wither

function refuel()
    for i = 1, 16 do -- loop through the slots
      turtle.select(i) -- change to the slot
      turtle.refuel()
    end
end

function fillSand()
    local spaceSand = turtle.getItemSpace(1)
    SandC=peripheral.wrap("right")
    SandC.condenseItems()
    SandC.pushItemIntoSlot("south", 1, spaceSand, 1)
end

function fillSkull()
    local spaceSkull = turtle.getItemSpace(2)
    SkullC=peripheral.wrap("back")
    SkullC.condenseItems()
    SkullC.pushItemIntoSlot("west", 1, spaceSkull, 2)
end

function fillFuel()
    local spaceFuel = turtle.getItemSpace(3)
    FuelC=peripheral.wrap("bottom")
    FuelC.condenseItems()
    FuelC.pushItemIntoSlot("up", 1, spaceFuel, 3)
end

function getSand()
    turtle.select(1)
end

function getSkull()
    turtle.select(2)
end

function findSignal()
    local signalChest = peripheral.wrap("front")
    if signalChest.getStackInSlot(1) ~= nil then
        print ("got signal, time to work")
        return true
    else
        print("no signal, keep looking")
        return false
    end
end

function readySetGo()
    local signal = redstone.getInput("left")
    if signal ~= true and findSignal() then
        print ("lets go!")
        buildWither()
    else
        print ("wither already spawned")
    end
end

function buildWither()
    fillSand()
    fillSkull()
    fillFuel()
    refuel()
    getSand()
    turtle.up()
    turtle.up()
    turtle.up()
    turtle.up()
    turtle.forward()
    turtle.forward()
    turtle.forward()
    turtle.down()
    turtle.down()
    turtle.forward()
    turtle.forward()
    turtle.forward()
    turtle.placeDown()
    turtle.turnLeft()
    turtle.place()
    turtle.turnLeft()
    turtle.turnLeft()
    turtle.place()
    turtle.up()
    turtle.placeDown()
    getSkull()
    turtle.place()
    turtle.turnLeft()
    turtle.turnLeft()
    turtle.place()
    turtle.up()
    turtle.placeDown()
    turtle.turnLeft()
    turtle.forward()
    turtle.down()
    turtle.down()
    turtle.forward()
    turtle.forward()
    turtle.up()
    turtle.up()
    turtle.forward()
    turtle.forward()
    turtle.forward()
    turtle.turnLeft()
    turtle.turnLeft()
    turtle.down()
    turtle.down()
    turtle.down()
    turtle.down()
    print ("wither done")
    os.sleep(10)
end

while true do
    readySetGo()
    os.sleep(5)
end