//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="HLSFAllocationHandle"
// 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.Collections;
using System.Collections.Generic;
using System.Drawing;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

using Allocator = StgSharp.HighPerformance.Memory.HybridLayerSegregatedFitAllocator;

namespace StgSharp.HighPerformance.Memory
{
    public readonly unsafe struct HlsfHandle
    {

        internal readonly Allocator.Entry* EntryHandle;
        public readonly nuint AllocSize;

        internal HlsfHandle(
                 Allocator.Entry* handle,
                 nuint s
        )
        {
            EntryHandle = handle;
            Pointer = (byte*)handle->Position;
            AllocSize = s;

            // Console.WriteLine($"{(ulong)handle->PreviousNear}<->{(ulong)handle->NextNear},\t{handle->Size}");
        }

        public readonly ref byte this[
                                 uint index
        ]
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get
            {
                ArgumentOutOfRangeException.ThrowIfGreaterThanOrEqual(index, AllocSize);
                return ref Pointer[index];
            }
        }

        public readonly byte* Pointer { get; init; }

        public readonly Span<byte> BufferHandle => new(Pointer, (int)AllocSize);

        public readonly Enumerator GetEnumerator()
        {
            return new Enumerator(this);
        }

        public ref struct Enumerator : IEnumerator<byte>
        {

            private HlsfHandle _handle;

            private uint _index = ~0u;

            internal Enumerator(
                     HlsfHandle span
            )
            {
                _handle = span;
                Span = span.BufferHandle;
            }

            public ref byte RefCurrent => ref _handle[_index];

            public Span<byte> Span { get; init; }

            public readonly void Dispose() { }

            public bool MoveNext()
            {
                _index++;
                return _index < _handle.AllocSize;
            }

            public void Reset()
            {
                _index = 0;
            }

            object IEnumerator.Current => RefCurrent;

            byte IEnumerator<byte>.Current => RefCurrent;

        }

    }
}