iColor = 3 -- if first is less, color is red
      end
      for i = 1, 4 do
        if sOut:sub(i, i) == "%" then
          td.send(i, sOp, iColor)
        else
          td.send(i, sOut:sub(i, i), iColor)
        end
      end
      wait(iWaitTime / 2)
    elseif tPast.toggle == 1 then
      print("Redisplay")
      td.sendWord(tostring(tPast[1]), 2)
      wait(iWaitTime / 2)
    end
    tPast.toggle = tPast.toggle - 1
    if tPast.toggle < 1 then
      tPast.toggle = 3
    end
  end
end

local ok, err = pcall(main)

if not ok then
  printError(err)
  local ecode
  os.sleep(3) -- allow turtles to finish redrawing if just redrawn.
  if err == "Terminated" then
    td.sendWord("E000", 3)
    return
  elseif err == "Failed over ten times to update." then
    td.sendWord("E001", 3)
  else
    td.sendWord("E???", 3)
  end
end
os.sleep(30)
os.reboot()