using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;

namespace Microsoft.AspNetCore.SignalR.Client.Tests
{
    delegate Task<HttpResponseMessage> RequestDelegate(HttpRequestMessage requestMessage, CancellationToken cancellationToken);

    public class TestHttpMessageHandler : HttpMessageHandler
    {
        private List<HttpRequestMessage> _receivedRequests = new List<HttpRequestMessage>();
        private RequestDelegate _app;

        private List<Func<RequestDelegate, RequestDelegate>> _middleware = new List<Func<RequestDelegate, RequestDelegate>>();

        public bool Disposed { get; private set; }

        public IReadOnlyList<HttpRequestMessage> ReceivedRequests
        {
            get
            {
                lock (_receivedRequests)
                {
                    return _receivedRequests.ToArray();
                }
            }
        }

        public TestHttpMessageHandler(bool autoNegotiate = true, bool handleFirstPoll = true)
        {
            if (autoNegotiate)
            {
                OnNegotiate((_, cancellationToken) => ResponseUtils.CreateResponse(HttpStatusCode.OK, ResponseUtils.CreateNegotiationContent()));
            }

            if (handleFirstPoll)
            {
                var firstPoll = true;
                OnRequest(async (request, next, cancellationToken) =>
                {
                    if (ResponseUtils.IsLongPollRequest(request) && firstPoll)
                    {
                        firstPoll = false;
                        return ResponseUtils.CreateResponse(HttpStatusCode.OK);
                    }
                    else
                    {
                        return await next();
                    }
                });
            }
        }

        protected override void Dispose(bool disposing)
        {
            Disposed = true;
            base.Dispose(disposing);
        }

        protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            await Task.Yield();

            lock (_receivedRequests)
            {
                _receivedRequests.Add(request);

                if (_app == null)
                {
                    _middleware.Reverse();
                    RequestDelegate handler = BaseHandler;
                    foreach (var middleware in _middleware)
                    {
                        handler = middleware(handler);
                    }

                    _app = handler;
                }
            }

            return await _app(request, cancellationToken);
        }

        public static TestHttpMessageHandler CreateDefault()
        {
            var testHttpMessageHandler = new TestHttpMessageHandler();

            var deleteCts = new CancellationTokenSource();

            testHttpMessageHandler.OnSocketSend((_, __) => ResponseUtils.CreateResponse(HttpStatusCode.Accepted));
            testHttpMessageHandler.OnLongPoll(async cancellationToken =>
            {
                var cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, deleteCts.Token);

                // Just block until canceled
                var tcs = new TaskCompletionSource<object>();
                using (cts.Token.Register(() => tcs.TrySetResult(null)))
                {
                    await tcs.Task;
                }
                return ResponseUtils.CreateResponse(HttpStatusCode.NoContent);
            });
            testHttpMessageHandler.OnRequest((request, next, cancellationToken) =>
            {
                if (request.Method.Equals(HttpMethod.Delete) && request.RequestUri.PathAndQuery.StartsWith("/?id="))
                {
                    deleteCts.Cancel();
                    return Task.FromResult(ResponseUtils.CreateResponse(HttpStatusCode.Accepted));
                }

                return next();
            });

            return testHttpMessageHandler;
        }

        public void OnRequest(Func<HttpRequestMessage, Func<Task<HttpResponseMessage>>, CancellationToken, Task<HttpResponseMessage>> handler)
        {
            void OnRequestCore(Func<RequestDelegate, RequestDelegate> middleware)
            {
                _middleware.Add(middleware);
            }

            OnRequestCore(next =>
            {
                return (request, cancellationToken) =>
                {
                    return handler(request, () => next(request, cancellationToken), cancellationToken);
                };
            });
        }

        public void OnGet(string pathAndQuery, Func<HttpRequestMessage, CancellationToken, Task<HttpResponseMessage>> handler) => OnRequest(HttpMethod.Get, pathAndQuery, handler);
        public void OnPost(string pathAndQuery, Func<HttpRequestMessage, CancellationToken, Task<HttpResponseMessage>> handler) => OnRequest(HttpMethod.Post, pathAndQuery, handler);
        public void OnPut(string pathAndQuery, Func<HttpRequestMessage, CancellationToken, Task<HttpResponseMessage>> handler) => OnRequest(HttpMethod.Put, pathAndQuery, handler);
        public void OnDelete(string pathAndQuery, Func<HttpRequestMessage, CancellationToken, Task<HttpResponseMessage>> handler) => OnRequest(HttpMethod.Delete, pathAndQuery, handler);
        public void OnHead(string pathAndQuery, Func<HttpRequestMessage, CancellationToken, Task<HttpResponseMessage>> handler) => OnRequest(HttpMethod.Head, pathAndQuery, handler);
        public void OnOptions(string pathAndQuery, Func<HttpRequestMessage, CancellationToken, Task<HttpResponseMessage>> handler) => OnRequest(HttpMethod.Options, pathAndQuery, handler);
        public void OnTrace(string pathAndQuery, Func<HttpRequestMessage, CancellationToken, Task<HttpResponseMessage>> handler) => OnRequest(HttpMethod.Trace, pathAndQuery, handler);

        public void OnRequest(HttpMethod method, string pathAndQuery, Func<HttpRequestMessage, CancellationToken, Task<HttpResponseMessage>> handler)
        {
            OnRequest((request, next, cancellationToken) =>
            {
                if (request.Method.Equals(method) && string.Equals(request.RequestUri.PathAndQuery, pathAndQuery))
                {
                    return handler(request, cancellationToken);
                }
                else
                {
                    return next();
                }
            });
        }

        public void OnNegotiate(Func<HttpRequestMessage, CancellationToken, HttpResponseMessage> handler) => OnNegotiate((req, cancellationToken) => Task.FromResult(handler(req, cancellationToken)));

        public void OnNegotiate(Func<HttpRequestMessage, CancellationToken, Task<HttpResponseMessage>> handler)
        {
            OnRequest((request, next, cancellationToken) =>
            {
                if (ResponseUtils.IsNegotiateRequest(request))
                {
                    return handler(request, cancellationToken);
                }
                else
                {
                    return next();
                }
            });
        }

        public void OnLongPollDelete(Func<CancellationToken, HttpResponseMessage> handler) => OnLongPollDelete((cancellationToken) => Task.FromResult(handler(cancellationToken)));

        public void OnLongPollDelete(Func<CancellationToken, Task<HttpResponseMessage>> handler)
        {
            OnRequest((request, next, cancellationToken) =>
            {
                if (ResponseUtils.IsLongPollDeleteRequest(request))
                {
                    return handler(cancellationToken);
                }
                else
                {
                    return next();
                }
            });
        }

        public void OnLongPoll(Func<CancellationToken, HttpResponseMessage> handler) => OnLongPoll(cancellationToken => Task.FromResult(handler(cancellationToken)));

        public void OnLongPoll(Func<CancellationToken, Task<HttpResponseMessage>> handler)
        {
            OnLongPoll((request, token) => handler(token));
        }

        public void OnLongPoll(Func<HttpRequestMessage, CancellationToken, HttpResponseMessage> handler)
        {
            OnLongPoll((request, token) => Task.FromResult(handler(request, token)));
        }

        public void OnLongPoll(Func<HttpRequestMessage, CancellationToken, Task<HttpResponseMessage>> handler)
        {
            OnRequest((request, next, cancellationToken) =>
            {
                if (ResponseUtils.IsLongPollRequest(request))
                {
                    return handler(request, cancellationToken);
                }
                else
                {
                    return next();
                }
            });
        }

        public void OnSocketSend(Func<byte[], CancellationToken, HttpResponseMessage> handler) => OnSocketSend((data, cancellationToken) => Task.FromResult(handler(data, cancellationToken)));

        public void OnSocketSend(Func<byte[], CancellationToken, Task<HttpResponseMessage>> handler)
        {
            OnRequest(async (request, next, cancellationToken) =>
            {
                if (ResponseUtils.IsSocketSendRequest(request))
                {
                    var data = await request.Content.ReadAsByteArrayAsync();
                    return await handler(data, cancellationToken);
                }
                else
                {
                    return await next();
                }
            });
        }

        private Task<HttpResponseMessage> BaseHandler(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            return Task.FromException<HttpResponseMessage>(new InvalidOperationException($"Http endpoint not implemented: {request.Method} {request.RequestUri}"));
        }
    }
}