using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Threading.Tasks;
using Emby.Server.Implementations.Udp;
using MediaBrowser.Common.Configuration;
using MediaBrowser.Common.Net;
using MediaBrowser.Controller;
using MediaBrowser.Controller.Plugins;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;
using IConfigurationManager = MediaBrowser.Common.Configuration.IConfigurationManager;

namespace Emby.Server.Implementations.EntryPoints
{
    /// <summary>
    /// Class responsible for registering all UDP broadcast endpoints and their handlers.
    /// </summary>
    public sealed class UdpServerEntryPoint : IServerEntryPoint
    {
        /// <summary>
        /// The port of the UDP server.
        /// </summary>
        public const int PortNumber = 7359;

        /// <summary>
        /// The logger.
        /// </summary>
        private readonly ILogger<UdpServerEntryPoint> _logger;
        private readonly IServerApplicationHost _appHost;
        private readonly IConfiguration _config;
        private readonly IConfigurationManager _configurationManager;
        private readonly INetworkManager _networkManager;

        /// <summary>
        /// The UDP server.
        /// </summary>
        private readonly List<UdpServer> _udpServers;
        private readonly CancellationTokenSource _cancellationTokenSource = new CancellationTokenSource();
        private bool _disposed;

        /// <summary>
        /// Initializes a new instance of the <see cref="UdpServerEntryPoint" /> class.
        /// </summary>
        /// <param name="logger">Instance of the <see cref="ILogger{UdpServerEntryPoint}"/> interface.</param>
        /// <param name="appHost">Instance of the <see cref="IServerApplicationHost"/> interface.</param>
        /// <param name="configuration">Instance of the <see cref="IConfiguration"/> interface.</param>
        /// <param name="configurationManager">Instance of the <see cref="IConfigurationManager"/> interface.</param>
        /// <param name="networkManager">Instance of the <see cref="INetworkManager"/> interface.</param>
        public UdpServerEntryPoint(
            ILogger<UdpServerEntryPoint> logger,
            IServerApplicationHost appHost,
            IConfiguration configuration,
            IConfigurationManager configurationManager,
            INetworkManager networkManager)
        {
            _logger = logger;
            _appHost = appHost;
            _config = configuration;
            _configurationManager = configurationManager;
            _networkManager = networkManager;
            _udpServers = new List<UdpServer>();
        }

        /// <inheritdoc />
        public Task RunAsync()
        {
            CheckDisposed();

            if (!_configurationManager.GetNetworkConfiguration().AutoDiscovery)
            {
                return Task.CompletedTask;
            }

            try
            {
                // Linux needs to bind to the broadcast addresses to get broadcast traffic
                // Windows receives broadcast fine when binding to just the interface, it is unable to bind to broadcast addresses
                if (OperatingSystem.IsLinux())
                {
                    // Add global broadcast listener
                    var server = new UdpServer(_logger, _appHost, _config, IPAddress.Broadcast, PortNumber);
                    server.Start(_cancellationTokenSource.Token);
                    _udpServers.Add(server);

                    // Add bind address specific broadcast listeners
                    // IPv6 is currently unsupported
                    var validInterfaces = _networkManager.GetInternalBindAddresses().Where(i => i.AddressFamily == AddressFamily.InterNetwork);
                    foreach (var intf in validInterfaces)
                    {
                        var broadcastAddress = NetworkUtils.GetBroadcastAddress(intf.Subnet);
                        _logger.LogDebug("Binding UDP server to {Address} on port {PortNumber}", broadcastAddress, PortNumber);

                        server = new UdpServer(_logger, _appHost, _config, broadcastAddress, PortNumber);
                        server.Start(_cancellationTokenSource.Token);
                        _udpServers.Add(server);
                    }
                }
                else
                {
                    // Add bind address specific broadcast listeners
                    // IPv6 is currently unsupported
                    var validInterfaces = _networkManager.GetInternalBindAddresses().Where(i => i.AddressFamily == AddressFamily.InterNetwork);
                    foreach (var intf in validInterfaces)
                    {
                        var intfAddress = intf.Address;
                        _logger.LogDebug("Binding UDP server to {Address} on port {PortNumber}", intfAddress, PortNumber);

                        var server = new UdpServer(_logger, _appHost, _config, intfAddress, PortNumber);
                        server.Start(_cancellationTokenSource.Token);
                        _udpServers.Add(server);
                    }
                }
            }
            catch (SocketException ex)
            {
                _logger.LogWarning(ex, "Unable to start AutoDiscovery listener on UDP port {PortNumber}", PortNumber);
            }

            return Task.CompletedTask;
        }

        private void CheckDisposed()
        {
            if (_disposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
        }

        /// <inheritdoc />
        public void Dispose()
        {
            if (_disposed)
            {
                return;
            }

            _cancellationTokenSource.Cancel();
            _cancellationTokenSource.Dispose();
            foreach (var server in _udpServers)
            {
                server.Dispose();
            }

            _udpServers.Clear();
            _disposed = true;
        }
    }
}