Implement collisions. (does not work yet, still code errors)

4 files changed, 221 insertions, 213 deletions

diff --git a/advtrains/couple.lua b/advtrains/couple.lua
index 7e99571..b09961f 100644
--- a/advtrains/couple.lua
+++ b/advtrains/couple.lua
@@ -61,15 +61,12 @@ minetest.register_entity("advtrains:discouple", {
 	end,
 })
 
---advtrains:couple
---when two trains overlap with their end-positions, this entity will be spawned and both trains set its id into appropiate fields for them to know when to free them again. The entity will destroy automatically when it recognizes that any of the trains left the common position. 
---[[fields
-train_id_1
-train_id_2
-train1_is_backpos
-train2_is_backpos
-]]
-
+-- advtrains:couple
+-- Couple entity 
+local function lockmarker(obj)
+	minetest.spawn_entity(obj:get_pos(), "advtrains.lockmarker")
+	obj:remove()
+end
 
 minetest.register_entity("advtrains:couple", {
 	visual="sprite",
@@ -99,30 +96,61 @@ minetest.register_entity("advtrains:couple", {
 			if type(clicker)~="string" then pname=clicker:get_player_name() end
 			if not minetest.check_player_privs(pname, "train_operator") then return end
 			
+			local train1=advtrains.trains[self.train_id_1]
+			local train2=advtrains.trains[self.train_id_2]
+			advtrains.train_ensure_init(self.train_id_1, train1)
+			advtrains.train_ensure_init(self.train_id_2, train2)
+			
 			local id1, id2=self.train_id_1, self.train_id_2
-			if self.train1_is_backpos and not self.train2_is_backpos then
-				advtrains.do_connect_trains(id1, id2, clicker)
-				--case 2 (second train is front)
-			elseif self.train2_is_backpos and not self.train1_is_backpos then
-				advtrains.do_connect_trains(id2, id1, clicker)
-				--case 3 
-			elseif self.train1_is_backpos and self.train2_is_backpos then
-				advtrains.invert_train(id2)
-				advtrains.do_connect_trains(id1, id2, clicker)
-				--case 4 
-			elseif not self.train1_is_backpos and not self.train2_is_backpos then
-				advtrains.invert_train(id1)
+			local bp1, bp2 = self.t1_is_backpos, self.t2_is_backpos
+			if not bp1 then
+				if train1.couple_lock_front then
+					lockmarker(self.object)
+					return
+				end
+				if not bp2 then
+					if train2.couple_lock_front then
+						lockmarker(self.object)
+						return
+					end
+					advtrains.invert_train(id1)
+					advtrains.do_connect_trains(id1, id2, clicker)
+				else
+					if train2.couple_lock_back then
+						lockmarker(self.object)
+						return
+					end
+					advtrains.do_connect_trains(id2, id1, clicker)
+				end
+			else
+				if train1.couple_lock_back then
+					lockmarker(self.object)
+					return
+				end
+				if not bp2 then
+					if train2.couple_lock_front then
+						lockmarker(self.object)
+						return
+					end
+					advtrains.do_connect_trains(id1, id2, clicker)
+				else
+					if train2.couple_lock_back then
+						lockmarker(self.object)
+						return
+					end
+					advtrains.invert_train(id2)
 				advtrains.do_connect_trains(id1, id2, clicker)
+				end
 			end
+			
 			atprint("Coupled trains", id1, id2)
 			self.object:remove()
 		end)
 	end,
 	on_step=function(self, dtime)
 		return advtrains.pcall(function()
-			advtrains.atprint_context_tid=sid(self.train_id_1)
-			advtrains.atprint_context_tid_full=self.train_id_1
-			local t=os.clock()
+			advtrains.atprint_context_tid=self.train_id_1
+
 			if not self.train_id_1 or not self.train_id_2 then atprint("Couple: train ids not set!") self.object:remove() return end
 			local train1=advtrains.trains[self.train_id_1]
 			local train2=advtrains.trains[self.train_id_2]
@@ -131,10 +159,9 @@ minetest.register_entity("advtrains:couple", {
 				self.object:remove()
 				return
 			end
-			if not train1.path or not train2.path or not train1.index or not train2.index or not train1.end_index or not train2.end_index then
-				atprint("Couple: paths or end_index missing. Might happen when paths got cleared")
-				return
-			end
+			
+			advtrains.train_ensure_init(self.train_id_1, train1)
+			advtrains.train_ensure_init(self.train_id_2, train2)
 			
 			if train1.velocity>0 or train2.velocity>0 then
 				if not self.position_set then --ensures that train stands a single time before check fires. Using flag below
@@ -148,15 +175,15 @@ minetest.register_entity("advtrains:couple", {
 			if not self.position_set then
 				local tp1
 				if not self.train1_is_backpos then
-					tp1=advtrains.get_real_index_position(train1.path, train1.index)
+					tp1=advtrains.path_get_interpolated(train1, train1.index)
 				else
-					tp1=advtrains.get_real_index_position(train1.path, train1.end_index)
+					tp1=advtrains.path_get_interpolated(train1, train1.end_index)
 				end
 				local tp2
 				if not self.train2_is_backpos then
-					tp2=advtrains.get_real_index_position(train2.path, train2.index)
+					tp2=advtrains.path_get_interpolated(train2, train2.index)
 				else
-					tp2=advtrains.get_real_index_position(train2.path, train2.end_index)
+					tp2=advtrains.path_get_interpolated(train2, train2.end_index)
 				end
 				local pos_median=advtrains.pos_median(tp1, tp2)
 				if not vector.equals(pos_median, self.object:getpos()) then
@@ -166,7 +193,7 @@ minetest.register_entity("advtrains:couple", {
 			end
 			atprintbm("couple step", t)
 			advtrains.atprint_context_tid=nil
-			advtrains.atprint_context_tid_full=nil
+
 		end)
 	end,
 })
diff --git a/advtrains/init.lua b/advtrains/init.lua
index 93b25e5..21af66d 100644
--- a/advtrains/init.lua
+++ b/advtrains/init.lua
@@ -105,6 +105,7 @@ atwarn=function(t, ...)
 end
 sid=function(id) if id then return string.sub(id, -6) end end
 
+
 --ONLY use this function for temporary debugging. for consistent debug prints use atprint
 atdebug=function(t, ...)
 	local text=advtrains.print_concat_table({t, ...})
@@ -124,6 +125,12 @@ if minetest.settings:get_bool("advtrains_enable_debugging") then
 	dofile(advtrains.modpath.."/debugringbuffer.lua")
 end
 
+function assertt(var, typ)
+	if type(var)~=typ then
+		error("Assertion failed, variable has to be of type "..typ)
+	end
+end
+
 dofile(advtrains.modpath.."/helpers.lua");
 --dofile(advtrains.modpath.."/debugitems.lua");
 
@@ -196,6 +203,7 @@ function advtrains.avt_load()
 				--remove wagon_save entries that are not part of a train
 				local todel=advtrains.merge_tables(advtrains.wagon_save)
 				for tid, train in pairs(advtrains.trains) do
+					train.id = tid
 					for _, wid in ipairs(train.trainparts) do
 						todel[wid]=nil
 					end
diff --git a/advtrains/occupation.lua b/advtrains/occupation.lua
index 3007723..6316bd3 100644
--- a/advtrains/occupation.lua
+++ b/advtrains/occupation.lua
@@ -145,8 +145,6 @@ function o.clear_item(train_id, pos)
 				atwarn("Duplicate occupation entry at",pos,"for train",train_id,":",t)
 				i = i - 2
 			end
-			local oldoid = t[i+1] or 0
-			addchg(pos, train_id, oldoid, 0)
 			moving = true
 		end
 		if moving then
@@ -167,7 +165,7 @@ function o.check_collision(pos, train_id)
 		if t[i]~=train_id then
 			local idx = t[i+1]
 			local train = advtrains.trains[train_id]
-			advtrains.train_ensure_clean(train_id, train)
+			advtrains.train_ensure_init(train_id, train)
 			if idx >= train.end_index and idx <= train.index then
 				return true
 			end
@@ -177,4 +175,27 @@ function o.check_collision(pos, train_id)
 	return false
 end
 
+-- Gets a mapping of train id's to indexes of trains that share this path item with this train
+-- The train itself will not be included.
+-- If the requested index position is off-track, returns {}.
+-- returns (table with train_id->index), position
+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)
+		return {}, pos
+	end
+	local pos = advtrains.round_vector_floor_y(ppos)
+	local t = occget(pos)
+	local r = {}
+	local i = 1
+	local train_id = train.id
+	while t[i] do
+		if t[i]~=train_id then
+			r[train_id] = t[i+1]
+		end
+		i = i + 2
+	end
+	return r, pos
+end
 advtrains.occ = o
diff --git a/advtrains/trainlogic.lua b/advtrains/trainlogic.lua
index 373e7ce..129722a 100644
--- a/advtrains/trainlogic.lua
+++ b/advtrains/trainlogic.lua
@@ -69,26 +69,20 @@ advtrains.mainloop_trainlogic=function(dtime)
 	
 	for k,v in pairs(advtrains.trains) do
 		advtrains.atprint_context_tid=sid(k)
-		advtrains.atprint_context_tid_full=k
-		advtrains.train_ensure_clean(k, v)
+		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_full=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_full=k
 		advtrains.train_step_c(k, v, dtime)
 	end
 	
 	advtrains.atprint_context_tid=nil
-	advtrains.atprint_context_tid_full=nil
-	
-	advtrains.occ.end_step()
 	
 	atprintbm("trainsteps", t)
 	endstep()
@@ -174,39 +168,6 @@ local function assertdef(tbl, var, def)
 end
 
 
--- Calculates the indices where the window borders of the occupation windows are.
--- TODO adapt this code to new system, probably into a callback
-local function calc_occwindows(id, train)
-	local end_index = advtrains.path_get_index_by_offset(train, train.index, -train.trainlen)
-	train.end_index = end_index
-	local cpl_b = end_index - COUPLE_ZONE
-	local safety_b = advtrains.path_get_index_by_offset(train, cpl_b, -SAFETY_ZONE)
-	local cpl_f = end_index + COUPLE_ZONE
-	local safety_f = advtrains.path_get_index_by_offset(train, cpl_f, SAFETY_ZONE)
-	
-	-- calculate brake distance
-	local acc_all = t_accel_all[1]
-	local acc_eng = t_accel_eng[1]
-	local nwagons = #train.trainparts
-	local acc = acc_all + (acc_eng*train.locomotives_in_train)/nwagons
-	local vel = train.velocity
-	local brakedst = (vel*vel) / (2*acc)
-	
-	local brake_i = math.max(advtrains.path_get_index_by_offset(train, train.index, brakedst + BRAKE_SPACE), safety_f)
-	local aware_i = advtrains.path_get_index_by_offset(train, brake_i, AWARE_ZONE)
-	
-	return {
-		safety_b,
-		cpl_b,
-		end_index,
-		train.index,
-		cpl_f,
-		safety_f,
-		brake_i,
-		aware_i,
-	}
-end
-
 -- Small local util function to recalculate train's end index
 local function recalc_end_index(train)
 	train.end_index = advtrains.path_get_index_by_offset(train, train.index, -train.trainlen)
@@ -218,11 +179,11 @@ end
 local callbacks_new_path = {}
 local callbacks_update = {}
 
-function advtrains.tb_register_on_new_path(func)
+function advtrains.te_register_on_new_path(func)
 	assertt(func, "function")
 	table.insert(callbacks_new_path, func)
 end
-function advtrains.tb_register_on_update(func)
+function advtrains.te_register_on_update(func)
 	assertt(func, "function")
 	table.insert(callbacks_update, func)
 end
@@ -239,11 +200,11 @@ local function run_callbacks_update(id, train)
 end
 
 
--- train_ensure_clean: responsible for creating a state that we can work on, after one of the following events has happened:
+-- train_ensure_init: responsible for creating a state that we can work on, after one of the following events has happened:
 -- - the train's path got cleared
 -- - save files were loaded
 -- Additionally, this gets called outside the step cycle to initialize and/or remove a train, then occ_write_mode is set.
-function advtrains.train_ensure_clean(id, train)
+function advtrains.train_ensure_init(id, train)
 	train.dirty = true
 	if train.no_step then return end
 
@@ -451,6 +412,12 @@ if train.no_step or train.wait_for_path then return end
 	
 	local train_moves=(train.velocity~=0)
 	
+	--- Check whether this train can be coupled to another, and set couple entities accordingly
+	if not train.was_standing and not train_moves then
+		advtrains.train_check_couples(train)
+	end
+	train.was_standing = not train_moves
+	
 	if train_moves then
 		
 		local collpos
@@ -529,8 +496,8 @@ end
 
 advtrains.te_register_on_new_path(function(id, train)
 	train.tnc = {
-		old_index = atround(train.index)
-		old_end_index = atround(train.end_index)
+		old_index = atround(train.index),
+		old_end_index = atround(train.end_index),
 	}
 end)
 advtrains.te_register_on_update(function(id, train)
@@ -550,6 +517,39 @@ advtrains.te_register_on_update(function(id, train)
 	end
 end)
 
+-- Calculates the indices where the window borders of the occupation windows are.
+-- TODO adapt this code to new system, probably into a callback (probably only the brake distance code is needed)
+local function calc_occwindows(id, train)
+	local end_index = advtrains.path_get_index_by_offset(train, train.index, -train.trainlen)
+	train.end_index = end_index
+	local cpl_b = end_index - COUPLE_ZONE
+	local safety_b = advtrains.path_get_index_by_offset(train, cpl_b, -SAFETY_ZONE)
+	local cpl_f = end_index + COUPLE_ZONE
+	local safety_f = advtrains.path_get_index_by_offset(train, cpl_f, SAFETY_ZONE)
+	
+	-- calculate brake distance
+	local acc_all = t_accel_all[1]
+	local acc_eng = t_accel_eng[1]
+	local nwagons = #train.trainparts
+	local acc = acc_all + (acc_eng*train.locomotives_in_train)/nwagons
+	local vel = train.velocity
+	local brakedst = (vel*vel) / (2*acc)
+	
+	local brake_i = math.max(advtrains.path_get_index_by_offset(train, train.index, brakedst + BRAKE_SPACE), safety_f)
+	local aware_i = advtrains.path_get_index_by_offset(train, brake_i, AWARE_ZONE)
+	
+	return {
+		safety_b,
+		cpl_b,
+		end_index,
+		train.index,
+		cpl_f,
+		safety_f,
+		brake_i,
+		aware_i,
+	}
+end
+
 --TODO: Collisions!
 
 
@@ -573,7 +573,7 @@ function advtrains.create_new_train_at(pos, connid, ioff, trainparts)
 	atdebug("Created new train:",t)
 	
 	
-	advtrains.train_ensure_clean(new_id, advtrains.trains[new_id])
+	advtrains.train_ensure_init(new_id, advtrains.trains[new_id])
 	
 	return new_id
 end
@@ -581,7 +581,7 @@ end
 function advtrains.remove_train(id)
 	local train = advtrains.trains[id]
 	
-	advtrains.train_ensure_clean(id, train)
+	advtrains.train_ensure_init(id, train)
 	
 	advtrains.path_invalidate(train)
 	
@@ -597,7 +597,7 @@ end
 function advtrains.add_wagon_to_train(wagon_id, train_id, index)
 	local train=advtrains.trains[train_id]
 	
-	advtrains.train_ensure_clean(train_id, train)
+	advtrains.train_ensure_init(train_id, train)
 	
 	if index then
 		table.insert(train.trainparts, index, wagon_id)
@@ -691,7 +691,7 @@ function advtrains.split_train_at_wagon(wagon_id)
 	local train=advtrains.trains[old_id]
 	local _, wagon = advtrains.get_wagon_prototype(data)
 	
-	advtrains.train_ensure_clean(old_id, train)
+	advtrains.train_ensure_init(old_id, train)
 	
 	local index=advtrains.path_get_index_by_offset(train, train.index, -(data.pos_in_train + wagon.wagon_span))
 	
@@ -727,140 +727,95 @@ function advtrains.split_train_at_wagon(wagon_id)
 	
 end
 
---there are 4 cases:
---1/2. F<->R F<->R regular, put second train behind first
---->frontpos of first train will match backpos of second
---3.   F<->R R<->F flip one of these trains, take the other as new train
---->backpos's will match
---4.   R<->F F<->R flip one of these trains and take it as new parent
---->frontpos's will match
+-- coupling
+local CPL_CHK_DST = 1
+local CPL_ZONE = 2
 
---true when trains are facing each other. needed on colliding.
--- check done by iterating paths and checking their direction
---returns nil when not on the same track at all OR when required path items are not generated. this distinction may not always be needed.
--- TODO Will be changed when implementing coupling.
-function advtrains.trains_facing(train1, train2)
-	local sr_pos=train1.path[atround(train1.index)]
-	local sr_pos_p=train1.path[atround(train1.index)-1]
-
-	for i=advtrains.minN(train2.path), advtrains.maxN(train2.path) do
-		if vector.equals(sr_pos, train2.path[i]) then
-			if train2.path[i+1] and vector.equals(sr_pos_p, train2.path[i+1]) then return true end
-			if train2.path[i-1] and vector.equals(sr_pos_p, train2.path[i-1]) then return false end
-			return nil
-		end
-	end
-	return nil
+-- train.couple_* contain references to ObjectRefs of couple objects, which contain all relevant information
+-- These objectRefs will delete themselves once the couples no longer match
+local function createcouple(pos, train1, t1_is_front, train2, t2_is_front)
+	local obj=minetest.add_entity(pos, "advtrains:couple")
+	if not obj then error("Failed creating couple object!") return end
+	local le=obj:get_luaentity()
+	le.train_id_1=train1.id
+	le.train_id_2=train2.id
+	le.train1_is_backpos=not t1_is_front
+	le.train2_is_backpos=not t2_is_front
 end
 
-function advtrains.collide_and_spawn_couple(id1, pos, id2, t1_is_backpos)
-	if minetest.settings:get_bool("advtrains_disable_collisions") then
-		return
-	end
-	
-	atprint("COLLISION: ",sid(id1)," and ",sid(id2)," at ",pos,", t1_is_backpos=",(t1_is_backpos and "true" or "false"))
-	--TODO:
-	local train1=advtrains.trains[id1]
-	
-	-- do collision
-	train1.recently_collided_with_env=true
-	train1.velocity=0.5*train1.velocity
-	train1.movedir=train1.movedir*-1
-	train1.tarvelocity=0
-	
-	local train2=advtrains.trains[id2]
-	
-	if not train1 or not train2 then return end
-	
-	local found
-	for i=advtrains.minN(train1.path), advtrains.maxN(train1.path) do
-		if vector.equals(train1.path[i], pos) then
-			found=true
+function advtrains.train_check_couples(train)
+	if train.cpl_front then
+		if not train.cpl_front:getyaw() then
+			-- objectref is no longer valid. reset.
+			train.cpl_front = nil
 		end
 	end
-	if not found then
-		atprint("Err: pos not in path. Not spawning a couple")
-		return 
-	end
-	
-	local frontpos2=train2.path[atround(train2.detector_old_index)]
-	local backpos2=train2.path[atround(train2.detector_old_end_index)]
-	local t2_is_backpos
-	atprint("End positions: ",frontpos2,backpos2)
-	
-	t2_is_backpos = vector.distance(backpos2, pos) < vector.distance(frontpos2, pos)
-	
-	atprint("t2_is_backpos="..(t2_is_backpos and "true" or "false"))
-	
-	local t1_has_couple, t1_couple_lck
-	if t1_is_backpos then
-		t1_has_couple=train1.couple_eid_back
-		t1_couple_lck=train1.couple_lck_back
-	else
-		t1_has_couple=train1.couple_eid_front
-		t1_couple_lck=train1.couple_lck_front
-	end
-	local t2_has_couple, t2_couple_lck
-	if t2_is_backpos then
-		t2_has_couple=train2.couple_eid_back
-		t2_couple_lck=train2.couple_lck_back
-	else
-		t2_has_couple=train2.couple_eid_front
-		t2_couple_lck=train2.couple_lck_front
-	end
-	
-	if t1_has_couple then
-		if minetest.object_refs[t1_has_couple] then minetest.object_refs[t1_has_couple]:remove() end
-	end
-	if t2_has_couple then
-		if minetest.object_refs[t2_has_couple] then minetest.object_refs[t2_has_couple]:remove() end
+	if not train.cpl_front then
+		-- recheck front couple
+		local front_trains, pos = advtrains.occ.get_occupations(train, atround(train.index) + CPL_CHK_DST)
+		for tid, idx in pairs(front_trains) do
+			local other_train = advtrains.trains[tid]
+			advtrains.train_ensure_init(tid, other_train)
+			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)
+					break
+				end
+				if idx<=other_train.end_index and idx>=other_train.end_index - CPL_ZONE then
+					createcouple(pos, train, true, other_train, false)
+					break
+				end
+			end
+		end
 	end
-	if t1_couple_lck or t2_couple_lck then
-		minetest.add_entity(pos, "advtrains:lockmarker")
-		return
+	if train.cpl_back then
+		if not train.cpl_back:getyaw() then
+			-- objectref is no longer valid. reset.
+			train.cpl_back = nil
+		end
 	end
-	local obj=minetest.add_entity(pos, "advtrains:couple")
-	if not obj then atprint("failed creating object") return end
-	local le=obj:get_luaentity()
-	le.train_id_1=id1
-	le.train_id_2=id2
-	le.train1_is_backpos=t1_is_backpos
-	le.train2_is_backpos=t2_is_backpos
-	--find in object_refs
-	local p_aoi
-	for aoi, compare in pairs(minetest.object_refs) do
-		if compare==obj then
-			if t1_is_backpos then
-				train1.couple_eid_back=aoi
-			else
-				train1.couple_eid_front=aoi
-			end
-			if t2_is_backpos then
-				train2.couple_eid_back=aoi
-			else
-				train2.couple_eid_front=aoi
+	if not train.cpl_back then
+		-- recheck back couple
+		local back_trains, pos = advtrains.occ.get_occupations(train, atround(train.end_index) - CPL_CHK_DST)
+		for tid, idx in pairs(back_trains) do
+			local other_train = advtrains.trains[tid]
+			advtrains.train_ensure_init(tid, other_train)
+			if other_train.velocity == 0 then
+				if idx>=other_train.index and idx<=other_train.index + CPL_ZONE then
+					createcouple(pos, train, false, other_train, true)
+					break
+				end
+				if idx<=other_train.end_index and idx>=other_train.end_index - CPL_ZONE then
+					createcouple(pos, train, false, other_train, false)
+					break
+				end
 			end
-			p_aoi=aoi
 		end
 	end
-	atprint("Couple spawned (ActiveObjectID ",p_aoi,")")
 end
---order of trains may be irrelevant in some cases. check opposite cases. TODO does this work?
---pos1 and pos2 are just needed to form a median.
 
 
-function advtrains.do_connect_trains(first_id, second_id, player)
+
+-- relevant code for this comment is in couple.lua
+
+--there are 4 cases:
+--1/2. F<->R F<->R regular, put second train behind first
+--->frontpos of first train will match backpos of second
+--3.   F<->R R<->F flip one of these trains, take the other as new train
+--->backpos's will match
+--4.   R<->F F<->R flip one of these trains and take it as new parent
+--->frontpos's will match
+
+
+function advtrains.do_connect_trains(first_id, second_id)
 	local first, second=advtrains.trains[first_id], advtrains.trains[second_id]
 	
-	if not first or not second or not first.index or not second.index or not first.end_index or not second.end_index then
-		return false
-	end
+	advtrains.train_ensure_init(first_id, first)
+	advtrains.train_ensure_init(second_id, second)
 	
 	if first.couple_lck_back or second.couple_lck_front then
 		-- trains are ordered correctly!
-		if player then
-			minetest.chat_send_player(player:get_player_name(), "Can't couple: couples locked!")
-		end
+		-- Note, this is already checked in the rightclick step of the couple entity before trains are actually reversed
 		return
 	end
 	
@@ -870,24 +825,21 @@ function advtrains.do_connect_trains(first_id, second_id, player)
 	for _,v in ipairs(second.trainparts) do
 		table.insert(first.trainparts, v)
 	end
-	--kick it like physics (with mass being #wagons)
-	local new_velocity=((first.velocity*first_wagoncnt)+(second.velocity*second_wagoncnt))/(first_wagoncnt+second_wagoncnt)
+	
 	local tmp_cpl_lck=second.couple_lck_back
-	advtrains.trains[second_id]=nil
-	advtrains.update_trainpart_properties(first_id)
-	local train1=advtrains.trains[first_id]
-	train1.velocity=new_velocity
-	train1.tarvelocity=0
-	train1.couple_eid_front=nil
-	train1.couple_eid_back=nil
-	train1.couple_lck_back=tmp_cpl_lck
+	
+	advtrains.remove_train(second_id)
+	
+	first.velocity=0
+	first.tarvelocity=0
+	first.couple_lck_back=tmp_cpl_lck
 	return true
 end
 
 function advtrains.invert_train(train_id)
 	local train=advtrains.trains[train_id]
 	
-	advtrains.train_ensure_clean(train_id, train)
+	advtrains.train_ensure_init(train_id, train)
 	
 	advtrains.path_setrestore(train, true)