/****************************************************************************
* Copyright (C) 2014-2015 Intel Corporation.   All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy 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 of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
* @file arena.h
*
* @brief Arena memory manager
*        The arena is convenient and fast for managing allocations for any of
*        our allocations that are associated with operations and can all be freed
*        once when their operation has completed. Allocations are cheap since
*        most of the time its simply an increment of an offset. Also, no need to
*        free individual allocations. All of the arena memory can be freed at once.
*
******************************************************************************/
#pragma once

#include <mutex>
#include <algorithm>
#include <atomic>
#include "core/utils.h"

static const size_t ARENA_BLOCK_ALIGN = 64;

struct ArenaBlock
{
    size_t      blockSize = 0;
    ArenaBlock* pNext = nullptr;
};
static_assert(sizeof(ArenaBlock) <= ARENA_BLOCK_ALIGN,
    "Increase BLOCK_ALIGN size");

class DefaultAllocator
{
public:
    ArenaBlock* AllocateAligned(size_t size, size_t align)
    {
        SWR_ASSUME_ASSERT(size >= sizeof(ArenaBlock));

        ArenaBlock* p = new (AlignedMalloc(size, align)) ArenaBlock();
        p->blockSize = size;
        return p;
    }

    void Free(ArenaBlock* pMem)
    {
        if (pMem)
        {
            SWR_ASSUME_ASSERT(pMem->blockSize < size_t(0xdddddddd));
            AlignedFree(pMem);
        }
    }
};

// Caching Allocator for Arena
template<uint32_t NumBucketsT = 8, uint32_t StartBucketBitT = 12>
struct CachingAllocatorT : DefaultAllocator
{
    ArenaBlock* AllocateAligned(size_t size, size_t align)
    {
        SWR_ASSUME_ASSERT(size >= sizeof(ArenaBlock));
        SWR_ASSUME_ASSERT(size <= uint32_t(-1));

        uint32_t bucket = GetBucketId(size);

        {
            // search cached blocks
            std::lock_guard<std::mutex> l(m_mutex);
            ArenaBlock* pPrevBlock = &m_cachedBlocks[bucket];
            ArenaBlock* pBlock = SearchBlocks(pPrevBlock, size, align);

            if (pBlock)
            {
                m_cachedSize -= pBlock->blockSize;
                if (pBlock == m_pLastCachedBlocks[bucket])
                {
                    m_pLastCachedBlocks[bucket] = pPrevBlock;
                }
            }
            else
            {
                pPrevBlock = &m_oldCachedBlocks[bucket];
                pBlock = SearchBlocks(pPrevBlock, size, align);

                if (pBlock)
                {
                    m_oldCachedSize -= pBlock->blockSize;
                    if (pBlock == m_pOldLastCachedBlocks[bucket])
                    {
                        m_pOldLastCachedBlocks[bucket] = pPrevBlock;
                    }
                }
            }

            if (pBlock)
            {
                SWR_ASSUME_ASSERT(pPrevBlock && pPrevBlock->pNext == pBlock);
                pPrevBlock->pNext = pBlock->pNext;
                pBlock->pNext = nullptr;

                return pBlock;
            }

            m_totalAllocated += size;

#if 0
            {
                static uint32_t count = 0;
                char buf[128];
                sprintf_s(buf, "Arena Alloc %d 0x%llx bytes - 0x%llx total\n", ++count, uint64_t(size), uint64_t(m_totalAllocated));
                OutputDebugStringA(buf);
            }
#endif
        }

        if (bucket && bucket < (CACHE_NUM_BUCKETS - 1))
        {
            // Make all blocks in this bucket the same size
            size = size_t(1) << (bucket + 1 + CACHE_START_BUCKET_BIT);
        }

        return this->DefaultAllocator::AllocateAligned(size, align);
    }

    void Free(ArenaBlock* pMem)
    {
        if (pMem)
        {
            std::unique_lock<std::mutex> l(m_mutex);
            InsertCachedBlock(GetBucketId(pMem->blockSize), pMem);
        }
    }

    void FreeOldBlocks()
    {
        if (!m_cachedSize) { return; }
        std::lock_guard<std::mutex> l(m_mutex);

        bool doFree = (m_oldCachedSize > MAX_UNUSED_SIZE);

        for (uint32_t i = 0; i < CACHE_NUM_BUCKETS; ++i)
        {
            if (doFree)
            {
                ArenaBlock* pBlock = m_oldCachedBlocks[i].pNext;
                while (pBlock)
                {
                    ArenaBlock* pNext = pBlock->pNext;
                    m_oldCachedSize -= pBlock->blockSize;
                    m_totalAllocated -= pBlock->blockSize;
                    this->DefaultAllocator::Free(pBlock);
                    pBlock = pNext;
                }
                m_oldCachedBlocks[i].pNext = nullptr;
                m_pOldLastCachedBlocks[i] = &m_oldCachedBlocks[i];
            }

            if (m_pLastCachedBlocks[i] != &m_cachedBlocks[i])
            {
                if (i && i < (CACHE_NUM_BUCKETS - 1))
                {
                    // We know that all blocks are the same size.
                    // Just move the list over.
                    m_pLastCachedBlocks[i]->pNext = m_oldCachedBlocks[i].pNext;
                    m_oldCachedBlocks[i].pNext = m_cachedBlocks[i].pNext;
                    m_cachedBlocks[i].pNext = nullptr;
                    if (m_pOldLastCachedBlocks[i]->pNext)
                    {
                        m_pOldLastCachedBlocks[i] = m_pLastCachedBlocks[i];
                    }
                    m_pLastCachedBlocks[i] = &m_cachedBlocks[i];
                }
                else
                {
                    // The end buckets can have variable sized lists.
                    // Insert each block based on size
                    ArenaBlock* pBlock = m_cachedBlocks[i].pNext;
                    while (pBlock)
                    {
                        ArenaBlock* pNext = pBlock->pNext;
                        pBlock->pNext = nullptr;
                        m_cachedSize -= pBlock->blockSize;
                        InsertCachedBlock<true>(i, pBlock);
                        pBlock = pNext;
                    }

                    m_pLastCachedBlocks[i] = &m_cachedBlocks[i];
                    m_cachedBlocks[i].pNext = nullptr;
                }
            }
        }

        m_oldCachedSize += m_cachedSize;
        m_cachedSize = 0;
    }

    CachingAllocatorT()
    {
        for (uint32_t i = 0; i < CACHE_NUM_BUCKETS; ++i)
        {
            m_pLastCachedBlocks[i] = &m_cachedBlocks[i];
            m_pOldLastCachedBlocks[i] = &m_oldCachedBlocks[i];
        }
    }

    ~CachingAllocatorT()
    {
        // Free all cached blocks
        for (uint32_t i = 0; i < CACHE_NUM_BUCKETS; ++i)
        {
            ArenaBlock* pBlock = m_cachedBlocks[i].pNext;
            while (pBlock)
            {
                ArenaBlock* pNext = pBlock->pNext;
                this->DefaultAllocator::Free(pBlock);
                pBlock = pNext;
            }
            pBlock = m_oldCachedBlocks[i].pNext;
            while (pBlock)
            {
                ArenaBlock* pNext = pBlock->pNext;
                this->DefaultAllocator::Free(pBlock);
                pBlock = pNext;
            }
        }
    }

private:
    static uint32_t GetBucketId(size_t blockSize)
    {
        uint32_t bucketId = 0;

#if defined(BitScanReverseSizeT)
        BitScanReverseSizeT((unsigned long*)&bucketId, (blockSize - 1) >> CACHE_START_BUCKET_BIT);
        bucketId = std::min<uint32_t>(bucketId, CACHE_NUM_BUCKETS - 1);
#endif

        return bucketId;
    }

    template <bool OldBlockT = false>
    void InsertCachedBlock(uint32_t bucketId, ArenaBlock* pNewBlock)
    {
        SWR_ASSUME_ASSERT(bucketId < CACHE_NUM_BUCKETS);

        ArenaBlock* pPrevBlock = OldBlockT ? &m_oldCachedBlocks[bucketId] : &m_cachedBlocks[bucketId];
        ArenaBlock* pBlock = pPrevBlock->pNext;

        while (pBlock)
        {
            if (pNewBlock->blockSize >= pBlock->blockSize)
            {
                // Insert here
                break;
            }
            pPrevBlock = pBlock;
            pBlock = pBlock->pNext;
        }

        // Insert into list
        SWR_ASSUME_ASSERT(pPrevBlock);
        pPrevBlock->pNext = pNewBlock;
        pNewBlock->pNext = pBlock;

        if (OldBlockT)
        {
            if (m_pOldLastCachedBlocks[bucketId] == pPrevBlock)
            {
                m_pOldLastCachedBlocks[bucketId] = pNewBlock;
            }

            m_oldCachedSize += pNewBlock->blockSize;
        }
        else
        {
            if (m_pLastCachedBlocks[bucketId] == pPrevBlock)
            {
                m_pLastCachedBlocks[bucketId] = pNewBlock;
            }

            m_cachedSize += pNewBlock->blockSize;
        }
    }

    static ArenaBlock* SearchBlocks(ArenaBlock*& pPrevBlock, size_t blockSize, size_t align)
    {
        ArenaBlock* pBlock = pPrevBlock->pNext;
        ArenaBlock* pPotentialBlock = nullptr;
        ArenaBlock* pPotentialPrev = nullptr;

        while (pBlock)
        {
            if (pBlock->blockSize >= blockSize)
            {
                if (pBlock == AlignUp(pBlock, align))
                {
                    if (pBlock->blockSize == blockSize)
                    {
                        // Won't find a better match
                        break;
                    }

                    // We could use this as it is larger than we wanted, but
                    // continue to search for a better match
                    pPotentialBlock = pBlock;
                    pPotentialPrev = pPrevBlock;
                }
            }
            else
            {
                // Blocks are sorted by size (biggest first)
                // So, if we get here, there are no blocks 
                // large enough, fall through to allocation.
                pBlock = nullptr;
                break;
            }

            pPrevBlock = pBlock;
            pBlock = pBlock->pNext;
        }

        if (!pBlock)
        {
            // Couldn't find an exact match, use next biggest size
            pBlock = pPotentialBlock;
            pPrevBlock = pPotentialPrev;
        }

        return pBlock;
    }

    // buckets, for block sizes < (1 << (start+1)), < (1 << (start+2)), ...
    static const uint32_t   CACHE_NUM_BUCKETS       = NumBucketsT;
    static const uint32_t   CACHE_START_BUCKET_BIT  = StartBucketBitT;
    static const size_t     MAX_UNUSED_SIZE         = sizeof(MEGABYTE);

    ArenaBlock              m_cachedBlocks[CACHE_NUM_BUCKETS];
    ArenaBlock*             m_pLastCachedBlocks[CACHE_NUM_BUCKETS];
    ArenaBlock              m_oldCachedBlocks[CACHE_NUM_BUCKETS];
    ArenaBlock*             m_pOldLastCachedBlocks[CACHE_NUM_BUCKETS];
    std::mutex              m_mutex;

    size_t                  m_totalAllocated = 0;

    size_t                  m_cachedSize = 0;
    size_t                  m_oldCachedSize = 0;
};
typedef CachingAllocatorT<> CachingAllocator;

template<typename T = DefaultAllocator, size_t BlockSizeT = 128 * sizeof(KILOBYTE)>
class TArena
{
public:
    TArena(T& in_allocator)  : m_allocator(in_allocator) {}
    TArena()                 : m_allocator(m_defAllocator) {}
    ~TArena()
    {
        Reset(true);
    }

    void* AllocAligned(size_t size, size_t  align)
    {
        if (0 == size)
        {
            return nullptr;
        }

        SWR_ASSERT(align <= ARENA_BLOCK_ALIGN);

        if (m_pCurBlock)
        {
            ArenaBlock* pCurBlock = m_pCurBlock;
            size_t offset = AlignUp(m_offset, align);

            if ((offset + size) <= pCurBlock->blockSize)
            {
                void* pMem = PtrAdd(pCurBlock, offset);
                m_offset = offset + size;
                return pMem;
            }

            // Not enough memory in this block, fall through to allocate
            // a new block
        }

        static const size_t ArenaBlockSize = BlockSizeT;
        size_t blockSize = std::max(size + ARENA_BLOCK_ALIGN, ArenaBlockSize);

        // Add in one BLOCK_ALIGN unit to store ArenaBlock in.
        blockSize = AlignUp(blockSize, ARENA_BLOCK_ALIGN);

        ArenaBlock* pNewBlock = m_allocator.AllocateAligned(blockSize, ARENA_BLOCK_ALIGN);    // Arena blocks are always simd byte aligned.
        SWR_ASSERT(pNewBlock != nullptr);

        if (pNewBlock != nullptr)
        {
            m_offset = ARENA_BLOCK_ALIGN;
            pNewBlock->pNext = m_pCurBlock;

            m_pCurBlock = pNewBlock;
        }

        return AllocAligned(size, align);
    }

    void* Alloc(size_t  size)
    {
        return AllocAligned(size, 1);
    }

    void* AllocAlignedSync(size_t size, size_t align)
    {
        void* pAlloc = nullptr;

        m_mutex.lock();
        pAlloc = AllocAligned(size, align);
        m_mutex.unlock();

        return pAlloc;
    }

    void* AllocSync(size_t size)
    {
        void* pAlloc = nullptr;

        m_mutex.lock();
        pAlloc = Alloc(size);
        m_mutex.unlock();

        return pAlloc;
    }

    void Reset(bool removeAll = false)
    {
        m_offset = ARENA_BLOCK_ALIGN;

        if (m_pCurBlock)
        {
            ArenaBlock *pUsedBlocks = m_pCurBlock->pNext;
            m_pCurBlock->pNext = nullptr;
            while (pUsedBlocks)
            {
                ArenaBlock* pBlock = pUsedBlocks;
                pUsedBlocks = pBlock->pNext;

                m_allocator.Free(pBlock);
            }

            if (removeAll)
            {
                m_allocator.Free(m_pCurBlock);
                m_pCurBlock = nullptr;
            }
        }
    }

    bool IsEmpty()
    {
        return (m_pCurBlock == nullptr) || (m_offset == ARENA_BLOCK_ALIGN && m_pCurBlock->pNext == nullptr);
    }

private:

    ArenaBlock*         m_pCurBlock = nullptr;
    size_t              m_offset    = ARENA_BLOCK_ALIGN;

    /// @note Mutex is only used by sync allocation functions.
    std::mutex          m_mutex;

    DefaultAllocator    m_defAllocator;
    T&                  m_allocator;
};

using StdArena      = TArena<DefaultAllocator>;
using CachingArena  = TArena<CachingAllocator>;
