// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Buffers;
using System.Diagnostics;
using System.Net;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Hosting.Server;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Server.Kestrel.Core;
using Microsoft.AspNetCore.Testing;
using Microsoft.Extensions.DependencyInjection;
using Xunit;

namespace Microsoft.AspNetCore.Server.Kestrel.InMemory.FunctionalTests.TestTransport
{
    /// <summary>
    /// In-memory TestServer
    /// </summary
    public class TestServer : IDisposable, IStartup
    {
        private readonly MemoryPool<byte> _memoryPool;
        private readonly RequestDelegate _app;
        private readonly InMemoryTransportFactory _transportFactory;
        private readonly IWebHost _host;

        public TestServer(RequestDelegate app)
            : this(app, new TestServiceContext())
        {
        }

        public TestServer(RequestDelegate app, TestServiceContext context)
            : this(app, context, new ListenOptions(new IPEndPoint(IPAddress.Loopback, 0)))
        {
            // The endpoint is ignored, but this ensures no cert loading happens for HTTPS endpoints.
        }

        public TestServer(RequestDelegate app, TestServiceContext context, ListenOptions listenOptions)
            : this(app, context, options => options.ListenOptions.Add(listenOptions), _ => { })
        {
        }

        public TestServer(RequestDelegate app, TestServiceContext context, Action<ListenOptions> configureListenOptions)
            : this(app, context, options =>
                {
                    var listenOptions = new ListenOptions(new IPEndPoint(IPAddress.Loopback, 0))
                    {
                        KestrelServerOptions = options
                    };

                    configureListenOptions(listenOptions);
                    options.ListenOptions.Add(listenOptions);
                },
                _ => { })
        {
        }

        public TestServer(RequestDelegate app, TestServiceContext context, Action<KestrelServerOptions> configureKestrel, Action<IServiceCollection> configureServices)
        {
            _app = app;
            Context = context;
            _memoryPool = context.MemoryPoolFactory();
            _transportFactory = new InMemoryTransportFactory();
            HttpClientSlim = new InMemoryHttpClientSlim(this);

            var hostBuilder = new WebHostBuilder()
                .ConfigureServices(services =>
                {
                    configureServices(services);

                    services.AddSingleton<IStartup>(this);
                    services.AddSingleton(context.LoggerFactory);

                    services.AddSingleton<IServer>(sp =>
                    {
                        context.ServerOptions.ApplicationServices = sp;
                        configureKestrel(context.ServerOptions);

                        // Prevent ListenOptions reuse. This is easily done accidentally when trying to debug a test by running it
                        // in a loop, but will cause problems because only the app func from the first loop will ever be invoked.
                        Assert.All(context.ServerOptions.ListenOptions, lo =>
                            Assert.Equal(context.ExpectedConnectionMiddlewareCount, lo._middleware.Count));

                        return new KestrelServer(_transportFactory, context);
                    });
                });

            _host = hostBuilder.Build();

            _host.Start();
        }

        public int Port => 0;

        public TestServiceContext Context { get; }

        public InMemoryHttpClientSlim HttpClientSlim { get; }

        public InMemoryConnection CreateConnection()
        {
            var transportConnection = new InMemoryTransportConnection(_memoryPool, Context.Log);
            _ = HandleConnection(transportConnection);
            return new InMemoryConnection(transportConnection);
        }

        public Task StopAsync()
        {
            return _host.StopAsync();
        }

        public void Dispose()
        {
            _host.Dispose();
            _memoryPool.Dispose();
        }

        void IStartup.Configure(IApplicationBuilder app)
        {
            app.Run(_app);
        }

        IServiceProvider IStartup.ConfigureServices(IServiceCollection services)
        {
            return services.BuildServiceProvider();
        }

        private async Task HandleConnection(InMemoryTransportConnection transportConnection)
        {
            try
            {
                var middlewareTask =  _transportFactory.ConnectionDispatcher.OnConnection(transportConnection);
                var transportTask = CancellationTokenAsTask(transportConnection.ConnectionClosed);

                await transportTask;
                await middlewareTask;

                transportConnection.Dispose();
            }
            catch (Exception ex)
            {
               Debug.Assert(false, $"Unexpected exception: {ex}.");
            }
        }

        private static Task CancellationTokenAsTask(CancellationToken token)
        {
            if (token.IsCancellationRequested)
            {
                return Task.CompletedTask;
            }

            var tcs = new TaskCompletionSource<object>();
            token.Register(() => tcs.SetResult(null));
            return tcs.Task;
        }
    }
}