if FirstLoad then
	s_AchievementReceivedSignals = {}
	s_AchievementUnlockedSignals = {}
	_AchievementsToUnlock = {}
	_UnlockThread = false
	g_SteamIdToAchievementName = {}
	g_AchievementNameToSteamId = {}
end

function OnMsg.DataLoaded()
	g_SteamIdToAchievementName = {}
	g_AchievementNameToSteamId = {}
	ForEachPreset(Achievement, function(achievement, group_list) 
		local steam_id = achievement.steam_id ~= "" and achievement.steam_id or achievement.id
		g_SteamIdToAchievementName[steam_id] = achievement.id
		g_AchievementNameToSteamId[achievement.id] = steam_id
	end)
end

-- Steam account -> AccountStorage sync policy 
TransferUnlockedAchievementsFromSteam = true

function OnSteamAchievementsReceived()
	Msg(s_AchievementReceivedSignals)
end

function OnSteamAchievementUnlocked(unlock_status)
	if unlock_status == "success" then
		Msg(s_AchievementUnlockedSignals)
	end
end

local function WaitGetAchievements()
	if IsSteamLoggedIn() and SteamQueryAchievements(table.values(table.map(AchievementPresets, "steam_id"))) then
		local ok, data
		if WaitMsg( s_AchievementReceivedSignals, 5 * 1000 ) then
			data = SteamGetAchievements()
			if data then
				return true, table.map(data, g_SteamIdToAchievementName)
			end
		end
	end

	return false
end

local function GetSteamAchievementIds(achievements)
	local steam_achievements = { }
	for i, name in ipairs(achievements) do
		if AchievementPresets[name] then
			local steam_id = g_AchievementNameToSteamId[name]
			if not steam_id then
				print("Achievement", name, "doesn't have a Steam ID!")
			else
				table.insert(steam_achievements, steam_id)
			end
		end
	end
	return steam_achievements
end

local function WaitAchievementUnlock(achievements)
	if not Platform.steam or not IsSteamLoggedIn() then
		return true
	end
	local steam_achievements = GetSteamAchievementIds(achievements)
	local steam_unlocked = SteamUnlockAchievements(steam_achievements) and WaitMsg(s_AchievementUnlockedSignals, 5*1000)
	if not steam_unlocked then
		-- Currently our publisher wants to test if achievements work even if they haven't been
		-- created in the steam backend.
		-- To do this we unlock all achievements in AccountStorage even if they haven't been unlocked in steam.
		-- We also pop a notification if steam failed to unlock the achievement.
		Msg("SteamUnlockAchievementsFailed", steam_achievements)
	end
	return true
end

-------------------------------------------[ Higher level functions ]-----------------------------------------------

-- Asynchronous version, launches a thread
function AsyncAchievementUnlock(achievement)
	_AchievementsToUnlock[achievement] = true
	if not IsValidThread(_UnlockThread) then
		_UnlockThread = CreateRealTimeThread( function()
			local achievement = next(_AchievementsToUnlock)
			while achievement do
				if WaitAchievementUnlock{achievement} then
					Msg("AchievementUnlocked", achievement)
				else
					AccountStorage.achievements.unlocked[achievement] = false
				end
				_AchievementsToUnlock[achievement] = nil
				achievement = next(_AchievementsToUnlock)
			end
		end)
	end
end

function SynchronizeAchievements()
	if not IsSteamLoggedIn() then return end
	
	-- check progress, auto-unlock if sufficient progress is made
	for k, v in pairs(AccountStorage.achievements.progress) do
		_CheckAchievementProgress(k, "don't unlock in provider")
	end
	
	local account_storage_unlocked = AccountStorage.achievements.unlocked
	CreateRealTimeThread(function()
		if account_storage_unlocked ~= AccountStorage.achievements.unlocked then
			print("Synchronize achievements aborted!")
			return
		end
		
		-- transfer unlocked achievements to Steam account
		WaitAchievementUnlock(table.keys(account_storage_unlocked))

		if not TransferUnlockedAchievementsFromSteam then
			return
		end
		
		if account_storage_unlocked ~= AccountStorage.achievements.unlocked then
			print("Synchronize achievements aborted!")
			return
		end
		
		-- transfer unlocked achievements to AccountStorage
		local ok, steam_unlocked = WaitGetAchievements()
		
		if account_storage_unlocked ~= AccountStorage.achievements.unlocked then
			print("Synchronize achievements aborted!")
			return
		end
		
		if not ok then
			print("Synchronize achievements failed!")
			return
		end
		
		local save = false
		for i = 1, #steam_unlocked do
			local id = steam_unlocked[i]
			if not account_storage_unlocked[id] then
				save = true
			end
			account_storage_unlocked[id] = true
		end
		if save then
			SaveAccountStorage(5000)
		end
	end)
end

function CheatPlatformUnlockAllAchievements()
	if not Platform.steam or not IsSteamLoggedIn() then end
	local steam_achievements = GetSteamAchievementIds(table.keys(AchievementPresets, true))
	SteamUnlockAchievements(steam_achievements)
end

function CheatPlatformResetAllAchievements()
	if not Platform.steam or not IsSteamLoggedIn() then end
	local steam_achievements = GetSteamAchievementIds(table.keys(AchievementPresets, true))
	SteamResetAchievements(steam_achievements)
end