//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="Matrix.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 StgSharp.HighPerformance;
using System;
using System.Numerics;
using System.Runtime.CompilerServices;
using hlsfAllocator = global::StgSharp.HighPerformance.Memory.HybridLayerSegregatedFitAllocator;
using hlsfHandle = global::StgSharp.HighPerformance.Memory.HybridLayerSegregatedFitAllocationHandle;

namespace StgSharp.Mathematics
{
    public abstract unsafe partial class Matrix<T> where T: unmanaged, INumber<T>
    {

        private protected readonly int t_count = 16 / sizeof(T);

        private protected readonly int t_size = sizeof(T);

        private protected Matrix() { }

        public abstract ref T this[int column, int row]
        {
            get;
        }

        public abstract unsafe Matrix<T> this[ReadOnlySpan<MatrixIndex> column, ReadOnlySpan<MatrixIndex> row]
        {
            get;
            set;
        }

        public int ColumnCount { get; init; }

        public int RowCount { get; init; }

        protected int KernelColumnCount { get; init; }

        protected int KernelRowCount { get; init; }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static Matrix<T> FromHlsf(int column, int row, hlsfAllocator allocator)
        {
            return new HlsfMatrix<T>(column, row, allocator);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public abstract MatrixSegmentEnumeration GetColumnEnumeration();

        public abstract ref MatrixKernel GetMatrixKernel(int column, int row);

        public abstract MatrixSegmentEnumeration GetRowEnumeration();

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public abstract MatrixSegmentEnumeration GetSequentialEnumeration();

        [Obsolete("This method does not contain boarder check, so be careful on size or use indexer instead.", false)]
        public abstract ref T UnsafeIndex(int column, int row);

        private protected void AssertIndex(int column, int row)
        {
            if (column < 0 || column >= ColumnCount) {
                throw new ArgumentOutOfRangeException(nameof(column));
            }

            if (row < 0 || row >= RowCount) {
                throw new ArgumentOutOfRangeException(nameof(row));
            }
        }

        public readonly unsafe ref struct MatrixSegmentEnumeration(
                                          MatrixKernel* source,
                                          int size,
                                          int stride,
                                          int secondaryStride)
        {

            private readonly MatrixKernel* _source = source;
            private readonly int _secondaryStride = secondaryStride;
            private readonly int _size = size;
            private readonly int _stride = stride;

            public Enumerator GetEnumerator()
            {
                return new Enumerator(_source, _size, _stride, _size, _secondaryStride);
            }

            public ref struct Enumerator(MatrixKernel* source, int end, int stride, int size, int secondaryStride)
            {

                private MatrixKernel* _current = source - stride;
                private readonly MatrixKernel* _end = source + end;
                private readonly MatrixKernel* _source = source;
                private readonly int _secondaryStride = secondaryStride;
                private readonly int _size = size;
                private readonly int _stride = stride;

                public readonly MatrixSegment Current
                {
[MethodImpl(MethodImplOptions.AggressiveInlining)]
                    get => new(_current, _size, _secondaryStride);
                }

                public readonly void Dispose() { }

                public bool MoveNext()
                {
                    _current += _stride;
                    return _current < _end;
                }

                public void Reset()
                {
                    _current = _source - _stride;
                }

            }

        }

        public readonly unsafe ref struct MatrixSegment(MatrixKernel* source, int size, int stride)
        {

            private readonly MatrixKernel* _source = source;
            private readonly int _size = size;
            private readonly int _stride = stride;

            public ref MatrixKernel this[int index]
            {
                get
                {
                    if (index < 0 || index >= _size) {
                        throw new ArgumentOutOfRangeException(nameof(index));
                    }
                    return ref _source[index * _stride];
                }
            }

            public Enumerator GetEnumerator()
            {
                return new Enumerator(_source, _size, _stride);
            }

            public ref struct Enumerator(MatrixKernel* source, int end, int stride)
            {

                private readonly MatrixKernel* _end = source + end;
                private readonly MatrixKernel* _source = source;
                private readonly int _stride = stride;

                public MatrixKernel* Current
                {
[MethodImpl(MethodImplOptions.AggressiveInlining)]
                    get;
[MethodImpl(MethodImplOptions.AggressiveInlining)]
                    private set;
                } = source - stride;

                public void Dispose() { }

                public bool MoveNext()
                {
                    Current += _stride;
                    return Current < _end;
                }

                public void Reset()
                {
                    Current = _source - _stride;
                }

            }

        }

    }
}