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


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

advtrains.train_accel_force=2--per second and divided by number of wagons
advtrains.train_brake_force=3--per second, not divided by number of wagons
advtrains.train_roll_force=0.5--per second, not divided by number of wagons, acceleration when rolling without brake
advtrains.train_emerg_force=10--for emergency brakes(when going off track)

advtrains.audit_interval=10


advtrains.trains={}
advtrains.wagon_save={}

--load initially
advtrains.fpath=minetest.get_worldpath().."/advtrains"
local file, err = io.open(advtrains.fpath, "r")
if not file then
	local er=err or "Unknown Error"
	atprint("Failed loading advtrains save file "..er)
else
	local tbl = minetest.deserialize(file:read("*a"))
	if type(tbl) == "table" then
		advtrains.trains=tbl
	end
	file:close()
end
advtrains.fpath_ws=minetest.get_worldpath().."/advtrains_wagon_save"
local file, err = io.open(advtrains.fpath_ws, "r")
if not file then
	local er=err or "Unknown Error"
	atprint("Failed loading advtrains save file "..er)
else
	local tbl = minetest.deserialize(file:read("*a"))
	if type(tbl) == "table" then
		advtrains.wagon_save=tbl
	end
	file:close()
end


advtrains.save = function()
	atprint("saving")
	advtrains.invalidate_all_paths()
	local datastr = minetest.serialize(advtrains.trains)
	if not datastr then
		minetest.log("error", " Failed to serialize train data!")
		return
	end
	local file, err = io.open(advtrains.fpath, "w")
	if err then
		return err
	end
	file:write(datastr)
	file:close()
	
	-- update wagon saves
	for _,wagon in pairs(minetest.luaentities) do
		if wagon.is_wagon and wagon.initialized then
			wagon:get_staticdata()
		end
	end
	--cross out userdata
	for w_id, data in pairs(advtrains.wagon_save) do
		data.name=nil
		data.object=nil
		if data.driver then
			data.driver_name=data.driver:get_player_name()
			data.driver=nil
		else
			data.driver_name=nil
		end
		if data.discouple then
			data.discouple.object:remove()
			data.discouple=nil
		end
	end
	--atprint(dump(advtrains.wagon_save))
	datastr = minetest.serialize(advtrains.wagon_save)
	if not datastr then
		minetest.log("error", " Failed to serialize train data!")
		return
	end
	file, err = io.open(advtrains.fpath_ws, "w")
	if err then
		return err
	end
	file:write(datastr)
	file:close()
	
	advtrains.save_trackdb()
	advtrains.atc.save()
end
minetest.register_on_shutdown(advtrains.save)

advtrains.save_and_audit_timer=advtrains.audit_interval
minetest.register_globalstep(function(dtime)
	advtrains.save_and_audit_timer=advtrains.save_and_audit_timer-dtime
	if advtrains.save_and_audit_timer<=0 then
		local t=os.clock()
		
		--save
		advtrains.save()
		advtrains.save_and_audit_timer=advtrains.audit_interval
		atprintbm("saving", t)
	end
	--regular train step
	local t=os.clock()
	for k,v in pairs(advtrains.trains) do
		advtrains.train_step(k, v, dtime)
	end
	
	--see tracks.lua
	if advtrains.detector.clean_step_before then
		advtrains.detector.finalize_restore()
	end
	
	atprintbm("trainsteps", t)
	endstep()
end)

function advtrains.train_step(id, train, dtime)
	--Legacy: set drives_on and max_speed
	if not train.drives_on or not train.max_speed then
		advtrains.update_trainpart_properties(id)
	end
	--TODO check for all vars to be present
	if not train.velocity then
		train.velocity=0
	end
	if not train.movedir or (train.movedir~=1 and train.movedir~=-1) then
		train.movedir=1
	end
	--very unimportant thing: check if couple is here
	if train.couple_eid_front and (not minetest.luaentities[train.couple_eid_front] or not minetest.luaentities[train.couple_eid_front].is_couple) then train.couple_eid_front=nil end
	if train.couple_eid_back and (not minetest.luaentities[train.couple_eid_back] or not minetest.luaentities[train.couple_eid_back].is_couple) then train.couple_eid_back=nil end
	
	--skip certain things (esp. collision) when not moving
	local train_moves=(train.velocity~=0)
	
	--if not train.last_pos then advtrains.trains[id]=nil return end
	
	if not advtrains.pathpredict(id, train) then 
		atprint("pathpredict failed(returned false)")
		train.velocity=0
		train.tarvelocity=0
		return
	end
	
	local path=advtrains.get_or_create_path(id, train)
	if not path then
		train.velocity=0
		train.tarvelocity=0
		atprint("train has no path for whatever reason")
		return 
	end
	
	local train_end_index=advtrains.get_train_end_index(train)
	--apply off-track handling:
	local front_off_track=train.max_index_on_track and train.index>train.max_index_on_track
	local back_off_track=train.min_index_on_track and train_end_index<train.min_index_on_track
	if front_off_track and back_off_track then--allow movement in both directions
		if train.tarvelocity>1 then train.tarvelocity=1 end
	elseif front_off_track then--allow movement only backward
		if train.movedir==1 and train.tarvelocity>0 then train.tarvelocity=0 end
		if train.movedir==-1 and train.tarvelocity>1 then train.tarvelocity=1 end
	elseif back_off_track then--allow movement only forward
		if train.movedir==-1 and train.tarvelocity>0 then train.tarvelocity=0 end
		if train.movedir==1 and train.tarvelocity>1 then train.tarvelocity=1 end
	end
	
	--update advtrains.detector
	if not train.detector_old_index then
		train.detector_old_index = math.floor(train_end_index)
		train.detector_old_end_index = math.floor(train_end_index)
	end
	local ifo, ifn, ibo, ibn = train.detector_old_index, math.floor(train.index), train.detector_old_end_index, math.floor(train_end_index)
	if ifn>ifo then
		for i=ifo, ifn do
			if path[i] then
				advtrains.detector.enter_node(path[i], id)
			end
		end
	elseif ifn<ifo then
		for i=ifn, ifo do
			if path[i] then
				advtrains.detector.leave_node(path[i], id)
			end
		end
	end
	if ibn<ibo then
		for i=ibn, ibn do
			if path[i] then
				advtrains.detector.enter_node(path[i], id)
			end
		end
	elseif ibn>ibo then
		for i=ibo, ibn do
			if path[i] then
				advtrains.detector.leave_node(path[i], id)
			end
		end
	end
	train.detector_old_index = math.floor(train.index)
	train.detector_old_end_index = math.floor(train_end_index)
	
	--remove?
	if #train.trainparts==0 then
		atprint("[train "..sid(id).."] has empty trainparts, removing.")
		advtrains.detector.leave_node(path[train.detector_old_index], id)
		advtrains.trains[id]=nil
		return
	end
	
	if train_moves then
		--check for collisions by finding objects
		
		--heh, new collision again.
		--this time, based on NODES and the advtrains.detector.on_node table.
		local collpos
		local coll_grace=1
		if train.movedir==1 then
			collpos=advtrains.get_real_index_position(path, train.index-coll_grace)
		else
			collpos=advtrains.get_real_index_position(path, train_end_index+coll_grace)
		end
		if collpos then
			local rcollpos=advtrains.round_vector_floor_y(collpos)
			for x=-1,1 do
				for z=-1,1 do
					local testpos=vector.add(rcollpos, {x=x, y=0, z=z})
					local testpts=minetest.pos_to_string(testpos)
					if advtrains.detector.on_node[testpts] and advtrains.detector.on_node[testpts]~=id then
						if advtrains.trains[advtrains.detector.on_node[testpts]] then
							--collides
							advtrains.spawn_couple_on_collide(id, testpos, advtrains.detector.on_node[testpts], train.movedir==-1)
							
							train.recently_collided_with_env=true
							train.velocity=0.5*train.velocity
							train.movedir=train.movedir*-1
							train.tarvelocity=0
						else
							--unexistant train left in this place
							advtrains.detector.on_node[testpts]=nil
						end
					end
				end
			end
		end
	end
	--check for any trainpart entities if they have been unloaded. do this only if train is near a player, to not spawn entities into unloaded areas
	--todo function will be taken by update_trainpart_properties
	train.check_trainpartload=(train.check_trainpartload or 0)-dtime
	local node_range=(math.max((minetest.setting_get("active_block_range") or 0),1)*16)
	if train.check_trainpartload<=0 then
		local ori_pos=advtrains.get_real_index_position(path, train.index) --not much to calculate
		--atprint("[train "..id.."] at "..minetest.pos_to_string(vector.round(ori_pos)))
		
		local should_check=false
		for _,p in ipairs(minetest.get_connected_players()) do
			should_check=should_check or ((vector.distance(ori_pos, p:getpos())<node_range))
		end
		if should_check then
			advtrains.update_trainpart_properties(id)
		end
		train.check_trainpartload=2
	end
	
	
	--handle collided_with_env
	if train.recently_collided_with_env then
		train.tarvelocity=0
		if not train_moves then
			train.recently_collided_with_env=false--reset status when stopped
		end
	end
	if train.locomotives_in_train==0 then
		train.tarvelocity=0
	end
	
	--interpret ATC command
	if train.atc_brake_target and train.atc_brake_target>=train.velocity then
		train.atc_brake_target=nil
	end
	if train.atc_wait_finish then
		if not train.atc_brake_target and train.velocity==train.tarvelocity then
			train.atc_wait_finish=nil
		end
	end
	if train.atc_command then
		if 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
	end
	
	--make brake adjust the tarvelocity if necessary
	if train.brake and (math.ceil(train.velocity)-1)<train.tarvelocity then
		train.tarvelocity=math.max((math.ceil(train.velocity)-1), 0)
	end
	--apply tarvel(but with physics in mind!)
	if train.velocity~=train.tarvelocity then
		local applydiff=0
		local mass=#train.trainparts
		local diff=train.tarvelocity-train.velocity
		if diff>0 then--accelerating, force will be brought on only by locomotives.
			--atprint("accelerating with default force")
			applydiff=(math.min((advtrains.train_accel_force*train.locomotives_in_train*dtime)/mass, math.abs(diff)))
		else--decelerating
			if front_off_track or back_off_track or train.recently_collided_with_env then --every wagon has a brake, so not divided by mass.
				--atprint("braking with emergency force")
				applydiff= -(math.min((advtrains.train_emerg_force*dtime), math.abs(diff)))
			elseif train.brake or (train.atc_brake_target and train.atc_brake_target<train.velocity) then
				--atprint("braking with default force")
				--no math.min, because it can grow beyond tarvelocity, see up there
				--dont worry, it will never fall below zero.
				applydiff= -((advtrains.train_brake_force*dtime))
			else
				--atprint("roll")
				applydiff= -(math.min((advtrains.train_roll_force*dtime), math.abs(diff)))
			end
		end
		train.last_accel=(applydiff*train.movedir)
		train.velocity=math.min(math.max( train.velocity+applydiff , 0), train.max_speed or 10)
	else
		train.last_accel=0
	end
	
	--move
	--TODO 3,5 + 0.7
	train.index=train.index and train.index+(((train.velocity*train.movedir)/(train.path_dist[math.floor(train.index)] or 1))*dtime) or 0
	
end


--structure of train table:
--[[
trains={
	[train_id]={
		trainparts={
			[n]=wagon_id
		}
		path={path}
		velocity
		tarvelocity
		index
		trainlen
		path_inv_level
		last_pos       |
		last_dir       | for pathpredicting.
	}
}
--a wagon itself has the following properties:
wagon={
	unique_id
	train_id
	pos_in_train (is index difference, including train_span stuff)
	pos_in_trainparts (is index in trainparts tabel of trains)
}
inherited by metatable:
wagon_proto={
	wagon_span
}
]]

--returns new id
function advtrains.create_new_train_at(pos, pos_prev)
	local newtrain_id=os.time()..os.clock()