local function proxyFor(name, required)
  local address = component and component.list(name)()
  if not address and required then
    --error("missing component '" .. name .. "'")
  end
  return address and component.proxy(address) or nil
end

local drone = proxyFor("drone", true)
local nav = proxyFor("navigation", true)
local range = 15

local charger = nil
local farm = nil
local storage = nil

local function updateWaypoints()
  for _, w in ipairs(nav.findWaypoints(range)) do
    if w.label == "charger" then
      charger = w
    elseif w.label == "farm" then
      farm = w
    elseif w.label == "storage" then
      storage = w
    end
  end

  if charger == nil or farm == nil or storage == nil then
    error("waypoints missing")
    os.exit()
  end
end

-- Keep track of our own position, relative to our starting position.
local px, py, pz = 0, 0, 0

local function moveTo(x, y, z)
  if type(x) == "table" then
    x, y, z = x[1], x[2], x[3]
  end
  local rx, ry, rz = x - px, y - py, z - pz
  drone.move(rx, ry, rz)
  px, py, pz = x, y, z
end

while true do
  updateWaypoints()
--moveTo(charger.position.x, charger.position.y, charger.position.z)
end