local PrefabObjectPool = {}

PrefabObjectPool.__index = PrefabObjectPool

function PrefabObjectPool.New(prefab,capcity)
	if prefab == nil then
		error("[PrefabObjectPool]prefab should not be nil")
	end
	local self = {}
	setmetatable(self,PrefabObjectPool)
	self.prefab = prefab
	self.queue = LuaQueue.New()
	self.usedItems = LuaList.New()
	self.capcity = capcity
	return self
end

-- 預先生成指定個數的物件
-- count 需要生成的個數，最大不能超過池大小，若為空則表示直接將池填充滿
function PrefabObjectPool:Prewarm(count)
	if count == nil then
		if self.capcity == nil then
			error("[PrefabObjectPool]invalid state")
		else
			count = self.capcity
		end
	elseif count > self.capcity then
		count = self.capcity
	end

	for i=1,count do
		local obj =  GameObject.Instantiate(self.prefab)
		self:Put(obj)
	end
end

-- 回收一個物件到物件池
function PrefabObjectPool:Put(obj)
	if self.usedItems:Contains(obj) then
		self.usedItems:Remove(obj)
		obj:SetActive(false)
		self.queue:Enqueue(obj)
	else
		error("[PrefabObjectPool]invalid state")
	end
end

-- 從物件池中獲取一個物件，若池為空的，則從Prefab建立一個新的
-- 當物件到達池上限時，會把最早使用的物件回收並作為新物件返回
function PrefabObjectPool:Get()
	local obj = nil
	if self.queue.Count == 0 then
		if self.usedItems.Count == self.capcity then
			obj = self.usedItems[0]
			obj:SetActive(false)
			self.usedItems:RemoveAt(0)
		else
			obj = GameObject.Instantiate(self.prefab)
		end
	else
		obj = self.queue:Dequeue()
	end

	self.usedItems:Add(obj)
	obj:SetActive(true)
	return obj
end

-- 將所有被使用的物件全部回收
function PrefabObjectPool:RecycleAll()
	local count = self.usedItems.Count
	for i=count-1,0, -1 do
		local item = self.usedItems[i]
		self:Put(item)
	end
	self.usedItems:Clear()
end

--清空物件池Destroy
function PrefabObjectPool:Clear()

	self:RecycleAll();

	for i = 0, self.queue.Count - 1 do
		GameObject.Destroy(self.queue:Dequeue());
	end

	self.queue:Clear();
end

return PrefabObjectPool