//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="HLSFAllocator.Free"
// Project: StgSharp
// AuthorGroup: Nitload
// Copyright (c) Nitload. 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.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using hlsfHandle = StgSharp.HighPerformance.Memory.HybridLayerSegregatedFitAllocationHandle;

namespace StgSharp.HighPerformance.Memory
{
    public unsafe partial class HybridLayerSegregatedFitAllocator
    {

        /// <summary>
        ///   Minimal collect: linear scan, merge contiguous empty Blocks into one, push merged head
        ///   back to bucket. Caller-responsible design: no slicing or redistribution.
        /// </summary>
        public void Collect()
        {
            Entry* cur = _positionHead;
            while (cur != null && cur != _spareMemory)
            {
                if (cur->State != EntryState.Empty)
                {
                    cur = cur->NextNear;
                    continue;
                }

                Entry* runHead = cur;
                Entry* next = runHead->NextNear;

                // Remove head from bucket if currently registered
                int headLevel = runHead->Level;
                int headSeg = DetermineSegmentIndex(runHead->Size, headLevel);
                TryRemoveFromBucket(headLevel, headSeg, (BucketNode*)runHead->Position);

                while (next != null &&
                       next != _spareMemory &&
                       next->State == EntryState.Empty &&
                       IsAdjacentTo(runHead, next))
                {
                    int lvl = next->Level;
                    int seg = DetermineSegmentIndex(next->Size, lvl);
                    TryRemoveFromBucket(lvl, seg, (BucketNode*)next->Position);

                    runHead->Size += next->Size;
                    RemoveFromPositionChain(next);
                    next = runHead->NextNear;
                }

                // Recompute level for merged block and push once
                runHead->Level = GetLevelFromSize(runHead->Size);
                int finalLevel = runHead->Level;
                int finalSeg = DetermineSegmentIndex(runHead->Size, finalLevel);
                ((BucketNode*)runHead->Position)->EntryRef = runHead; // ensure consistency
                PushLevel(finalLevel, finalSeg, (BucketNode*)runHead->Position);

                cur = next;
            }
        }

        /// <summary>
        ///   Free allocated memory block and perform adjacent block merging
        /// </summary>
        /// <param name="handle">
        ///   Handle to the allocated memory block
        /// </param>
        public void Free(hlsfHandle handle)
        {
            Entry* e = handle.EntryHandle;
            if (e == null) {
                return;
            }
            if (e->State != EntryState.Allocated) {
                return;
            }

            // Mark as empty so it can be merged
            e->State = EntryState.Empty;

            // Try merge with adjacent free blocks and remove them from buckets
            MergeAndRemoveFromBuckets(e);

            // Calculate final level and segment for the merged block
            uint finalSize = e->Size;
            int finalLevel = GetLevelFromSize(finalSize);
            int finalSegment = DetermineSegmentIndex(finalSize, finalLevel);

            // Push the merged entry back to appropriate bucket
            PushLevel(finalLevel, finalSegment, (BucketNode*)e->Position);
        }

    }
}