-- autorouting for pneumatic tubes

local function in_table(table,element)
	for _,el in ipairs(table) do
		if el==element then return true end
	end
	return false
end

local function is_tube(nodename)
	return in_table(pipeworks.tubenodes,nodename)
end

if pipeworks == nil then
	pipeworks = {}
end

--a function for determining which side of the node we are on
local function nodeside(node, tubedir)
	if node and (node.param2 < 0 or node.param2 > 23) then node.param2 = 0 end

	--get a vector pointing back
	local backdir = minetest.facedir_to_dir(node.param2)

	--check whether the vector is equivalent to the tube direction; if it is, the tube's on the backside
	if backdir.x == tubedir.x and backdir.y == tubedir.y and backdir.z == tubedir.z then
		return "back"
	end

	--check whether the vector is antiparallel with the tube direction; that indicates the front
	if backdir.x == -tubedir.x and backdir.y == -tubedir.y and backdir.z == -tubedir.z then
		return "front"
	end

	--facedir is defined in terms of the top-bottom axis of the node; we'll take advantage of that
	local topdir = ({[0]={x=0, y=1, z=0},
	{x=0, y=0, z=1},
	{x=0, y=0, z=-1},
	{x=1, y=0, z=0},
	{x=-1, y=0, z=0},
	{x=0, y=-1, z=0}})[math.floor(node.param2/4)]

	--is this the top?
	if topdir.x == tubedir.x and topdir.y == tubedir.y and topdir.z == tubedir.z then
		return "top"
	end

	--or the bottom?
	if topdir.x == -tubedir.x and topdir.y == -tubedir.y and topdir.z == -tubedir.z then
		return "bottom"
	end

	--we shall apply some maths to obtain the right-facing vector
	local rightdir = {x=topdir.y*backdir.z - backdir.y*topdir.z,
	y=topdir.z*backdir.x - backdir.z*topdir.x,
	z=topdir.x*backdir.y - backdir.x*topdir.y}

	--is this the right side?
	if rightdir.x == tubedir.x and rightdir.y == tubedir.y and rightdir.z == tubedir.z then
		return "right"
	end

	--or the left?
	if rightdir.x == -tubedir.x and rightdir.y == -tubedir.y and rightdir.z == -tubedir.z then
		return "left"
	end

	--we should be done by now; initiate panic mode
	minetest.log("error", "nodeside has been confused by its parameters; see pipeworks autoplace_tubes.lua, line 78")
end

local function tube_autoroute(pos)
	local active = {0, 0, 0, 0, 0, 0}
	local nctr = minetest.get_node(pos)
	if not is_tube(nctr.name) then return end

	local adjustments = {
		{ x=-1, y=0, z=0 },
		{ x=1, y=0, z=0  },
		{ x=0, y=-1, z=0 },
		{ x=0, y=1, z=0  },
		{ x=0, y=0, z=-1 },
		{ x=0, y=0, z=1 }
	}
	-- xm = 1, xp = 2, ym = 3, yp = 4, zm = 5, zp = 6

	local positions = {}
	local nodes = {}
	for i,adj in ipairs(adjustments) do
		positions[i] = {x=pos.x+adj.x, y=pos.y+adj.y, z=pos.z+adj.z}
		nodes[i] = minetest.get_node(positions[i])
	end

	for i,node in ipairs(nodes) do
		local idef = minetest.registered_nodes[node.name]
		-- handle the tubes themselves
		if is_tube(node.name) then
			active[i] = 1
		-- handle new style connectors
		elseif idef.tube and idef.tube.connect_sides then
			local dir = adjustments[i]
			if idef.tube.connect_sides[nodeside(node, {x=-dir.x, y=-dir.y, z=-dir.z})] then active[i] = 1 end
		end
	end

	-- all sides checked, now figure which tube to use.

	local nsurround = ""
	for i,n in ipairs(active) do
		nsurround = nsurround .. n
	end
	local newname = string.sub(nctr.name, 1, -7)..nsurround
	if newname == nctr.name then return end
	nctr.name = newname
	minetest.swap_node(pos, nctr)
end

function pipeworks.scan_for_tube_objects(pos)
	if pos == nil then return end
	tube_autoroute({ x=pos.x-1, y=pos.y  , z=pos.z   })
	tube_autoroute({ x=pos.x+1, y=pos.y  , z=pos.z   })
	tube_autoroute({ x=pos.x  , y=pos.y-1, z=pos.z   })
	tube_autoroute({ x=pos.x  , y=pos.y+1, z=pos.z   })
	tube_autoroute({ x=pos.x  , y=pos.y  , z=pos.z-1 })
	tube_autoroute({ x=pos.x  , y=pos.y  , z=pos.z+1 })
	tube_autoroute(pos)
end

minetest.register_on_placenode(function(pos, newnode, placer, oldnode, itemstack)
	if minetest.registered_items[newnode.name]
	  and minetest.registered_items[newnode.name].tube
	  and minetest.registered_items[newnode.name].tube.connect_sides then
		pipeworks.scan_for_tube_objects(pos)
	end
end)

minetest.register_on_dignode(function(pos, oldnode, digger)
	if minetest.registered_items[oldnode.name]
	  and minetest.registered_items[oldnode.name].tube
	  and minetest.registered_items[oldnode.name].tube.connect_sides then
		pipeworks.scan_for_tube_objects(pos)
	end
end)