View difference between Paste ID: e5072iZj and FhwQc1pk

 local backgroundColor = colors.blue
 local altBackgroundColor = colors.lightBlue
-local greetingOne = "Please choose your"
+local greetingOne = "active link: "
-local greetingTwo = "destination"
+--"Please choose your"
 local greetingTwo = "no active link"
 --"destination"
 local timerDelay = 8
 
 -- computer front points northward
 local dirs = {front="north",left="east",back="south",right="west"}
 local dir = nil
 
 local mon = peripheral.find("monitor")
 
 local chest = nil
 local slot = nil
 
 for i,v in pairs(rs.getSides()) do
   if peripheral.getType(v) == "ender_chest" then
     chest = peripheral.wrap(v)
     dir = dirs[v]
   elseif peripheral.getType(v) == "book_receptacle" then
     slot = peripheral.wrap(v)
   end
 end
 
 if not chest or not dir or not slot or not mon then print("Error while trying to find chest, slot or monitor"); error() end
 
-    if slot.pushItem(dir,1,1) ~= 1 then print("Error while moving book to chest"); error() end
+local chestSlot = nil
 
 function removeActiveBook()
   if slot.getStackInSlot(1) then
 print("remove ",chestSlot)
     if chestSlot then
       if slot.pushItemIntoSlot(dir,1,1,chestSlot) ~=1 then
         if slot.pushItem(dir,1,1) ~= 1 then print("Error while moving book into chest"); error() end
       end
       chestSlot = nil
     else
       if slot.pushItem(dir,1,1) ~= 1 then print("Error while moving book to chest"); error() end
     end
   end
 end
 
 removeActiveBook()
 sleep(1)
 
 local nDest = 4
 local destTable = {}
 local timer = nil
 
 function padStr(str, len)
   if #str > len then do return string.sub(str,1,len) end
   else do return str .. string.rep(' ', len - #str) end
   end
-    if slot.pullItem(dir,destTable[monY - 3],1) ~= 1 then print("Error while moving book to slot") end
+
 
 function waitForTouchEvent()
   repeat
     event, side, monX, monY = os.pullEvent() --"monitor_touch")
     if event == "timer" and side == timer then
       removeActiveBook()
       drawUserInterface()
     end
   until event == "monitor_touch"
   removeActiveBook()
   if nDest > 0 and (monY-3 > 0) and (monY-3 <= nDest) then
-  mon.write(greetingOne)
+    chestSlot = destTable[monY - 3]
-  mon.setCursorPos(1,2)
+    print("place ",chestSlot)
-  mon.write(greetingTwo)
+    if slot.pullItem(dir,chestSlot,1) ~= 1 then chestSlot = nil; print("Error while moving book to slot") end
     timer = os.startTimer(timerDelay)
   end
 end
 
 function drawUserInterface()
   destTable = {}
   local books = chest.getAllStacks()
   local monX, monY = mon.getSize()
   mon.setBackgroundColor(backgroundColor)
   mon.clear()
   mon.setCursorPos(1,1)
   local active = slot.getStackInSlot(1)
   if active and active.rawName == "item.myst.linkbook" then
     mon.write(greetingOne)
     mon.setCursorPos(1,2)
     mon.write(active.destination)
   else
     mon.write(greetingTwo)
   end
   --
   --mon.write(greetingTwo)
   nDest = 0
   local i = 0
   for n,book in pairs(books) do
     if book.rawName == "item.myst.linkbook" then
       i = i + 1
       destTable[i] = n
       mon.setCursorPos(1, i + 3)
       if (i % 2 == 0) then
         mon.setBackgroundColor(altBackgroundColor)
       else
         mon.setBackgroundColor(backgroundColor)
       end
       name = padStr(book.destination,monX)
       mon.write(name)
     end
   end
   if not i then
     mon.setCursorPos(1, 4)
     mon.write("No Entries")
   end
   nDest = #destTable
 end
 
 while true do
   drawUserInterface()
   waitForTouchEvent()
 end