games/devtest/mods/testnodes/textures/testnodes_liquidsource_r6.png

--trackplacer.lua
--holds code for the track-placing system. the default 'track' item will be a craftitem that places rails as needed. this will neither place or change switches nor place vertical rails.

--all new trackplacer code
local tp={
	tracks={}
}

function tp.register_tracktype(nnprefix, n_suffix)
	if tp.tracks[nnprefix] then return end--due to the separate registration of slopes and flats for the same nnpref, definition would be overridden here. just don't.
	tp.tracks[nnprefix]={
		default=n_suffix,
		single_conn={},
		single_conn_1={},
		single_conn_2={},
		double_conn={},
		double_conn_1={},
		double_conn_2={},
		--keys:conn1_conn2 (example:1_4)
		--values:{name=x, param2=x}
		twcycle={},
		twrotate={},--indexed by suffix, list, tells order of rotations
		modify={},
	}
end
function tp.add_double_conn(nnprefix, suffix, rotation, conns)
	local nodename=nnprefix.."_"..suffix..rotation
	for i=0,3 do
		tp.tracks[nnprefix].double_conn[((conns.conn1+4*i)%16).."_"..((conns.conn2+4*i)%16)]={name=nodename, param2=i}
		tp.tracks[nnprefix].double_conn[((conns.conn2+4*i)%16).."_"..((conns.conn1+4*i)%16)]={name=nodename, param2=i}
		tp.tracks[nnprefix].double_conn_1[((conns.conn1+4*i)%16).."_"..((conns.conn2+4*i)%16)]={name=nodename, param2=i}
		tp.tracks[nnprefix].double_conn_2[((conns.conn2+4*i)%16).."_"..((conns.conn1+4*i)%16)]={name=nodename, param2=i}
	end
	tp.tracks[nnprefix].modify[nodename]=true
end
function tp.add_single_conn(nnprefix, suffix, rotation, conns)
	local nodename=nnprefix.."_"..suffix..rotation
	for i=0,3 do
		tp.tracks[nnprefix].single_conn[((conns.conn1+4*i)%16)]={name=nodename, param2=i}
		tp.tracks[nnprefix].single_conn[((conns.conn2+4*i)%16)]={name=nodename, param2=i}
		tp.tracks[nnprefix].single_conn_1[((conns.conn1+4*i)%16)]={name=nodename, param2=i}
		tp.tracks[nnprefix].single_conn_2[((conns.conn2+4*i)%16)]={name=nodename, param2=i}
	end
	tp.tracks[nnprefix].modify[nodename]=true
end


function tp.add_worked(nnprefix, suffix, rotation, cycle_follows)
	tp.tracks[nnprefix].twcycle[suffix]=cycle_follows
	if not tp.tracks[nnprefix].twrotate[suffix] then tp.tracks[nnprefix].twrotate[suffix]={} end
	table.insert(tp.tracks[nnprefix].twrotate[suffix], rotation)
end


--[[
	rewrite algorithm.
	selection criteria: these will never be changed or even selected:
	- tracks being already connected on both sides
	- tracks that are already connected on one side but are not bendable to the desired position
	the following situations can occur:
	1. there are two more than two rails around
		1.1 there is one or more subset(s) that can be directly connected
			-> choose the first possibility
		2.2 not
			-> choose the first one and orient straight
	2. there's exactly 1 rail around
		-> choose and orient straight
	3. there's no rail around
		-> set straight
]]

local function istrackandbc(pos_p, conn)
	local tpos = pos_p
	local cnode=minetest.get_node(advtrains.dirCoordSet(tpos, conn.c))
	if advtrains.is_track_and_drives_on(cnode.name, advtrains.all_tracktypes) then
		local cconns=advtrains.get_track_connections(cnode.name, cnode.param2)
		return advtrains.conn_matches_to(conn, cconns)
	end
	--try the same 1 node below
	tpos = {x=tpos.x, y=tpos.y-1, z=tpos.z}
	cnode=minetest.get_node(advtrains.dirCoordSet(tpos, conn.c))
	if advtrains.is_track_and_drives_on(cnode.name, advtrains.all_tracktypes) then
		local cconns=advtrains.get_track_connections(cnode.name, cnode.param2)
		return advtrains.conn_matches_to(conn, cconns)
	end
	return false
end

function tp.find_already_connected(pos)
	local dnode=minetest.get_node(pos)
	local dconns=advtrains.get_track_connections(dnode.name, dnode.param2)
	local found_conn
	for connid, conn in ipairs(dconns) do
		if istrackandbc(pos, conn) then
			if found_conn then --we found one in previous iteration
				return true, true --signal that it's connected
			else
				found_conn = conn.c
			end
		end
	end
	return found_conn
end
function tp.rail_and_can_be_bent(originpos, conn)
ofs	hex dump	ascii
0000	89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52 00 00 00 10 00 00 00 10 08 06 00 00 00 1f f3 ff	.PNG........IHDR................
0020	61 00 00 00 5b 49 44 41 54 78 01 63 60 68 37 d9 8c 82 97 39 a0 60 42 f2 83 d4 00 bf 23 a5 70 1c	a...[IDATx.c`h7....9.`B.....#.p.
0040	be be 08 86 71 18 80 69 23 b2 26 64 c3 b0 b9 08 8f 01 98 36 d2 c6 00 ca bd 40 79 20 12 8e 46 aa	....q..i#.&d.......6.....@y...F.
0060	19 80 ee 3d b2 d2 01 98 66 5e e6 08 c2 64 a5 03 cc 30 21 31 e9 c2 34 92 69 00 e5 2e c0 94 07 00	...=....f^...d...0!1..4.i.......
0080	a9 ce aa 4c f4 b3 28 7f 00 00 00 00 49 45 4e 44 ae 42 60 82	...L..(.....IEND.B`.