// From: https://dev.to/mckabue/an-aspnet-core-request---response-logger-middleware-clb

using System;
using System.IO;
using System.Text;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Internal;
using Microsoft.IO;

// https://exceptionnotfound.net/using-middleware-to-log-requests-and-responses-in-asp-net-core/
// https://gist.github.com/elanderson/c50b2107de8ee2ed856353dfed9168a2
// https://stackoverflow.com/a/52328142/3563013
// https://stackoverflow.com/a/43404745/3563013
// https://gist.github.com/elanderson/c50b2107de8ee2ed856353dfed9168a2#gistcomment-2319007
public class RequestResponseLoggingMiddleware
{
    private readonly RequestDelegate _next;
    private readonly RecyclableMemoryStreamManager _recyclableMemoryStreamManager;
    private readonly Action<RequestProfilerModel> _requestResponseHandler;
    private const int ReadChunkBufferLength = 4096;

    public RequestResponseLoggingMiddleware(RequestDelegate next, Action<RequestProfilerModel> requestResponseHandler)
    {
        _next = next;
        _recyclableMemoryStreamManager = new RecyclableMemoryStreamManager();
        _requestResponseHandler = requestResponseHandler;
    }

    public async Task Invoke(HttpContext context)
    {
        var model = new RequestProfilerModel
        {
            RequestTime = new DateTimeOffset(),
            Context = context,
            Request = await FormatRequest(context)
        };

        Stream originalBody = context.Response.Body;

        using (MemoryStream newResponseBody = _recyclableMemoryStreamManager.GetStream())
        {
            context.Response.Body = newResponseBody;

            await _next(context);

            newResponseBody.Seek(0, SeekOrigin.Begin);
            await newResponseBody.CopyToAsync(originalBody);

            newResponseBody.Seek(0, SeekOrigin.Begin);
            model.Response = FormatResponse(context, newResponseBody);
            model.ResponseTime = new DateTimeOffset();
            _requestResponseHandler(model);
        }
    }

    private string FormatResponse(HttpContext context, MemoryStream newResponseBody)
    {
        HttpRequest request = context.Request;
        HttpResponse response = context.Response;

        return $"Http Response Information: {Environment.NewLine}" +
                $"Schema:{request.Scheme} {Environment.NewLine}" +
                $"Host: {request.Host} {Environment.NewLine}" +
                $"Path: {request.Path} {Environment.NewLine}" +
                $"QueryString: {request.QueryString} {Environment.NewLine}" +
                $"StatusCode: {response.StatusCode} {Environment.NewLine}" +
                $"Response Body: {ReadStreamInChunks(newResponseBody)}";
    }

    private async Task<string> FormatRequest(HttpContext context)
    {
        HttpRequest request = context.Request;

        return $"Http Request Information: {Environment.NewLine}" +
                    $"Schema:{request.Scheme} {Environment.NewLine}" +
                    $"Host: {request.Host} {Environment.NewLine}" +
                    $"Path: {request.Path} {Environment.NewLine}" +
                    $"QueryString: {request.QueryString} {Environment.NewLine}" +
                    $"Request Body: {await GetRequestBody(request)}";
    }

    public async Task<string> GetRequestBody(HttpRequest request)
    {
        request.EnableBuffering();
        request.EnableRewind();
        using (var requestStream = _recyclableMemoryStreamManager.GetStream())
        {
            await request.Body.CopyToAsync(requestStream);
            request.Body.Seek(0, SeekOrigin.Begin);
            return ReadStreamInChunks(requestStream);
        }
    }

    private static string ReadStreamInChunks(Stream stream)
    {
        stream.Seek(0, SeekOrigin.Begin);
        string result;
        using (var textWriter = new StringWriter())
        using (var reader = new StreamReader(stream))
        {
            var readChunk = new char[ReadChunkBufferLength];
            int readChunkLength;
            //do while: is useful for the last iteration in case readChunkLength < chunkLength
            do
            {
                readChunkLength = reader.ReadBlock(readChunk, 0, ReadChunkBufferLength);
                textWriter.Write(readChunk, 0, readChunkLength);
            } while (readChunkLength > 0);

            result = textWriter.ToString();
        }

        return result;
    }

    public class RequestProfilerModel
    {
        public DateTimeOffset RequestTime { get; set; }
        public HttpContext Context { get; set; }
        public string Request { get; set; }
        public string Response { get; set; }
        public DateTimeOffset ResponseTime { get; set; }
    }
}