trees = 8
spacing = 3


function checkIfSlotIsItem(slot, name)
    local sslot = turtle.getSelectedSlot()
    turtle.select(slot)
    local item = turtle.getItemDetail(slot)
    if item ~= nil then
        turtle.select(sslot)
        return item["name"] == name
    end
    return false
end

function findItem(name)
    for slot = 1, 16 do
        if checkIfSlotIsItem(slot, name) then
            return slot
        end
    end
    return -1
end

function checkIfHaveItem(name)
    return findItem(name) ~= -1
end

function findEmpty()
    for slot = 1, 16 do
        local count = turtle.getItemCount(slot)
        if count == 0 then
          return slot
        end
    end
    return -1
end


function plant_or_harvest()
  local isthere, data = turtle.inspect()
  if isthere then
    if data["name"] == "minecraft:spruce_log" then
      local cslot = findItem("minecraft:spruce_log")
      if cslot == -1 then
        cslot = findEmpty()
      end
      turtle.select(cslot)
      turtle.dig()
      turtle.forward()
      while turtle.detectUp() do
        turtle.digUp()
        turtle.up()
      end
      while not turtle.detectDown() do
        turtle.down()
      end
      turtle.back()
      plant_or_harvest()
    end
  else
    local sapling = findItem("minecraft:spruce_sapling")
    if sapling ~= -1 then
      turtle.select(sapling)
      turtle.place()
      turtle.select(1)
    end
  end

end


while true do
  if turtle.getFuelLevel() < 100 then
    turtle.suckDown()
    local fSlot = findItem("minecraft:charcoal")
    if fSlot ~= -1 then
      turtle.refuel(turtle.getItemCount(fSlot))
    else
      print("Ran out of Fuel!")
      break
    end
  end
  turtle.forward()
  turtle.forward()
  turtle.turnRight()
  for n = 1, trees do
    turtle.turnLeft()
    plant_or_harvest()
    turtle.select(1)
    turtle.suck()
    turtle.turnRight()
    if n ~= trees then
      for i = 1, spacing do
        turtle.forward()
      end
    end
  end
  turtle.turnLeft()
  turtle.turnLeft()
  for n = 1, trees do
    for i = 1, spacing do
      turtle.turnRight()
      turtle.suck()
      turtle.turnLeft()
      turtle.turnLeft()
      turtle.suck()
      turtle.turnRight()
      turtle.forward()
      turtle.suck()
    end
  end
  for i = 1, spacing do
    turtle.back()
  end
  turtle.turnLeft()
  turtle.forward()
  turtle.forward()
  local cslot = findItem("minecraft:spruce_log")
  if cslot == -1 then
    cslot = findEmpty()
  end
  turtle.select(cslot)
  turtle.drop()
  turtle.select(1)
  turtle.turnLeft()
  turtle.turnLeft()
  sleep(60)
end