--atan2 counts angles clockwise, minetest does counterclockwise

minetest.register_privilege("train_place", {
	description = "Player can place trains on tracks not owned by player",
	give_to_singleplayer= false,
});
minetest.register_privilege("train_remove", {
	description = "Player can remove trains not owned by player",
	give_to_singleplayer= false,
});
minetest.register_privilege("train_operator", {
	description = "Player may operate trains and switch signals. Given by default. Revoke to prevent players from griefing automated subway systems.",
	give_to_singleplayer= true,
	default= true,
});

local wagon={
	collisionbox = {-0.5,-0.5,-0.5, 0.5,0.5,0.5},
	--physical = true,
	visual = "mesh",
	mesh = "wagon.b3d",
	visual_size = {x=3, y=3},
	textures = {"black.png"},
	is_wagon=true,
	wagon_span=1,--how many index units of space does this wagon consume
	has_inventory=false,
}


function wagon:train()
	return advtrains.trains[self.train_id]
end

--[[about 'initalized':
	when initialized is false, the entity hasn't got any data yet and should wait for these to be set before doing anything
	when loading an existing object (with staticdata), it will be set
	when instanciating a new object via add_entity, it is not set at the time on_activate is called.
	then, wagon:initialize() will be called
	
	wagon will save only uid in staticdata, no serialized table
]]
function wagon:on_activate(sd_uid, dtime_s)
	if sd_uid~="" then
		--destroy when loaded from static block.
		self.object:remove()
		return
	end
	self.object:set_armor_groups({immortal=1})
	self.entity_name=self.name
end

function wagon:get_staticdata()
	return advtrains.pcall(function()
		if not self:ensure_init() then return end
		atprint("[wagon "..((self.unique_id and self.unique_id~="" and self.unique_id) or "no-id").."]: saving to wagon_save")
		--serialize inventory, if it has one
		if self.has_inventory then
			local inv=minetest.get_inventory({type="detached", name="advtrains_wgn_"..self.unique_id})
			self.ser_inv=advtrains.serialize_inventory(inv)
		end
		--save to table before being unloaded
		advtrains.wagon_save[self.unique_id]=advtrains.save_keys(self, {
			"seatp", "owner", "ser_inv", "wagon_flipped", "train_id"
		})
		advtrains.wagon_save[self.unique_id].entity_name=self.name
		return self.unique_id
	end)
end
--returns: uid of wagon
function wagon:init_new_instance(train_id, properties)
	local new_id=advtrains.random_id()
	while advtrains.wagon_save[new_id] do new_id=advtrains.random_id() end--ensure uniqueness
	self.unique_id=new_id
	self.train_id=train_id
	for k,v in pairs(properties) do
		if k~="name" and k~="object" then
			self[k]=v
		end
	end
	self:init_shared()
	self.initialized=true
	atprint("init_new_instance "..self.unique_id.." ("..self.train_id..")")
	return self.unique_id
end
function wagon:init_from_wagon_save(uid)
	if not advtrains.wagon_save[uid] then
		self.object:remove()
		return
	end
	self.unique_id=uid
	for k,v in pairs(advtrains.wagon_save[uid]) do
		if k~="name" and k~="object" then
			self[k]=v
		end
	end
	if not self.train_id or not self:train() then
		self.object:remove()
		return
	end
	self:init_shared()
	self.initialized=true
	minetest.after(0.2, function() self:reattach_all() end)
	atprint("init_from_wagon_save "..self.unique_id.." ("..self.train_id..")")
end
function wagon:init_shared()
	if self.has_inventory then
		local uid_noptr=self.unique_id..""
		--to be used later
		local inv=minetest.create_detached_inventory("advtrains_wgn_"..self.unique_id, {
			allow_move = function(inv, from_list, from_index, to_list, to_index, count, player)
				return count
			end,
			allow_put = function(inv, listname, index, stack, player)
				return stack:get_count()
			end,
			allow_take = function(inv, listname, index, stack, player)
				return stack:get_count()
			end
		})
		if self.ser_inv then
			advtrains.deserialize_inventory(self.ser_inv, inv)
		end
		if self.inventory_list_sizes then
			for lst, siz in pairs(self.inventory_list_sizes) do
				inv:set_size(lst, siz)
			end
		end
	end
	if self.doors then
		self.door_anim_timer=0
		self.door_state=0
	end
	if self.custom_on_activate then
		self:custom_on_activate(dtime_s)
	end
	-- reset line and infotext cache to update object properties on first call
	self.line_cache=nil
	self.infotext_cache=nil
end
function wagon:ensure_init()
	if self.initialized then
		if self.noninitticks then self.noninitticks=nil end
		return true
	end
	if not self.noninitticks then self.noninitticks=0 end
	self.noninitticks=self.noninitticks+1
	if self.noninitticks>20 then
		self.object:remove()
	else
		self.object:setvelocity({x=0,y=0,z=0})
	end
	return false
end

-- Remove the wagon
function wagon:on_punch(puncher, time_from_last_punch, tool_capabilities, direction)
	return advtrains.pcall(function()
		if not self:ensure_init() then return end
		if not puncher or not puncher:is_player() then
			return
		end
		if self.owner and puncher:get_player_name()~=self.owner and (not minetest.check_player_privs(puncher, {train_remove = true })) then
		   minetest.chat_send_player(puncher:get_player_name(), attrans("This wagon is owned by @1, you can't destroy it.", self.owner));
		   return
		end
		
		if minetest.settings:get_bool("creative_mode") then
			if not self:destroy() then return end
			
			local inv = puncher:get_inventory()
			if not inv:contains_item("main", self.name) then
				inv:add_item("main", self.name)
			end
		else
			local pc=puncher:get_player_control()
			if not pc.sneak then
				minetest.chat_send_player(puncher:get_player_name(), attrans("Warning: If you destroy this wagon, you only get some steel back! If you are sure, hold Sneak and left-click the wagon."))
				return
			end

			if not self:destroy() then return end

			local inv = puncher:get_inventory()
			for _,item in ipairs(self.drops or {self.name}) do
				inv:add_item("main", item)
			end
		end
	end)
end
function wagon:destroy()
	--some rules:
	-- you get only some items back
	-- single left-click shows warning
	-- shift leftclick destroys
	-- not when a driver is inside
	
	for _,_ in pairs(self.seatp) do
		return
	end
	
	if self.custom_may_destroy then
		if not self.custom_may_destroy(self, puncher, time_from_last_punch, tool_capabilities, direction) then
			return
		end
	end
	if self.custom_on_destroy then
		self.custom_on_destroy(self, puncher, time_from_last_punch, tool_capabilities, direction)
	end
	
	atprint("[wagon "..((self.unique_id and self.unique_id~="" and self.unique_id) or "no-id").."]: destroying")
	
	self.object:remove()

	table.remove(self:train().trainparts, self.pos_in_trainparts)
	advtrains.update_trainpart_properties(self.train_id)
	advtrains.wagon_save[self.unique_id]=nil
	if self.discouple then self.discouple.object:remove() end--will have no effect on unloaded objects
	return true
end


function wagon:on_step(dtime)
	return advtrains.pcall(function()
		if not self:ensure_init() then return end
		
		local t=os.clock()
		local pos = self.object:getpos()
		
		if not pos then
			atprint("["..self.unique_id.."][fatal] missing position (object:getpos() returned nil)")
			return
		end

		self.entity_name=self.name
		
		--is my train still here
		if not self.train_id or not self:train() then
			atprint("[wagon "..self.unique_id.."] missing train_id, destroying")
			self.object:remove()
			return
		end
		if not self.seatp then
			self.seatp={}
		end
		if not self.seatpc then
			self.seatpc={}
		end
		
		--Legacy: remove infotext since it does not work this way anyways
		self.infotext=nil

		--custom on_step function
		if self.custom_on_step then
			self:custom_on_step(self, dtime)
		end

		--driver control
		for seatno, seat in ipairs(self.seats) do
			local driver=self.seatp[seatno] and minetest.get_player_by_name(self.seatp[seatno])
			local has_driverstand=seat.driving_ctrl_access and self.seatp[seatno] and minetest.check_player_privs(self.seatp[seatno], {train_operator=true})
			if has_driverstand and driver then
				advtrains.update_driver_hud(driver:get_player_name(), self:train(), self.wagon_flipped)
			elseif driver then
				--only show the inside text
				local inside=self:train().text_inside or ""
				advtrains.set_trainhud(driver:get_player_name(), inside)
			end
			if driver and driver:get_player_control_bits()~=self.seatpc[seatno] then
				local pc=driver:get_player_control()
				self.seatpc[seatno]=driver:get_player_control_bits()
				
				if has_driverstand then
					--regular driver stand controls
					advtrains.on_control_change(pc, self:train(), self.wagon_flipped)
					--sound horn when required
					if self.horn_sound and pc.aux1 and not pc.sneak and not self.horn_handle then
						self.horn_handle = minetest.sound_play(self.horn_sound, {
							object = self.object,
							gain = 1.0, -- default
							max_hear_distance = 128, -- default, uses an euclidean metric
							loop = true,
						})
					elseif not pc.aux1 and self.horn_handle then
						minetest.sound_stop(self.horn_handle)
						self.horn_handle = nil
					end
				else
					-- If on a passenger seat and doors are open, get off when W or D pressed.
					local pass = self.seatp[seatno] and minetest.get_player_by_name(self.seatp[seatno])
					if pass and self:train().door_open~=0 then
					local pc=pass:get_player_control()
						if pc.up or pc.down then
							self:get_off(seatno)
						end
					end		      
				end
				if pc.aux1 and pc.sneak then
					self:get_off(seatno)
				end
			end
		end
		
		--check infotext
		local outside=self:train().text_outside or ""
		
		local gp=self:train()
		--show off-track information in outside text instead of notifying the whole server about this
		local front_off_track=gp.max_index_on_track and gp.index and gp.index>gp.max_index_on_track
		local back_off_track=gp.min_index_on_track and gp.end_index and gp.end_index<gp.min_index_on_track
		if front_off_track or back_off_track then
			outside = outside .."\n!!! Train off track !!!"
		end
		
		if self.infotext_cache~=outside  then
			self.object:set_properties({infotext=outside})
			self.infotext_cache=outside
		end
		
		local fct=self.wagon_flipped and -1 or 1
		--set line number
		if self.name == "advtrains:subway_wagon" and gp.line and gp.line~=self.line_cache then
			local new_line_tex="advtrains_subway_wagon.png^advtrains_subway_wagon_line"..gp.line..".png"
			self.object:set_properties({
				textures={new_line_tex},
		 	})
			self.line_cache=gp.line
		elseif self.line_cache~=nil and gp.line==nil then
			self.object:set_properties({
				textures=self.textures,
		 	})
			self.line_cache=nil
		end
		--door animation
		if self.doors then
			if (self.door_anim_timer or 0)<=0 then
				local dstate = (gp.door_open or 0) * fct
				if dstate ~= self.door_state then
					local at
					--meaning of the train.door_open field:
					-- -1: left doors (rel. to train orientation)
					--  0: closed
					--  1: right doors
					--this code produces the following behavior:
					-- if changed from 0 to +-1, play open anim. if changed from +-1 to 0, play close.
					-- if changed from +-1 to -+1, first close and set 0, then it will detect state change again and run open.
					if self.door_state == 0 then
						if self.doors.open.sound then minetest.sound_play(self.doors.open.sound, {object = self.object}) end
						at=self.doors.open[dstate]
						self.object:set_animation(at.frames, at.speed or 15, at.blend or 0, false)
						self.door_state = dstate
					else
						if self.doors.close.sound then minetest.sound_play(self.doors.close.sound, {object = self.object}) end
						at=self.doors.close[self.door_state or 1]--in case it has not been set yet
						self.object:set_animation(at.frames, at.speed or 15, at.blend or 0, false)
						self.door_state = 0
					end
					self.door_anim_timer = at.time
				end
			else
				self.door_anim_timer = (self.door_anim_timer or 0) - dtime
			end
		end
		
		--DisCouple
		if self.pos_in_trainparts and self.pos_in_trainparts>1 then
			if gp.velocity==0 then
				if not self.discouple or not self.discouple.object:getyaw() then
					local object=minetest.add_entity(pos, "advtrains:discouple")
					if object then
						local le=object:get_luaentity()
						le.wagon=self
						--box is hidden when attached, so unuseful.
						--object:set_attach(self.object, "", {x=0, y=0, z=self.wagon_span*10}, {x=0, y=0, z=0})
						self.discouple=le
					else
						atprint("Couldn't spawn DisCouple")
					end
				end
			else
				if self.discouple and self.discouple.object:getyaw() then
					self.discouple.object:remove()
				end
			end
		end
		--for path to be available. if not, skip step
		if not gp.path then
			self.object:setvelocity({x=0, y=0, z=0})
			return
		end
		if not self.pos_in_train then
			--why ever. but better continue next step...
			advtrains.update_trainpart_properties(self.train_id)
			return
		end
		
		local index=advtrains.get_real_path_index(self:train(), self.pos_in_train)
		--atprint("trainindex "..gp.index.." wagonindex "..index)
		
		--automatic get_on
		--needs to know index and path
		if self.door_entry and gp.door_open and gp.door_open~=0 and gp.velocity==0 then
			--using the mapping created by the trainlogic globalstep
			for i, ino in ipairs(self.door_entry) do
				--fct is the flipstate flag from door animation above
				local aci = index + ino*fct
				local ix1=gp.path[math.floor(aci)]
				local ix2=gp.path[math.floor(aci+1)]
				-- the two wanted positions are ix1 and ix2 + (2nd-1st rotated by 90deg)
				-- (x z) rotated by 90deg is (-z x)  (http://stackoverflow.com/a/4780141)
				local add = { x = (ix2.z-ix1.z)*gp.door_open, y = 0, z = (ix1.x-ix2.x)*gp.door_open }
				local pts1=vector.round(vector.add(ix1, add))
				local pts2=vector.round(vector.add(ix2, add))
				if minetest.get_item_group(minetest.get_node(pts1).name, "platform")>0 then
					local ckpts={
						pts1,
						pts2,
						vector.add(pts1, {x=0, y=1, z=0}),
						vector.add(pts2, {x=0, y=1, z=0}),
					}
					for _,ckpos in ipairs(ckpts) do
						local cpp=minetest.pos_to_string(ckpos)
						if advtrains.playersbypts[cpp] then
							self:on_rightclick(advtrains.playersbypts[cpp])
						end
					end
				end
			end
		end
		
		--position recalculation
		local first_pos=gp.path[math.floor(index)]
		local second_pos=gp.path[math.floor(index)+1]
		if not first_pos or not second_pos then
			--atprint(" object "..self.unique_id.." path end reached!")
			self.object:setvelocity({x=0,y=0,z=0})
			return
		end
		
		--checking for environment collisions(a 3x3 cube around the center)
		if not gp.recently_collided_with_env then
			local collides=false
			local exh = self.extent_h or 1
			local exv = self.extent_v or 2
			for x=-exh,exh do
				for y=0,exv do
					for z=-exh,exh do
						local node=minetest.get_node_or_nil(vector.add(first_pos, {x=x, y=y, z=z}))
						if (advtrains.train_collides(node)) then
							collides=true
						end
					end
				end
			end
			if collides then
				if self.collision_count and self.collision_count>10 then
					--enable collision mercy to get trains stuck in walls out of walls
					--actually do nothing except limiting the velocity to 1
					gp.velocity=math.min(gp.velocity, 1)
					gp.tarvelocity=math.min(gp.tarvelocity, 1)
				else
					gp.recently_collided_with_env=true
					gp.velocity=2*gp.velocity
					gp.movedir=-gp.movedir
					gp.tarvelocity=0
					self.collision_count=(self.collision_count or 0)+1
				end
			else
				self.collision_count=nil
			end
		end
		
		--FIX: use index of the wagon, not of the train.
		local velocity=(gp.velocity*gp.movedir)/(gp.path_dist[math.floor(index)] or 1)
		local acceleration=(gp.last_accel or 0)/(gp.path_dist[math.floor(index)] or 1)
		local factor=index-math.floor(index)
		local actual_pos={x=first_pos.x-(first_pos.x-second_pos.x)*factor, y=first_pos.y-(first_pos.y-second_pos.y)*factor, z=first_pos.z-(first_pos.z-second_pos.z)*factor,}
		local velocityvec={x=(first_pos.x-second_pos.x)*velocity*-1, z=(first_pos.z-second_pos.z)*velocity*-1, y=(first_pos.y-second_pos.y)*velocity*-1}
		local accelerationvec={x=(first_pos.x-second_pos.x)*acceleration*-1, z=(first_pos.z-second_pos.z)*acceleration*-1, y=(first_pos.y-second_pos.y)*acceleration*-1}
		
		--some additional positions to determine orientation
		local aposfwd=gp.path[math.floor(index+2)]
		local aposbwd=gp.path[math.floor(index-1)]
		
		local yaw
		if aposfwd and aposbwd then
			yaw=advtrains.get_wagon_yaw(aposfwd, second_pos, first_pos, aposbwd, factor)+math.pi--TODO remove when cleaning up
		else
			yaw=math.atan2((first_pos.x-second_pos.x), (second_pos.z-first_pos.z))
		end
		if self.wagon_flipped then
			yaw=yaw+math.pi
		end
		
		self.updatepct_timer=(self.updatepct_timer or 0)-dtime
		if not self.old_velocity_vector 
				or not vector.equals(velocityvec, self.old_velocity_vector)
				or not self.old_acceleration_vector 
				or not vector.equals(accelerationvec, self.old_acceleration_vector)
				or self.old_yaw~=yaw
				or self.updatepct_timer<=0 then--only send update packet if something changed
				self.object:setpos(actual_pos)
			self.object:setvelocity(velocityvec)
			self.object:setacceleration(accelerationvec)
			
			if #self.seats > 0 and self.old_yaw ~= yaw then
				if not self.player_yaw then
					self.player_yaw = {}
				end
				if not self.old_yaw then
					self.old_yaw=yaw
				end
				for _,name in pairs(self.seatp) do
					local p = minetest.get_player_by_name(name)
					if p then
						if not self.turning then
							-- save player looking direction offset
							self.player_yaw[name] = p:get_look_horizontal()-self.old_yaw
						end
						-- set player looking direction using calculated offset
						p:set_look_horizontal(self.player_yaw[name]+yaw)
					end
				end
				self.turning = true							 
			elseif self.old_yaw == yaw then
				-- train is no longer turning
				self.turning = false
			end
			
			self.object:setyaw(yaw)
			self.updatepct_timer=2
			if self.update_animation then
				self:update_animation(gp.velocity, self.old_velocity)
			end
			if self.custom_on_velocity_change then
				self:custom_on_velocity_change(gp.velocity, self.old_velocity or 0)
			end
		end
		
		
		self.old_velocity_vector=velocityvec
		self.old_velocity = gp.velocity
		self.old_acceleration_vector=accelerationvec
		self.old_yaw=yaw
		atprintbm("wagon step", t)
	end)
end

function advtrains.get_real_path_index(train, pit)
	local pos_in_train_left=pit
	local index=train.index
	if pos_in_train_left>(index-math.floor(index))*(train.path_dist[math.floor(index)] or 1) then
		pos_in_train_left=pos_in_train_left - (index-math.floor(index))*(train.path_dist[math.floor(index)] or 1)
		index=math.floor(index)
		while pos_in_train_left>(train.path_dist[index-1] or 1) do
			pos_in_train_left=pos_in_train_left - (train.path_dist[index-1] or 1)
			index=index-1
		end
		index=index-(pos_in_train_left/(train.path_dist[index-1] or 1))
	else
		index=index-(pos_in_train_left/(train.path_dist[math.floor(index-1)] or 1))
	end
	return index
end

function wagon:on_rightclick(clicker)
	return advtrains.pcall(function()
		if not self:ensure_init() then return end
		if not clicker or not clicker:is_player() then
			return
		end
		if clicker:get_player_control().aux1 then
			--advtrains.dumppath(self:train().path)
			--minetest.chat_send_all("at index "..(self:train().index or "nil"))
			--advtrains.invert_train(self.train_id)
			atprint(dump(self))
			return
		end	
		local pname=clicker:get_player_name()
		local no=self:get_seatno(pname)
		if no then
			if self.seat_groups then
				local poss={}
				local sgr=self.seats[no].group
				for _,access in ipairs(self.seat_groups[sgr].access_to) do
					if self:check_seat_group_access(pname, access) then
						poss[#poss+1]={name=self.seat_groups[access].name, key="sgr_"..access}
					end
				end
				if self.has_inventory and self.get_inventory_formspec then
					poss[#poss+1]={name=attrans("Show Inventory"), key="inv"}
				end
				if self.owner==pname then
					poss[#poss+1]={name=attrans("Wagon properties"), key="prop"}
				end
				if not self.seat_groups[sgr].require_doors_open or self:train().door_open~=0 then
					poss[#poss+1]={name=attrans("Get off"), key="off"}
				else
					if clicker:get_player_control().sneak then
						poss[#poss+1]={name=attrans("Get off (forced)"), key="off"}
					else
						poss[#poss+1]={name=attrans("(Doors closed)"), key="dcwarn"}
					end
				end
				if #poss==0 then
					--can't do anything.
				elseif #poss==1 then
					self:seating_from_key_helper(pname, {[poss[1].key]=true}, no)
				else
					local form = "size[5,"..1+(#poss).."]"
					for pos,ent in ipairs(poss) do
						form = form .. "button_exit[0.5,"..(pos-0.5)..";4,1;"..ent.key..";"..ent.name.."]"
					end
					minetest.show_formspec(pname, "advtrains_seating_"..self.unique_id, form)
				end
			else
				self:get_off(no)
			end
		else
			--do not attach if already on a train
			if advtrains.player_to_train_mapping[pname] then return end
			if self.seat_groups then
				if #self.seats==0 then
					if self.has_inventory and self.get_inventory_formspec then
						minetest.show_formspec(pname, "advtrains_inv_"..self.unique_id, self:get_inventory_formspec(pname))
					end
					return
				end
				
				local doors_open = self:train().door_open~=0 or clicker:get_player_control().sneak
				for _,sgr in ipairs(self.assign_to_seat_group) do
					if self:check_seat_group_access(pname, sgr) then
						for seatid, seatdef in ipairs(self.seats) do
							if seatdef.group==sgr and not self.seatp[seatid] and (not self.seat_groups[sgr].require_doors_open or doors_open) then
								self:get_on(clicker, seatid)
								return
							end
						end
					end
				end
				minetest.chat_send_player(pname, attrans("Can't get on: wagon full or doors closed!"))
				minetest.chat_send_player(pname, attrans("Use Sneak+rightclick to bypass closed doors!"))
			else
				self:show_get_on_form(pname)
			end
		end
	end)
end

function wagon:get_on(clicker, seatno)
	if not self.seatp then self.seatp={}end
	if not self.seatpc then self.seatpc={}end--player controls in driver stands
	
	if not self.seats[seatno] then return end
	local oldno=self:get_seatno(clicker:get_player_name())
	if oldno then
		atprint("get_on: clearing oldno",seatno)
		advtrains.player_to_train_mapping[clicker:get_player_name()]=nil
		advtrains.clear_driver_hud(clicker:get_player_name())
		self.seatp[oldno]=nil
	end
	if self.seatp[seatno] and self.seatp[seatno]~=clicker:get_player_name() then
		atprint("get_on: throwing off",self.seatp[seatno],"from seat",seatno)
		self:get_off(seatno)
	end
	atprint("get_on: attaching",clicker:get_player_name())
	self.seatp[seatno] = clicker:get_player_name()
	self.seatpc[seatno] = clicker:get_player_control_bits()
	advtrains.player_to_train_mapping[clicker:get_player_name()]=self.train_id
	clicker:set_attach(self.object, "", self.seats[seatno].attach_offset, {x=0,y=0,z=0})
	clicker:set_eye_offset(self.seats[seatno].view_offset, self.seats[seatno].view_offset)
end
function wagon:get_off_plr(pname)
	local no=self:get_seatno(pname)
	if no then
		self:get_off(no)
	end
end
function wagon:get_seatno(pname)
	for no, cont in pairs(self.seatp) do
		if cont==pname then
			return no
		end
	end
	return nil
end
function wagon:get_off(seatno)
	if not self.seatp[seatno] then return end
	local pname = self.seatp[seatno]
	local clicker = minetest.get_player_by_name(pname)
	advtrains.player_to_train_mapping[pname]=nil
	advtrains.clear_driver_hud(pname)
	self.seatp[seatno]=nil
	self.seatpc[seatno]=nil
	if clicker then
		atprint("get_off: detaching",clicker:get_player_name())
		clicker:set_detach()
		clicker:set_eye_offset({x=0,y=0,z=0}, {x=0,y=0,z=0})
		local gp=self:train()
		--code as in step - automatic get on
		if self.door_entry and gp.door_open and gp.door_open~=0 and gp.velocity==0 and gp.index and gp.path then
			local index=advtrains.get_real_path_index(gp, self.pos_in_train)
			--using the mapping created by the trainlogic globalstep
			for i, ino in ipairs(self.door_entry) do
				local aci = index + ino*(self.wagon_flipped and -1 or 1)
				local ix1=gp.path[math.floor(aci)]
				local ix2=gp.path[math.floor(aci+1)]
				-- the two wanted positions are ix1 and ix2 + (2nd-1st rotated by 90deg)
				-- (x z) rotated by 90deg is (-z x)  (http://stackoverflow.com/a/4780141)
				-- multiplied by 2 here, to place off on platform, y of add is 1.
				local add = { x = (ix2.z-ix1.z)*gp.door_open, y = 0, z = (ix1.x-ix2.x)*gp.door_open}
				local oadd = { x = (ix2.z-ix1.z)*gp.door_open*2, y = 1, z = (ix1.x-ix2.x)*gp.door_open*2}
				local platpos=vector.round(vector.add(ix1, add))
				local offpos=vector.round(vector.add(ix1, oadd))
				atprint("platpos:", platpos, "offpos:", offpos)
				if minetest.get_item_group(minetest.get_node(platpos).name, "platform")>0 then
					minetest.after(0.2, function() clicker:setpos(offpos) end)
					return
				end
			end
		else--if not door_entry, or paths missing, fall back to old method
			local objpos=advtrains.round_vector_floor_y(self.object:getpos())
			local yaw=self.object:getyaw()
			local isx=(yaw < math.pi/4) or (yaw > 3*math.pi/4 and yaw < 5*math.pi/4) or (yaw > 7*math.pi/4)
			--abuse helper function
			for _,r in ipairs({-1, 1}) do
				local p=vector.add({x=isx and r or 0, y=0, z=not isx and r or 0}, objpos)
				local offp=vector.add({x=isx and r*2 or 0, y=1, z=not isx and r*2 or 0}, objpos)
				if minetest.get_item_group(minetest.get_node(p).name, "platform")>0 then
					minetest.after(0.2, function() clicker:setpos(offp) end)
					return
				end
			end
		end
	end
end
function wagon:show_get_on_form(pname)
	if not self.initialized then return end
	if #self.seats==0 then
		if self.has_inventory and self.get_inventory_formspec then
			minetest.show_formspec(pname, "advtrains_inv_"..self.unique_id, self:get_inventory_formspec(pname))
		end
		return
	end
	local form, comma="size[5,8]label[0.5,0.5;"..attrans("Select seat:").."]textlist[0.5,1;4,6;seat;", ""
	for seatno, seattbl in ipairs(self.seats) do
		local addtext, colorcode="", ""
		if self.seatp and self.seatp[seatno] then
			colorcode="#FF0000"
			addtext=" ("..self.seatp[seatno]..")"
		end
		form=form..comma..colorcode..seattbl.name..addtext
		comma=","
	end
	form=form..";0,false]"
	if self.has_inventory and self.get_inventory_formspec then
		form=form.."button_exit[1,7;3,1;inv;"..attrans("Show Inventory").."]"
	end
	minetest.show_formspec(pname, "advtrains_geton_"..self.unique_id, form)
end
function wagon:show_wagon_properties(pname)
	local numsgr=0
	if self.seat_groups then
		numsgr=#self.seat_groups
	end
	if not self.seat_access then
		self.seat_access={}
	end
	--[[
	fields: seat access: empty: everyone
	checkbox: lock couples
	button: save
	]]
	local form="size[5,"..(numsgr*1.5+7).."]"
	local at=0
	if self.seat_groups then
		for sgr,sgrdef in pairs(self.seat_groups) do
			local text = attrans("Access to @1",sgrdef.name)
			form=form.."field[0.5,"..(0.5+at*1.5)..";4,1;sgr_"..sgr..";"..text..";"..(self.seat_access[sgr] or "").."]"
			at=at+1
		end
	end
	form=form.."checkbox[0,"..(at*1.5)..";lock_couples;"..attrans("Lock couples")..";"..(self.lock_couples and "true" or "false").."]"
	if self:train() then --just in case
		form=form.."field[0.5,"..(1.5+at*1.5)..";4,1;text_outside;"..attrans("Text displayed outside on train")..";"..(self:train().text_outside or "").."]"
		form=form.."field[0.5,"..(2.5+at*1.5)..";4,1;text_inside;"..attrans("Text displayed inside train")..";"..(self:train().text_inside or "").."]"
	end
	form=form.."button_exit[0.5,"..(3+at*1.5)..";4,1;save;"..attrans("Save wagon properties").."]"
	minetest.show_formspec(pname, "advtrains_prop_"..self.unique_id, form)
end
minetest.register_on_player_receive_fields(function(player, formname, fields)
	return advtrains.pcall(function()
		local uid=string.match(formname, "^advtrains_geton_(.+)$")
		if uid then
			for _,wagon in pairs(minetest.luaentities) do
				if wagon.is_wagon and wagon.initialized and wagon.unique_id==uid then
					if fields.inv then
						if wagon.has_inventory and wagon.get_inventory_formspec then
							minetest.show_formspec(player:get_player_name(), "advtrains_inv_"..uid, wagon:get_inventory_formspec(player:get_player_name()))
						end
					elseif fields.seat then
						local val=minetest.explode_textlist_event(fields.seat)
						if val and val.type~="INV" and not wagon.seatp[player:get_player_name()] then
						--get on
							wagon:get_on(player, val.index)
							--will work with the new close_formspec functionality. close exactly this formspec.
							minetest.show_formspec(player:get_player_name(), formname, "")
						end
					end
				end
			end
		end
		uid=string.match(formname, "^advtrains_seating_(.+)$")
		if uid then
			for _,wagon in pairs(minetest.luaentities) do
				if wagon.is_wagon and wagon.initialized and wagon.unique_id==uid then
					local pname=player:get_player_name()
					local no=wagon:get_seatno(pname)
					if no then
						if wagon.seat_groups then
							wagon:seating_from_key_helper(pname, fields, no)
						end
					end
				end
			end
		end
		uid=string.match(formname, "^advtrains_prop_(.+)$")
		if uid then
			for _,wagon in pairs(minetest.luaentities) do
				if wagon.is_wagon and wagon.initialized and wagon.unique_id==uid then
					local pname=player:get_player_name()
					if pname~=wagon.owner then
						return true
					end
					if fields.save or not fields.quit then
						for sgr,sgrdef in pairs(wagon.seat_groups) do
							if fields["sgr_"..sgr] then
								local fcont = fields["sgr_"..sgr]
								wagon.seat_access[sgr] = fcont~="" and fcont or nil
							end
						end
						if fields.lock_couples then
							wagon.lock_couples = fields.lock_couples == "true"
						end
						if fields.text_outside then
							if fields.text_outside~="" then
								wagon:train().text_outside=fields.text_outside
							else
								wagon:train().text_outside=nil
							end
						end
						if fields.text_inside then
							if fields.text_inside~="" then
								wagon:train().text_inside=fields.text_inside
							else
								wagon:train().text_inside=nil
							end
						end
						
					end
				end
			end
		end
	end)
end)
function wagon:seating_from_key_helper(pname, fields, no)
	local sgr=self.seats[no].group
	for _,access in ipairs(self.seat_groups[sgr].access_to) do
		if fields["sgr_"..access] and self:check_seat_group_access(pname, access) then
			for seatid, seatdef in ipairs(self.seats) do
				if seatdef.group==access and not self.seatp[seatid] then
					self:get_on(minetest.get_player_by_name(pname), seatid)
					return
				end
			end
		end
	end
	if fields.inv and self.has_inventory and self.get_inventory_formspec then
		minetest.show_formspec(player:get_player_name(), "advtrains_inv_"..self.unique_id, wagon:get_inventory_formspec(player:get_player_name()))
	end
	if fields.prop and self.owner==pname then
		self:show_wagon_properties(pname)
	end
	if fields.dcwarn then
		minetest.chat_send_player(pname, attrans("Doors are closed! Use Sneak+rightclick to ignore the closed doors and get off!"))
	end
	if fields.off then
		self:get_off(no)
	end
end
function wagon:check_seat_group_access(pname, sgr)
	if not self.seat_access then
		return true
	end
	local sae=self.seat_access[sgr]
	if not sae or sae=="" then
		return true
	end
	for name in string.gmatch(sae, "%S+") do
		if name==pname then
			return true
		end
	end
	return false
end
function wagon:reattach_all()
	if not self.seatp then self.seatp={} end
	for seatno, pname in pairs(self.seatp) do
		local p=minetest.get_player_by_name(pname)
		if p then
			self:get_on(p ,seatno)
		end
	end
end

function advtrains.register_wagon(sysname_p, prototype, desc, inv_img)
	local sysname = sysname_p
	if not string.match(sysname, ":") then
		sysname = "advtrains:"..sysname_p
	end
	setmetatable(prototype, {__index=wagon})
	minetest.register_entity(":"..sysname,prototype)
	
	minetest.register_craftitem(":"..sysname, {
		description = desc,
		inventory_image = inv_img,
		wield_image = inv_img,
		stack_max = 1,
		
		on_place = function(itemstack, placer, pointed_thing)
			return advtrains.pcall(function()
				if not pointed_thing.type == "node" then
					return
				end
				

				local node=minetest.get_node_or_nil(pointed_thing.under)
				if not node then atprint("[advtrains]Ignore at placer position") return itemstack end
				local nodename=node.name
				if(not advtrains.is_track_and_drives_on(nodename, prototype.drives_on)) then
					atprint("no track here, not placing.")
					return itemstack
				end
				if not minetest.check_player_privs(placer, {train_place = true }) and minetest.is_protected(pointed_thing.under, placer:get_player_name()) then
					minetest.record_protection_violation(pointed_thing.under, placer:get_player_name())
					return
				end
				local tconns=advtrains.get_track_connections(node.name, node.param2)
				local yaw = placer:get_look_horizontal() + (math.pi/2)
				local plconnid = advtrains.yawToClosestConn(yaw, tconns)
				
				local prevpos = advtrains.get_adjacent_rail(pointed_thing.under, tconns, plconnid, prototype.drives_on)
				if not prevpos then return end
				local id=advtrains.create_new_train_at(pointed_thing.under, prevpos)
				
				local ob=minetest.add_entity(pointed_thing.under, sysname)
				if not ob then
					atprint("couldn't add_entity, aborting")
				end
				local le=ob:get_luaentity()
				
				le.owner=placer:get_player_name()
				
				local wagon_uid=le:init_new_instance(id, {})
				
				advtrains.add_wagon_to_train(le, id)
				if not minetest.settings:get_bool("creative_mode") then
					itemstack:take_item()
				end
				return itemstack
				
			end)
		end,
	})
end

--[[
	wagons can define update_animation(self, velocity) if they have a speed-dependent animation
	this function will be called when the velocity vector changes or every 2 seconds.
]]