local function sign(v)
	return v > 0 and 1 or (v == 0 and 0 or -1)
end

do -- Robot state
	local turtleState = {
		position = {x = 85, y = 66, z = 165},
		orientation = {x = 0, z = -1},
	}

	local _turtleForward = turtle.forward
	turtle.forward = function()
		turtleState.position.x = turtleState.position.x + turtleState.orientation.x
		turtleState.position.z = turtleState.position.z + turtleState.orientation.z

		return _turtleForward()
	end

	local _turtleBack = turtle.back
	turtle.back = function(...)
		turtleState.position.x = turtleState.position.x - turtleState.orientation.x
		turtleState.position.z = turtleState.position.z - turtleState.orientation.z

		return _turtleBack(...)
	end

	local _turtleUp = turtle.up
	turtle.up = function(...)
		turtleState.position.y = turtleState.position.y + 1

		return _turtleUp(...)
	end

	local _turtleDown = turtle.down
	turtle.down = function(...)
		turtleState.position.y = turtleState.position.y - 1

		return _turtleDown(...)
	end

	local _turtleTurnLeft = turtle.turnLeft
	turtle.turnLeft = function(...)
		local oldOrientationX = turtleState.orientation.x
		local oldOrientationZ = turtleState.orientation.z

		turtleState.orientation.x =  oldOrientationZ
		turtleState.orientation.z = -oldOrientationX

		return _turtleTurnLeft(...)
	end

	local _turtleTurnRight = turtle.turnRight
	turtle.turnRight = function(...)
		local oldOrientationX = turtleState.orientation.x
		local oldOrientationZ = turtleState.orientation.z

		turtleState.orientation.x = -oldOrientationZ
		turtleState.orientation.z =  oldOrientationX

		return _turtleTurnRight(...)
	end

	turtle.getPosition = function()
		return turtleState.position.x, turtleState.position.y, turtleState.position.z
	end

	turtle.getOrientation = function()
		return turtleState.orientation.x, turtleState.orientation.z
	end

	turtle.orientX = function(targetX)
		if (turtleState.orientation.x == targetX) then
			return
		end

		if (turtleState.orientation.x == -targetX) then
			turtle.turnLeft()
			turtle.turnLeft()

			return
		end

		if (turtleState.orientation.z == targetX) then
			turtle.turnLeft()

			return
		end

		if (turtleState.orientation.z == -targetX) then
			turtle.turnRight()

			return
		end
	end

	turtle.orientZ = function(targetZ)
		if (turtleState.orientation.z == targetZ) then
			return
		end

		if (turtleState.orientation.z == -targetZ) then
			turtle.turnLeft()
			turtle.turnLeft()

			return
		end

		if (turtleState.orientation.x == targetZ) then
			turtle.turnRight()

			return
		end

		if (turtleState.orientation.x == -targetZ) then
			turtle.turnLeft()

			return
		end
	end

	turtle.gotoX = function(targetX)
		local dx = targetX - turtleState.position.x

		if (dx == 0) then
			return
		end

		turtle.orientX(sign(dx))

		for i = 1, math.abs(dx) do
			turtle.forward()
		end
	end

	turtle.gotoZ = function(targetZ)
		local dz = targetZ - turtleState.position.z

		if (dz == 0) then
			return
		end

		turtle.orientZ(sign(dz))

		for i = 1, math.abs(dz) do
			turtle.forward()
		end
	end
end

local function harvest()
	for i = 1, 7 do
		turtle.forward()
	end

	turtle.gotoX(73)
	turtle.gotoZ(156)
end

harvest()

local x, y, z = turtle.getPosition()
print(x, y, z)

local ox, oz = turtle.getOrientation()
print(ox, oz)