save data module

local CACHE_EXPIRY_TIME = 60*10
local PASSIVE_SAVE_FREQUENCY = 60*1
local PASSIVE_GRANULARITY = 5
local SERIALIZE = {}
local DESERIALIZE = {}
local SAVE_ON_LEAVE = true
local DEBUG = false
if game.Players.LocalPlayer then
	error("PlayerDataStore requested on the client, is a server-only module.", 2)
end
local function DeepCopy(tb)
	if type(tb) == 'table' then
		local new = {}
		for k, v in pairs(tb) do
			new[k] = DeepCopy(v)
		end
		return new
	else
		return tb
	end
end
local function SpawnNow(func)
	local ev = Instance.new('BindableEvent')
	ev.Event:connect(func)
	ev:Fire()
end
local SaveData = {}
function SaveData.new(playerDataStore, userId)
	local this = {}
	this.userId = userId
	this.lastSaved = 0
	this.locked = false
	this.unlocked = Instance.new('BindableEvent')
	this.onupdate = Instance.new('BindableEvent')
	this.regendata = Instance.new('BindableEvent')
	this.dataSet = nil
	this.dirtyKeySet = {}
	this.ownedKeySet = {}
	local function ownKey(key)
		this.ownedKeySet[key] = true
	end
	local function dirtyKey(key)
		this.dirtyKeySet[key] = true
	end
	local function markAsTouched(key)
		ownKey(key)
		playerDataStore:markAsTouched(this)
	end
	local function markAsDirty(key)
		ownKey(key)
		dirtyKey(key)
		playerDataStore:markAsDirty(this)
	end
	function this:makeReady(data)
		this.dataSet = data
		this.lastSaved = tick()
		playerDataStore:markAsTouched(this)
		this.regendata:Fire()
	end
	function this:waitForUnlocked()
		while this.locked do
			this.unlocked.Event:wait()
		end
	end
	function this:lock()
		this.locked = true
	end
	function this:unlock()
		this.locked = false
		this.unlocked:Fire()
		this.regendata:Fire()
	end
	function this:Get(key)
		if type(key) ~= 'string' then
			error("Bad argument #1 to SaveData::Get() (string expected)", 2)
		end
		if DEBUG then
			print("SaveData<"..this.userId..">::Get("..key..")")
		end
		markAsTouched(key)
		local value = this.dataSet[key]
		if value == nil and DESERIALIZE[key] then
			local v = DESERIALIZE[key](nil)
			this.dataSet[key] = v
			return v
		else
			return value
		end
	end
	function this:Set(key, value, allowErase)
		if type(key) ~= 'string' then
			error("Bad argument #1 to SaveData::Set() (string expected)", 2)
		end
		if value == nil and not allowErase then
			error("Attempt to SaveData::Set('"..key.."', nil) without allowErase = true", 2)
		end
		if DEBUG then
			print("SaveData<"..this.userId..">::Set("..key..", "..tostring(value)..")")
		end
		markAsDirty(key)
		local oldvalue = this.dataSet[key]
		this.dataSet[key] = value
		this.onupdate:Fire(key, value, oldvalue)
	end
	function this:Update(keyList, func)
		if type(keyList) ~= 'table' then
			error("Bad argument #1 to SaveData::Update() (table of keys expected)", 2)
		end
		if type(func) ~= 'function' then
			error("Bad argument #2 to SaveData::Update() (function expected)", 2)
		end
		if DEBUG then
			print("SaveData<"..this.userId..">::Update("..table.concat(keyList, ", ")..", "..tostring(func)..")")
		end
		playerDataStore:doUpdate(this, keyList, func)
	end
	function this:Flush()
		if DEBUG then
			print("SaveData<"..this.userId..">::Flush()")
		end
		playerDataStore:doSave(this)
	end

	return this
end
local PlayerDataStore = {}
function PlayerDataStore.new(DATASTORE_NAME, INITIAL_DATA)
	local this = {}
	local DataStoreService = game:GetService('DataStoreService')
	local mDataStore = DataStoreService:GetDataStore(DATASTORE_NAME)
	local mUserIdSaveDataCache = setmetatable({}, {__mode = 'v'})
	local mTouchedSaveDataCacheSet = {}
	local mOnlinePlayerSaveDataMap = {}
	local mDirtySaveDataSet = {}
	local mOnRequestUserIdSet = {}
	local mRequestCompleted = Instance.new('BindableEvent')
	local mSavingCount = 0
	local INITIAL_DATA = INITIAL_DATA or {}
	local function userIdToKey(userId)
		return 'PlayerData_'..userId
	end
	function this:markAsTouched(saveData)
		if DEBUG then print("PlayerDataStore::markAsTouched("..saveData.userId..")") end
		mTouchedSaveDataCacheSet[saveData] = true
		saveData.lastTouched = tick()
		mUserIdSaveDataCache[saveData.userId] = saveData
	end
	function this:markAsDirty(saveData)
		if DEBUG then print("PlayerDataStore::markAsDirty("..saveData.userId..")") end
		this:markAsTouched(saveData)
		mDirtySaveDataSet[saveData] = true
		mUserIdSaveDataCache[saveData.userId] = saveData
	end
	local function initialData(userId)
		return DeepCopy(INITIAL_DATA)
	end
	local function collectDataToSave(saveData)
		local toSave = {}
		local toErase = {}
		for key, _ in pairs(saveData.dirtyKeySet) do
			local value = saveData.dataSet[key]
			if value ~= nil then
				if SERIALIZE[key] then
					toSave[key] = SERIALIZE[key](value)
				else
					toSave[key] = DeepCopy(value)
				end
			else
				table.insert(toErase, key)
			end
			saveData.dirtyKeySet[key] = nil
		end
		return toSave, toErase
	end
	function this:doSave(saveData)
		if DEBUG then print("PlayerDataStore::doSave("..saveData.userId..") {") end
		saveData.lastSaved = tick()
		mDirtySaveDataSet[saveData] = nil

		if next(saveData.dirtyKeySet) then
			local toSave, toErase = collectDataToSave(saveData)
			saveData:waitForUnlocked()
			saveData:lock()
			mSavingCount = mSavingCount + 1
			mDataStore:UpdateAsync(userIdToKey(saveData.userId), function(oldData)
				if not oldData then
					oldData = initialData(saveData.userId)
				end
				if DEBUG then print("\tattempting save:") end
				for key, data in pairs(toSave) do
					if DEBUG then print("\t\tsaving `"..key.."` = "..tostring(data)) end
					oldData[key] = data
				end
				for _, key in pairs(toErase) do
					if DEBUG then print("\t\tsaving `"..key.."` = nil [ERASING])") end
					oldData[key] = nil
				end
				return oldData
			end)
			if DEBUG then print("\t saved.") end
			mSavingCount = mSavingCount - 1
			saveData:unlock()
		elseif DEBUG then
			print("\tnothing to save")
		end
		if DEBUG then print("}") end
	end
	function this:doUpdate(saveData, keyList, updaterFunc)
		if DEBUG then print("PlayerDataStore::doUpdate("..saveData.userId..", {"..table.concat(keyList, ", ").."}, "..tostring(updaterFunc)..") {") end
		saveData:waitForUnlocked()
		saveData:lock()
		mSavingCount = mSavingCount + 1
		saveData.lastSaved = tick()
		mDirtySaveDataSet[saveData] = nil
		local updateKeySet = {}
		for _, key in pairs(keyList) do
			saveData.ownedKeySet[key] = true
			updateKeySet[key] = true
		end
		local toSave, toErase = collectDataToSave(saveData)
		mDataStore:UpdateAsync(userIdToKey(saveData.userId), function(oldData)
			if DEBUG then print("\ttrying update:") end
			if not oldData then
				oldData = initialData(saveData.userId)
			end
			local valueList = {}
			for i, key in pairs(keyList) do
				local value = saveData.dataSet[key]
				if value == nil and DESERIALIZE[key] then
					valueList[i] = DESERIALIZE[key](nil)
				else
					valueList[i] = value
				end
			end
			local results = {updaterFunc(unpack(valueList, 1, #keyList))}
			for i, result in pairs(results) do
				local key = keyList[i]
				if SERIALIZE[key] then
					local serialized = SERIALIZE[key](result)
					if DEBUG then print("\t\tsaving result: `"..key.."` = "..tostring(serialized).." [SERIALIZED]") end
					oldData[key] = serialized
				else
					if DEBUG then print("\t\tsaving result: `"..key.."` = "..tostring(result)) end
					oldData[key] = result
				end
				saveData.dataSet[key] = result
			end
			for key, value in pairs(toSave) do
				if not updateKeySet[key] then
					if DEBUG then print("\t\tsaving unsaved value: `"..key.."` = "..tostring(value)) end
					oldData[key] = value
				end
			end
			for _, key in pairs(toErase) do
				if not updateKeySet[key] then
					if DEBUG then print("\t\tsaving unsaved value: `"..key.."` = nil [ERASING]") end
					oldData[key] = nil
				end
			end
			print("Save Size", #game.HttpService:JSONEncode(oldData)) -- TO REMOVE
			return oldData
		end)
		mSavingCount = mSavingCount - 1
		saveData:unlock()
		if DEBUG then print("}") end
	end
	local function doLoad(userId)
		if DEBUG then print("PlayerDataStore::doLoad("..userId..") {") end
		local saveData;
		saveData = mUserIdSaveDataCache[userId]
		if saveData then
			if DEBUG then print("\tRecord was already in cache") end
			this:markAsTouched(saveData)
			if DEBUG then print("}") end
			return saveData
		end
		if mOnRequestUserIdSet[userId] then
			if DEBUG then print("\tRecord already requested, wait for it...") end
			while true do
				saveData = mRequestCompleted.Event:wait()()
				if saveData.userId == userId then
					this:markAsTouched(saveData)
					if DEBUG then
						print("\tRecord successfully retrieved by another thread")
						print("}")
					end
					return saveData
				end
			end
		else
			if DEBUG then print("\tRequest record...") end
			mOnRequestUserIdSet[userId] = true
			local data = mDataStore:GetAsync(userIdToKey(userId)) or initialData(userId)
			for key, value in pairs(data) do
				if DESERIALIZE[key] then
					data[key] = DESERIALIZE[key](value)
				end
			end
			saveData = SaveData.new(this, userId)
			saveData:makeReady(data)
			this:markAsTouched(saveData)
			mOnRequestUserIdSet[userId] = nil
			mRequestCompleted:Fire(function() return saveData end)
			if DEBUG then
				print("\tRecord successfully retrieved from data store")
				print("}")
			end
			return saveData
		end
	end
	local function HandlePlayer(player)
		if DEBUG then print("PlayerDataStore> Player "..player.userId.." Entered > Load Data") end
		local saveData = doLoad(player.userId)
		if player.Parent then
			mOnlinePlayerSaveDataMap[player] = saveData
		end
	end
	game.Players.PlayerAdded:connect(HandlePlayer)
	for _, player in pairs(game.Players:GetChildren()) do
		if player:IsA('Player') then
			HandlePlayer(player)
		end
	end
	game.Players.PlayerRemoving:connect(function(player)
		local oldSaveData = mOnlinePlayerSaveDataMap[player]
		mOnlinePlayerSaveDataMap[player] = nil
		if SAVE_ON_LEAVE and oldSaveData then
			if DEBUG then print("PlayerDataStore> Player "..player.userId.." Left with data to save > Save Data") end
			this:doSave(oldSaveData)
		end
	end)
	game.OnClose = function()
		if DEBUG then print("PlayerDataStore> OnClose Shutdown\n\tFlushing...") end
		this:FlushAll()
		if DEBUG then print("\tFlushed, additional wait...") end
		while mSavingCount > 0 do
			wait()
		end
		if DEBUG then print("\tShutdown completed normally.") end
	end
	local function removeTimedOutCacheEntries()
		local now = tick()
		for saveData, _ in pairs(mTouchedSaveDataCacheSet) do
			if (now - saveData.lastTouched) > CACHE_EXPIRY_TIME then
				if mDirtySaveDataSet[saveData] then
					if DEBUG then print(">> Cache expired for: "..saveData.userId..", has unsaved changes, wait.") end
					SpawnNow(function() this:doSave(saveData) end)
				else
					if DEBUG then print(">> Cache expired for: "..saveData.userId..", removing.") end
					mTouchedSaveDataCacheSet[saveData] = nil
				end
			end
		end
	end
	local function passiveSaveUnsavedChanges()
		local now = tick()
		for saveData, _ in pairs(mDirtySaveDataSet) do
			if (now - saveData.lastSaved) > PASSIVE_SAVE_FREQUENCY then
				if DEBUG then print("PlayerDataStore>> Passive save for: "..saveData.userId) end
				SpawnNow(function()
					this:doSave(saveData)
				end)
			end
		end
	end
	spawn(function()
		while true do
			removeTimedOutCacheEntries()
			passiveSaveUnsavedChanges()
			wait(PASSIVE_GRANULARITY)
		end
	end)
	function this:GetSaveData(player)
		if not player or not player:IsA('Player') then
			error("Bad argument #1 to PlayerDataStore::GetSaveData(), Player expected", 2)
		end
		return doLoad(player.userId)
	end
	function this:GetSaveDataById(userId)
		if type(userId) ~= 'number' then
			error("Bad argument #1 to PlayerDataStore::GetSaveDataById(), userId expected", 2)
		end
		return doLoad(userId)
	end
	function this:FlushAll()
		local savesRunning = 0
		local complete = Instance.new('BindableEvent')
		for saveData, _ in pairs(mDirtySaveDataSet) do
			SpawnNow(function()
				savesRunning = savesRunning + 1
				this:doSave(saveData)
				savesRunning = savesRunning - 1
				if savesRunning <= 0 then
					complete:Fire()
				end
			end)
		end
		if savesRunning > 0 then
			complete.Event:wait()
		end
	end
	return this
end
return PlayerDataStore