local pos = {x = 0, y = 0, z = 0, face = 0}

local function addToPos(n)
	if pos.face == Faces.FORWARD then
		pos.z = pos.z + n
	elseif pos.face == Faces.BACK then
		pos.z = pos.z - n
	elseif pos.face == Faces.RIGHT then
		pos.x = pos.x + n
	elseif pos.face == Faces.LEFT then
		pos.x = pos.x - n
	end
end

local function addToFace(n)
	pos.face = (pos.face + n) % 4
	if pos.face < 0 then
		pos.face = 4 + pos.face
	end
end

Faces = {
	FORWARD = 0;
	RIGHT = 1;
	BACK = 2;
	LEFT = 3;
};

function getPos()
	return {
		x = pos.x;
		y = pos.y;
		z = pos.z;
		face = pos.face;
	}
end

function dig()
	while turtle.detect() do turtle.dig() end
end
function digUp()
	while turtle.detectUp() do turtle.digUp() end
end
function digDown()
	while turtle.detectDown() do turtle.digDown() end
end

function right()
	turtle.turnRight()
	addToFace(1)
end
function left()
	turtle.turnLeft()
	addToFace(-1)
end

function forward()
	while not turtle.forward() do end
	addToPos(1)
end
function back()
	while not turtle.back() do end
	addToPos(-1)
end
function up()
	while not turtle.up() do end
	pos.y = pos.y + 1
end
function down()
	while not turtle.down() do end
	pos.y = pos.y - 1
end

function digForwards()
	dig()
	forward()
	digUp()
	digDown()
end

function alterturn(i)
	if i % 2 == 1 then
		right()
	else
		left()
	end
end

function selectItem()
	if turtle.getItemCount(turtle.getSelectedSlot()) > 0 then
		return
	end
	for i = 1, 16 do
		if turtle.getItemCount(i) > 0 then
			turtle.select(i)
			return true
		end
	end
	turtle.select(1)
	return false
end

function turnTo(face)
	if pos.face == 0 and face == 3 or
			pos.face == 1 and face == 0 or
			pos.face == 2 and face == 1 or
			pos.face == 3 and face == 2 then
		left()
	else
		while pos.face ~= face do
			right()
		end
	end
end

function goTo(dest)
	 -- Correct X value
	if dest.x > pos.x then
		turnTo(Faces.RIGHT)
	elseif dest.x < pos.x then
		turnTo(Faces.LEFT)
	end
	for i = 1, math.abs(dest.x - pos.x) do
		forward()
	end

	 -- Correct Z value
	if dest.z > pos.z then
		turnTo(Faces.FORWARD)
	elseif dest.z < pos.z then
		turnTo(Faces.BACK)
	end
	for i = 1, math.abs(dest.z - pos.z) do
		forward()
	end

	 -- Correct Y value
	while dest.y > pos.y do up() end
	while dest.y < pos.y do down() end

	 -- Correct facing
	turnTo(dest.face)
end