pipeworks/autoplace_tubes.lua

-- autorouting for pneumatic tubes

function tube_scanforobjects(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

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

function is_tube(nodename)
	return in_table(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 not tubedir or
	   not node or
	   not (type(node.param2) == "number" and node.param2 > 0 and node.param2 < 23) then
		return "back"
	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

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.

    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
    local meta=minetest.get_meta(pos)
    local meta0=meta:to_table() -- XXX: hacky_swap_node
    nctr.name = newname
    minetest.add_node(pos, nctr)
    local meta=minetest.get_meta(pos)
    meta:from_table(meta0)
	local nctr = minetest.get_node(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
		tube_scanforobjects(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
		tube_scanforobjects(pos)
	end
end)