local next = next

function on_active_tick(event)
  local active_mining_drills = storage.active.mining_drills
  local passive_mining_drills = storage.passive.mining_drills

  local miners = table.remove_key(active_mining_drills, event.tick) or {}
  for _, miner in pairs(miners) do
    if miner.valid then
      local status = miner.status
      if status == defines.entity_status.no_minable_resources then
        miner.order_deconstruction(miner.force, nil)
      elseif status ~= defines.entity_status.working then
        passive_mining_drills[miner.unit_number] = miner
        script.on_nth_tick(passive_tick, on_passive_tick)
      end
    end
  end

  if next(active_mining_drills) == nil then
    script.on_nth_tick(active_tick, nil)
    return
  end
end

function on_passive_tick(event)
  local passive_mining_drills = storage.passive.mining_drills

  for id, miner in pairs(passive_mining_drills) do
    if miner.valid then
      local status = miner.status
      if status == defines.entity_status.no_minable_resources then
        miner.order_deconstruction(miner.force, nil)
        passive_mining_drills[id] = nil
      elseif status == defines.entity_status.working then
        passive_mining_drills[id] = nil
      end
    else
      passive_mining_drills[id] = nil
    end
  end

  if next(passive_mining_drills) == nil then
    script.on_nth_tick(passive_tick, nil)
    return
  end
end