﻿/*
 * Licensed 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.
 */

namespace DotPulsar.Internal
{
    using Abstractions;
    using PulsarApi;
    using System;
    using System.Diagnostics;
    using System.Threading;
    using System.Threading.Tasks;

    public sealed class PingPongHandler : IAsyncDisposable
    {
        private readonly IConnection _connection;
        private readonly TimeSpan _keepAliveInterval;
        private readonly Timer _timer;
        private readonly CommandPing _ping;
        private readonly CommandPong _pong;
        private long _lastCommand;

        public PingPongHandler(IConnection connection, TimeSpan keepAliveInterval)
        {
            _connection = connection;
            _keepAliveInterval = keepAliveInterval;
            _timer = new Timer(Watch);
            _timer.Change(_keepAliveInterval, TimeSpan.Zero);
            _ping = new CommandPing();
            _pong = new CommandPong();
            _lastCommand = Stopwatch.GetTimestamp();
        }

        public bool Incoming(BaseCommand.Type commandType)
        {
            Interlocked.Exchange(ref _lastCommand, Stopwatch.GetTimestamp());

            if (commandType == BaseCommand.Type.Ping)
            {
                Task.Factory.StartNew(() => SendPong());
                return true;
            }

            return commandType == BaseCommand.Type.Pong;
        }

        private void Watch(object? state)
        {
            try
            {
                var lastCommand = Interlocked.Read(ref _lastCommand);
                var now = Stopwatch.GetTimestamp();
                var elapsed = TimeSpan.FromSeconds((now - lastCommand) / Stopwatch.Frequency);
                if (elapsed >= _keepAliveInterval)
                {
                    Task.Factory.StartNew(() => SendPing());
                    _timer.Change(_keepAliveInterval, TimeSpan.Zero);
                }
                else
                    _timer.Change(_keepAliveInterval.Subtract(elapsed), TimeSpan.Zero);
            }
            catch
            {
                // Ignore
            }
        }

        private async Task SendPing()
        {
            try
            {
                await _connection.Send(_ping, default).ConfigureAwait(false);
            }
            catch { }
        }

        private async Task SendPong()
        {
            try
            {
                await _connection.Send(_pong, default).ConfigureAwait(false);
            }
            catch { }
        }

#if NETSTANDARD2_0
        public ValueTask DisposeAsync()
        {
            _timer.Dispose();
            return new ValueTask();
        }
#else
        public async ValueTask DisposeAsync()
        {
            await _timer.DisposeAsync().ConfigureAwait(false);
        }
#endif
    }
}