Optimize world respawn point reselection by only considering positions within 3 nodes of tree nodes and when validating a position can still pathfind to a tree start checking trees from the closest to the respawn point

mods/PLAYER/mcl_spawn/init.lua

@@ -146,60 +146,87 @@ local function good_for_respawn(pos, player)
 	local def0 = minetest.registered_nodes[nn0]
 	local def1 = minetest.registered_nodes[nn1]
 	local def2 = minetest.registered_nodes[nn2]
+
+	-- Be safe around undefined nodes
+	if not def0 then return false end
+	if not def1 then return false end
+	if not def2 then return false end
+
 	return def0.walkable and (not def1.walkable) and (not def2.walkable) and
 		(def1.damage_per_second == nil or def2.damage_per_second <= 0) and
 		(def1.damage_per_second == nil or def2.damage_per_second <= 0)
 end
 
-local function can_find_tree(pos1, trees)
-	if not emerge_pos1 or not emerge_pos2 then return false end
-	local trees = trees or get_trees(pos1)
-	if not trees then return false end
 
-	if (attempts_to_find_trees * 3 < #trees) then
-		-- random search
-		for i = 1, attempts_to_find_trees do
-			local pos2 = trees[math.random(1,#trees)]
-			if not minetest.is_protected(pos2, "") then
-				if pos2.x < pos1.x then
-					pos2.x = pos2.x + 1
-				elseif pos2.x > pos1.x then
-					pos2.x = pos2.x - 1
-				end
-				if pos2.z < pos1.z then
-					pos2.z = pos2.z + 1
-				elseif pos2.z > pos1.z then
-					pos2.z = pos2.z - 1
-				end
-				local way = minetest.find_path(pos1, pos2, res, 1, 3, "A*_noprefetch")
-				if way then
-					return true
+local ADJACENT_OFFSETS = {
+	vector.new( 1,0, 0),
+	vector.new(-1,0, 0),
+	vector.new( 0,0, 1),
+	vector.new( 0,0,-1),
+	vector.new( 0,1, 0),
+}
+
+local function pathfind_next_to(target, pos1, distance)
+	local closest_free_pos = nil
+	local closest_free_dist = nil
+	for j=1,4 do
+		local test_pos = vector.add(target, ADJACENT_OFFSETS[j])
+		if minetest.get_node(test_pos).name == "air" and minetest.get_node(vector.offset(test_pos,0,-1,0)).name ~= "air" then
+			local new_dist = vector.distance(pos1, test_pos)
+			if not closest_free_pos or new_dist < closest_free_dist then
+				closest_free_pos = test_pos
+				closest_free_dist = new_dist
 			end
 		end
 	end
+
+	local way = false
+	if closest_free_pos then
+		return minetest.find_path(pos1, closest_free_pos, distance, 1, 3, "A*_noprefetch")
+	end
+end
+
+local function can_find_tree(pos1, trees)
+	local start_time = minetest.get_us_time()
+
+	if not emerge_pos1 or not emerge_pos2 then
+		minetest.log("verbose", "[mcl_spawn] Missing emerge position in can_find_tree()")
+		return false
+	end
+	local trees = trees or get_trees(pos1)
+	if not trees then
+		minetest.log("verbose", "[mcl_spawn] No trees in area in can_find_tree()")
 		return false
 	end
 
-	for i, pos2 in ipairs(trees) do
-		-- full search
-		if not minetest.is_protected(pos2, "") then
-			if pos2.x < pos1.x then
-				pos2.x = pos2.x + 1
-			elseif pos2.x > pos1.x then
-				pos2.x = pos2.x - 1
+	-- Search from closest to furthest from pos1
+	for i = 2,#trees do
+		for j = 1,(i-1) do
+			if vector.distance(pos1,trees[j]) > vector.distance(pos1,trees[j+1]) then
+				local tmp = trees[j+1]
+				trees[j] = trees[j+1]
+				trees[j+1] = tmp
 			end
-			if pos2.z < pos1.z then
-				pos2.z = pos2.z + 1
-			elseif pos2.z > pos1.z then
-				pos2.z = pos2.z - 1
 		end
-			local way = minetest.find_path(pos1, pos2, res, 1, 3, "A*_noprefetch")
+	end
+
+	for i = 1,#trees do
+		local possible_tree = trees[i]
+
+		local start_pathfind = minetest.get_us_time()
+		local way = pathfind_next_to(possible_tree, pos1, res)
+		local stop_pathfind = minetest.get_us_time()
+
+		if stop_pathfind > start_time + 0.25e6 then
+			minetest.log("info","[mcl_spawn] can_find_tree() timed out")
+			return false;
+		end
+
 		if way then
 			return true
 		end
 	end
-		if i > attempts_to_find_trees then return false end
-	end
+
 	return false
 end
 
@@ -285,86 +312,52 @@ local function next_biome()
 	return false
 end
 
+local function find_spawn_in_area(pos1, pos2)
+	local nodes = minetest.find_nodes_in_area(pos1, pos2, {"group:tree"})
+	if #nodes <= 0 then return nil end
+
+	for i = 1,#nodes do
+		local pos = nodes[i]
+
+		local candidates = minetest.find_nodes_in_area_under_air(
+			vector.offset(pos,-3,-2,-3),
+			vector.offset(pos, 3, 2, 3),
+			{"group:solid"}
+		)
+
+		for j = 1,#candidates do
+			local candidate = vector.offset(candidates[j],0,1,0)
+			local gfs = good_for_respawn(candidate)
+			local way = false
+			if vector.distance(candidate, pos) <= 1 then
+				way = true
+			else
+				local way = pathfind_next_to(candidate, pos, 5)
+			end
+			if gfs and way then
+				return candidate
+			end
+		end
+	end
+
+	return nil
+end
+
 local function ecb_search_continue(blockpos, action, calls_remaining, param)
 	if calls_remaining <= 0 then
 		emerge_pos1 = {x = wsp.x-half_res, y = alt_min, z = wsp.z-half_res}
 		emerge_pos2 = {x = wsp.x+half_res, y = alt_max, z = wsp.z+half_res}
-		local nodes = minetest.find_nodes_in_area_under_air(emerge_pos1, emerge_pos2, node_groups_white_list)
-		minetest.log("verbose", "[mcl_spawn] Data emerge callback: "..minetest.pos_to_string(wsp).." - "..tostring(nodes and #nodes) .. " node(s) found under air")
-		if nodes then
-			if no_trees_area_counter >= 0 then
-				local trees = get_trees(emerge_pos1, emerge_pos2)
-				if trees and #trees > 0 then
-					no_trees_area_counter = 0
-					if attempts_to_find_pos * 3 < #nodes then
-						-- random
-						for i=1, attempts_to_find_pos do
-							wsp = nodes[math.random(1,#nodes)]
-							if wsp then
-								wsp.y = wsp.y + 1
-								if good_for_respawn(wsp) and can_find_tree(wsp, trees) then
+		local start_time = minetest.get_us_time()
+
+		local spawn_pos = find_spawn_in_area(emerge_pos1, emerge_pos2)
+		if spawn_pos then
+			wsp = spawn_pos
 			minetest.log("action", "[mcl_spawn] Dynamic world spawn randomly determined to be "..minetest.pos_to_string(wsp))
 			searched = true
 			success = true
 			return
 		end
-							end
-						end
-					else
-						-- in a sequence
-						for i=1, math.min(#nodes, attempts_to_find_pos) do
-							wsp = nodes[i]
-							if wsp then
-								wsp.y = wsp.y + 1
-								if good_for_respawn(wsp) and can_find_tree(wsp, trees) then
-									minetest.log("action", "[mcl_spawn] Dynamic world spawn determined to be "..minetest.pos_to_string(wsp))
-									searched = true
-									success = true
-									return
-								end
-							end
-						end
-					end
-				else
-					no_trees_area_counter = no_trees_area_counter + 1
-					if no_trees_area_counter > 10 then
-						minetest.log("verbose", "[mcl_spawn] More than 10 times no trees at all! Won't search trees next 200 calls")
-						no_trees_area_counter = -200
-					end
-				end
-			else -- seems there are no trees but we'll check it later, after next 200 calls
-				no_trees_area_counter = no_trees_area_counter + 1
-				if attempts_to_find_pos * 3 < #nodes then
-					-- random
-					for i=1, attempts_to_find_pos do
-						wsp = nodes[math.random(1,#nodes)]
-						if wsp then
-							wsp.y = wsp.y + 1
-							if good_for_respawn(wsp) then
-								minetest.log("action", "[mcl_spawn] Dynamic world spawn randomly determined to be "..minetest.pos_to_string(wsp) .. " (no trees)")
-								searched = true
-								success = true
-								return
-							end
-						end
-					end
-				else
-					-- in a sequence
-					for i=1, math.min(#nodes, attempts_to_find_pos) do
-						wsp = nodes[i]
-						if wsp then
-							wsp.y = wsp.y + 1
-							if good_for_respawn(wsp) then
-								minetest.log("action", "[mcl_spawn] Dynamic world spawn determined to be "..minetest.pos_to_string(wsp) .. " (no trees)")
-								searched = true
-								success = true
-								return
-							end
-						end
-					end
-				end
-			end
-		end
+
 		next_pos()
 		mcl_spawn.search()
 	end
@@ -565,8 +558,24 @@ function mcl_spawn.shadow_worker()
 
 	if success then
 		local wsp_node = minetest.get_node(wsp)
-		if not (wsp_node and wsp_node.name == "ignore")
-		and ((not good_for_respawn(wsp)) or ((no_trees_area_counter >= 0) and not can_find_tree(wsp))) then
+		local spawn_bad = false
+
+		if not spawn_bad and not wsp_node or wsp_node.name == "ignore" then
+			spawn_bad = true
+			minetest.log("verbose", "[mcl_spawn] World spawn point could not be checked or is 'ignore' wsp_node="..dump(wsp_node))
+		end
+
+		if not spawn_bad and not good_for_respawn(wsp) then
+			spawn_bad = true
+			minetest.log("verbose", "[mcl_spawn] World spawn point is not good for respawn")
+		end
+
+		if not spawn_bad and ( (no_trees_area_counter >= 0) and not can_find_tree(wsp) ) then
+			spawn_bad = true
+			minetest.log("verbose", "[mcl_spawn] No trees near spawn point")
+		end
+
+		if spawn_bad then
 			success = false
 			minetest.log("action", "[mcl_spawn] World spawn position isn't safe anymore: "..minetest.pos_to_string(wsp))
 			mcl_spawn.search()