#region Copyright notice and license

// Copyright 2015-2016 gRPC authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#endregion

using System;
using System.Linq;
using System.Threading.Tasks;
using Google.Protobuf;
using Grpc.Core;
using InteropTestsWebsite;

namespace Grpc.Testing
{
    // Implementation copied from https://github.com/grpc/grpc/blob/master/src/csharp/Grpc.IntegrationTesting/TestServiceImpl.cs
    public class TestServiceImpl : TestService.TestServiceBase
    {
        public override Task<Empty> EmptyCall(Empty request, ServerCallContext context)
        {
            return Task.FromResult(new Empty());
        }

        public override async Task<SimpleResponse> UnaryCall(SimpleRequest request, ServerCallContext context)
        {
            await EnsureEchoMetadataAsync(context, request.ResponseCompressed?.Value ?? false);
            EnsureEchoStatus(request.ResponseStatus, context);
            EnsureCompression(request.ExpectCompressed, context);

            var response = new SimpleResponse { Payload = CreateZerosPayload(request.ResponseSize) };
            return response;
        }

        public override async Task StreamingOutputCall(StreamingOutputCallRequest request, IServerStreamWriter<StreamingOutputCallResponse> responseStream, ServerCallContext context)
        {
            await EnsureEchoMetadataAsync(context, request.ResponseParameters.Any(rp => rp.Compressed?.Value ?? false));
            EnsureEchoStatus(request.ResponseStatus, context);

            foreach (var responseParam in request.ResponseParameters)
            {
                responseStream.WriteOptions = !(responseParam.Compressed?.Value ?? false)
                    ? new WriteOptions(WriteFlags.NoCompress)
                    : null;

                var response = new StreamingOutputCallResponse { Payload = CreateZerosPayload(responseParam.Size) };
                await responseStream.WriteAsync(response);
            }
        }

        public override async Task<StreamingInputCallResponse> StreamingInputCall(IAsyncStreamReader<StreamingInputCallRequest> requestStream, ServerCallContext context)
        {
            await EnsureEchoMetadataAsync(context);

            int sum = 0;
            await requestStream.ForEachAsync(request =>
            {
                EnsureCompression(request.ExpectCompressed, context);

                sum += request.Payload.Body.Length;
                return Task.CompletedTask;
            });
            return new StreamingInputCallResponse { AggregatedPayloadSize = sum };
        }

        public override async Task FullDuplexCall(IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream, ServerCallContext context)
        {
            await EnsureEchoMetadataAsync(context);

            await requestStream.ForEachAsync(async request =>
            {
                EnsureEchoStatus(request.ResponseStatus, context);
                foreach (var responseParam in request.ResponseParameters)
                {
                    var response = new StreamingOutputCallResponse { Payload = CreateZerosPayload(responseParam.Size) };
                    await responseStream.WriteAsync(response);
                }
            });
        }

        public override Task HalfDuplexCall(IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream, ServerCallContext context)
        {
            throw new NotImplementedException();
        }

        private static Payload CreateZerosPayload(int size)
        {
            return new Payload { Body = ByteString.CopyFrom(new byte[size]) };
        }

        private static async Task EnsureEchoMetadataAsync(ServerCallContext context, bool enableCompression = false)
        {
            var echoInitialList = context.RequestHeaders.Where((entry) => entry.Key == "x-grpc-test-echo-initial").ToList();

            // Append grpc internal compression header if compression is requested by the client
            if (enableCompression)
            {
                echoInitialList.Add(new Metadata.Entry("grpc-internal-encoding-request", "gzip"));
            }

            if (echoInitialList.Any()) {
                var entry = echoInitialList.Single();
                await context.WriteResponseHeadersAsync(new Metadata { entry });
            }

            var echoTrailingList = context.RequestHeaders.Where((entry) => entry.Key == "x-grpc-test-echo-trailing-bin").ToList();
            if (echoTrailingList.Any()) {
                context.ResponseTrailers.Add(echoTrailingList.Single());
            }
        }

        private static void EnsureEchoStatus(EchoStatus responseStatus, ServerCallContext context)
        {
            if (responseStatus != null)
            {
                var statusCode = (StatusCode)responseStatus.Code;
                context.Status = new Status(statusCode, responseStatus.Message);
            }
        }

        private static void EnsureCompression(BoolValue? expectCompressed, ServerCallContext context)
        {
            if (expectCompressed != null)
            {
                // ServerCallContext.RequestHeaders filters out grpc-* headers
                // Get grpc-encoding from HttpContext instead
                var encoding = context.GetHttpContext().Request.Headers.SingleOrDefault(h => h.Key == "grpc-encoding").Value.SingleOrDefault();
                if (expectCompressed.Value)
                {
                    if (encoding == null || encoding == "identity")
                    {
                        throw new RpcException(new Status(StatusCode.InvalidArgument, string.Empty));
                    }
                }
            }
        }
    }
}