--advtrains by orwell96, see readme.txt

advtrains.dir_trans_tbl={
	[0]={x=0, z=1},
	[1]={x=1, z=2},
	[2]={x=1, z=1},
	[3]={x=2, z=1},
	[4]={x=1, z=0},
	[5]={x=2, z=-1},
	[6]={x=1, z=-1},
	[7]={x=1, z=-2},
	[8]={x=0, z=-1},
	[9]={x=-1, z=-2},
	[10]={x=-1, z=-1},
	[11]={x=-2, z=-1},
	[12]={x=-1, z=0},
	[13]={x=-2, z=1},
	[14]={x=-1, z=1},
	[15]={x=-1, z=2},
}

function advtrains.dirCoordSet(coord, dir)
	local x,z
	if advtrains.dir_trans_tbl[dir] then
		x,z=advtrains.dir_trans_tbl[dir].x, advtrains.dir_trans_tbl[dir].z
	else
		error("advtrains: in helpers.lua/dirCoordSet() given dir="..(dir or "nil"))
	end
	return {x=coord.x+x, y=coord.y, z=coord.z+z}
end
function advtrains.dirToCoord(dir)
	return advtrains.dirCoordSet({x=0, y=0, z=0}, dir)
end

function advtrains.maxN(list, expectstart)
	local n=expectstart or 0
	while list[n] do
		n=n+1
	end
	return n-1
end

function advtrains.minN(list, expectstart)
	local n=expectstart or 0
	while list[n] do
		n=n-1
	end
	return n+1
end

--vertical_transmit:
--[[
rely1, rely2 tell to which height the connections are pointed to. 1 means it will go up the next node

]]

function advtrains.conway(midreal, prev, drives_on)--in order prev,mid,return
	local mid=advtrains.round_vector_floor_y(midreal)
	
	local midnode_ok, middir1, middir2, midrely1, midrely2=advtrains.get_rail_info_at(mid, drives_on)
	if not midnode_ok then
		return nil 
	end
	
	local next, chkdir, chkrely, y_offset
	y_offset=0
	--atprint("[advtrains] in order mid1,mid2",middir1,middir2)
	--try if it is dir1
	local cor1=advtrains.dirCoordSet(mid, middir2)--<<<<
	if cor1.x==prev.x and cor1.z==prev.z then--this was previous
		next=advtrains.dirCoordSet(mid, middir1)
		if midrely1>=1 then
			next.y=next.y+1
			--atprint("[advtrains]found midrely1 to be >=1: next is now "..(next and minetest.pos_to_string(next) or "nil"))
			y_offset=1
		end
		chkdir=middir1
		chkrely=midrely1
		--atprint("[advtrains]dir2 applied next pos:",minetest.pos_to_string(next),"(chkdir is ",chkdir,")")
	end
	--dir2???
	local cor2=advtrains.dirCoordSet(mid, middir1)--<<<<
	if math.floor(cor2.x+0.5)==math.floor(prev.x+0.5) and math.floor(cor2.z+0.5)==math.floor(prev.z+0.5) then
		next=advtrains.dirCoordSet(mid, middir2)--dir2 wird überprüft, alles gut.
		if midrely2>=1 then
			next.y=next.y+1
			--atprint("[advtrains]found midrely2 to be >=1: next is now "..(next and minetest.pos_to_string(next) or "nil"))
			y_offset=1
		end
		chkdir=middir2
		chkrely=midrely2
		--atprint("[advtrains] dir2 applied next pos:",minetest.pos_to_string(next),"(chkdir is ",chkdir,")")
	end