using Google.Protobuf;
using System;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Net.Http.Formatting;
using System.Net.Http.Headers;
using System.Threading.Tasks;
using Tango.PMR.Stubs;

namespace Tango.MachineService
{
    /// <summary>
    /// Represents a protobuf web request/response formatter capable of formatting messages using protobuf.
    /// </summary>
    /// <seealso cref="System.Net.Http.Formatting.MediaTypeFormatter" />
    public class ProtoBufFormatter : MediaTypeFormatter
    {
        private static readonly MediaTypeHeaderValue mediaType = new MediaTypeHeaderValue("application/x-protobuf");

        /// <summary>
        /// Initializes a new instance of the <see cref="ProtoBufFormatter"/> class.
        /// </summary>
        public ProtoBufFormatter()
        {
            SupportedMediaTypes.Add(mediaType);
        }

        /// <summary>
        /// Gets the default type of the media.
        /// </summary>
        /// <value>
        /// The default type of the media.
        /// </value>
        public static MediaTypeHeaderValue DefaultMediaType
        {
            get { return mediaType; }
        }

        /// <summary>
        /// Queries whether this <see cref="T:System.Net.Http.Formatting.MediaTypeFormatter" /> can deserializean object of the specified type.
        /// </summary>
        /// <param name="type">The type to deserialize.</param>
        /// <returns>
        /// true if the <see cref="T:System.Net.Http.Formatting.MediaTypeFormatter" /> can deserialize the type; otherwise, false.
        /// </returns>
        public override bool CanReadType(Type type)
        {
            return true;
        }

        /// <summary>
        /// Queries whether this <see cref="T:System.Net.Http.Formatting.MediaTypeFormatter" /> can serializean object of the specified type.
        /// </summary>
        /// <param name="type">The type to serialize.</param>
        /// <returns>
        /// true if the <see cref="T:System.Net.Http.Formatting.MediaTypeFormatter" /> can serialize the type; otherwise, false.
        /// </returns>
        public override bool CanWriteType(Type type)
        {
            return true;
        }

        /// <summary>
        /// Reads from stream asynchronous.
        /// </summary>
        /// <param name="type">The type.</param>
        /// <param name="stream">The stream.</param>
        /// <param name="content">The content.</param>
        /// <param name="formatterLogger">The formatter logger.</param>
        /// <returns></returns>
        public override Task<object> ReadFromStreamAsync(Type type, Stream stream, HttpContent content, IFormatterLogger formatterLogger)
        {
            var tcs = new TaskCompletionSource<object>();

            try
            {
                MessageParser parser = type.GetProperty("Parser").GetValue(null, null) as MessageParser;
                IMessage req = parser.ParseFrom(stream);
                tcs.SetResult(req);
            }
            catch (Exception ex)
            {
                tcs.SetException(ex);
            }

            return tcs.Task;
        }

        /// <summary>
        /// Writes to stream asynchronous.
        /// </summary>
        /// <param name="type">The type.</param>
        /// <param name="value">The value.</param>
        /// <param name="stream">The stream.</param>
        /// <param name="content">The content.</param>
        /// <param name="transportContext">The transport context.</param>
        /// <returns></returns>
        public override Task WriteToStreamAsync(Type type, object value, Stream stream, HttpContent content, TransportContext transportContext)
        {
            if (value is IMessage)
            {
                var tcs = new TaskCompletionSource<object>();

                try
                {
                    (value as IMessage).WriteTo(stream);
                    tcs.SetResult(null);
                }
                catch (Exception ex)
                {
                    tcs.SetException(ex);
                }

                return tcs.Task;
            }

            return base.WriteToStreamAsync(type, value, stream, content, transportContext);
        }
    }
}