os.loadAPI("/apis/storage")

local db = storage

local pos = {}

for _, k in ipairs({

"X", "Y", "Z", "F"

}) do

local v = db.get(k)

pos[k] = v and v - 0 or 0

end

local function horizontal (s)

local d = 0 == pos.F % 2 and "Z" or "X"

local c = 0 == pos.F % 3 and 1 or -1

pos[d] = pos[d] + c * s

db.set(d, pos[d])

end

function forward () horizontal(1) end

function back () horizontal(-1) end

local function turn (d)

pos.F = (pos.F + 4 + d) % 4

db.set("F", pos.F)

end

function turnRight () turn(1) end

function turnLeft () turn(-1) end

local function vertical (s)

pos.Y = pos.Y + s

db.set("Y", pos.Y)

end

function up () vertical(1) end

function down () vertical(-1) end

get = {

["X"] = function () return pos.X end,

["Y"] = function () return pos.Y end,

["Z"] = function () return pos.Z end,

["F"] = function () return pos.F end

}

function setHome ()

for i, d in ipairs({

"X", "Y", "Z", "F"

}) do

pos[d] = 0

db.set(d, 0)

end

end

function hook ()

local t = turtle

if t.position then return false end

t.position = {}

for i, v in ipairs({

"forward", "back", "up", "down",

"turnLeft", "turnRight"

}) do

t.position[v] = t[v]

t[v] = function ()

local ret = t.position[v]()

if ret then position[v]() end

return ret

end

end

return true

end