using System;
using System.Buffers;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace CodeWalker.Core.Utils
{
    public static class StreamingExtensions
    {
        public static Task<int> ReadAsync(this BinaryReader br, byte[] buffer, int index, int count)
        {
            return br.BaseStream.ReadAsync(buffer, index, count);
        }


        public static void CopyToFast(this Stream stream, Stream destination)
        {
            var buffer = ArrayPool<byte>.Shared.Rent(81920);
            try
            {
                int read;
                while ((read = stream.Read(buffer, 0, buffer.Length)) != 0)
                    destination.Write(buffer, 0, read);
            }
            finally
            {
                ArrayPool<byte>.Shared.Return(buffer);
            }
        }

        public static async Task CopyToFastAsync(this Stream stream, Stream destination, int bufferSize = 131072, CancellationToken cancellationToken = default)
        {
            var buffer = ArrayPool<byte>.Shared.Rent(bufferSize);
            try
            {
                int bytesRead;
                while ((bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length, cancellationToken).ConfigureAwait(false)) != 0)
                {
                    await destination.WriteAsync(buffer, 0, bytesRead, cancellationToken).ConfigureAwait(false);
                }
            }
            catch(Exception ex)
            {
                Console.WriteLine(ex.ToString());
                throw;
            }
            finally
            {
                ArrayPool<byte>.Shared.Return(buffer);
            }

        }

        private static async Task FinishWriteAsync(Task writeTask, byte[] localBuffer)
        {
            try
            {
                await writeTask.ConfigureAwait(false);
            }
            finally
            {
                ArrayPool<byte>.Shared.Return(localBuffer);
            }
        }

        public static ValueTask WriteAsync(this Stream stream, Memory<byte> buffer, CancellationToken cancellationToken = default)
        {
            if (MemoryMarshal.TryGetArray(buffer, out ArraySegment<byte> array))
            {
                return new ValueTask(stream.WriteAsync(array.Array!, array.Offset, array.Count, cancellationToken));
            }

            byte[] sharedBuffer = ArrayPool<byte>.Shared.Rent(buffer.Length);
            buffer.Span.CopyTo(sharedBuffer);
            return new ValueTask(FinishWriteAsync(stream.WriteAsync(sharedBuffer, 0, buffer.Length, cancellationToken), sharedBuffer));
        }

        public static void Write(this Stream stream, ReadOnlySpan<byte> buffer)
        {
            byte[] sharedBuffer = ArrayPool<byte>.Shared.Rent(buffer.Length);
            try
            {
                buffer.CopyTo(sharedBuffer);
                stream.Write(sharedBuffer, 0, buffer.Length);
            }
            finally
            {
                ArrayPool<byte>.Shared.Return(sharedBuffer);
            }
        }

        public static int Read(this Stream stream, Span<byte> buffer)
        {
            byte[] sharedBuffer = ArrayPool<byte>.Shared.Rent(buffer.Length);
            try
            {
                int numRead = stream.Read(sharedBuffer, 0, buffer.Length);
                if ((uint)numRead > (uint)buffer.Length)
                {
                    throw new IOException("Stream too long!");
                }

                new ReadOnlySpan<byte>(sharedBuffer, 0, numRead).CopyTo(buffer);
                return numRead;
            }
            finally
            {
                ArrayPool<byte>.Shared.Return(sharedBuffer);
            }
        }

        public static int Read(this Stream stream, Memory<byte> buffer)
        {
            if (MemoryMarshal.TryGetArray(buffer, out ArraySegment<byte> array))
            {
                return stream.Read(array.Array!, array.Offset, array.Count);
            }

            byte[] sharedBuffer = ArrayPool<byte>.Shared.Rent(buffer.Length);
            try
            {
                int numRead = stream.Read(sharedBuffer, 0, buffer.Length);
                if ((uint)numRead > (uint)buffer.Length)
                {
                    throw new IOException("Stream too long!");
                }

                new ReadOnlySpan<byte>(sharedBuffer, 0, numRead).CopyTo(buffer.Span);
                return numRead;
            }
            finally
            {
                ArrayPool<byte>.Shared.Return(sharedBuffer);
            }
        }

        public static ValueTask<int> ReadAsync(this Stream stream, Memory<byte> buffer, CancellationToken cancellationToken = default)
        {
            if (MemoryMarshal.TryGetArray(buffer, out ArraySegment<byte> array))
            {
                return new ValueTask<int>(stream.ReadAsync(array.Array!, array.Offset, array.Count, cancellationToken));
            }

            byte[] sharedBuffer = ArrayPool<byte>.Shared.Rent(buffer.Length);
            return FinishReadAsync(stream.ReadAsync(sharedBuffer, 0, buffer.Length, cancellationToken), sharedBuffer, buffer);

            static async ValueTask<int> FinishReadAsync(Task<int> readTask, byte[] localBuffer, Memory<byte> localDestination)
            {
                try
                {
                    int result = await readTask.ConfigureAwait(false);
                    new ReadOnlySpan<byte>(localBuffer, 0, result).CopyTo(localDestination.Span);
                    return result;
                }
                finally
                {
                    ArrayPool<byte>.Shared.Return(localBuffer);
                }
            }
        }
    }
}