--
-- Helper functions
--

cart_func = {}

function cart_func:get_sign(z)
	if z == 0 then
		return 0
	else
		return z/math.abs(z)
	end
end

-- Returns the velocity as a unit vector
-- The smaller part of the vector will be turned to 0
function cart_func:velocity_to_dir(v)
	if math.abs(v.x) > math.abs(v.z) then
		return {x=cart_func:get_sign(v.x), y=cart_func:get_sign(v.y), z=0}
	else
		return {x=0, y=cart_func:get_sign(v.y), z=cart_func:get_sign(v.z)}
	end
end

function cart_func:is_rail(p)
	local nn = minetest.get_node(p).name
  --print("*!* is_rail p x=",p.x," y=",p.y," z=",p.z," nn=",nn," group rail=", minetest.get_item_group(nn, "rail"))
  if nn == "ignore" then
    nn=cart_func:get_content_voxel(p)
    print("carts: is_rail hit ignore, trying again with get_content: now nn=",nn," group rail=", minetest.get_item_group(nn, "rail"),"p x=",p.x," y=",p.y," z=",p.z)
  end
	return minetest.get_item_group(nn, "rail") ~= 0
end

function cart_func:check_rail_in_direction(pos, dir)
	local p = cart_func.v3:add(pos, dir)
	if cart_func:is_rail(p) then
		return true
	else
    return false
	end
end -- cart:check_rail_in_direction


function cart_func:is_int(z)
	z = math.abs(z)
	return math.abs(math.floor(z+0.5)-z) <= 0.1
end

cart_func.v3 = {}

function cart_func.v3:add(v1, v2)
	return {x=v1.x+v2.x, y=v1.y+v2.y, z=v1.z+v2.z}
end

function cart_func.v3:copy(v)
	return {x=v.x, y=v.y, z=v.z}
end

function cart_func.v3:round(v)
	return {
		x = math.floor(v.x+0.5),
		y = math.floor(v.y+0.5),
		z = math.floor(v.z+0.5),
	}
end

function cart_func.v3:equal(v1, v2)
	return v1.x == v2.x and v1.y == v2.y and v1.z == v2.z
end


function cart_func:get_content_voxel(pos)
    local t1 = os.clock()
    local vm = minetest.get_voxel_manip()
    local pos1, pos2 = vm:read_from_map(vector.add(pos, {x=-1,y=-1,z=-1}),vector.add(pos, {x=1,y=1,z=1}))
    local a = VoxelArea:new{
        MinEdge=pos1,
        MaxEdge=pos2,
    }

    local data = vm:get_data()
    local vi = a:indexp(pos)
    local railid = data[vi]
    local real_name = minetest.get_name_from_content_id(railid)
    print(string.format("voxel-ing rail: elapsed time: %.2fms", (os.clock() - t1) * 1000))
    return real_name
end