// 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.
 
 
using System.IO;
using System.Net.Http.Headers;
using System.ServiceModel.Diagnostics;
using System.Runtime;
using System.Threading;
using System.Threading.Tasks;
 
namespace System.ServiceModel.Channels
{
    public abstract class MessageEncoder
    {
        private const int DefaultConnectionBufferSize = 8192;
 
        public abstract string ContentType { get; }
 
        public abstract string MediaType { get; }
 
        public abstract MessageVersion MessageVersion { get; }
 
        public virtual T GetProperty<T>() where T : class
        {
            if (typeof(T) == typeof(FaultConverter))
            {
                return (T)(object)FaultConverter.GetDefaultFaultConverter(MessageVersion);
            }
 
            return null;
        }
 
        public Message ReadMessage(Stream stream, int maxSizeOfHeaders)
        {
            return ReadMessage(stream, maxSizeOfHeaders, null);
        }
 
        public virtual ValueTask<Message> ReadMessageAsync(Stream stream, int maxSizeOfHeaders, string contentType)
        {
            return new ValueTask<Message>(ReadMessage(stream, maxSizeOfHeaders, contentType));
        }
 
        public virtual ValueTask<Message> ReadMessageAsync(ArraySegment<byte> buffer, BufferManager bufferManager, string contentType)
        {
            return new ValueTask<Message>(ReadMessage(buffer, bufferManager, contentType));
        }
 
        public abstract Message ReadMessage(Stream stream, int maxSizeOfHeaders, string contentType);
 
        public Message ReadMessage(ArraySegment<byte> buffer, BufferManager bufferManager)
        {
            Message message = ReadMessage(buffer, bufferManager, null);
            return message;
        }
 
        public abstract Message ReadMessage(ArraySegment<byte> buffer, BufferManager bufferManager, string contentType);
 
        // used for buffered streaming
        internal async Task<ArraySegment<byte>> BufferMessageStreamAsync(Stream stream, BufferManager bufferManager, int maxBufferSize, CancellationToken cancellationToken)
        {
            byte[] buffer = bufferManager.TakeBuffer(DefaultConnectionBufferSize);
            int offset = 0;
            int currentBufferSize = Math.Min(buffer.Length, maxBufferSize);
 
            while (offset < currentBufferSize)
            {
                int count = await stream.ReadAsync(buffer, offset, currentBufferSize - offset, cancellationToken);
                if (count == 0)
                {
                    stream.Dispose();
                    break;
                }
 
                offset += count;
                if (offset == currentBufferSize)
                {
                    if (currentBufferSize >= maxBufferSize)
                    {
                        throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(MaxMessageSizeStream.CreateMaxReceivedMessageSizeExceededException(maxBufferSize));
                    }
 
                    currentBufferSize = Math.Min(currentBufferSize * 2, maxBufferSize);
                    byte[] temp = bufferManager.TakeBuffer(currentBufferSize);
                    Buffer.BlockCopy(buffer, 0, temp, 0, offset);
                    bufferManager.ReturnBuffer(buffer);
                    buffer = temp;
                }
            }
 
            return new ArraySegment<byte>(buffer, 0, offset);
        }
 
        // used for buffered streaming
        internal virtual async Task<Message> ReadMessageAsync(Stream stream, BufferManager bufferManager, int maxBufferSize, string contentType, CancellationToken cancellationToken)
        {
            return ReadMessage(await BufferMessageStreamAsync(stream, bufferManager, maxBufferSize, cancellationToken), bufferManager, contentType);
        }
 
        public override string ToString()
        {
            return ContentType;
        }
 
        public abstract void WriteMessage(Message message, Stream stream);
 
        public virtual IAsyncResult BeginWriteMessage(Message message, Stream stream, AsyncCallback callback, object state)
        {
            return WriteMessageAsync(message, stream).AsTask().ToApm(callback, state);
        }
 
        public virtual void EndWriteMessage(IAsyncResult result)
        {
            result.ToApmEnd();
        }
 
        public ArraySegment<byte> WriteMessage(Message message, int maxMessageSize, BufferManager bufferManager)
        {
            return WriteMessage(message, maxMessageSize, bufferManager, 0);
        }
 
        public abstract ArraySegment<byte> WriteMessage(Message message, int maxMessageSize,
            BufferManager bufferManager, int messageOffset);
 
        public virtual ValueTask WriteMessageAsync(Message message, Stream stream)
        {
            WriteMessage(message, stream);
            return default;
        }
 
        public virtual ValueTask<ArraySegment<byte>> WriteMessageAsync(Message message, int maxMessageSize,
            BufferManager bufferManager, int messageOffset)
        {
            return new ValueTask<ArraySegment<byte>>(WriteMessage(message, maxMessageSize, bufferManager, messageOffset));
        }
 
        public virtual bool IsContentTypeSupported(string contentType)
        {
            if (contentType == null)
            {
                throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentNullException(nameof(contentType)));
            }
 
            return IsContentTypeSupported(contentType, ContentType, MediaType);
        }
 
        internal bool IsContentTypeSupported(string contentType, string supportedContentType, string supportedMediaType)
        {
            if (supportedContentType == contentType)
            {
                return true;
            }
 
            if (contentType.Length > supportedContentType.Length &&
                contentType.StartsWith(supportedContentType, StringComparison.Ordinal) &&
                contentType[supportedContentType.Length] == ';')
            {
                return true;
            }
 
            // now check case-insensitively
            if (contentType.StartsWith(supportedContentType, StringComparison.OrdinalIgnoreCase))
            {
                if (contentType.Length == supportedContentType.Length)
                {
                    return true;
                }
                else if (contentType.Length > supportedContentType.Length)
                {
                    char ch = contentType[supportedContentType.Length];
 
                    // Linear Whitespace is allowed to appear between the end of one property and the semicolon.
                    // LWS = [CRLF]? (SP | HT)+
                    if (ch == ';')
                    {
                        return true;
                    }
 
                    // Consume the [CRLF]?
                    int i = supportedContentType.Length;
                    if (ch == '\r' && contentType.Length > supportedContentType.Length + 1 && contentType[i + 1] == '\n')
                    {
                        i += 2;
                        ch = contentType[i];
                    }
 
                    // Look for a ';' or nothing after (SP | HT)+
                    if (ch == ' ' || ch == '\t')
                    {
                        i++;
                        while (i < contentType.Length)
                        {
                            ch = contentType[i];
                            if (ch != ' ' && ch != '\t')
                            {
                                break;
                            }
 
                            ++i;
                        }
                    }
                    if (ch == ';' || i == contentType.Length)
                    {
                        return true;
                    }
                }
            }
 
            // sometimes we get a contentType that has parameters, but our encoders
            // merely expose the base content-type, so we will check a stripped version
            try
            {
                MediaTypeHeaderValue parsedContentType = MediaTypeHeaderValue.Parse(contentType);
 
                if (supportedMediaType.Length > 0 && !supportedMediaType.Equals(parsedContentType.MediaType, StringComparison.OrdinalIgnoreCase))
                {
                    return false;
                }
 
                if (!IsCharSetSupported(parsedContentType.CharSet))
                {
                    return false;
                }
            }
            catch (FormatException)
            {
                // bad content type, so we definitely don't support it!
                return false;
            }
 
            return true;
        }
 
        internal virtual bool IsCharSetSupported(string charset)
        {
            return false;
        }
 
        internal void ThrowIfMismatchedMessageVersion(Message message)
        {
            if (message.Version != MessageVersion)
            {
                throw TraceUtility.ThrowHelperError(
                    new ProtocolException(SRP.Format(SRP.EncoderMessageVersionMismatch, message.Version, MessageVersion)),
                    message);
            }
        }
    }
}