path: root/advtrains/trainlogic.lua

--trainlogic.lua
--controls train entities stuff about connecting/disconnecting/colliding trains and other things

local setting_overrun_mode = minetest.settings:get("advtrains_overrun_mode")

local benchmark=false
local bm={}
local bmlt=0
local bmsteps=0
local bmstepint=200
atprintbm=function(action, ta)
	if not benchmark then return end
	local t=(os.clock()-ta)*1000
	if not bm[action] then
		bm[action]=t
	else
		bm[action]=bm[action]+t
	end
	bmlt=bmlt+t
end
function endstep()
	if not benchmark then return end
	bmsteps=bmsteps-1
	if bmsteps<=0 then
		bmsteps=bmstepint
		for key, value in pairs(bm) do
			minetest.chat_send_all(key.." "..(value/bmstepint).." ms avg.")
		end
		minetest.chat_send_all("Total time consumed by all advtrains actions per step: "..(bmlt/bmstepint).." ms avg.")
		bm={}
		bmlt=0
	end
end

--acceleration for lever modes (trainhud.lua), per wagon
local t_accel_all={
	[0] = -10,
	[1] = -3,
	[11] = -2, -- calculation base for LZB
	[2] = -0.5,
	[4] = 0.5,
}
--acceleration per engine
local t_accel_eng={
	[0] = 0,
	[1] = 0,
	[11] = 0,
	[2] = 0,
	[4] = 1.5,
}

local VLEVER_EMERG = 0
local VLEVER_BRAKE = 1
local VLEVER_LZBCALC = 11
local VLEVER_ROLL = 2
local VLEVER_HOLD = 3
local VLEVER_ACCEL = 4

-- How far in front of a whole index with LZB 0 restriction the train should come to a halt
-- value must be between 0 and 0.5, exclusively
local LZB_ZERO_APPROACH_DIST = 0.1
-- Speed the train temporarily approaches the stop point with
local LZB_ZERO_APPROACH_SPEED = 0.2



tp_player_tmr = 0

advtrains.mainloop_trainlogic=function(dtime, stepno)
	--build a table of all players indexed by pts. used by damage and door system.
	advtrains.playersbypts={}
	for _, player in pairs(minetest.get_connected_players()) do
		if not advtrains.player_to_train_mapping[player:get_player_name()] then
			--players in train are not subject to damage
			local ptspos=minetest.pos_to_string(vector.round(player:getpos()))
			advtrains.playersbypts[ptspos]=player
		end
	end
	
	if tp_player_tmr<=0 then
		-- teleport players to their train every 2 seconds
		for _, player in pairs(minetest.get_connected_players()) do
			advtrains.tp_player_to_train(player)
		end
		tp_player_tmr = 2
	else
		tp_player_tmr = tp_player_tmr - dtime
	end
	--regular train step
	--[[ structure:
	1. make trains calculate their occupation windows when needed (a)
	2. when occupation tells us so, restore the occupation tables (a)
	4. make trains move and update their new occupation windows and write changes
	   to occupation tables (b)
	5. make trains do other stuff (c)
	]]--
	local t=os.clock()
	
	for k,v in pairs(advtrains.trains) do
		advtrains.atprint_context_tid=k
		atprint("=== Step",stepno,"===")
		advtrains.train_ensure_init(k, v)
	end
	
	advtrains.lock_path_inval = true
	
	for k,v in pairs(advtrains.trains) do
		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=k
		advtrains.train_step_c(k, v, dtime)
	end
	
	advtrains.lock_path_inval = false
	
	advtrains.atprint_context_tid=nil
	
	atprintbm("trainsteps", t)
	endstep()
end

function advtrains.tp_player_to_train(player)
	local pname = player:get_player_name()
	local id=advtrains.player_to_train_mapping[pname]
	if id then
		local train=advtrains.trains[id]
		if not train then advtrains.player_to_train_mapping[pname]=nil return end
		--set the player to the train position.
		--minetest will emerge the area and load the objects, which then will call reattach_all().
		--because player is in mapping, it will not be subject to dying.
		player:setpos(train.last_pos)
	end
end
minetest.register_on_joinplayer(function(player)
		advtrains.hud[player:get_player_name()] = nil
		advtrains.hhud[player:get_player_name()] = nil
		--independent of this, cause all wagons of the train which are loaded to reattach their players
		--needed because already loaded wagons won't call reattach_all()
		for _,wagon in pairs(minetest.luaentities) do
			if wagon.is_wagon and wagon.initialized and wagon.train_id==id then
				wagon:reattach_all()
			end
		end
end)


minetest.register_on_dieplayer(function(player)
		local pname=player:get_player_name()
		local id=advtrains.player_to_train_mapping[pname]
		if id then
			local train=advtrains.trains[id]
			if not train then advtrains.player_to_train_mapping[pname]=nil return end
			for _,wagon in pairs(minetest.luaentities) do
				if wagon.is_wagon and wagon.initialized and wagon.train_id==id then
					--when player dies, detach him from the train
					--call get_off_plr on every wagon since we don't know which one he's on.
					wagon:get_off_plr(pname)
				end
			end
		end
end)

--[[

Zone diagram of a train (copy from occupation.lua!):
              |___| |___| --> Direction of travel
              oo oo+oo oo
=|=======|===|===========|===|=======|===================|========|===
 |SafetyB|CpB|   Train   |CpF|SafetyF|        Brake      |Aware   |
[1]     [2] [3]         [4] [5]     [6]                 [7]      [8]
This mapping from indices in occwindows to zone ids is contained in WINDOW_ZONE_IDS


The occupation system has been abandoned. The constants will still be used
to determine the couple distance
(because of the reverse lookup, the couple system simplifies a lot...)

]]--
-- unless otherwise stated, in meters.
local SAFETY_ZONE = 10
local COUPLE_ZONE = 2 --value in index positions!
local BRAKE_SPACE = 10
local AWARE_ZONE = 10
local WINDOW_ZONE_IDS = {
	2, -- 1 - SafetyB
	4, -- 2 - CpB
	1, -- 3 - Train
	5, -- 4 - CpF
	3, -- 5 - SafetyF
	6, -- 6 - Brake
	7, -- 7 - Aware
}


-- If a variable does not exist in the table, it is assigned the default value
local function assertdef(tbl, var, def)
	if not tbl[var] then
		tbl[var] = def
	end
end

function advtrains.get_acceleration(train, lever)
	local acc_all = t_accel_all[lever]
	if not acc_all then return 0 end
	
	local acc_eng = t_accel_eng[lever]
	local nwagons = #train.trainparts
	if nwagons == 0 then
		-- empty train! avoid division through zero
		return -1
	end
	local acc = acc_all + (acc_eng*train.locomotives_in_train)/nwagons
	return acc
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)
end

-- Occupation Callback system
-- see occupation.lua
-- signature is advtrains.te_register_on_<?>(function(id, train) ... end)

local function mkcallback(name)
	local callt = {}
	advtrains["te_register_on_"..name] = function(func)
		assertt(func, "function")
		table.insert(callt, func)
	end
	return callt, function(id, train, param1, param2, param3)
		for _,f in ipairs(callt) do
			f(id, train, param1, param2, param3)
		end
	end
end

local callbacks_new_path, run_callbacks_new_path = mkcallback("new_path")
local callbacks_invahead
callbacks_invahead, advtrains.run_callbacks_invahead = mkcallback("invalidate_ahead") -- (id, train, start_idx)
local callbacks_update, run_callbacks_update = mkcallback("update")
local callbacks_create, run_callbacks_create = mkcallback("create")
local callbacks_remove, run_callbacks_remove = mkcallback("remove")


-- 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_init(id, train)
	if not train then
		atwarn("train_ensure_init: Called with id =",id,"but a nil train!")
		atwarn(debug.traceback())
		return nil
	end
	
	train.dirty = true
	if train.no_step then
		atprint("in ensure_init: no_step set, train step ignored!")
		return nil
	end

	assertdef(train, "velocity", 0)
	--assertdef(train, "tarvelocity", 0)
	assertdef(train, "acceleration", 0)
	assertdef(train, "id", id)
	
	
	if not train.drives_on or not train.max_speed then
		atprint("in ensure_init: missing properties, updating!")
		advtrains.update_trainpart_properties(id)
	end
	
	--restore path
	if not train.path then
		atprint("in ensure_init: Needs restoring path...")
		if not train.last_pos then
			atlog("Train",id,": Restoring path failed, no last_pos set! Train will be disabled. You can try to fix the issue in the save file.")
			train.no_step = true
			return nil
		end
		if not train.last_connid then
			atwarn("Train",id,": Restoring path: no last_connid set! Will assume 1")
			train.last_connid = 1
			--[[
			Why this fix was necessary:
			Issue: Migration problems on Grand Theft Auto Minetest
			1. Run of this code, warning printed.
			2. path_create failed with result==nil (there was an unloaded node, wait_for_path set)
			3. in consequence, the supposed call to path_setrestore does not happen
			4. train.last_connid is still unset
			5. next step, warning is printed again
			Result: log flood.
			]]
		end
		
		local result = advtrains.path_create(train, train.last_pos, train.last_connid or 1, train.last_frac or 0)
		
		atprint("in ensure_init: path_create result ",result)
		
		if result==false then
			atlog("Train",id,": Restoring path failed, node at",train.last_pos,"is gone! Train will be disabled. You can try to place a rail at this position and restart the server.")
			train.no_step = true
			return nil
		elseif result==nil then
			if not train.wait_for_path then
				atlog("Train",id,": Can't initialize: Waiting for the (yet unloaded) node at",train.last_pos," to be loaded.")
			end
			train.wait_for_path = true
			return false
		end
		-- by now, we should have a working initial path
		train.wait_for_path = false
		
		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)
		
		-- run on_new_path callbacks
		run_callbacks_new_path(id, train)
	end
	
	train.dirty = false -- TODO einbauen!
	return true
end

local function v_target_apply(v_targets, lever, vel)
	v_targets[lever] = v_targets[lever] and math.min(v_targets[lever], vel) or vel
end

function advtrains.train_step_b(id, train, dtime)
	if train.no_step or train.wait_for_path or not train.path then return end
	
	-- in this code, we check variables such as path_trk_? and path_dist. We need to ensure that the path is known for the whole 'Train' zone
	advtrains.path_get(train, atfloor(train.index + 2))
	advtrains.path_get(train, atfloor(train.end_index - 1))
	
	--[[ again, new velocity control:
	There are two heterogenous means of control:
	-> set a fixed acceleration and ignore speed (user)
	-> steer towards a target speed, distance doesn't matter
		-> needs to specify the maximum acceleration/deceleration values they are willing to accelerate/brake with
	-> Reach a target speed after a certain distance (LZB, handled specially)
	
	]]--
	
	--- 3. handle velocity influences ---
	-- Variables for "desired velocities" of various parts of the code
	local v_targets = {} --Table keys: VLEVER_*
	
	local train_moves=(train.velocity~=0)
	
	if train.recently_collided_with_env then
		if not train_moves then
			train.recently_collided_with_env=nil--reset status when stopped
		end
		atprint("in train_step_b: applying collided_with_env")
		v_target_apply(v_targets, VLEVER_EMERG, 0)
	end
	if train.locomotives_in_train==0 then
		atprint("in train_step_b: applying no_locomotives")
		v_target_apply(v_targets, VLEVER_ROLL, 0)
	end
	
	-- interlocking speed restriction
	if train.speed_restriction then
		atprint("in train_step_b: applying interlocking speed restriction",train.speed_restriction)
		v_target_apply(v_targets, VLEVER_BRAKE, train.speed_restriction)
	end
	
	--apply off-track handling:
	local front_off_track = train.index>train.path_trk_f
	local back_off_track=train.end_index<train.path_trk_b
	train.off_track = front_off_track or back_off_track
	
	if back_off_track then
		atprint("in train_step_b: applying back_off_track")
		v_target_apply(v_targets, VLEVER_EMERG, 1)
	else
		if front_off_track then
			atprint("in train_step_b: applying front_off_track")
			v_target_apply(v_targets, VLEVER_EMERG, 0)
		end
	end
	
	
	--interpret ATC command and apply auto-lever control when not actively controlled
	local v0 = train.velocity
	
	if train.ctrl_user then
		atprint("in train_step_b: ctrl_user active, resetting atc")
		advtrains.atc.train_reset_command(train)
	else
		if train.atc_command then
			if (not train.atc_delay or train.atc_delay<=0) and not train.atc_wait_finish then
				advtrains.atc.execute_atc_command(id, train)
			else
				train.atc_delay=train.atc_delay-dtime
			end
		elseif train.atc_delay then
			train.atc_delay = nil
		end
	
		local braketar = train.atc_brake_target
		local emerg = false -- atc_brake_target==-1 means emergency brake (BB command)
		if braketar == -1 then
			braketar = 0
			emerg = true
		end
		atprint("in train_step_b: ATC: brake state braketar=",braketar,"emerg=",emerg)
		if braketar and braketar>=v0 then
			atprint("in train_step_b: ATC: brake target cleared")
			train.atc_brake_target=nil
			braketar = nil
		end
		--if train.tarvelocity and train.velocity==train.tarvelocity then
		--	train.tarvelocity = nil
		--end
		if train.atc_wait_finish then
			if not train.atc_brake_target and (not train.tarvelocity or train.velocity==train.tarvelocity) then
				train.atc_wait_finish=nil
			end
		end
		
		if train.tarvelocity and train.tarvelocity>v0 then
			atprint("in train_step_b: applying ATC ACCEL", train.tarvelocity)
			v_target_apply(v_targets, VLEVER_ACCEL, train.tarvelocity)
		end
		if train.tarvelocity and train.tarvelocity<v0 then
			if (braketar and braketar<v0) then
				if emerg then
					atprint("in train_step_b: applying ATC EMERG", train.tarvelocity)
					v_target_apply(v_targets, VLEVER_EMERG, 0)
				else
					atprint("in train_step_b: applying ATC BRAKE", train.tarvelocity)
					v_target_apply(v_targets, VLEVER_BRAKE, braketar)
				end
			else
				atprint("in train_step_b: applying ATC ROLL", train.tarvelocity)
				v_target_apply(v_targets, VLEVER_ROLL, train.tarvelocity)
			end
		end
	end
	
	local userc = train.ctrl_user
	if userc then
		atprint("in train_step_b: applying user control", userc)
		v_target_apply(v_targets, userc, userc==VLEVER_ACCEL and train.max_speed or 0)
	end
	
	--- 2b. look at v_target, determine the effective v_target and desired acceleration ---
	local tv_target, tv_lever
	
	if v_targets[VLEVER_ACCEL] then
		if v_targets[VLEVER_ACCEL] > v0 then
			tv_target = v_targets[VLEVER_ACCEL]
			tv_lever = VLEVER_ACCEL
		end
	end
	for _,lever in ipairs({VLEVER_ROLL, VLEVER_BRAKE, VLEVER_EMERG}) do
		if v_targets[lever] then
			if v_targets[lever] <= v0 then
				if not tv_target then
					tv_target = v_targets[lever]
				else
					tv_target = math.min(v_targets[lever], tv_target)
				end
			end
			if v_targets[lever] < v0 then
				tv_lever = lever
			end
		end
	end
	atprint("in train_step_b: Resulting control before LZB: lever", tv_lever, "target", tv_target)
	--train.debug = dump({tv_target,tv_lever})
	
	--- 2c. If no tv_lever set, honor the user control ---
	local a_lever = tv_lever
	if not tv_lever then
		-- default to holding current speed
		a_lever = VLEVER_HOLD
	end
	
	train.lever = a_lever
	
	atprint("in train_step_b: Current index",train.index,"end",train.end_index,"vel",train.velocity)
	
	--- 3a. calculate the acceleration required to reach the speed restriction in path_speed (LZB) ---
	-- Iterates over the path nodes we WOULD pass if we were continuing with the speed assumed by actual_lever
	-- and determines the MINIMUM of path_speed in this range.
	-- Then, determines acceleration so that we can reach this 'overridden' target speed in this step (but short-circuited)
	local lzb_next_zero_barrier -- if defined, train should not pass this point as it's a 0-LZB
	local new_index_v_base -- which v was assumed when curr_tv was calculated
	local new_index_curr_tv -- pre-calculated new train index in lzb check
	
	if not a_lever or a_lever > VLEVER_BRAKE then
		-- only needs to run if we're not yet braking anyway
		new_index_v_base = v0 + (advtrains.get_acceleration(train, tv_lever) * dtime)
		local dst_curr_v = new_index_v_base * dtime
		train.dist_moved_this_step = dst_curr_v
		new_index_curr_tv = advtrains.path_get_index_by_offset(train, train.index, dst_curr_v)
		local i = atfloor(train.index)
		local lzb_target
		local psp
		while true do
			psp = train.path_speed[i]
			if psp then
				lzb_target = lzb_target and math.min(lzb_target, psp) or psp
				if psp == 0 and not lzb_next_zero_barrier then
					atprint("in train_step_b: Found zero barrier: ",i)
					lzb_next_zero_barrier = i - LZB_ZERO_APPROACH_DIST
				end
			end
			if i > new_index_curr_tv then
				break
			end
			i = i + 1
		end
		
		atprint("in train_step_b: LZB calculation yields newindex=",new_index_curr_tv," basev=",new_index_v_base," lzbtarget=",lzb_target,"zero_barr=",lzb_next_zero_barrier,"")
		
		if lzb_target and lzb_target <= v0 then
			-- apply to tv_target after the actual calculation happened
			a_lever = VLEVER_BRAKE
			if tv_target and tv_target > lzb_target then
				if lzb_target < LZB_ZERO_APPROACH_SPEED and lzb_next_zero_barrier then
					if train.index >= lzb_next_zero_barrier then
						tv_target = 0
						a_lever = VLEVER_BRAKE
						atprint("in train_step_b: -!- Hit zero approach barrier -!- applying brake")
						--atdebug("zeroappr cancelling train has passed idx=",train.index, "za_idx=",lzb_zeroappr_target_index)
					else
						-- if we are in front of a zero barrier, make sure we reach it by
						-- keeping the velocity at a small value >0
						atprint("in train_step_b: In zero approach, applying ZERO_APPROACH_SPEED")
						tv_target = LZB_ZERO_APPROACH_SPEED
					end
				else
					atprint("in train_step_b: applying LZB brake to",lzb_target)
					tv_target = lzb_target
				end
			end
		-- Case: v0 is below lzb_target, but a_lever is ACCEL and resulting v would be greater than lzb_target
		-- limit tv_target to the lzb target.
		elseif lzb_target and a_lever >= VLEVER_ACCEL then 
			tv_target = lzb_target
		end
	end
	
	--- 3b. now that we know tv_target and a_lever, calculate effective new v and change it on train
	atprint("in train_step_b: Final control: target",tv_target,"lever",a_lever)
	
	local dv = advtrains.get_acceleration(train, a_lever) * dtime
	local v1
	local tv_effective = false
	if tv_target and (math.abs(dv) > math.abs(tv_target - v0)) then
		atprint("in train_step_b: hit tv_target ",tv_target,"with v=",v0, "dv=",dv)
		v1 = tv_target
		tv_effective = true
	else
		v1 = v0 +dv
	end
	--train.debug = "tv_target="..(tv_target or "nil").." v0="..v0.." v1="..v1
	
	if v1 > train.max_speed then
		v1 = train.max_speed
	end
	if v1 < 0 then
		v1 = 0
	end
	
	train.acceleration = (v1 - v0) / dtime
	train.velocity = v1
	atprint("in train_step_b: New velocity",v1," (yields acceleration",train.acceleration,")")
	
	--- 4. move train ---
	-- if we have calculated the new end index before, don't do that again
	if not new_index_v_base or new_index_v_base ~= v1 then
		local tv_vdiff = advtrains.get_acceleration(train, tv_lever) * dtime
		local dst_curr_v = v1 * dtime
		train.dist_moved_this_step = dst_curr_v
		new_index_curr_tv = advtrains.path_get_index_by_offset(train, train.index, dst_curr_v)
		atprint("in train_step_b: movement calculation (re)done, yields newindex=",new_index_curr_tv)
	else
		atprint("in train_step_b: movement calculation reusing from LZB newindex=",new_index_curr_tv)
	end
	
	-- if the zeroappr mechanism has hit, go no further than zeroappr index
	if lzb_next_zero_barrier and new_index_curr_tv > lzb_next_zero_barrier then
		atprint("in train_step_b: Zero barrier hit, clipping to newidx_tv=",new_index_curr_tv, "zb_idx=",lzb_next_zero_barrier)
		new_index_curr_tv = lzb_next_zero_barrier
	end
	train.index = new_index_curr_tv
	
	recalc_end_index(train)
	atprint("in train_step_b: New index",train.index,"end",train.end_index,"vel",train.velocity)
end

function advtrains.train_step_c(id, train, dtime)
	if train.no_step or train.wait_for_path or not train.path then return end
	
	-- all location/extent-critical actions have been done.
	-- calculate the new occupation window
	run_callbacks_update(id, train)
	
	-- Return if something(TM) damaged the path
	if train.no_step or train.wait_for_path or not train.path then return end
	
	advtrains.path_clear_unused(train)
	
	advtrains.path_setrestore(train)
	
	-- less important stuff
	
	train.check_trainpartload=(train.check_trainpartload or 0)-dtime
	if train.check_trainpartload<=0 then
		advtrains.spawn_wagons(id)
		train.check_trainpartload=2
	end
	
	--- 8. check for collisions with other trains and damage players ---
	
	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 collided = false
		local coll_grace=1
		local collindex = advtrains.path_get_index_by_offset(train, train.index, -coll_grace)
		local collpos = advtrains.path_get(train, atround(collindex))
		if collpos then
			local rcollpos=advtrains.round_vector_floor_y(collpos)
			local is_loaded_area = advtrains.is_node_loaded(rcollpos)
			for x=-train.extent_h,train.extent_h do
				for z=-train.extent_h,train.extent_h do
					local testpos=vector.add(rcollpos, {x=x, y=0, z=z})
					--- 8a Check collision ---
					if not collided then

						local col_tr = advtrains.occ.check_collision(testpos, id)
						if col_tr then
							advtrains.train_check_couples(train)
							train.velocity = 0
							advtrains.atc.train_reset_command(train)
							collided = true
						end

						--- 8b damage players ---
						if is_loaded_area and train.velocity > 3 and (setting_overrun_mode=="drop" or setting_overrun_mode=="normal") then
							local testpts = minetest.pos_to_string(testpos)
							local player=advtrains.playersbypts[testpts]
							if player and player:get_hp()>0 and advtrains.is_damage_enabled(player:get_player_name()) then
								--atdebug("damage found",player:get_player_name())
								if setting_overrun_mode=="drop" then
									--instantly kill player
									--drop inventory contents first, to not to spawn bones
									local player_inv=player:get_inventory()
									for i=1,player_inv:get_size("main") do
										minetest.add_item(testpos, player_inv:get_stack("main", i))
									end
									for i=1,player_inv:get_size("craft") do
										minetest.add_item(testpos, player_inv:get_stack("craft", i))
									end
									-- empty lists main and craft
									player_inv:set_list("main", {})
									player_inv:set_list("craft", {})
								end
								player:set_hp(0)
							end
						end
					end
				end
			end
			--- 8c damage other objects ---
			if is_loaded_area then
				local objs = minetest.get_objects_inside_radius(rcollpos, 2)
				for _,obj in ipairs(objs) do
					if not obj:is_player() and obj:get_armor_groups().fleshy and obj:get_armor_groups().fleshy > 0 
							and obj:get_luaentity() and obj:get_luaentity().name~="signs:text" then
						obj:punch(obj, 1, { full_punch_interval = 1.0, damage_groups = {fleshy = 1000}, }, nil)
					end
				end
			end
		end
	end
end

-- Default occupation callbacks for node callbacks
-- (remember, train.end_index is set separately because callbacks are
--  asserted to rely on this)

local function mknodecallback(name)
	local callt = {}
	advtrains["tnc_register_on_"..name] = function(func, prio)
		assertt(func, "function")
		if prio then
			table.insert(callt, 1, func)
		else
			table.insert(callt, func)
		end
	end
	return callt, function(pos, id, train, index, paramx1, paramx2, paramx3)
		for _,f in ipairs(callt) do
			f(pos, id, train, index, paramx1, paramx2, paramx3)
		end
	end
end

-- enter/leave-node callbacks
-- signature is advtrains.tnc_register_on_enter/leave(function(pos, id, train, index) ... end)
local callbacks_enter_node, run_callbacks_enter_node = mknodecallback("enter")
local callbacks_leave_node, run_callbacks_leave_node = mknodecallback("leave")

-- Node callback for approaching
-- Might be called multiple times, whenever path is recalculated. Also called for the first node the train is standing on, then has_entered is true.
-- signature is function(pos, id, train, index, has_entered, lzbdata)
-- has_entered: true if the "enter" callback has already been executed for this train in this location
-- lzbdata: arbitrary data (shared between all callbacks), deleted when LZB is restarted.
-- These callbacks are called in order of distance as train progresses along tracks, so lzbdata can be used to
-- keep track of a train's state once it passes this point
local callbacks_approach_node, run_callbacks_approach_node = mknodecallback("approach")


local function tnc_call_enter_callback(pos, train_id, train, index)
	--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
		mregnode.advtrains.on_train_enter(pos, train_id, train, index)
	end

	-- call other registered callbacks
	run_callbacks_enter_node(pos, train_id, train, index)
	
	-- check for split points
	if mregnode and mregnode.at_conns and #mregnode.at_conns == 3 and train.path_cp[index] == 3 then
		-- train came from connection 3 of a switch, so it split points.
		if not train.points_split then
			train.points_split = {}
		end
		train.points_split[advtrains.encode_pos(pos)] = true
		--atdebug(train_id,"split points at",pos)
	end
end
local function tnc_call_leave_callback(pos, train_id, train, index)
	--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
		mregnode.advtrains.on_train_leave(pos, train_id, train, index)
	end
	
	-- call other registered callbacks
	run_callbacks_leave_node(pos, train_id, train, index)
	
	-- split points do not matter anymore. clear them
	if train.points_split then
		if train.points_split[advtrains.encode_pos(pos)] then
			train.points_split[advtrains.encode_pos(pos)] = nil
			--atdebug(train_id,"has passed split points at",pos)
		end
		-- any entries left?
		for _,_ in pairs(train.points_split) do
			return
		end
		train.points_split = nil
	end
	-- WARNING possibly unreachable place!
end

function advtrains.tnc_call_approach_callback(pos, train_id, train, index, lzbdata)
	--atdebug("tnc approach",pos,train_id, lzbdata)
	local has_entered = atround(train.index) == index
	
	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_approach then
		mregnode.advtrains.on_train_approach(pos, train_id, train, index, has_entered, lzbdata)
	end
	
	-- call other registered callbacks
	run_callbacks_approach_node(pos, train_id, train, index, has_entered, lzbdata)
end

-- === te callback definition for tnc node callbacks ===

advtrains.te_register_on_new_path(function(id, train)
	train.tnc = {
		old_index = atround(train.index),
		old_end_index = atround(train.end_index),
	}
	--atdebug(id,"tnc init",train.index,train.end_index)
end)

advtrains.te_register_on_update(function(id, train)
	local new_index = atround(train.index)
	local new_end_index = atround(train.end_index)
	local old_index = train.tnc.old_index
	local old_end_index = train.tnc.old_end_index
	while old_index < new_index do
		old_index = old_index + 1
		local pos = advtrains.round_vector_floor_y(advtrains.path_get(train,old_index))
		tnc_call_enter_callback(pos, id, train, old_index)
	end
	while old_end_index < new_end_index do
		local pos = advtrains.round_vector_floor_y(advtrains.path_get(train,old_end_index))
		tnc_call_leave_callback(pos, id, train, old_end_index)
		old_end_index = old_end_index + 1
	end
	train.tnc.old_index = new_index
	train.tnc.old_end_index = new_end_index
end)

advtrains.te_register_on_create(function(id, train)
	local index = atround(train.index)
	local end_index = atround(train.end_index)
	while end_index <= index do
		local pos = advtrains.round_vector_floor_y(advtrains.path_get(train,end_index))
		tnc_call_enter_callback(pos, id, train, end_index)
		end_index = end_index + 1
	end
	--atdebug(id,"tnc create",train.index,train.end_index)
end)

advtrains.te_register_on_remove(function(id, train)
	local index = atround(train.index)
	local end_index = atround(train.end_index)
	while end_index <= index do
		local pos = advtrains.round_vector_floor_y(advtrains.path_get(train,end_index))
		tnc_call_leave_callback(pos, id, train, end_index)
		end_index = end_index + 1
	end
	--atdebug(id,"tnc remove",train.index,train.end_index)
end)

--returns new id
function advtrains.create_new_train_at(pos, connid, ioff, trainparts)
	local new_id=advtrains.random_id()
	while advtrains.trains[new_id] do new_id=advtrains.random_id() end--ensure uniqueness
	
	local t={}
	t.id = new_id
	
	t.last_pos=pos
	t.last_connid=connid
	t.last_frac=ioff
	
	--t.tarvelocity=0
	t.velocity=0
	t.trainparts=trainparts
	
	advtrains.trains[new_id] = t
	--atdebug("Created new train:",t)
	
	if not advtrains.train_ensure_init(new_id, advtrains.trains[new_id]) then
		atwarn("create_new_train_at",pos,connid,"failed! This might lead to temporary bugs.")
		return
	end
	
	run_callbacks_create(new_id, advtrains.trains[new_id])
	
	return new_id
end

function advtrains.remove_train(id)
	local train = advtrains.trains[id]
	
	if not advtrains.train_ensure_init(id, train) then
		atwarn("remove_train",id,"failed! This might lead to temporary bugs.")
		return
	end
	
	run_callbacks_remove(id, train)
	
	advtrains.path_invalidate(train)
	advtrains.couple_invalidate(train)
	
	local tp = train.trainparts
	--atdebug("Removing train",id,"leftover trainparts:",tp)
	
	advtrains.trains[id] = nil
	
	return tp
	
end


function advtrains.add_wagon_to_train(wagon_id, train_id, index)
	local train=advtrains.trains[train_id]
	
	if not advtrains.train_ensure_init(train_id, train) then
		atwarn("Train",train_id,"is not initialized! Operation aborted!")
		return
	end
	
	if index then
		table.insert(train.trainparts, index, wagon_id)
	else
		table.insert(train.trainparts, wagon_id)
	end
	
	advtrains.update_trainpart_properties(train_id)
	recalc_end_index(train)
	run_callbacks_update(train_id, train)
end

-- Note: safe_decouple_wagon() has been moved to wagons.lua

-- 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]
	train.drives_on=advtrains.merge_tables(advtrains.all_tracktypes)
	--FIX: deep-copy the table!!!
	train.max_speed=20
	train.extent_h = 0;
	
	local rel_pos=0
	local count_l=0
	local shift_dcpl_lock=false
	for i, w_id in ipairs(train.trainparts) do
		
		local data = advtrains.wagons[w_id]
		
		-- 1st: update wagon data (pos_in_train a.s.o)
		if data then
			local wagon = advtrains.wagon_prototypes[data.type or data.entity_name]
			if not wagon then
				atwarn("Wagon '",data.type,"' couldn't be found. Please check that all required modules are loaded!")
				wagon = advtrains.wagon_prototypes["advtrains:wagon_placeholder"]

			end
			rel_pos=rel_pos+wagon.wagon_span
			data.train_id=train_id
			data.pos_in_train=rel_pos
			data.pos_in_trainparts=i
			if wagon.is_locomotive then
				count_l=count_l+1
			end
			if invert_flipstate then
				data.wagon_flipped = not data.wagon_flipped
				shift_dcpl_lock, data.dcpl_lock = data.dcpl_lock, shift_dcpl_lock
			end
			rel_pos=rel_pos+wagon.wagon_span
			
			if wagon.drives_on then
				for k,_ in pairs(train.drives_on) do
					if not wagon.drives_on[k] then
						train.drives_on[k]=nil
					end
				end
			end
			train.max_speed=math.min(train.max_speed, wagon.max_speed)
			train.extent_h = math.max(train.extent_h, wagon.extent_h or 1);
		end
	end
	train.trainlen = rel_pos
	train.locomotives_in_train = count_l
end


local ablkrng = advtrains.wagon_load_range
-- This function checks whether entities need to be spawned for certain wagons, and spawns them.
-- Called from train_step_*(), not required to check init.
function advtrains.spawn_wagons(train_id)
	local train = advtrains.trains[train_id]
	
	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 #",i,": Saved train ID",data.train_id,"did not match!")
				data.train_id = train_id
			end
			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))
				
				if advtrains.position_in_range(pos, ablkrng) then
					--atdebug("wagon",w_id,"spawning")
					local wt = advtrains.get_wagon_prototype(data)
					local wagon = minetest.add_entity(pos, wt):get_luaentity()
					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

function advtrains.split_train_at_fc(train, count_empty, length_limit)
	-- splits train at first different current FC by convention,
	-- locomotives have empty FC so are ignored
	-- count_empty is used to split off locomotives
	-- length_limit limits the length of the first train to length_limit wagons
	local train_id = train.id
	local fc = false
	local ind = 0
	for i = 1, #train.trainparts do
		local w_id = train.trainparts[i]
		local data = advtrains.wagons[w_id]
		if length_limit and i > length_limit then
			ind = i
			break
		end
		if data then
			local wfc = advtrains.get_cur_fc(data)
			if  wfc ~= "" or count_empty then
				if  fc then
					if fc ~= wfc then
						ind = i
						break
					end
				else
					fc = wfc
				end
			end
		end
	end
	if ind > 0 then
		return advtrains.split_train_at_index(train, ind), fc
	end
	if fc then
		return nil, fc
	end
end

function advtrains.train_step_fc(train)
	for i=1,#train.trainparts do
		local w_id = train.trainparts[i]
		local data = advtrains.wagons[w_id]
		if data then
			advtrains.step_fc(data)
		end
	end
end

function advtrains.split_train_at_index(train, index)
	-- this function splits a train at index, creating a new train from the back part of the train.

	local train_id=train.id
	if index > #train.trainparts then
		-- index specified too long
		return
	end
	local w_id = train.trainparts[index]
	local data = advtrains.wagons[w_id]
	local _, wagon = advtrains.get_wagon_prototype(data)
	if not advtrains.train_ensure_init(train_id, train) then
		atwarn("Train",train_id,"is not initialized! Operation aborted!")
		return
	end

	local p_index=advtrains.path_get_index_by_offset(train, train.index, - data.pos_in_train + wagon.wagon_span)
	local pos, connid, frac = advtrains.path_getrestore(train, p_index)
	local tp = {}
	for k,v in ipairs(train.trainparts) do
		if k >= index then
			table.insert(tp, v)
			train.trainparts[k] = nil
		end
	end
	advtrains.update_trainpart_properties(train_id)
	recalc_end_index(train)
	run_callbacks_update(train_id, train)
	
	--create subtrain
	local newtrain_id=advtrains.create_new_train_at(pos, connid, frac, tp)
	local newtrain=advtrains.trains[newtrain_id]
	
	newtrain.velocity=train.velocity
	return newtrain_id -- return new train ID, so new train can be manipulated

end

function advtrains.split_train_at_wagon(wagon_id)
	--get train
	local data = advtrains.wagons[wagon_id]
	advtrains.split_train_at_index(advtrains.trains[data.train_id], data.pos_in_trainparts)
end

-- coupling
local CPL_CHK_DST = -1
local CPL_ZONE = 2

-- 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 id1 = train1.id
	local id2 = train2.id
	if train1.autocouple or train2.autocouple then
		-- couple trains
		train1.autocouple = nil
		train2.autocouple = nil		
		minetest.after(0, advtrains.safe_couple_trains, id1, id2, t1_is_front, t2_is_front, false, false, train1.velocity, train2.velocity)
		return
	end
	
	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=id1
	le.train_id_2=id2
	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)
	if t1_is_front then
		train1.cpl_front = obj
	else
		train1.cpl_back = obj
	end
	if t2_is_front then
		train2.cpl_front = obj
	else
		train2.cpl_back = obj
	end
	
end

function advtrains.train_check_couples(train)
	--atdebug("rechecking couples")
	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 train.cpl_front then
		-- recheck front couple
		local front_trains, pos = advtrains.occ.get_occupations(train, atround(train.index) + CPL_CHK_DST)
		if advtrains.is_node_loaded(pos) then -- if the position is loaded...
			for tid, idx in pairs(front_trains) do
				local other_train = advtrains.trains[tid]
				if not advtrains.train_ensure_init(tid, other_train) then
					atwarn("Train",tid,"is not initialized! Couldn't check couples!")
					return
				end
				--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)
						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
	end
	if train.cpl_back then
		if not train.cpl_back:getyaw() then
			-- objectref is no longer valid. reset.
			train.cpl_back = nil
		end
	end
	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)
		if advtrains.is_node_loaded(pos) then -- if the position is loaded...
			for tid, idx in pairs(back_trains) do
				local other_train = advtrains.trains[tid]
				if not advtrains.train_ensure_init(tid, other_train) then
					atwarn("Train",tid,"is not initialized! Couldn't check couples!")
					return
				end
				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
			end
		end
	end
end

function advtrains.couple_invalidate(train)
	if train.cpl_back then
		train.cpl_back:remove()
		train.cpl_back = nil
	end
	if train.cpl_front then
		train.cpl_front:remove()
		train.cpl_front = nil
	end
	train.was_standing = nil
end

-- 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, vel)
	local first, second=advtrains.trains[first_id], advtrains.trains[second_id]
	
	if not advtrains.train_ensure_init(first_id, first) then
		atwarn("Train",first_id,"is not initialized! Operation aborted!")
		return
	end
	if not advtrains.train_ensure_init(second_id, second) then
		atwarn("Train",second_id,"is not initialized! Operation aborted!")
		return
	end
	
	local first_wagoncnt=#first.trainparts
	local second_wagoncnt=#second.trainparts
	
	for _,v in ipairs(second.trainparts) do
		table.insert(first.trainparts, v)
	end
	
	advtrains.remove_train(second_id)
	if vel < 0 then
		advtrains.invert_train(first_id)
		vel = -vel
	end
	first.velocity= vel or 0
	
	advtrains.update_trainpart_properties(first_id)
	advtrains.couple_invalidate(first)
	return true
end

function advtrains.invert_train(train_id)
	local train=advtrains.trains[train_id]
	
	if not advtrains.train_ensure_init(train_id, train) then
		atwarn("Train",train_id,"is not initialized! Operation aborted!")
		return
	end
	
	advtrains.path_setrestore(train, true)
	
	-- rotate some other stuff
	if train.door_open then
		train.door_open = - train.door_open
	end
	if train.atc_command then
		train.atc_arrow = not train.atc_arrow
	end
	
	advtrains.path_invalidate(train, true)
	advtrains.couple_invalidate(train)
	
	local old_trainparts=train.trainparts
	train.trainparts={}
	for k,v in ipairs(old_trainparts) do
		table.insert(train.trainparts, 1, v)--notice insertion at first place
	end
	advtrains.update_trainpart_properties(train_id, true)
	
	-- recalculate path
	advtrains.train_ensure_init(train_id, train)
	
	-- If interlocking present, check whether this train is in a section and then set as shunt move after reversion
	if advtrains.interlocking and train.il_sections and #train.il_sections > 0 then
		train.is_shunt = true
		train.speed_restriction = advtrains.SHUNT_SPEED_MAX
	else
		train.is_shunt = false
		train.speed_restriction = nil
	end
end

-- returns: train id, index of one of the trains that stand at this position.
function advtrains.get_train_at_pos(pos)
	local t = advtrains.occ.get_trains_at(pos)
	for tid,idx in pairs(t) do
		return tid, idx
	end
end


-- ehm... I never adapted this function to the new path system ?!
function advtrains.invalidate_all_paths(pos)
	local tab
	if pos then
		-- if position given, check occupation system
		tab = advtrains.occ.get_trains_over(pos)
	else
		tab = advtrains.trains
	end
	
	for id, _ in pairs(tab) do
		advtrains.invalidate_path(id)
	end
end

-- Calls invalidate_path_ahead on all trains occupying (having paths over) this node
-- Can be called during train step.
function advtrains.invalidate_all_paths_ahead(pos)
	local tab = advtrains.occ.get_trains_over(pos)
	
	for id,index in pairs(tab) do
		local train = advtrains.trains[id]
		advtrains.path_invalidate_ahead(train, index, true)
	end
end

function advtrains.invalidate_path(id)
	--atdebug("Path invalidate:",id)
	local v=advtrains.trains[id]
	if not v then return end
	advtrains.path_invalidate(v)
	advtrains.couple_invalidate(v)
	v.dirty = true
end

--not blocking trains group
function advtrains.train_collides(node)
	if node and minetest.registered_nodes[node.name] and minetest.registered_nodes[node.name].walkable then
		if not minetest.registered_nodes[node.name].groups.not_blocking_trains then
			return true
		end
	end
	return false
end

local nonblocknodes={
	"default:fence_wood",
	"default:fence_acacia_wood",
	"default:fence_aspen_wood",
	"default:fence_pine_wood",
	"default:fence_junglewood",
	"default:torch",
	"bones:bones",
	
	"default:sign_wall",
	"signs:sign_wall",
	"signs:sign_wall_blue",
	"signs:sign_wall_brown",
	"signs:sign_wall_orange",
	"signs:sign_wall_green",
	"signs:sign_yard",
	"signs:sign_wall_white_black",
	"signs:sign_wall_red",
	"signs:sign_wall_white_red",
	"signs:sign_wall_yellow",
	"signs:sign_post",
	"signs:sign_hanging",
	
	
}
minetest.after(0, function()
	for _,name in ipairs(nonblocknodes) do
		if minetest.registered_nodes[name] then
			minetest.registered_nodes[name].groups.not_blocking_trains=1
		end
	end
end)