Quarry control

function mine(d)
  if (d=="stop") then
    redstone.setOutput("bottom",false)
    redstone.setOutput("front",true)
  elseif (d=="start") then
    redstone.setOutput("bottom",true)
    redstone.setOutput("front",false)
  end
end

while true do
  event = os.pullEvent()
  if event == "redstone" then
    if redstone.getInput("back")==true then

      print("Back redstone")

      mine("stop")

      sleep(5)
      for i=1,8 do
        print(i)
        redstone.setOutput("left",true)
        sleep(0.9)
        redstone.setOutput("left",false)
        sleep(0.9)
      end

      mine("start")

    elseif redstone.getInput("top")==true then

      print("Top redstone")

      mine("stop")

      sleep(5)

      a=true
      while a==true do
        ev = os.pullEvent()
        if ev=="redstone" then
          if redstone.getInput("top")==false then
            a=false
          end
        end
      end

      mine("start")

    end
  end
end