/****************************************************************************
 Copyright (c) 2021-2023 Xiamen Yaji Software Co., Ltd.
 
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 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights to
 use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
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 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.

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****************************************************************************/

#pragma once

#include <algorithm>
#include <cstdint>
#include <functional>
#include "base/TypeDef.h"
#include "base/std/container/vector.h"

namespace cc {

namespace memop {

template <typename T>
class Pool final {
public:
    using CtorFunc = std::function<T *()>;
    using DtorFunc = std::function<void(T *)>;
    /**
     * @en Constructor with the allocator of elements and initial pool size
     * @zh 使用元素的构造器和初始大小的构造函数
     * @param ctor The allocator of elements in pool, it's invoked directly without `new`
     * @param elementsPerBatch Initial pool size, this size will also be the incremental size when the pool is overloaded
     */
    Pool(const CtorFunc &ctor, const DtorFunc &dtor, uint32_t elementsPerBatch)
    : _ctor(ctor),
      _dtor(dtor),
      _elementsPerBatch(std::max(elementsPerBatch, static_cast<uint32_t>(1))) {
        CC_ASSERT(_ctor);
        CC_ASSERT(_dtor);
        _nextAvail = static_cast<index_t>(_elementsPerBatch - 1);

        for (uint32_t i = 0; i < _elementsPerBatch; ++i) {
            _freepool.push_back(ctor());
        }
    }

    Pool(const Pool &) = delete;
    Pool(Pool &&) = delete;
    ~Pool() = default;
    Pool &operator=(const Pool &) = delete;
    Pool &operator=(Pool &&) = delete;

    /**
     * @en Take an object out of the object pool.
     * @zh 从对象池中取出一个对象。
     * @return An object ready for use. This function always return an object.
     */
    T *alloc() {
        if (_nextAvail < 0) {
            _freepool.resize(_elementsPerBatch);
            for (uint32_t i = 0; i < _elementsPerBatch; ++i) {
                _freepool[i] = _ctor();
            }
            _nextAvail = static_cast<index_t>(_elementsPerBatch - 1);
        }

        return _freepool[_nextAvail--];
    }

    /**
     * @en Put an object back into the object pool.
     * @zh 将一个对象放回对象池中。
     * @param obj The object to be put back into the pool
     */
    void free(T *obj) {
        ++_nextAvail;
        if (_nextAvail >= _freepool.size()) {
            _freepool.resize(_freepool.size() + 1);
        }
        _freepool[_nextAvail] = obj;
    }

    /**
     * @en Put multiple objects back into the object pool.
     * @zh 将一组对象放回对象池中。
     * @param objs An array of objects to be put back into the pool
     */
    void freeArray(const ccstd::vector<T *> &objs) {
        _freepool.reserve(_nextAvail + 1 + objs.size());
        _freepool.insert(_freepool.begin() + _nextAvail + 1,
                         objs.begin(), objs.end());
        _nextAvail += static_cast<index_t>(objs.size());
    }

    /**
     * @en Destroy all elements and clear the pool.
     * @zh 释放对象池中所有资源并清空缓存池。
     * @param dtor The destructor function, it will be invoked for all elements in the pool
     */
    void destroy() {
        for (int i = 0; i <= _nextAvail; ++i) {
            _dtor(_freepool[i]);
        }
        _nextAvail = -1;
        _freepool.clear();
        _freepool.shrink_to_fit();
    }

private:
    CtorFunc _ctor{nullptr};
    DtorFunc _dtor{nullptr};
    uint32_t _elementsPerBatch{0};
    index_t _nextAvail{-1};
    ccstd::vector<T *> _freepool;
};

} // namespace memop

} // namespace cc