when placing elevator show where nearest one is

elevator.lua

@@ -2,6 +2,89 @@
 -- The network name is determined automaticly from the position (x/z coordinates).
 -- >utor: Sokomine
 
+travelnet.show_nearest_elevator = function( pos, owner_name, param2 )
+	if( not( pos ) or not(pos.x) or not(pos.z) or not( owner_name )) then
+		return;
+	end
+
+	if( not( travelnet.targets[ owner_name ] )) then
+		minetest.chat_send_player( owner_name, "Congratulations! This is your first elevator."..
+			"You can build an elevator network by placing further elevators somewhere above "..
+			"or below this one. Just make sure that the x and z coordinate are the same.");
+		return;
+	end
+
+	local network_name = tostring( pos.x )..','..tostring( pos.z );
+	-- will this be an elevator that will be added to an existing network?
+	if( travelnet.targets[ owner_name ][ network_name ]
+	  -- does the network have any members at all?
+	  and next( travelnet.targets[ owner_name ][ network_name ], nil )) then
+		minetest.chat_send_player( owner_name, "This elevator will automaticly connect to the "..
+			"other elevators you have placed at diffrent heights. Just enter a station name "..
+			"and click on \"store\" to set it up. Or just punch it to set the height as station "..
+			"name.");
+		return;
+	end
+
+	local nearest_name = "";
+	local nearest_dist = 100000000;
+	local nearest_dist_x = 0;
+	local nearest_dist_z = 0;
+	for network_name, data in pairs( travelnet.targets[ owner_name ] ) do
+		local station_name = next( data, nil );
+		if( station_name and data[ station_name ][ "nr" ] and data[ station_name ].pos) then
+			local station_pos = data[ station_name ].pos;
+			local dist = math.ceil(math.sqrt(
+					  ( station_pos.x - pos.x ) * ( station_pos.x - pos.x )
+					+ ( station_pos.z - pos.z ) * ( station_pos.z - pos.z )));
+			-- find the nearest one; store network_name and (minimal) distance
+			if( dist < nearest_dist ) then
+				nearest_dist = dist;
+				nearest_dist_x = station_pos.x - pos.x;
+				nearest_dist_z = station_pos.z - pos.z;
+				nearest_name = network_name;
+			end
+		end
+	end
+	if( nearest_name ~= "" ) then
+		local text = "Your nearest elevator network is located ";
+		-- in front of/behind
+		if(    (param2==0 and nearest_dist_z>=0)or (param2==2 and nearest_dist_z<=0)) then
+			text = text..tostring( math.abs(nearest_dist_z )).." m behind this elevator and ";
+		elseif((param2==1 and nearest_dist_x>=0)or (param2==3 and nearest_dist_x<=0)) then
+			text = text..tostring( math.abs(nearest_dist_x )).." m behind this elevator and ";
+		elseif((param2==0 and nearest_dist_z< 0)or (param2==2 and nearest_dist_z> 0)) then
+			text = text..tostring( math.abs(nearest_dist_z )).." m in front of this elevator and ";
+		elseif((param2==1 and nearest_dist_x< 0)or (param2==3 and nearest_dist_x> 0)) then
+			text = text..tostring( math.abs(nearest_dist_x )).." m in front of this elevator and ";
+		else text = text.." ERROR ";
+		end
+
+		-- right/left
+		if(    (param2==0 and nearest_dist_x< 0)or (param2==2 and nearest_dist_x> 0)) then
+			text = text..tostring( math.abs(nearest_dist_x )).." m to the left";
+		elseif((param2==1 and nearest_dist_z>=0)or (param2==3 and nearest_dist_z<=0)) then
+			text = text..tostring( math.abs(nearest_dist_z )).." m to the left";
+		elseif((param2==0 and nearest_dist_x>=0)or (param2==2 and nearest_dist_x<=0)) then
+			text = text..tostring( math.abs(nearest_dist_x )).." m to the right";
+		elseif((param2==1 and nearest_dist_z< 0)or (param2==3 and nearest_dist_z> 0)) then
+			text = text..tostring( math.abs(nearest_dist_z )).." m to the right";
+		else text = text.." ERROR ";
+		end
+
+		minetest.chat_send_player( owner_name, text..
+			", located at x="..tostring( pos.x+nearest_dist_x)..
+			", z="..tostring( pos.z+nearest_dist_z)..
+			" This elevator here will start a new shaft/network." );
+	else
+		minetest.chat_send_player( owner_name, "This is your first elevator. It differs from "..
+			"travelnet networks by only allowing movement in vertical direction (up or down). "..
+			"All further elevators which you will place at the same x,z coordinates at differnt "..
+			"heights will be able to connect to this elevator.");
+	end
+end
+
+
 minetest.register_node("travelnet:elevator", {
 	description = "Elevator",
 	drawtype = "mesh",
@@ -59,6 +142,7 @@ minetest.register_node("travelnet:elevator", {
        local p = {x=pos.x, y=pos.y+1, z=pos.z}
        local p2 = minetest.dir_to_facedir(placer:get_look_dir())
        minetest.add_node(p, {name="travelnet:elevator_top", paramtype2="facedir", param2=p2})
+       travelnet.show_nearest_elevator( pos, placer:get_player_name(), p2 );
     end,
     
     on_receive_fields = travelnet.on_receive_fields,

init.lua

@@ -26,6 +26,8 @@
             TNT and DungeonMasters ought to leave travelnets and elevators untouched now.
             Added function to register elevator doors.
             Added elevator doors made out of tin ingots.
+            Provide information about the nearest elevator network when placing a new elevator. This
+              ought to make it easier to find the right spot.
  16.07.17 - Merged several PR from others (Typo, screenshot, documentation, mesecon support, bugfix).
             Added buttons to move stations up or down in the list, independent on when they where added.
             Fixed undeclared globals.