arg = {...}

length = arg[1]
height = arg[2]

cSlot = 1
slots = 16
turtle.select(13)
turtle.refuel()
turtle.select(1)

if (length == nil or height == nil) then
print ("Usage: wall <length> <heigth>")
return
end

function empty()
  if (turtle.getItemCount(slots) == 0) then
    print(string.format("I am empty. Please load more mats in slot %d to continue.", slots))
    while (turtle.getItemCount(slots) == 0 ) do
      sleep(1)
    end
  end
  if (turtle.getItemCount(cSlot) == 0) then
    cSlot = cSlot + 1
    turtle.select(cSlot)
  end
end

function plcUp()
  if (turtle.detectUp()) then
    turtle.digUp()
  end
  turtle.placeUp()
end
function plcDown()
  if (turtle.detectDown()) then
    turtle.digDown()
  end
  turtle.placeDown()
end
function plcBehind()
  turtle.turnRight()
  turtle.turnRight()
  turtle.place()
  turtle.turnRight()
  turtle.turnRight()
end

for i=0, (height/3-1), 1 do
  for j=1,(length - 1), 1 do
  empty()
  if (j>1) then
    plcBehind()
  end
  plcUp()
  plcDown()
  turtle.forward()
  end
  plcDown()
  plcBehind()
  turtle.up()
  plcDown()
  turtle.up()
  plcDown()
  turtle.up()
  turtle.turnRight()
  turtle.turnRight()
end
print("\nSurface complete.")