//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="HLSFAllocator.cs"
// 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;
using hlsfHandle = StgSharp.Mathematics.Memory.hlsfHandle;

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 readonly Action<nuint> _freeHandle;
        private bool disposedValue;
        private readonly int _align;
        private readonly long _maxSize;
        private readonly nuint _size;
        private readonly SlabAllocator<Entry> _entries;

        internal HybridLayerSegregatedFitAllocator(
                 nuint byteSize,
                 int align,
                 long maxBlockSize,
                 Func<nuint, int, nuint> allocator,
                 Action<nuint> freeHandle,
                 SlabAllocator<Entry>? entryManager)
            : this(byteSize, align, maxBlockSize, (void*)allocator(byteSize, align), freeHandle, entryManager) { }

        internal HybridLayerSegregatedFitAllocator(
                 nuint byteSize,
                 int align,
                 long maxBlockSize,
                 void* externalPointer,
                 Action<nuint> freeHandle,
                 SlabAllocator<Entry>? entryManager = null)
        {
            if (align < 16 || (align & (align - 1)) != 0) {
                throw new ArgumentException(
                                "Alignment must be a power of two and at least 16 bytes.");
            }
            _entries = entryManager ?? SlabAllocator.Create<Entry>(64, SlabBufferLayout.Chunked, false);
            m_Buffer = (byte*)externalPointer;
            _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;
            _freeHandle = freeHandle ?? (static _ => { });
        }

        public HybridLayerSegregatedFitAllocator(nuint byteSize)
            : this(
            byteSize, 16, 32U * 1024U * 1024U, NativeMemory.AlignedAlloc(byteSize, 16), ptr => NativeMemory.AlignedFree((void*)ptr)) { }

        public HybridLayerSegregatedFitAllocator(nuint byteSize, uint maxBlockSize)
            : this(
            byteSize, 16, maxBlockSize, NativeMemory.AlignedAlloc(byteSize, 16), ptr => NativeMemory.AlignedFree((void*)ptr)) { }

        public HybridLayerSegregatedFitAllocator(nuint byteSize, int align)
            : this(
            byteSize, align, 32U * 1024U * 1024U, NativeMemory.AlignedAlloc(byteSize, 16), ptr => NativeMemory.AlignedFree((void*)ptr)) { }

        public HybridLayerSegregatedFitAllocator(nuint byteSize, int align, long maxBlockSize)
            : this(byteSize, align, maxBlockSize, NativeMemory.AlignedAlloc(byteSize, 16), ptr => NativeMemory.AlignedFree((void*)ptr)) { }

        public partial hlsfHandle Alloc(long size);

        public partial void Collect();

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

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

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

    }
}