local BGM={
	default=false,
	getList=function()error("Cannot getList before initialize!")end,
	getCount=function()return 0 end,
	play=NULL,
	freshVolume=NULL,
	stop=NULL,
	--nowPlay=[str:playing ID]
	--playing=[src:playing SRC]
}
function BGM.setDefault(bgm)
	BGM.default=bgm
end
function BGM.init(list)
	BGM.init=nil
	local Sources={}

	local simpList={}
	for _,v in next,list do
		table.insert(simpList,v.name)
		Sources[v.name]=v.path
	end
	table.sort(simpList)
	function BGM.getList()return simpList end
	local count=#simpList
	function BGM.getCount()return count end

	local function load(name)
		if type(Sources[name])=='string'then
			if love.filesystem.getInfo(Sources[name])then
				Sources[name]=love.audio.newSource(Sources[name],'stream')
				Sources[name]:setLooping(true)
				Sources[name]:setVolume(0)
				return true
			else
				MES.new('warn',"No BGM file: "..Sources[name],5)
			end
		elseif Sources[name]then
			return true
		elseif name then
			MES.new('warn',"No BGM: "..name,5)
		end
	end
	function BGM.loadAll()for name in next,Sources do load(name)end end
	local function fadeOut(src)
		while true do
			coroutine.yield()
			local v=src:getVolume()-.025*SETTING.bgm
			src:setVolume(v>0 and v or 0)
			if v<=0 then
				src:stop()
				return true
			end
		end
	end
	local function fadeIn(src)
		while true do
			coroutine.yield()
			local v=SETTING.bgm
			v=math.min(v,src:getVolume()+.025*v)
			src:setVolume(v)
			if v>=SETTING.bgm then
				return true
			end
		end
	end
	local function removeCurFadeOut(task,code,src)
		return task.code==code and task.args[1]==src
	end
	function BGM.play(name)
		if not name then name=BGM.default end
		if not load(name)then return end
		if SETTING.bgm==0 then
			BGM.nowPlay=name
			BGM.playing=Sources[name]
			return true
		end
		if name and Sources[name]then
			if BGM.nowPlay~=name then
				if BGM.nowPlay then TASK.new(fadeOut,BGM.playing)end
				TASK.removeTask_iterate(removeCurFadeOut,fadeOut,Sources[name])
				TASK.removeTask_code(fadeIn)

				TASK.new(fadeIn,Sources[name])
				BGM.nowPlay=name
				BGM.playing=Sources[name]
				BGM.playing:play()
			end
			return true
		end
	end
	function BGM.freshVolume()
		if BGM.playing then
			local v=SETTING.bgm
			if v>0 then
				BGM.playing:setVolume(v)
				BGM.playing:play()
			elseif BGM.nowPlay then
				BGM.playing:pause()
			end
		end
	end
	function BGM.stop()
		TASK.removeTask_code(fadeIn)
		if BGM.nowPlay then TASK.new(fadeOut,BGM.playing)end
		BGM.nowPlay,BGM.playing=nil
	end
end
return BGM