src/jthread

--trackplacer.lua
--holds code for the track-placing system. the default 'track' item will be a craftitem that places rails as needed. this will neither place or change switches nor place vertical rails.

--all new trackplacer code
local tp={
	tracks={}
}

function tp.register_tracktype(nnprefix, n_suffix)
	tp.tracks[nnprefix]={
		default=n_suffix,
		single_conn={},
		double_conn={},
		--keys:conn1_conn2 (example:1_4)
		--values:{name=x, param2=x}
		twcycle={},
		twrotate={},--indexed by suffix, list, tells order of rotations
		modify={}
	}
end
function tp.add_double_conn(nnprefix, suffix, rotation, conns)
	local nodename=nnprefix.."_"..suffix..rotation
	for i=0,3 do
		tp.tracks[nnprefix].double_conn[((conns.conn1+4*i)%16).."_"..((conns.conn2+4*i)%16)]={name=nodename, param2=i}
		tp.tracks[nnprefix].double_conn[((conns.conn2+4*i)%16).."_"..((conns.conn1+4*i)%16)]={name=nodename, param2=i}
	end
	tp.tracks[nnprefix].modify[nodename]=true
end
function tp.add_single_conn(nnprefix, suffix, rotation, conns)
	local nodename=nnprefix.."_"..suffix..rotation
	for i=0,3 do
		tp.tracks[nnprefix].single_conn[((conns.conn1+4*i)%16)]={name=nodename, param2=i}
		tp.tracks[nnprefix].single_conn[((conns.conn2+4*i)%16)]={name=nodename, param2=i}
	end
	tp.tracks[nnprefix].modify[nodename]=true
end

function tp.add_worked(nnprefix, suffix, rotation, cycle_follows)
	tp.tracks[nnprefix].twcycle[suffix]=cycle_follows
	if not tp.tracks[nnprefix].twrotate[suffix] then tp.tracks[nnprefix].twrotate[suffix]={} end
	table.insert(tp.tracks[nnprefix].twrotate[suffix], rotation)
end


--[[
	rewrite algorithm.
	selection criteria: these will never be changed or even selected:
	- tracks being already connected on both sides
	- tracks that are already connected on one side but are not bendable to the desired position
	the following situations can occur:
	1. there are two more than two rails around
		1.1 there is one or more subset(s) that can be directly connected
			-> choose the first possibility
		2.2 not
			-> choose the first one and orient straight
	2. there's exactly 1 rail around
		-> choose and orient straight
	3. there's no rail around
		-> set straight
]]
function tp.find_already_connected(pos)--TODO vertical calculations(check node below)
	local function istrackandbc(pos, conn)
		local cnode=minetest.get_node(advtrains.dirCoordSet(pos, conn))
		local bconn=(conn+8)%16
		if advtrains.is_track_and_drives_on(cnode.name, advtrains.all_tracktypes) then
			local cconn1, cconn2=advtrains.get_track_connections(cnode.name, cnode.param2)
			return cconn1==bconn or cconn2==bconn
		end
		return false
	end
	local dnode=minetest.get_node(pos)
	local dconn1, dconn2=advtrains.get_track_connections(dnode.name, dnode.param2)
	local t={[true]="true", [false]="false"}
	if istrackandbc(pos, dconn1) and istrackandbc(pos, dconn2) then return dconn1, dconn2
	elseif istrackandbc(pos, dconn1) then return dconn1
	elseif istrackandbc(pos, dconn2) then return dconn2
	end
	return nil
end
function tp.rail_and_can_be_bent(originpos, conn, nnpref)
	local pos=advtrains.dirCoordSet(originpos, conn)
	local newdir=(conn+8)%16
	local node=minetest.get_node(pos)
	local tr=tp.tracks[nnpref]
	if not advtrains.is_track_and_drives_on(node.name, advtrains.all_tracktypes) then
		return false
	end
	--rail at other end?
	local adj1, adj2=tp.find_already_connected(pos)
	if adj1 and adj2 then
		return false--dont destroy existing track
	elseif adj1 and not adj2 then
		if tr.double_conn[adj1.."_"..newdir] then
			return true--if exists, connect new rail and old end
		end
		return false
	else
		if tr.single_conn[newdir] then--just rotate old rail to right orientation
			return true
		end
		return false
	end
end
function tp.bend_rail(originpos, conn, nnpref)
	local pos=advtrains.dirCoordSet(originpos, conn)
	local newdir=(conn+8)%16
	local node=minetest.get_node(pos)
	local tr=tp.tracks[nnpref]
	--is rail already connected? no need to bend.
	local conn1, conn2=advtrains.get_track_connections(node.name, node.param2)
	if newdir==conn1 or newdir==conn2 then
		return
	end
	--rail at other end?
	local adj1, adj2=tp.find_already_connected(pos)
	if adj1 and adj2 then
		return false--dont destroy existing track
	elseif adj1 and not adj2 then
		if tr.double_conn[adj1.."_"..newdir] then
			minetest.set_node(pos, tr.double_conn[adj1.."_"..newdir])
			return true--if exists, connect new rail and old end
		end
		return false
	else
		if tr.single_conn[newdir] then--just rotate old rail to right orientation
			minetest.set_node(pos, tr.single_conn[newdir])
			return true
		end
		return false
	end
end
function tp.placetrack(pos, nnpref)
	--1. find all rails that are likely to be connected
	local tr=tp.tracks[nnpref]
	local p_rails={}
	for i=0,15 do
		if tp.rail_and_can_be_bent(pos, i, nnpref) then
			p_rails[#p_rails+1]=i
		end
	end
	if #p_rails==0 then
		minetest.set_node(pos, {name=nnpref.."_"..tr.default})
	elseif #p_rails==1 then
		tp.bend_rail(pos, p_rails[1], nnpref)
		minetest.set_node(pos, tr.single_conn[p_rails[1]])
	else
		--iterate subsets
		for k1, conn1 in ipairs(p_rails) do
			for k2, conn2 in ipairs(p_rails) do
				if k1~=k2 then
					if (tr.double_conn[conn1.."_"..conn2]) then
						tp.bend_rail(pos, conn1, nnpref)
						tp.bend_rail(pos, conn2, nnpref)
						minetest.set_node(pos, tr.double_conn[conn1.."_"..conn2])
						return
					end
				end
			end
		end
		--not found
		tp.bend_rail(pos, p_rails[1], nnpref)
		minetest.set_node(pos, tr.single_conn[p_rails[1]])
	end
end


function tp.register_track_placer(nnprefix, imgprefix, dispname)
	minetest.register_craftitem(nnprefix.."_placer",{
		description = dispname,
		inventory_image = imgprefix.."_placer.png",
		wield_image = imgprefix.."_placer.png",
		groups={},
		on_place = function(itemstack, placer, pointed_thing)
		        local name = placer:get_player_name()
			if not name then
			   return itemstack
			end
			if pointed_thing.type=="node" then
				local pos=pointed_thing.above
				local upos=pointed_thing.under
				if minetest.is_protected(pos,name) and minetest.is_protected(upos,name) then
				   return itemstack
				end
				if minetest.registered_nodes[minetest.get_node(pos).name] and minetest.registered_nodes[minetest.get_node(pos).name].buildable_to
					and minetest.registered_nodes[minetest.get_node(upos).name] and minetest.registered_nodes[minetest.get_node(upos).name].walkable then
					tp.placetrack(pos, nnprefix)
					if not minetest.setting_getbool("creative_mode") then
						itemstack:take_item()
					end
				end
			end
			return itemstack
		end,
	})
end


minetest.register_craftitem("advtrains:trackworker",{
	description = "Track Worker Tool\n\nLeft-click: change rail type (straight/curve/switch)\nRight-click: rotate rail/bumper/signal/etc.",
	groups = {cracky=1}, -- key=name, value=rating; rating=1..3.
	inventory_image = "advtrains_trackworker.png",
	wield_image = "advtrains_trackworker.png",
	stack_max = 1,
	on_place = function(itemstack, placer, pointed_thing)
		local name = placer:get_player_name()
		if not name then
			return
		end
		if pointed_thing.type=="node" then
			local pos=pointed_thing.under
			if minetest.is_protected(pos, name) then
				return
			end
			local node=minetest.get_node(pos)

			--if not advtrains.is_track_and_drives_on(minetest.get_node(pos).name, advtrains.all_tracktypes) then return end
			if advtrains.is_train_at_pos(pos) then return end

			local nnprefix, suffix, rotation=string.match(node.name, "^(.+)_([^_]+)(_[^_]+)$")
			--print(node.name.."\npattern recognizes:"..nodeprefix.." / "..railtype.." / "..rotation)
			if not tp.tracks[nnprefix] or not tp.tracks[nnprefix].twrotate[suffix] then
				nnprefix, suffix=string.match(node.name, "^(.+)_([^_]+)$")
				rotation = ""
				if not tp.tracks[nnprefix] or not tp.tracks[nnprefix].twrotate[suffix] then
					minetest.chat_send_player(placer:get_player_name(), "This node can't be rotated using the trackworker!")
					return
				end
			end
			local modext=tp.tracks[nnprefix].twrotate[suffix]

			if rotation==modext[#modext] then --increase param2
				minetest.set_node(pos, {name=nnprefix.."_"..suffix..modext[1], param2=(node.param2+1)%4})
				return
			else
				local modpos
				for k,v in pairs(modext) do if v==rotation then modpos=k end end
					if not modpos then
						minetest.chat_send_player(placer:get_player_name(), "This node can't be rotated using the trackworker!")
					return
				end
				minetest.set_node(pos, {name=nnprefix.."_"..suffix..modext[modpos+1], param2=node.param2})
			end
			advtrains.invalidate_all_paths()
		end
	end,
	on_use=function(itemstack, user, pointed_thing)
	        local name = user:get_player_name()
		if not name then
		   return
		end
		if pointed_thing.type=="node" then
			local pos=pointed_thing.under
			local node=minetest.get_node(pos)
			if minetest.is_protected(pos, name) then
			   return
			end
			
			--if not advtrains.is_track_and_drives_on(minetest.get_node(pos).name, advtrains.all_tracktypes) then return end
			if advtrains.is_train_at_pos(pos) then return end
			local nnprefix, suffix, rotation=string.match(node.name, "^(.+)_([^_]+)(_[^_]+)$")
	        --print(node.name.."\npattern recognizes:"..nodeprefix.." / "..railtype.." / "..rotation)
		    if not tp.tracks[nnprefix] or not tp.tracks[nnprefix].twcycle[suffix] then
			  nnprefix, suffix=string.match(node.name, "^(.+)_([^_]+)$")
			  rotation = ""
			  if not tp.tracks[nnprefix] or not tp.tracks[nnprefix].twcycle[suffix] then
			    minetest.chat_send_player(user:get_player_name(), "This node can't be changed using the trackworker!")
			    return
			  end
		    end
			local nextsuffix=tp.tracks[nnprefix].twcycle[suffix]
			minetest.set_node(pos, {name=nnprefix.."_"..nextsuffix..rotation, param2=node.param2})
			--invalidate trains
			advtrains.invalidate_all_paths()
		else
			print(name, dump(tp.tracks))
		end
	end,
})

--putting into right place
advtrains.trackplacer=tp