//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="MatrixParallel.Publish"
// 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.
//
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//     
// -----------------------------------------------------------------------
// -----------------------------------------------------------------------
using StgSharp.Collections;
using StgSharp.HighPerformance;

using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;

namespace StgSharp.Mathematics.Numeric
{
    public static partial class MatrixParallel
    {

        private const int MIN_TASK_PER_THREAD = 256;
        private const int REC_TASK_PER_THREAD = 1024;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]

        internal static unsafe MatrixParallelHandle ScheduleTask(MatrixParallelTaskPackage* package)
        {
            MatrixParallelTaskPackage* nonGeneric = package;
            switch (nonGeneric->ComputeMode.OperationStyle)
            {
                case MatrixOperationStyle.BUFFER_INDEX:
                    return ScheduleBufferTask(nonGeneric);
                default:
                    throw new InvalidOperationException($"Unknown mode {nonGeneric->ComputeMode.OperationStyle}.");
            }
        }

        private static unsafe MatrixParallelHandle ScheduleBufferTask(
                                                   MatrixParallelTaskPackage* package)
        {
            int primCount = package->PrimCount;
            int secCount = package->SecCount;
            long count = (long)primCount * secCount;

            // Console.WriteLine($"amount of kernels is {count}");

            long recommendCount = count / 1024;
            MatrixParallelThread[] pool = LeadParallel((int)recommendCount);
            MatrixParallelHandle handle = new MatrixParallelHandle(pool);
            if (handle.Wraps.Length == 1)
            {
                // Console.WriteLine($"Scheduling into {pool.Length} threads.");
                ref long offsetRef = ref Unsafe.As<int, long>(ref package->PrimTileOffset);
                offsetRef = 0;
                ref long lengthRef = ref Unsafe.As<int, long>(ref package->PrimCount);
                lengthRef = count;
                handle.Wraps[0].WrapTask.Enqueue((nint)package);

                // Console.WriteLine($"Scheduling {count} kernels into thread");
                return handle;
            }
            long actual = count / pool.Length;
            long extra = count % pool.Length;

            long offset = 0;
            MatrixParallelTaskPackage* current = package;

            // Console.WriteLine($"Scheduling into {pool.Length} threads.");
            foreach (MatrixParallelWrap wrap in handle.Wraps)
            {
                long wrapTaskLength = actual * wrap.WrapTaskCapacity;
                long ex = Math.Min(extra, wrap.WrapTaskCapacity);
                long length = wrapTaskLength + ex;
                extra -= ex;
                ref long offsetRef = ref Unsafe.As<int, long>(ref current->PrimTileOffset);
                offsetRef = offset;
                ref long lengthRef = ref Unsafe.As<int, long>(ref current->PrimCount);
                lengthRef = length;
                wrap.WrapTask.Enqueue((nint) current);

                // Console.WriteLine($"Offset is {offset}");
                // Console.WriteLine($"Scheduling {length} kernels into {wrap.WrapTaskCapacity} threads");
                // Console.WriteLine();
                current = MatrixParallelFactory.FromExistPackage(current);
                offset += length;
            }
            return handle;
        }

        private static unsafe MatrixParallelHandle ScheduleKernelTask(
                                                   MatrixParallelTaskPackage* package)
        {
            int primCount = package->PrimCount;
            int secCount = package->SecCount;
            int tileWidth = (1024 / secCount) + 1;
            int tileCount = (primCount + tileWidth - 1) / tileWidth;

            MatrixParallelThread[] pool = LeadParallel(tileCount);
            /*
            if (pool.Length == 0)
            {
                // no need
                // LeadParallel has contained capacity check
            }
            /**/
            MatrixParallelHandle handle = new MatrixParallelHandle(pool);
            if (handle.Wraps.Length == 1)
            {
                handle.Wraps[0].WrapTask.Enqueue((nint)package);
                return handle;
            }
            int threadCount = pool.Length;
            int tilePerThreadLess = tileCount / threadCount;                           // tiles per thread without extra slice
            int columnAfterBaseTile = tileCount % threadCount * tileWidth;             // tile sliced into columns
            int extraColumnPerThread = columnAfterBaseTile / threadCount;
            int extraColumnCount = columnAfterBaseTile % threadCount;                  // columns to be sliced

            int total = primCount;
            MatrixParallelTaskPackage* current = package;
            foreach (MatrixParallelWrap wrap in handle.Wraps)
            {
                bool hasSlice = columnAfterBaseTile > 0;
                bool isLargeSlice = extraColumnCount > 0;

                // _count tiles for wrap
                int wrapWidth = wrap!.WrapTaskCapacity/**/;
                int columnFromSlicingCount = (hasSlice ? extraColumnPerThread : 0) * wrapWidth;
                int baseColumn = wrapWidth * tilePerThreadLess * tileWidth;
                int columnInWrap = baseColumn + columnFromSlicingCount + (isLargeSlice ? 1 : 0);

                // set tasks
                if (columnInWrap == 0)
                {
#if DEBUG
                    throw new InvalidOperationException("Zero tasks published.");
#else
                    break;
#endif
                }

                // update current task
                current->PrimColumnCountInTile = columnInWrap;
                current->SecColumnCountInTile = current->SecCount;
                current->SecTileOffset = 0;

                // remove tiles _count
                extraColumnCount--;
                columnAfterBaseTile -= columnFromSlicingCount;
                total -= columnInWrap;

                // set to wrap and push
                wrap.WrapTask.Enqueue((nint)current);

                if (total <= 0)
                {
                    break;
                }
                current = MatrixParallelFactory.FromExistPackage(current);
                current->PrimTileOffset += columnInWrap;
            }

            return handle;
        }

    }
}