// 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.Diagnostics;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;
using Xunit;

namespace Microsoft.AspNetCore.Testing
{
    /// <summary>
    /// Summary description for TestConnection
    /// </summary>
    public abstract class StreamBackedTestConnection : IDisposable
    {
        private static readonly TimeSpan Timeout = TimeSpan.FromMinutes(1);

        private readonly Stream _stream;
        private readonly StreamReader _reader;

        protected StreamBackedTestConnection(Stream stream)
        {
            _stream = stream;
            _reader = new StreamReader(_stream, Encoding.ASCII);
        }

        public Stream Stream => _stream;

        public StreamReader Reader => _reader;

        public abstract void ShutdownSend();

        public abstract void Reset();

        public virtual void Dispose()
        {
            _stream.Dispose();
        }

        public Task SendEmptyGet()
        {
            return Send("GET / HTTP/1.1",
                "Host:",
                "",
                "");
        }

        public Task SendEmptyGetWithUpgradeAndKeepAlive()
            => SendEmptyGetWithConnection("Upgrade, keep-alive");

        public Task SendEmptyGetWithUpgrade()
            => SendEmptyGetWithConnection("Upgrade");

        public Task SendEmptyGetAsKeepAlive()
            => SendEmptyGetWithConnection("keep-alive");

        private Task SendEmptyGetWithConnection(string connection)
        {
            return Send("GET / HTTP/1.1",
                "Host:",
                "Connection: " + connection,
                "",
                "");
        }

        public async Task SendAll(params string[] lines)
        {
            var text = string.Join("\r\n", lines);
            var writer = new StreamWriter(_stream, Encoding.GetEncoding("iso-8859-1"));
            await writer.WriteAsync(text).ConfigureAwait(false);
            await writer.FlushAsync().ConfigureAwait(false);
            await _stream.FlushAsync().ConfigureAwait(false);
        }

        public async Task Send(params string[] lines)
        {
            var text = string.Join("\r\n", lines);
            var writer = new StreamWriter(_stream, Encoding.GetEncoding("iso-8859-1"));
            for (var index = 0; index < text.Length; index++)
            {
                var ch = text[index];
                writer.Write(ch);
                await writer.FlushAsync().ConfigureAwait(false);
                // Re-add delay to help find socket input consumption bugs more consistently
                //await Task.Delay(TimeSpan.FromMilliseconds(5));
            }
            await writer.FlushAsync().ConfigureAwait(false);
            await _stream.FlushAsync().ConfigureAwait(false);
        }

        public async Task Receive(params string[] lines)
        {
            var expected = string.Join("\r\n", lines);
            var actual = new char[expected.Length];
            var offset = 0;

            try
            {
                while (offset < expected.Length)
                {
                    var data = new byte[expected.Length];
                    var task = _reader.ReadAsync(actual, offset, actual.Length - offset);
                    if (!Debugger.IsAttached)
                    {
                        task = task.TimeoutAfter(Timeout);
                    }
                    var count = await task.ConfigureAwait(false);
                    if (count == 0)
                    {
                        break;
                    }
                    offset += count;
                }
            }
            catch (TimeoutException ex) when (offset != 0)
            {
                throw new TimeoutException($"Did not receive a complete response within {Timeout}.{Environment.NewLine}{Environment.NewLine}" +
                    $"Expected:{Environment.NewLine}{expected}{Environment.NewLine}{Environment.NewLine}" +
                    $"Actual:{Environment.NewLine}{new string(actual, 0, offset)}{Environment.NewLine}",
                    ex);
            }

            Assert.Equal(expected, new string(actual, 0, offset));
        }

        public async Task ReceiveEnd(params string[] lines)
        {
            await Receive(lines).ConfigureAwait(false);
            var ch = new char[128];
            var count = await _reader.ReadAsync(ch, 0, 128).TimeoutAfter(Timeout).ConfigureAwait(false);
            var text = new string(ch, 0, count);
            Assert.Equal("", text);
        }

        public async Task WaitForConnectionClose()
        {
            var buffer = new byte[128];
            var bytesTransferred = await _stream.ReadAsync(buffer, 0, 128).TimeoutAfter(Timeout);

            if (bytesTransferred > 0)
            {
                throw new IOException(
                    $"Expected connection close, received data instead: \"{_reader.CurrentEncoding.GetString(buffer, 0, bytesTransferred)}\"");
            }
        }
    }
}