From 2a76d4a960aa29621dc8020f84eee241b41e10c0 Mon Sep 17 00:00:00 2001
From: orwell96 <orwell@bleipb.de>
Date: Tue, 29 May 2018 12:27:02 +0200
Subject: Fix final bugs and to-do's (u.a.save/load system)

---
 advtrains/couple.lua     |  4 +--
 advtrains/helpers.lua    |  4 +--
 advtrains/init.lua       | 65 +++++++++++++----------------------
 advtrains/occupation.lua |  6 ++--
 advtrains/path.lua       | 88 +++++++-----------------------------------------
 advtrains/trainlogic.lua | 75 ++++++++++++++++++++++++++---------------
 advtrains/wagons.lua     | 38 +++++----------------
 7 files changed, 100 insertions(+), 180 deletions(-)

diff --git a/advtrains/couple.lua b/advtrains/couple.lua
index a4eecf4..1aac0b3 100644
--- a/advtrains/couple.lua
+++ b/advtrains/couple.lua
@@ -34,7 +34,7 @@ minetest.register_entity("advtrains:discouple", {
 		return advtrains.pcall(function()
 			local pname = player:get_player_name()
 			if pname and pname~="" and self.wagon then
-				if self.wagon:safe_decouple(pname) then
+				if advtrains.safe_decouple_wagon(self.wagon.id, pname) then
 					self.object:remove()
 				else
 					minetest.add_entity(self.object:getpos(), "advtrains:lockmarker")
@@ -53,7 +53,7 @@ minetest.register_entity("advtrains:discouple", {
 				self.object:remove()
 				return
 			end
-			if not self.wagon:train() and self.wagon:train().velocity > 0 then
+			if not self.wagon:train() or self.wagon:train().velocity > 0 then
 				self.object:remove()
 				return
 			end
diff --git a/advtrains/helpers.lua b/advtrains/helpers.lua
index e060920..ce059de 100644
--- a/advtrains/helpers.lua
+++ b/advtrains/helpers.lua
@@ -37,7 +37,7 @@ advtrains.pos_add_dir = advtrains.dirCoordSet
 
 function advtrains.pos_add_angle(pos, ang)
 	-- 0 is +Z -> meaning of sin/cos swapped
-	return vector.add(pos, {x = -math.cos(ang), y = 0, z = math.sin(ang)})
+	return vector.add(pos, {x = -math.sin(ang), y = 0, z = math.cos(ang)})
 end
 
 function advtrains.dirToCoord(dir)
@@ -103,7 +103,7 @@ function advtrains.yawToClosestConn(yaw, conns)
 	local min_connid, min_diff=1, 10
 	for connid, conn in ipairs(conns) do
 		local yaw1 = advtrains.dir_to_angle(conn.c)
-		local diff = advtrains.minAngleDiffRad(yaw, yaw1)
+		local diff = math.abs(advtrains.minAngleDiffRad(yaw, yaw1))
 		if diff < min_diff then
 			min_connid = connid
 			min_diff = diff
diff --git a/advtrains/init.lua b/advtrains/init.lua
index d68b188..323d55a 100644
--- a/advtrains/init.lua
+++ b/advtrains/init.lua
@@ -41,14 +41,12 @@ function advtrains.pcall(fun)
 	local succ, return1, return2, return3, return4=xpcall(fun, function(err)
 			atwarn("Lua Error occured: ", err)
 			atwarn(debug.traceback())
-			if advtrains.atprint_context_tid_full then
-				advtrains.path_print(advtrains.trains[advtrains.atprint_context_tid_full], atdebug)
+			if advtrains.atprint_context_tid then
+				advtrains.path_print(advtrains.trains[advtrains.atprint_context_tid], atdebug)
 			end
 		end)
 	if not succ then
-		--reload_saves()
-		no_action=true --this does also not belong here!
-		minetest.request_shutdown()
+		reload_saves()
 	else
 		return return1, return2, return3, return4
 	end
@@ -123,6 +121,7 @@ if minetest.settings:get_bool("advtrains_enable_debugging") then
 		--atlog("@@",advtrains.atprint_context_tid,t,...)
 	end
 	dofile(advtrains.modpath.."/debugringbuffer.lua")
+	
 end
 
 function assertt(var, typ)
@@ -185,7 +184,8 @@ dofile(advtrains.modpath.."/log.lua")
 function advtrains.avt_load()
 	local file, err = io.open(advtrains.fpath, "r")
 	if not file then
-		minetest.log("error", " Failed to read advtrains save data from file "..advtrains.fpath..": "..(err or "Unknown Error"))
+		minetest.log("warning", " Failed to read advtrains save data from file "..advtrains.fpath..": "..(err or "Unknown Error"))
+		minetest.log("warning", " (this is normal when first enabling advtrains on this world)")
 	else
 		local tbl = minetest.deserialize(file:read("*a"))
 		if type(tbl) == "table" then
@@ -196,7 +196,7 @@ function advtrains.avt_load()
 				for id, train in pairs(advtrains.trains) do
 					train.id = id
 				end
-				advtrains.wagon_save = tbl.wagon_save
+				advtrains.wagons = tbl.wagon_save
 				advtrains.player_to_train_mapping = tbl.ptmap or {}
 				advtrains.ndb.load_data(tbl.ndb)
 				advtrains.atc.load_data(tbl.atc)
@@ -251,48 +251,30 @@ end
 
 advtrains.avt_save = function(remove_players_from_wagons)
 	--atprint("saving")
-	--No more invalidating.
-	--Instead, remove path a.s.o from the saved table manually
 	
-	-- update wagon saves
-	for _,wagon in pairs(minetest.luaentities) do
-		if wagon.is_wagon and wagon.initialized then
-			wagon:get_staticdata()
-		end
-	end
-	--cross out userdata
-	for w_id, data in pairs(advtrains.wagon_save) do
-		data.name=nil
-		data.object=nil
-		if data.driver then
-			data.driver_name=data.driver:get_player_name()
-			data.driver=nil
-		else
-			data.driver_name=nil
-		end
-		if data.discouple then
-			data.discouple.object:remove()
-			data.discouple=nil
-		end
-		if remove_players_from_wagons then
+	if remove_players_from_wagons then
+		for w_id, data in pairs(advtrains.wagons) do
 			data.seatp={}
 		end
-	end
-	if remove_players_from_wagons then
 		advtrains.player_to_train_mapping={}
 	end
 	
 	local tmp_trains={}
 	for id, train in pairs(advtrains.trains) do
 		--first, deep_copy the train
-		local v=advtrains.save_keys(train, {
-			"last_pos", "last_pos_prev", "movedir", "velocity", "tarvelocity",
-			"trainparts", "savedpos_off_track_index_offset", "recently_collided_with_env",
-			"atc_brake_target", "atc_wait_finish", "atc_command", "atc_delay", "door_open",
-			"text_outside", "text_inside", "couple_lck_front", "couple_lck_back", "line"
-		})
-		--then save it
-		tmp_trains[id]=v
+		if #train.trainparts > 0 then
+			local v=advtrains.save_keys(train, {
+				"last_pos", "last_connid", "last_frac", "velocity", "tarvelocity",
+				"trainparts", "recently_collided_with_env",
+				"atc_brake_target", "atc_wait_finish", "atc_command", "atc_delay", "door_open",
+				"text_outside", "text_inside", "couple_lck_front", "couple_lck_back", "line"
+			})
+			--then save it
+			tmp_trains[id]=v
+		else
+			atwarn("Train",id,"had no wagons left because of some bug. It is being deleted. Wave it goodbye!")
+			advtrains.remove_train(id)
+		end
 	end
 	
 	--versions:
@@ -356,7 +338,7 @@ minetest.register_globalstep(function(dtime_mt)
 		if save_timer<=0 then
 			local t=os.clock()
 			--save
-			--advtrains.save()
+			advtrains.save()
 			save_timer=save_interval
 			atprintbm("saving", t)
 		end
@@ -430,3 +412,4 @@ minetest.register_chatcommand("at_reroute",
 
 local tot=(os.clock()-lot)*1000
 minetest.log("action", "[advtrains] Loaded in "..tot.."ms")
+
diff --git a/advtrains/occupation.lua b/advtrains/occupation.lua
index 99de521..dd0235a 100644
--- a/advtrains/occupation.lua
+++ b/advtrains/occupation.lua
@@ -172,9 +172,9 @@ function o.check_collision(pos, train_id)
 		if ti~=train_id then
 			local idx = t[i+1]
 			local train = advtrains.trains[ti]
-			atdebug("checking train",t[i],"index",idx,"<>",train.index,train.end_index)
+			--atdebug("checking train",t[i],"index",idx,"<>",train.index,train.end_index)
 			if idx >= train.end_index and idx <= train.index then
-				atdebug("collides.")
+				--atdebug("collides.")
 				return true
 			end
 		end
@@ -190,7 +190,7 @@ end
 function o.get_occupations(train, index)
 	local ppos, ontrack = advtrains.path_get(train, index)
 	if not ontrack then
-		atdebug("Train",train.id,"get_occupations requested off-track",index)
+		atwarn("Train",train.id,"get_occupations requested off-track",index)
 		return {}, ppos
 	end
 	local pos = advtrains.round_vector_floor_y(ppos)
diff --git a/advtrains/path.lua b/advtrains/path.lua
index d810fd7..8bdb72b 100644
--- a/advtrains/path.lua
+++ b/advtrains/path.lua
@@ -1,76 +1,6 @@
 -- path.lua
 -- Functions for pathpredicting, put in a separate file. 
 
-function advtrains.conway(midreal, prev, drives_on)--in order prev,mid,return
-	local mid=advtrains.round_vector_floor_y(midreal)
-	
-	local midnode_ok, midconns=advtrains.get_rail_info_at(mid, drives_on)
-	if not midnode_ok then
-		return nil 
-	end
-	local pconnid
-	for connid, conn in ipairs(midconns) do
-		local tps = advtrains.dirCoordSet(mid, conn.c)
-		if tps.x==prev.x and tps.z==prev.z then
-			pconnid=connid
-		end
-	end
-	local nconnid = advtrains.get_matching_conn(pconnid, #midconns)
-	
-	local next, next_connid, _, nextrailheight = advtrains.get_adjacent_rail(mid, midconns, nconnid, drives_on)
-	if not next then
-		return nil
-	end
-	return vector.add(advtrains.round_vector_floor_y(next), {x=0, y=nextrailheight, z=0}), midconns[nconnid].c
-end
-
-function advtrains.pathpredict(id, train, gen_front, gen_back)
-	
-	local maxn=train.path_extent_max or 0
-	while maxn < gen_front do--pregenerate
-		local conway
-		if train.max_index_on_track == maxn then
-			--atprint("maxn conway for ",maxn,train.path[maxn],maxn-1,train.path[maxn-1])
-			conway=advtrains.conway(train.path[maxn], train.path[maxn-1], train.drives_on)
-		end
-		if conway then
-			train.path[maxn+1]=conway
-			train.max_index_on_track=maxn+1
-		else
-			--do as if nothing has happened and preceed with path
-			--but do not update max_index_on_track
-			atprint("over-generating path max to index ",(maxn+1)," (position ",train.path[maxn]," )")
-			train.path[maxn+1]=vector.add(train.path[maxn], vector.subtract(train.path[maxn], train.path[maxn-1]))
-		end
-		train.path_dist[maxn]=vector.distance(train.path[maxn+1], train.path[maxn])
-		maxn=maxn+1
-	end
-	train.path_extent_max=maxn
-	
-	local minn=train.path_extent_min or -1
-	while minn > gen_back do
-		local conway
-		if train.min_index_on_track == minn then
-			--atprint("minn conway for ",minn,train.path[minn],minn+1,train.path[minn+1])
-			conway=advtrains.conway(train.path[minn], train.path[minn+1], train.drives_on)
-		end
-		if conway then
-			train.path[minn-1]=conway
-			train.min_index_on_track=minn-1
-		else
-			--do as if nothing has happened and preceed with path
-			--but do not update min_index_on_track
-			atprint("over-generating path min to index ",(minn-1)," (position ",train.path[minn]," )")
-			train.path[minn-1]=vector.add(train.path[minn], vector.subtract(train.path[minn], train.path[minn+1]))
-		end
-		train.path_dist[minn-1]=vector.distance(train.path[minn], train.path[minn-1])
-		minn=minn-1
-	end
-	train.path_extent_min=minn
-	if not train.min_index_on_track then train.min_index_on_track=-1 end
-	if not train.max_index_on_track then train.max_index_on_track=0 end
-end
-
 -- Naming conventions:
 -- 'index' - An index of the train.path table.
 -- 'offset' - A value in meters that determines how far on the path to walk relative to a certain index
@@ -145,7 +75,7 @@ function advtrains.path_setrestore(train, invert)
 end
 -- Get restore position, connid and frac (in this order) for a train that will originate at the passed index
 -- If invert is set, it will return path_cp and multiply frac by -1, in order to reverse the train there.
-function advtrains.path_getrestore(train, index, invert, tmp)
+function advtrains.path_getrestore(train, index, invert)
 	local idx = index
 	local cns = train.path_cn
 	
@@ -153,7 +83,7 @@ function advtrains.path_getrestore(train, index, invert, tmp)
 		cns = train.path_cp
 	end
 	
-	fli = atfloor(index)
+	local fli = atfloor(index)
 	advtrains.path_get(train, fli)
 	if fli > train.path_trk_f then
 		fli = train.path_trk_f
@@ -161,9 +91,6 @@ function advtrains.path_getrestore(train, index, invert, tmp)
 	if fli < train.path_trk_b then
 		fli = train.path_trk_b
 	end
-	if not tmp then
-	atdebug ("getrestore ",atround(train.index),"calc",atround(index),fli)
-	end
 	return advtrains.path_get(train, fli),
 			cns[fli],
 			(idx - fli) * (invert and -1 or 1)
@@ -195,7 +122,13 @@ end
 function advtrains.path_print(train, printf)
 	printf("i:	CP	Position	Dir	CN		->Dist->")
 	for i = train.path_ext_b, train.path_ext_f do
+		if i==train.path_trk_b then
+			printf("--Back on-track border here--")
+		end
 		printf(i,":	",train.path_cp[i],"	",train.path[i],"	",train.path_dir[i],"	",train.path_cn[i],"		->",train.path_dist[i],"->")
+		if i==train.path_trk_f then
+			printf("--Front on-track border here--")		
+		end
 	end
 end
 
@@ -231,6 +164,7 @@ function advtrains.path_get(train, index)
 		else
 			-- off-track fallback behavior
 			adj_pos = advtrains.pos_add_angle(pos, train.path_dir[pef-1])
+			--atdebug("Offtrack overgenerating(front) at",adj_pos,"index",peb,"trkf",train.path_trk_f)
 			train.path_dir[pef] = train.path_dir[pef-1]
 		end
 		train.path[pef] = adj_pos
@@ -260,6 +194,7 @@ function advtrains.path_get(train, index)
 		else
 			-- off-track fallback behavior
 			adj_pos = advtrains.pos_add_angle(pos, train.path_dir[peb+1] + math.pi)
+			--atdebug("Offtrack overgenerating(back) at",adj_pos,"index",peb,"trkb",train.path_trk_b)
 			train.path_dir[peb] = train.path_dir[peb+1]
 		end
 		train.path[peb] = adj_pos
@@ -326,7 +261,6 @@ function advtrains.path_get_index_by_offset(train, index, offset)
 		idx = idx - 1
 		advtrains.path_get_adjacent(train, idx)
 		if not train.path_dist[idx] then
-			atdebug("second while",idx)
 			for i=-5,5 do
 				atdebug(idx+i,train.path_dist[idx+i])
 			end
@@ -363,6 +297,8 @@ function advtrains.path_clear_unused(train)
 		train.path_dir[i+1] = nil
 		train.path_ext_f = i - 1
 	end
+	train.path_trk_b = math.max(train.path_trk_b, train.path_ext_b)
+	train.path_trk_f = math.min(train.path_trk_f, train.path_ext_f)
 	
 	train.path_req_f = math.ceil(train.index)
 	train.path_req_b = math.floor(train.end_index or train.index)
diff --git a/advtrains/trainlogic.lua b/advtrains/trainlogic.lua
index feb35b5..df3ec92 100644
--- a/advtrains/trainlogic.lua
+++ b/advtrains/trainlogic.lua
@@ -1,7 +1,6 @@
 --trainlogic.lua
 --controls train entities stuff about connecting/disconnecting/colliding trains and other things
 
--- TODO: what should happen when a train has no trainparts anymore?
 
 local benchmark=false
 local bm={}
@@ -68,17 +67,17 @@ advtrains.mainloop_trainlogic=function(dtime)
 	local t=os.clock()
 	
 	for k,v in pairs(advtrains.trains) do
-		advtrains.atprint_context_tid=sid(k)
+		advtrains.atprint_context_tid=k
 		advtrains.train_ensure_init(k, v)
 	end
 	
 	for k,v in pairs(advtrains.trains) do
-		advtrains.atprint_context_tid=sid(k)
+		advtrains.atprint_context_tid=k
 		advtrains.train_step_b(k, v, dtime)
 	end
 	
 	for k,v in pairs(advtrains.trains) do
-		advtrains.atprint_context_tid=sid(k)
+		advtrains.atprint_context_tid=k
 		advtrains.train_step_c(k, v, dtime)
 	end
 	
@@ -242,7 +241,7 @@ function advtrains.train_ensure_init(id, train)
 		advtrains.update_trainpart_properties(id)
 		recalc_end_index(train)
 		
-		atdebug("Train",id,": Successfully restored path at",train.last_pos," connid",train.last_connid," frac",train.last_frac)
+		--atdebug("Train",id,": Successfully restored path at",train.last_pos," connid",train.last_connid," frac",train.last_frac)
 		
 		-- run on_new_path callbacks
 		run_callbacks_new_path(id, train)
@@ -470,8 +469,7 @@ end
 --  asserted to rely on this)
 
 local function tnc_call_enter_callback(pos, train_id)
-	--atprint("instructed to call enter calback")
-
+	--atdebug("tnc enter",pos,train_id)
 	local node = advtrains.ndb.get_node(pos) --this spares the check if node is nil, it has a name in any case
 	local mregnode=minetest.registered_nodes[node.name]
 	if mregnode and mregnode.advtrains and mregnode.advtrains.on_train_enter then
@@ -479,8 +477,7 @@ local function tnc_call_enter_callback(pos, train_id)
 	end
 end
 local function tnc_call_leave_callback(pos, train_id)
-	--atprint("instructed to call leave calback")
-
+	--atdebug("tnc leave",pos,train_id)
 	local node = advtrains.ndb.get_node(pos) --this spares the check if node is nil, it has a name in any case
 	local mregnode=minetest.registered_nodes[node.name]
 	if mregnode and mregnode.advtrains and mregnode.advtrains.on_train_leave then
@@ -493,7 +490,7 @@ advtrains.te_register_on_new_path(function(id, train)
 		old_index = atround(train.index),
 		old_end_index = atround(train.end_index),
 	}
-	atdebug(id,"tnc init",train.index,train.end_index)
+	--atdebug(id,"tnc init",train.index,train.end_index)
 end)
 
 advtrains.te_register_on_update(function(id, train)
@@ -523,7 +520,7 @@ advtrains.te_register_on_create(function(id, train)
 		tnc_call_enter_callback(pos, id)
 		end_index = end_index + 1
 	end
-	atdebug(id,"tnc create",train.index,train.end_index)
+	--atdebug(id,"tnc create",train.index,train.end_index)
 end)
 
 advtrains.te_register_on_remove(function(id, train)
@@ -534,7 +531,7 @@ advtrains.te_register_on_remove(function(id, train)
 		tnc_call_leave_callback(pos, id)
 		end_index = end_index + 1
 	end
-	atdebug(id,"tnc remove",train.index,train.end_index)
+	--atdebug(id,"tnc remove",train.index,train.end_index)
 end)
 
 -- Calculates the indices where the window borders of the occupation windows are.
@@ -570,8 +567,6 @@ local function calc_occwindows(id, train)
 	}
 end
 
---TODO: Collisions!
-
 
 --returns new id
 function advtrains.create_new_train_at(pos, connid, ioff, trainparts)
@@ -590,7 +585,7 @@ function advtrains.create_new_train_at(pos, connid, ioff, trainparts)
 	t.trainparts=trainparts
 	
 	advtrains.trains[new_id] = t
-	atdebug("Created new train:",t)
+	--atdebug("Created new train:",t)
 	
 	advtrains.train_ensure_init(new_id, advtrains.trains[new_id])
 	
@@ -610,7 +605,7 @@ function advtrains.remove_train(id)
 	advtrains.couple_invalidate(train)
 	
 	local tp = train.trainparts
-	atdebug("Removing train",id,"leftover trainparts:",tp)
+	--atdebug("Removing train",id,"leftover trainparts:",tp)
 	
 	advtrains.trains[id] = nil
 	
@@ -635,6 +630,23 @@ function advtrains.add_wagon_to_train(wagon_id, train_id, index)
 	run_callbacks_update(train_id, train)
 end
 
+function advtrains.safe_decouple_wagon(w_id, pname)
+	if not minetest.check_player_privs(pname, "train_operator") then
+		minetest.chat_send_player(pname, "Missing train_operator privilege")
+		return false
+	end
+	local data = advtrains.wagons[w_id]
+	if data.dcpl_lock then
+		minetest.chat_send_player(pname, "Couple is locked (ask owner or admin to unlock it)")
+		return false
+	end
+	atprint("wagon:discouple() Splitting train", data.train_id)
+	local train = advtrains.trains[data.train_id]
+	advtrains.log("Discouple", pname, train.last_pos, train.text_outside)
+	advtrains.split_train_at_wagon(w_id)
+	return true
+end
+
 -- this function sets wagon's pos_in_train(parts) properties and train's max_speed and drives_on (and more)
 function advtrains.update_trainpart_properties(train_id, invert_flipstate)
 	local train=advtrains.trains[train_id]
@@ -692,14 +704,15 @@ local ablkrng = minetest.settings:get("active_block_range")*16
 function advtrains.spawn_wagons(train_id)
 	local train = advtrains.trains[train_id]
 	
-	for i, w_id in ipairs(train.trainparts) do
+	for i = 1, #train.trainparts do
+		local w_id = train.trainparts[i]
 		local data = advtrains.wagons[w_id]
 		if data then
 			if data.train_id ~= train_id then
 				atwarn("Train",train_id,"Wagon #",1,": Saved train ID",data.train_id,"did not match!")
 				data.train_id = train_id
 			end
-			if not data.object or not data.object:getyaw() then
+			if not advtrains.wagon_objects[w_id] or not advtrains.wagon_objects[w_id]:getyaw() then
 				-- eventually need to spawn new object. check if position is loaded.
 				local index = advtrains.path_get_index_by_offset(train, train.index, -data.pos_in_train)
 				local pos   = advtrains.path_get(train, atfloor(index))
@@ -717,6 +730,10 @@ function advtrains.spawn_wagons(train_id)
 					wagon:set_id(w_id)
 				end
 			end
+		else
+			atwarn("Train",train_id,"Wagon #",1,": A wagon with id",w_id,"does not exist! Wagon will be removed from train.")
+			table.remove(train.trainparts, i)
+			i = i - 1
 		end
 	end
 end
@@ -745,6 +762,11 @@ function advtrains.split_train_at_wagon(wagon_id)
 		end
 	end
 	
+	--update train parts
+	advtrains.update_trainpart_properties(old_id)
+	recalc_end_index(train)
+	run_callbacks_update(old_id, train)
+	
 	--create subtrain
 	local newtrain_id=advtrains.create_new_train_at(pos, connid, frac, tp)
 	local newtrain=advtrains.trains[newtrain_id]
@@ -757,11 +779,6 @@ function advtrains.split_train_at_wagon(wagon_id)
 	newtrain.couple_lck_front=false
 	train.couple_lck_back=false
 	
-	--update train parts
-	advtrains.update_trainpart_properties(old_id)
-	recalc_end_index(train)
-	run_callbacks_update(old_id, train)
-	
 end
 
 -- coupling
@@ -778,7 +795,7 @@ local function createcouple(pos, train1, t1_is_front, train2, t2_is_front)
 	le.train_id_2=train2.id
 	le.t1_is_front=t1_is_front
 	le.t2_is_front=t2_is_front
-	atdebug("created couple between",train1.id,t1_is_front,train2.id,t2_is_front)
+	--atdebug("created couple between",train1.id,t1_is_front,train2.id,t2_is_front)
 	if t1_is_front then
 		train1.cpl_front = obj
 	else
@@ -793,7 +810,7 @@ local function createcouple(pos, train1, t1_is_front, train2, t2_is_front)
 end
 
 function advtrains.train_check_couples(train)
-	atdebug("rechecking couples")
+	--atdebug("rechecking couples")
 	if train.cpl_front then
 		if not train.cpl_front:getyaw() then
 			-- objectref is no longer valid. reset.
@@ -806,7 +823,7 @@ function advtrains.train_check_couples(train)
 		for tid, idx in pairs(front_trains) do
 			local other_train = advtrains.trains[tid]
 			advtrains.train_ensure_init(tid, other_train)
-			atdebug(train.id,"front: ",idx,"on",tid,atround(other_train.index),atround(other_train.end_index))
+			--atdebug(train.id,"front: ",idx,"on",tid,atround(other_train.index),atround(other_train.end_index))
 			if other_train.velocity == 0 then
 				if idx>=other_train.index and idx<=other_train.index + CPL_ZONE then
 					createcouple(pos, train, true, other_train, true)
@@ -924,8 +941,12 @@ function advtrains.invert_train(train_id)
 	advtrains.update_trainpart_properties(train_id, true)
 end
 
+-- returns: train id, index of one of the trains that stand at this position.
 function advtrains.get_train_at_pos(pos)
-	return advtrains.occ.get_trains_at(pos)[1]
+	local t = advtrains.occ.get_trains_at(pos)
+	for tid,idx in pairs(t) do
+		return tid, idx
+	end
 end
 
 function advtrains.invalidate_all_paths(pos)
diff --git a/advtrains/wagons.lua b/advtrains/wagons.lua
index 9ee44b2..5a2fffb 100644
--- a/advtrains/wagons.lua
+++ b/advtrains/wagons.lua
@@ -9,6 +9,7 @@
 
 advtrains.wagons = {}
 advtrains.wagon_prototypes = {}
+advtrains.wagon_objects = {}
 
 --
 function advtrains.create_wagon(wtype, owner)
@@ -21,7 +22,7 @@ function advtrains.create_wagon(wtype, owner)
 	wgn.id = new_id
 	---wgn.train_id = train_id   --- will get this via update_trainpart_properties
 	advtrains.wagons[new_id] = wgn
-	atdebug("Created new wagon:",wgn)
+	--atdebug("Created new wagon:",wgn)
 	return new_id
 end
 
@@ -60,9 +61,9 @@ function wagon:set_id(wid)
 	self.initialized = true
 	
 	local data = advtrains.wagons[self.id]
+	advtrains.wagon_objects[self.id] = self.object
 	
-	data.object = self.object
-	atdebug("Created wagon entity:",self.name," w_id",wid," t_id",data.train_id)
+	--atdebug("Created wagon entity:",self.name," w_id",wid," t_id",data.train_id)
 	
 	if self.has_inventory then
 		--to be used later
@@ -196,7 +197,7 @@ function wagon:destroy()
 			if self.discouple then self.discouple.object:remove() end--will have no effect on unloaded objects
 		end
 	end
-	atdebug("[wagon ", self.id, "]: destroying")
+	--atdebug("[wagon ", self.id, "]: destroying")
 	
 	self.object:remove()
 end
@@ -210,7 +211,7 @@ function wagon:on_step(dtime)
 		local data = advtrains.wagons[self.id]
 		
 		if not pos then
-			atdebug("["..self.id.."][fatal] missing position (object:getpos() returned nil)")
+			--atdebug("["..self.id.."][fatal] missing position (object:getpos() returned nil)")
 			return
 		end
 		
@@ -437,7 +438,6 @@ function wagon:on_step(dtime)
 				else
 					train.recently_collided_with_env=true
 					train.velocity=0
-					-- TODO what should happen when a train collides?
 					train.tarvelocity=0
 					self.collision_count=(self.collision_count or 0)+1
 				end
@@ -852,11 +852,7 @@ function wagon:handle_bordcom_fields(pname, formname, fields)
 	end
 	for i, tpid in ipairs(train.trainparts) do
 		if fields["dcpl_"..i] then
-			for _,wagon in pairs(minetest.luaentities) do
-				if wagon.is_wagon and wagon.initialized and wagon.id==tpid then
-					wagon:safe_decouple(pname)										-- TODO: Move this into external function (don't search entity?)
-				end
-			end
+			advtrains.safe_decouple_wagon(tpid, pname)
 		end
 		if i>1 and fields["dcpl_lck_"..i] then
 			local ent = advtrains.wagons[tpid]
@@ -1026,26 +1022,10 @@ function wagon:reattach_all()
 	end
 end
 
-function wagon:safe_decouple(pname)
-	if not minetest.check_player_privs(pname, "train_operator") then
-		minetest.chat_send_player(pname, "Missing train_operator privilege")
-		return false
-	end
-	local data = advtrains.wagons[self.id]
-	if data.dcpl_lock then
-		minetest.chat_send_player(pname, "Couple is locked (ask owner or admin to unlock it)")
-		return false
-	end
-	atprint("wagon:discouple() Splitting train", self.train_id)
-	advtrains.log("Discouple", pname, self.object:getpos(), self:train().text_outside)
-	advtrains.split_train_at_wagon(self.id)--found in trainlogic.lua
-	return true
-end
-
 function advtrains.get_wagon_prototype(data)
 	local wt = data.type
-	if not advtrains.wagon_prototypes[wt] then
-		atprint("Unable to load wagon type",wt,", using placeholder")
+	if not data.type or not advtrains.wagon_prototypes[wt] then
+		atwarn("Unable to load wagon type",wt,", using placeholder")
 		wt="advtrains:wagon_placeholder"
 	end
 	return wt, advtrains.wagon_prototypes[wt]
-- 
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