-- smartroute.lua
-- Implementation of the advtrains auto-route search

local atil = advtrains.interlocking
local ildb = atil.db
local sr = {}


local function otherside(s)
	if s==1 then return 2 else return 1 end
end

--route search implementation
-- Note this is similar to recursively_find_routes in database.lua, there used for the rscache

local function recursively_find_routes(s_pos, s_connid, searching_shunt, tcbseq, mark_pos, result_table, scan_limit)
	--atdebug("Recursively restarting at ",s_pos, s_connid, "limit left", scan_limit)
	local ti = advtrains.get_track_iterator(s_pos, s_connid, scan_limit, false)
	local pos, connid, bconnid = ti:next_branch()
	pos, connid, bconnid = ti:next_track()-- step once to get ahead of previous turnout
	local last_pos
	repeat
		-- record position in mark_pos
		local pts = advtrains.encode_pos(pos)
		mark_pos[pts] = true
		
		local node = advtrains.ndb.get_node_or_nil(pos)
		atdebug("(SmartRoute) Walk ",pos, "nodename", node.name, "entering at conn",bconnid)
		local ndef = minetest.registered_nodes[node.name]
		if ndef.advtrains and ndef.advtrains.node_state_map then
			-- Stop, this is a switchable node. Find out which conns we can go at
			atdebug("(SmartRoute) Found turnout ",pos, "nodename", node.name, "entering at conn",bconnid)
			local out_conns = ildb.get_possible_out_connids(node.name, bconnid)
			for oconnid, state in pairs(out_conns) do
				--atdebug("Going in direction",oconnid,"state",state)
				recursively_find_routes(pos, oconnid, searching_shunt, table.copy(tcbseq), table.copy(mark_pos), result_table, ti.limit)
			end
			return
		end
		--otherwise, this might be a tcb
		local tcb = ildb.get_tcb(pos)
		if tcb then
			local fsigd = { p = pos, s = connid }
			atdebug("(SmartRoute) Encounter TCB ",fsigd)
			tcbseq[#tcbseq+1] = fsigd
			-- check if this is a possible route endpoint
			local tcbs = tcb[connid]
			if tcbs.signal then
				local ndef = advtrains.ndb.get_ndef(tcbs.signal)
				if ndef and ndef.advtrains then
					if ndef.advtrains.route_role == "main" or ndef.advtrains.route_role == "main_distant"
							or ndef.advtrains.route_role == "end" or ndef.advtrains.route_role == "shunt" then
						-- signal is suitable target
						local is_mainsignal = ndef.advtrains.route_role ~= "shunt"
						-- record the found route in the results
						result_table[#result_table+1] = {
							tcbseq = table.copy(tcbseq),
							mark_pos = table.copy(mark_pos),
							shunt_route = not is_mainsignal,
							to_end_of_track = false,
							name = tcbs.signal_name or atil.sigd_to_string(fsigd)
						}
						-- if this is a main signal and/or we are only searching shunt routes, stop the search here
						if is_mainsignal or searching_shunt then
							atdebug("(SmartRoute) Terminating here because it is main or only shunt routes searched")
							return
						end
					end
				end
			end
		end
		-- Go forward
		last_pos = pos
		pos, connid, bconnid = ti:next_track()
	until not pos -- this stops the loop when either the track end is reached or the limit is hit
	--atdebug("recursively_find_routes: Reached track end or limit at", last_pos, ". This path is not saved, returning")
end

local function build_route_from_foundroute(froute, name)
	local route = {
		name = froute.name,
		use_rscache = true,
		smartroute_generated = true,
	}
	for _, sigd in ipairs(froute.tcbseq) do
		route[#route+1] = { next = sigd, locks = {} }
	end
	return route
end

-- Maximum scan length for track iterator
local TS_MAX_SCAN = 1000

function sr.init(pname, sigd)
	-- is start signal a shunt signal?
	local is_startsignal_shunt = false
	local tcbs = ildb.get_tcbs(sigd)
	if tcbs.signal then
		local ndef = advtrains.ndb.get_ndef(tcbs.signal)
		if ndef and ndef.advtrains then
			if ndef.advtrains.route_role == "shunt" then
				is_startsignal_shunt = true
			end
		end
	end
	local result_table = {}
	recursively_find_routes(sigd.p, sigd.s, is_startsignal_shunt, {}, {}, result_table, TS_MAX_SCAN)
	
	atdebug("Smartroute search finished:",result_table)
	
	-- Short-circuit logic right now for testing
	-- go through and delete all routes that are autogenerated
	local i = 1
	while i<=#tcbs.routes do
		if tcbs.routes[i].smartroute_generated then
			table.remove(tcbs.routes, i)
		else
			i=i+1
		end
	end
	-- just plainly create routes!
	for idx, froute in ipairs(result_table) do
		tcbs.routes[#tcbs.routes+1] = build_route_from_foundroute(froute)
	end
	atwarn("Smartroute done!")
end



--[[
	player1 = {
		origin = <sigd>
		found_routes = {
			{ tcbseq = {<sigd1>, <sigd2>, <end_sigd>}, mark_pos = { table with keys being encoded_pos of rails constituting route }, to_end_of_track = false, shunt_route = false }
		}
	}
]]--
local player_smartroute = {}

minetest.register_on_punchnode(function(pos, node, player, pointed_thing)
	local pname = player:get_player_name()
	if not minetest.check_player_privs(pname, "interlocking") then
		return
	end
	-- TODO
end)


advtrains.interlocking.smartroute = sr