#region License

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 Gremlin.Net.Driver.Exceptions;
using System;
using System.IO;
using System.Net.WebSockets;
using System.Threading;
using System.Threading.Tasks;
using Gremlin.Net.Process;

namespace Gremlin.Net.Driver
{
    internal interface IWebSocketConnection : IDisposable
    {
        Task ConnectAsync(Uri uri, CancellationToken cancellationToken);
        Task CloseAsync();
        Task SendMessageAsync(byte[] message, CancellationToken cancellationToken);
#if NET6_0_OR_GREATER
        Task SendMessageUncompressedAsync(byte[] message, CancellationToken cancellationToken);
#endif
        Task<byte[]> ReceiveMessageAsync();
        bool IsOpen { get; }
    }

    internal class WebSocketConnection : IWebSocketConnection
    {
        private const int ReceiveBufferSize = 1024;
        private const WebSocketMessageType MessageType = WebSocketMessageType.Binary;
        private readonly IClientWebSocket _client;
        private const string userAgentHeaderName = "User-Agent";

        public WebSocketConnection(IClientWebSocket client, WebSocketSettings settings)
        {
            if (settings.EnableUserAgentOnConnect)
            {
                client.Options.SetRequestHeader(userAgentHeaderName, Utils.UserAgent);
            }
            _client = client;

#if NET6_0_OR_GREATER
            if (settings.UseCompression)
            {
                _client.Options.DangerousDeflateOptions = settings.CompressionOptions;
            }
#endif
            settings.WebSocketConfigurationCallback?.Invoke(_client.Options);
        }

        public async Task ConnectAsync(Uri uri, CancellationToken cancellationToken)
        {
            await _client.ConnectAsync(uri, cancellationToken).ConfigureAwait(false);
        }

        public async Task CloseAsync()
        {
            if (CloseAlreadyInitiated) return;

            try
            {
                await
                    _client.CloseAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None)
                        .ConfigureAwait(false);
            }
            catch (Exception)
            {
                // Swallow exceptions silently as there is nothing to do when closing fails
            }
        }

        private bool CloseAlreadyInitiated => _client.State == WebSocketState.Closed ||
                                            _client.State == WebSocketState.Aborted ||
                                            _client.State == WebSocketState.CloseSent;
        
#if NET6_0_OR_GREATER
        public async Task SendMessageUncompressedAsync(byte[] message, CancellationToken cancellationToken)
        {
            await _client.SendAsync(new ArraySegment<byte>(message), MessageType,
                    WebSocketMessageFlags.EndOfMessage | WebSocketMessageFlags.DisableCompression,
                    cancellationToken)
                .ConfigureAwait(false);
        }
#endif
        
        public async Task SendMessageAsync(byte[] message, CancellationToken cancellationToken)
        {
            await
                _client.SendAsync(new ArraySegment<byte>(message), MessageType, true, cancellationToken)
                    .ConfigureAwait(false);
        }

        public async Task<byte[]> ReceiveMessageAsync()
        {
            using var ms = new MemoryStream();
            WebSocketReceiveResult received;
            var buffer = new byte[ReceiveBufferSize];

            do
            {
                var receiveBuffer = new ArraySegment<byte>(buffer);
                received = await _client.ReceiveAsync(receiveBuffer, CancellationToken.None).ConfigureAwait(false);
                if (received.MessageType == WebSocketMessageType.Close)
                {
                    throw new ConnectionClosedException(received.CloseStatus, received.CloseStatusDescription);
                }

                ms.Write(receiveBuffer.Array, receiveBuffer.Offset, received.Count);
            } while (!received.EndOfMessage);

            return ms.ToArray();
        }

        public bool IsOpen => _client.State == WebSocketState.Open;

        #region IDisposable Support

        private bool _disposed;

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool disposing)
        {
            if (!_disposed)
            {
                if (disposing)
                    _client?.Dispose();
                _disposed = true;
            }
        }

        #endregion
    }
}