receive

--Turtle-side Shop App
local w,h=term.getSize()

function receiveAll()
  id,sumChar,prot=rednet.receive("shop")
  id,cartItemsSerial,prot=rednet.receive("shop")
end

function processPackage()
  sum=tonumber(sumChar)
  cartItems=textutils.unserialize(cartItemsSerial)
end

function writeSum()
  term.setCursorPos(26,1)
  term.setTextColor(colors.red)
  term.write("    ")
  term.setCursorPos(26,1)
  term.write(sum)
end

function rednetGetInfo()
  rednet.open("left")
  receiveAll()
  processPackage()
  rednet.close("left")
end

function checkPayment()
  turtle.select(4)
  turtle.suck()
  turtle.select(1)
  if turtle.compareTo(4)==true then
    turtle.drop()
  end
  turtle.select(4)
  turtle.drop()
  turtle.select(1)
end

function buttonCheck()
  while true do
    local event,button,x,y=os.pullEvent("mouse_click")
    if ((x>=(w-8) and x<=(w)) and y==1) then
      checkPayment()
      break
    end
    if ((x>=(w-8) and x<=(w)) and y==3) then
      break
    end
  end
end

function terminalSetup()
  term.clear()
  term.setTextColor(colors.lightBlue)
  term.setCursorPos(1,1)
  term.write("Your Total Amount Due is:          ")
  term.setCursorPos(w-8,1)
  term.setTextColor(colors.white)
  term.setBackgroundColor(colors.lime)
  term.write(" SUBMIT ")
  term.setCursorPos(w-8,3)
  term.setBackgroundColor(colors.red)
  term.write(" CANCEL ")
  term.setBackgroundColor(colors.black)
  term.setCursorPos(1,3)
  term.setTextColor(colors.white)
  term.write("Place payment in the top-left ")
  term.setCursorPos(1,4)
  term.write("slot of the turtle. Then click")
  term.setCursorPos(1,5)
  term.write("either SUBMIT or CANCEL to tell")
  term.setCursorPos(1,6)
  term.write("the turtle to proceed to it's  ")
  term.setCursorPos(1,7)
  term.write("item gathering and payment pro-")
  term.setCursorPos(1,8)
  term.write("cessing. Please be patient.")
  term.setTextColor(colors.blue)
  term.setBackgroundColor(colors.gray)
  for i=1,w do
    term.setCursorPos(i,2)
    term.write("-")
  end
  term.setBackgroundColor(colors.black)
  term.setCursorPos(1,9)
end

terminalSetup()
while true do
  rednetGetInfo()
  writeSum()
  buttonCheck()
end