goto

local tArgs = {...}
local x, y, z, f
local xCur, yCur, zCur, fCur
local xDif, yDif, zDif
local posIn, posOut, pos

local function syncFile()
  posOut = io.open("data/pos.txt", "w")
  posOut:write(textutils.serialize({xCur, yCur, zCur, fCur}))
  posOut:close()
end

local function abort(msg)
  syncFile()
  print("ERROR: "..msg)
  do return end
end

local function up(n)
  for i = 1, n do
    while not turtle.up() do
      turtle.digUp()
    end
    yCur = yCur + 1
    syncFile()
  end
end

local function down(n)
  for i = 1, n do
    while not turtle.down() do
      turtle.digDown()
    end
    yCur = yCur - 1
    syncFile()
  end
end

local function moveF(dir, n)
  while fCur ~= dir do
    turtle.turnLeft()
    if dir < 0 or dir > 3 then
      do return end
    end
    if fCur ~= 0 then
      fCur = fCur - 1
    else
      fCur = 3
    end
    syncFile()
  end
  for i = 1, n do
    while not turtle.forward() do
      up()
    end
    if fCur == 0 then
      zCur = zCur + 1
    elseif fCur == 1 then
      xCur = xCur - 1
    elseif fCur == 2 then
      zCur = zCur - 1
    elseif fCur == 3 then
      xCur = xCur + 1
    else
      abort("invalid state for fCur")
    end
    syncFile()
  end
end

if not tArgs[1] or not tArgs[2] or not tArgs[3] then
  print("Usage: goto <x> <y> <z> [<f>]")
  do return end
end

x = tonumber(tArgs[1])
y = tonumber(tArgs[2])
z = tonumber(tArgs[3])

if tArgs[4] then
  f = tonumber(tArgs[4])
end

posIn = io.open("data/pos.txt", "r")
pos = posIn:read()
posIn:close()

pos = textutils.unserialize(pos)

xCur = tonumber(pos[1])
yCur = tonumber(pos[2])
zCur = tonumber(pos[3])
fCur = tonumber(pos[4])

xDif = x - xCur
zDif = z - zCur

if xDif < 0 then
  xDif = xDif * -1
  moveF(1, xDif)
else
  moveF(3, xDif)
end

if zDif < 0 then
  zDif = zDif * -1
  moveF(2, zDif)
else
  moveF(0, zDif)
end

yDif = y - yCur

if yDif < 0 then
  yDif = yDif * -1
  down(yDif)
else
  up(yDif)
end

if f then
  moveF(f, 0)
end

syncFile()