// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

/*============================================================
**
** 
** 
**
** Purpose: Create a Memorystream over an UnmanagedMemoryStream
**
===========================================================*/

using System;
using System.Runtime.InteropServices;
using System.Security.Permissions;
using System.Diagnostics.CodeAnalysis;
using System.Diagnostics.Contracts;
using System.Threading;
using System.Threading.Tasks;

namespace System.IO {
    // Needed for backwards compatibility with V1.x usages of the
    // ResourceManager, where a MemoryStream is now returned as an 
    // UnmanagedMemoryStream from ResourceReader.
    internal sealed class UnmanagedMemoryStreamWrapper : MemoryStream {
        private UnmanagedMemoryStream _unmanagedStream;
        
        internal UnmanagedMemoryStreamWrapper(UnmanagedMemoryStream stream) {
            _unmanagedStream = stream;
        }
        
        public override bool CanRead {
            [Pure]
            get { return _unmanagedStream.CanRead; }
        }
        
        public override bool CanSeek {
            [Pure]
            get { return _unmanagedStream.CanSeek; }
        }
        
        public override bool CanWrite {
            [Pure]
            get { return _unmanagedStream.CanWrite; }
        }
        
        protected override void Dispose(bool disposing)
        {
            try {
                if (disposing)
                    _unmanagedStream.Close();
            }
            finally {
                base.Dispose(disposing);
            }
        }
        
        public override void Flush() {
            _unmanagedStream.Flush();
        }
    
        public override byte[] GetBuffer() {
            throw new UnauthorizedAccessException(Environment.GetResourceString("UnauthorizedAccess_MemStreamBuffer"));
        }

        public override bool TryGetBuffer(out ArraySegment<byte> buffer) {
            buffer = default(ArraySegment<byte>);
            return false;
        }

        public override int Capacity {
            get { 
                return (int) _unmanagedStream.Capacity;
            }
            [SuppressMessage("Microsoft.Contracts", "CC1055")]  // Skip extra error checking to avoid *potential* AppCompat problems.
            set {
                throw new IOException(Environment.GetResourceString("IO.IO_FixedCapacity"));
            }
        }        
        
        public override long Length {
            get {
                return _unmanagedStream.Length;
            }
        }

        public override long Position {
            get { 
                return _unmanagedStream.Position;
            }
            set {
                _unmanagedStream.Position = value;
            }
        }
        
        public override int Read([In, Out] byte[] buffer, int offset, int count) {
            return _unmanagedStream.Read(buffer, offset, count);
        }
    
        public override int ReadByte() {
            return _unmanagedStream.ReadByte();
        }
            
        public override long Seek(long offset, SeekOrigin loc) {
            return _unmanagedStream.Seek(offset, loc);
        }

        public unsafe override byte[] ToArray() {
            if (!_unmanagedStream._isOpen) __Error.StreamIsClosed();
            if (!_unmanagedStream.CanRead) __Error.ReadNotSupported();

            byte[] buffer = new byte[_unmanagedStream.Length];
            Buffer.Memcpy(buffer, 0, _unmanagedStream.Pointer, 0, (int)_unmanagedStream.Length);
            return buffer;
        }
    
        public override void Write(byte[] buffer, int offset, int count) {
            _unmanagedStream.Write(buffer, offset, count);
        }
    
        public override void WriteByte(byte value) {
            _unmanagedStream.WriteByte(value);
        }
    
        // Writes this MemoryStream to another stream.
        public unsafe override void WriteTo(Stream stream) {
            if (stream==null)
                throw new ArgumentNullException(nameof(stream), Environment.GetResourceString("ArgumentNull_Stream"));
            Contract.EndContractBlock();

            if (!_unmanagedStream._isOpen) __Error.StreamIsClosed();
            if (!CanRead) __Error.ReadNotSupported();

            byte[] buffer = ToArray();
            
            stream.Write(buffer, 0, buffer.Length);
        }

        public override void SetLength(Int64 value) {

            // This was probably meant to call _unmanagedStream.SetLength(value), but it was forgotten in V.4.0.
            // Now this results in a call to the base which touches the underlying array which is never actually used.
            // We cannot fix it due to compat now, but we should fix this at the next SxS release oportunity.
            base.SetLength(value);
        }


        public override Task CopyToAsync(Stream destination, Int32 bufferSize, CancellationToken cancellationToken) {

            // The parameter checks must be in sync with the base version:
            if (destination == null)
                throw new ArgumentNullException(nameof(destination));
            
            if (bufferSize <= 0)
                throw new ArgumentOutOfRangeException(nameof(bufferSize), Environment.GetResourceString("ArgumentOutOfRange_NeedPosNum"));

            if (!CanRead && !CanWrite)
                throw new ObjectDisposedException(null, Environment.GetResourceString("ObjectDisposed_StreamClosed"));

            if (!destination.CanRead && !destination.CanWrite)
                throw new ObjectDisposedException(nameof(destination), Environment.GetResourceString("ObjectDisposed_StreamClosed"));

            if (!CanRead)
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnreadableStream"));

            if (!destination.CanWrite)
                throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnwritableStream"));

            Contract.EndContractBlock();

            return _unmanagedStream.CopyToAsync(destination, bufferSize, cancellationToken);
        }


        public override Task FlushAsync(CancellationToken cancellationToken) {

            return _unmanagedStream.FlushAsync(cancellationToken);
        }


        public override Task<Int32> ReadAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken) {

            return _unmanagedStream.ReadAsync(buffer, offset, count, cancellationToken);
        }


        public override Task WriteAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken) {

            return _unmanagedStream.WriteAsync(buffer, offset, count, cancellationToken);
        }

    }  // class UnmanagedMemoryStreamWrapper
}  // namespace