jecs/tools/lifetime_tracker.luau

local jecs = require("@jecs")
local ECS_GENERATION = jecs.ECS_GENERATION
local ECS_ID = jecs.ECS_ID
local __ = jecs.Wildcard
local pair = jecs.pair

local prettify = require("@tools/entity_visualiser").prettify

local pe = prettify

function print_centered_entity(entity, width: number)
	local entity_str = tostring(entity)
	local entity_length = #entity_str

	local padding_total = width - 2 - entity_length

	local padding_left = math.floor(padding_total / 2)
	local padding_right = padding_total - padding_left

	local centered_str = string.rep(" ", padding_left) .. entity_str .. string.rep(" ", padding_right)

	print("|" .. centered_str .. "|")
end

local function name(world, e)
	return world:get(world, e, jecs.Name) or pe(e)
end
local padding_enabled = false
local function pad()
	if padding_enabled then
		print("")
	end
end

type PatchedWorld = jecs.World & {
	print_entity_index: (world: PatchedWorld) -> (),
	print_snapshot: (world: PatchedWorld) -> (),
}

local function lifetime_tracker_add(world: jecs.World, opt): PatchedWorld
	local entity_index = world.entity_index
	local dense_array = entity_index.dense_array
	local component_index = world.component_index

	local ENTITY_RANGE = (jecs.Rest :: any) + 1

	padding_enabled = opt.padding_enabled

	local world_entity = world.entity
	world.entity = function(_, entity)
		if entity then
			return world_entity(world, entity)
		end
		local will_recycle = entity_index.max_id ~= entity_index.alive_count
		local e = world_entity(world)
		if will_recycle then
			print(`*recycled {pe(e)}`)
		else
			print(`*created {pe(e)}`)
		end
		pad()
		return e
	end
	world.print_entity_index = function()
		local max_id = entity_index.max_id
		local alive_count = entity_index.alive_count
		local alive = table.move(dense_array, 1 + jecs.Rest :: any, alive_count, 1, {})
		local dead = table.move(dense_array, alive_count + 1, max_id, 1, {})

		local sep = "|--------|"
		if #alive > 0 then
			print("|-alive--|")
			for i = 1, #alive do
				local e = pe(alive[i])
				print_centered_entity(e, 32)
				print(sep)
			end
			print("\n")
		end

		if #dead > 0 then
			print("|--dead--|")
			for i = 1, #dead do
				print_centered_entity(pe(dead[i]), 32)
				print(sep)
			end
		end
		pad()
	end
	local timelines = {}
	world.print_snapshot = function(_)
		local timeline = #timelines + 1
		local entity_column_width = 10
		local status_column_width = 8

		local header = string.format("| %-" .. entity_column_width .. "s |", "Entity")
		for i = 1, timeline do
			header = header .. string.format(" %-" .. status_column_width .. "s |", string.format("T%d", i))
		end

		local max_id = entity_index.max_id
		local alive_count = entity_index.alive_count
		local alive = table.move(dense_array, 1 + jecs.Rest :: any, alive_count, 1, {})
		local dead = table.move(dense_array, alive_count + 1, max_id, 1, {})

		local data = {}
		print("-------------------------------------------------------------------")
		print(header)

		-- Store the snapshot data for this timeline
		for i = ENTITY_RANGE, max_id do
			if dense_array[i] then
				local entity = dense_array[i]
				local id = ECS_ID(entity)
				local status = "alive"
				if not world:contains(entity) then
					status = "dead"
				end
				data[id] = status
			end
		end

		table.insert(timelines, data)

		-- Create a table to hold entity data for sorting
		local entities = {}
		for i = ENTITY_RANGE, max_id do
			if dense_array[i] then
				local entity = dense_array[i]
				local id = ECS_ID(entity)
				-- Push entity and id into the new `entities` table
				table.insert(entities, { entity = entity, id = id })
			end
		end

		-- Sort the entities by ECS_ID
		table.sort(entities, function(a, b)
			return a.id < b.id
		end)

		-- Print the sorted rows
		for _, entity_data in ipairs(entities) do
			local entity = entity_data.entity
			local id = entity_data.id
			local status = "alive"
			if id > alive_count then
				status = "dead"
			end
			local row = string.format("| %-" .. entity_column_width .. "s     |", pe(entity))
			for j = 1, timeline do
				local timeline_data = timelines[j]
				local entity_data = timeline_data[id]
				if entity_data then
					row = row .. string.format(" %-" .. status_column_width .. "s |", entity_data)
				else
					row = row .. string.format(" %-" .. status_column_width .. "s |", "-")
				end
			end
			print(row)
		end
		print("-------------------------------------------------------------------")
		pad()
	end
	local world_add = world.add
	local relations = {}
	world.add = function(_, entity: any, component: any)
		world_add(world, entity, component)
		if jecs.IS_PAIR(component) then
			local relation = jecs.pair_first(world, component)
			local target = jecs.pair_second(world, component)
			print(`*added ({pe(relation)}, {pe(target)}) to {pe(entity)}`)
			pad()
		end
	end

	local world_delete = world.delete
	world.delete = function(world, e)
		world_delete(world, e)

		local idr_t = component_index[pair(__, e)]
		if idr_t then
			for archetype_id in idr_t.cache do
				local archetype = world.archetypes[archetype_id]
				for _, id in archetype.types do
					if not jecs.IS_PAIR(id) then
						continue
					end
					local object = jecs.pair_second(world, id)
					if object ~= e then
						continue
					end
					local id_record = component_index[id]
					local flags = id_record.flags
					local flags_delete_mask: number = bit32.band(flags, jecs.ECS_ID_DELETE)
					if flags_delete_mask ~= 0 then
						for _, entity in archetype.entities do
							print(`*deleted dependant {pe(entity)} of {pe(e)}`)
							pad()
						end
						break
					else
						for _, entity in archetype.entities do
							print(
								`*removed dependency ({pe(jecs.pair_first(world, id))}, {pe(object)}) from {pe(entity)}`
							)
						end
					end
				end
			end
		end

		print(`*deleted {pe(e)}`)
		pad()
	end
	return world
end

return lifetime_tracker_add