//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="HLSFAllocator"
// Project: StgSharp
// AuthorGroup: Nitload Space
// Copyright (c) Nitload Space. 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 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.
//     
// -----------------------------------------------------------------------
// -----------------------------------------------------------------------
using System;
using System.Buffers;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Text;

namespace StgSharp.Mathematics.Memory
{
    public unsafe partial class HybridLayerSegregatedFitAllocator : IDisposable
    {

        // Bucket system field - directly in main allocator class
        private readonly BucketNode *[] _bucketHeads;

        // _spareMemory is also the beginning position of allocator
        private Entry *_spareMemory;
        private readonly byte* m_Buffer;
        private bool disposedValue;
        private readonly int _align;
        private readonly long _maxSize;
        private readonly nuint _size;
        private readonly SlabAllocator<Entry> _entries;

        public HybridLayerSegregatedFitAllocator(nuint byteSize)
        {
            if (byteSize < 64) {
                throw new InvalidOperationException();
            }
            _entries = SlabAllocator<Entry>.Create(64, SlabBufferLayout.Chunked, false);
            _size = byteSize;
            m_Buffer = (byte *)NativeMemory.AlignedAlloc(byteSize, 16);
            _align = 16;

            _bucketHeads = new BucketNode *[_levelSizeArray.Length * 3 + 1];

            _spareMemory = (Entry *)_entries.Allocate();
            _spareMemory->State = EntryState.Spare;
            _spareMemory->PreviousNear = _spareMemory;
            _spareMemory->NextNear = _spareMemory;
            _spareMemory->Position = (nuint)m_Buffer;
            _spareMemory->Size = (long)byteSize;

            _maxSize = 32U * 1024U * 1024U;
        }

        public HybridLayerSegregatedFitAllocator(nuint byteSize, uint maxBlockSize)
        {
            _entries = SlabAllocator<Entry>.Create(64, SlabBufferLayout.Chunked, false);
            m_Buffer = (byte *)NativeMemory.AlignedAlloc(byteSize, 16);
            _align = 16;
            _size = byteSize;

            _spareMemory = (Entry *)_entries.Allocate();
            _spareMemory->State = EntryState.Empty;
            _spareMemory->PreviousNear = _spareMemory;
            _spareMemory->NextNear = _spareMemory;
            _spareMemory->Position = (nuint)m_Buffer;
            _spareMemory->Size = (long)byteSize;

            int levelCountOrigin = _levelSizeArray.Length;
            int levelCount = GetLevelFromSize(maxBlockSize) + 1;
            Array.Resize(ref _levelSizeArray, levelCount);
            _bucketHeads = new BucketNode *[(levelCount * 3) + 1];
            int size = _levelSizeArray[^1];
            for (int i = levelCountOrigin; i < levelCount; i++)
            {
                size *= 4;
                _levelSizeArray[i] = size;
            }
            _maxSize = maxBlockSize;
        }

        public HybridLayerSegregatedFitAllocator(nuint byteSize, int align)
        {
            if (align < 16 || (align & (align - 1)) != 0) {
                throw new ArgumentException(
                                "Alignment must be a power of two and at least 16 bytes.");
            }
            _entries = SlabAllocator<Entry>.Create(64, SlabBufferLayout.Chunked, false);
            m_Buffer = (byte *)NativeMemory.AlignedAlloc(byteSize, (nuint)align);
            _align = align;
            _size = byteSize;

            _bucketHeads = new BucketNode *[_levelSizeArray.Length * 3 + 1];

            _spareMemory = (Entry *)_entries.Allocate();
            _spareMemory->State = EntryState.Empty;
            _spareMemory->PreviousNear = _spareMemory;
            _spareMemory->NextNear = _spareMemory;
            _spareMemory->Position = (nuint)m_Buffer;
            _spareMemory->Size = (long)byteSize;

            _maxSize = 32U * 1024U * 1024U;
        }

        public HybridLayerSegregatedFitAllocator(nuint byteSize, int align, long maxBlockSize)
        {
            if (align < 16 || (align & (align - 1)) != 0) {
                throw new ArgumentException(
                                "Alignment must be a power of two and at least 16 bytes.");
            }
            _entries = SlabAllocator<Entry>.Create(64, SlabBufferLayout.Chunked, false);
            m_Buffer = (byte*)NativeMemory.AlignedAlloc(byteSize, (nuint)align);
            _align = align;
            _size = byteSize;

            _spareMemory = (Entry *)_entries.Allocate();
            _spareMemory->State = EntryState.Empty;
            _spareMemory->PreviousNear = _spareMemory;
            _spareMemory->NextNear = _spareMemory;
            _spareMemory->Position = (nuint)m_Buffer;
            _spareMemory->Size = (long)byteSize;

            int levelCountOrigin = _levelSizeArray.Length;
            int levelCount = GetLevelFromSize(maxBlockSize) + 1;
            Array.Resize(ref _levelSizeArray, levelCount);
            _bucketHeads = new BucketNode *[levelCount * 3 + 1];
            int size = _levelSizeArray[^1];
            for (int i = levelCountOrigin; i < levelCount; i++)
            {
                size *= 4;
                _levelSizeArray[i] = size;
            }
            _maxSize = maxBlockSize;
        }

        public void Dispose()
        {
            Dispose(disposing:true);
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool disposing)
        {
            if (!disposedValue)
            {
                if (disposing) {
                    _entries.Dispose();
                }
                NativeMemory.AlignedFree(m_Buffer);
                disposedValue = true;
            }
        }

        ~HybridLayerSegregatedFitAllocator()
        {
            Dispose(disposing:false);
        }

    }
}