using System;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Security;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Text.RegularExpressions;
using System.Threading;
using System.Threading.Tasks;
using CommandLine;
using Emby.Drawing;
using Emby.Server.Implementations;
using Emby.Server.Implementations.EnvironmentInfo;
using Emby.Server.Implementations.IO;
using Emby.Server.Implementations.Networking;
using Jellyfin.Drawing.Skia;
using MediaBrowser.Common.Configuration;
using MediaBrowser.Controller.Drawing;
using MediaBrowser.Model.Globalization;
using MediaBrowser.Model.IO;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Serilog;
using Serilog.AspNetCore;
using ILogger = Microsoft.Extensions.Logging.ILogger;

namespace Jellyfin.Server
{
    public static class Program
    {
        private static readonly CancellationTokenSource _tokenSource = new CancellationTokenSource();
        private static readonly ILoggerFactory _loggerFactory = new SerilogLoggerFactory();
        private static ILogger _logger;
        private static bool _restartOnShutdown;
        private static IConfiguration appConfig;

        public static async Task Main(string[] args)
        {
            // For backwards compatibility.
            // Modify any input arguments now which start with single-hyphen to POSIX standard
            // double-hyphen to allow parsing by CommandLineParser package.
            const string pattern = @"^(-[^-\s]{2})"; // Match -xx, not -x, not --xx, not xx
            const string substitution = @"-$1"; // Prepend with additional single-hyphen
            var regex = new Regex(pattern);

            for (var i = 0; i < args.Length; i++)
            {
                args[i] = regex.Replace(args[i], substitution);
            }

            // Parse the command line arguments and either start the app or exit indicating error
            await Parser.Default.ParseArguments<StartupOptions>(args)
                .MapResult(
                    options => StartApp(options),
                    errs => Task.FromResult(0)).ConfigureAwait(false);
        }

        public static void Shutdown()
        {
            if (!_tokenSource.IsCancellationRequested)
            {
                _tokenSource.Cancel();
            }
        }

        public static void Restart()
        {
            _restartOnShutdown = true;

            Shutdown();
        }

        private static async Task StartApp(StartupOptions options)
        {
            ServerApplicationPaths appPaths = CreateApplicationPaths(options);

            // $JELLYFIN_LOG_DIR needs to be set for the logger configuration manager
            Environment.SetEnvironmentVariable("JELLYFIN_LOG_DIR", appPaths.LogDirectoryPath);

            appConfig = await CreateConfiguration(appPaths).ConfigureAwait(false);

            CreateLogger(appConfig, appPaths);

            _logger = _loggerFactory.CreateLogger("Main");

            AppDomain.CurrentDomain.UnhandledException += (sender, e)
                => _logger.LogCritical((Exception)e.ExceptionObject, "Unhandled Exception");

            // Intercept Ctrl+C and Ctrl+Break
            Console.CancelKeyPress += (sender, e) =>
            {
                if (_tokenSource.IsCancellationRequested)
                {
                    return; // Already shutting down
                }

                e.Cancel = true;
                _logger.LogInformation("Ctrl+C, shutting down");
                Environment.ExitCode = 128 + 2;
                Shutdown();
            };

            // Register a SIGTERM handler
            AppDomain.CurrentDomain.ProcessExit += (sender, e) =>
            {
                if (_tokenSource.IsCancellationRequested)
                {
                    return; // Already shutting down
                }

                _logger.LogInformation("Received a SIGTERM signal, shutting down");
                Environment.ExitCode = 128 + 15;
                Shutdown();
            };

            _logger.LogInformation("Jellyfin version: {Version}", Assembly.GetEntryAssembly().GetName().Version);

            EnvironmentInfo environmentInfo = new EnvironmentInfo(GetOperatingSystem());
            ApplicationHost.LogEnvironmentInfo(_logger, appPaths, environmentInfo);

            SQLitePCL.Batteries_V2.Init();

            // Allow all https requests
            ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(delegate { return true; } );

            var fileSystem = new ManagedFileSystem(_loggerFactory, environmentInfo, appPaths);

            using (var appHost = new CoreAppHost(
                appPaths,
                _loggerFactory,
                options,
                fileSystem,
                environmentInfo,
                new NullImageEncoder(),
                new NetworkManager(_loggerFactory, environmentInfo),
                appConfig))
            {
                await appHost.Init(new ServiceCollection()).ConfigureAwait(false);

                appHost.ImageProcessor.ImageEncoder = GetImageEncoder(fileSystem, appPaths, appHost.LocalizationManager);

                await appHost.RunStartupTasks().ConfigureAwait(false);

                // TODO: read input for a stop command

                try
                {
                    // Block main thread until shutdown
                    await Task.Delay(-1, _tokenSource.Token).ConfigureAwait(false);
                }
                catch (TaskCanceledException)
                {
                    // Don't throw on cancellation
                }
            }

            if (_restartOnShutdown)
            {
                StartNewInstance(options);
            }
        }

        /// <summary>
        /// Create the data, config and log paths from the variety of inputs(command line args,
        /// environment variables) or decide on what default to use.  For Windows it's %AppPath%
        /// for everything else the XDG approach is followed:
        /// https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html
        /// </summary>
        /// <param name="options">StartupOptions</param>
        /// <returns>ServerApplicationPaths</returns>
        private static ServerApplicationPaths CreateApplicationPaths(StartupOptions options)
        {
            // dataDir
            // IF      --datadir
            // ELSE IF $JELLYFIN_DATA_PATH
            // ELSE IF windows, use <%APPDATA%>/jellyfin
            // ELSE IF $XDG_DATA_HOME then use $XDG_DATA_HOME/jellyfin
            // ELSE    use $HOME/.local/share/jellyfin
            var dataDir = options.DataDir;

            if (string.IsNullOrEmpty(dataDir))
            {
                dataDir = Environment.GetEnvironmentVariable("JELLYFIN_DATA_PATH");

                if (string.IsNullOrEmpty(dataDir))
                {
                    // LocalApplicationData follows the XDG spec on unix machines
                    dataDir = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "jellyfin");
                }
            }

            Directory.CreateDirectory(dataDir);

            // configDir
            // IF      --configdir
            // ELSE IF $JELLYFIN_CONFIG_DIR
            // ELSE IF --datadir, use <datadir>/config (assume portable run)
            // ELSE IF <datadir>/config exists, use that
            // ELSE IF windows, use <datadir>/config
            // ELSE IF $XDG_CONFIG_HOME use $XDG_CONFIG_HOME/jellyfin
            // ELSE    $HOME/.config/jellyfin
            var configDir = options.ConfigDir;
            if (string.IsNullOrEmpty(configDir))
            {
                configDir = Environment.GetEnvironmentVariable("JELLYFIN_CONFIG_DIR");

                if (string.IsNullOrEmpty(configDir))
                {
                    if (options.DataDir != null || Directory.Exists(Path.Combine(dataDir, "config")) || RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
                    {
                        // Hang config folder off already set dataDir
                        configDir = Path.Combine(dataDir, "config");
                    }
                    else
                    {
                        // $XDG_CONFIG_HOME defines the base directory relative to which user specific configuration files should be stored.
                        configDir = Environment.GetEnvironmentVariable("XDG_CONFIG_HOME");

                        // If $XDG_CONFIG_HOME is either not set or empty, a default equal to $HOME /.config should be used.
                        if (string.IsNullOrEmpty(configDir))
                        {
                            configDir = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".config");
                        }

                        configDir = Path.Combine(configDir, "jellyfin");
                    }
                }
            }

            // cacheDir
            // IF      --cachedir
            // ELSE IF $JELLYFIN_CACHE_DIR
            // ELSE IF windows, use <datadir>/cache
            // ELSE IF XDG_CACHE_HOME, use $XDG_CACHE_HOME/jellyfin
            // ELSE    HOME/.cache/jellyfin
            var cacheDir = options.CacheDir;

            if (string.IsNullOrEmpty(cacheDir))
            {
                cacheDir = Environment.GetEnvironmentVariable("JELLYFIN_CACHE_DIR");

                if (string.IsNullOrEmpty(cacheDir))
                {
                    if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
                    {
                        // Hang cache folder off already set dataDir
                        cacheDir = Path.Combine(dataDir, "cache");
                    }
                    else
                    {
                        // $XDG_CACHE_HOME defines the base directory relative to which user specific non-essential data files should be stored.
                        cacheDir = Environment.GetEnvironmentVariable("XDG_CACHE_HOME");

                        // If $XDG_CACHE_HOME is either not set or empty, a default equal to $HOME/.cache should be used.
                        if (string.IsNullOrEmpty(cacheDir))
                        {
                            cacheDir = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".cache");
                        }

                        cacheDir = Path.Combine(cacheDir, "jellyfin");
                    }
                }
            }

            // logDir
            // IF      --logdir
            // ELSE IF $JELLYFIN_LOG_DIR
            // ELSE IF --datadir, use <datadir>/log (assume portable run)
            // ELSE    <datadir>/log
            var logDir = options.LogDir;

            if (string.IsNullOrEmpty(logDir))
            {
                logDir = Environment.GetEnvironmentVariable("JELLYFIN_LOG_DIR");

                if (string.IsNullOrEmpty(logDir))
                {
                    // Hang log folder off already set dataDir
                    logDir = Path.Combine(dataDir, "log");
                }
            }

            // Ensure the main folders exist before we continue
            try
            {
                Directory.CreateDirectory(logDir);
                Directory.CreateDirectory(configDir);
                Directory.CreateDirectory(cacheDir);
            }
            catch (IOException ex)
            {
                Console.Error.WriteLine("Error whilst attempting to create folder");
                Console.Error.WriteLine(ex.ToString());
                Environment.Exit(1);
            }

            return new ServerApplicationPaths(dataDir, logDir, configDir, cacheDir);
        }

        private static async Task<IConfiguration> CreateConfiguration(IApplicationPaths appPaths)
        {
            string configPath = Path.Combine(appPaths.ConfigurationDirectoryPath, "logging.json");

            if (!File.Exists(configPath))
            {
                // For some reason the csproj name is used instead of the assembly name
                using (Stream rscstr = typeof(Program).Assembly
                    .GetManifestResourceStream("Jellyfin.Server.Resources.Configuration.logging.json"))
                using (Stream fstr = File.Open(configPath, FileMode.CreateNew))
                {
                    await rscstr.CopyToAsync(fstr).ConfigureAwait(false);
                }
            }

            return new ConfigurationBuilder()
                .SetBasePath(appPaths.ConfigurationDirectoryPath)
                .AddJsonFile("logging.json")
                .AddEnvironmentVariables("JELLYFIN_")
                .AddInMemoryCollection(ConfigurationOptions.Configuration)
                .Build();
        }

        private static void CreateLogger(IConfiguration configuration, IApplicationPaths appPaths)
        {
            try
            {
                // Serilog.Log is used by SerilogLoggerFactory when no logger is specified
                Serilog.Log.Logger = new LoggerConfiguration()
                    .ReadFrom.Configuration(configuration)
                    .Enrich.FromLogContext()
                    .CreateLogger();
            }
            catch (Exception ex)
            {
                Serilog.Log.Logger = new LoggerConfiguration()
                    .WriteTo.Console(outputTemplate: "[{Timestamp:HH:mm:ss}] [{Level:u3}] {Message:lj}{NewLine}{Exception}")
                    .WriteTo.Async(x => x.File(
                        Path.Combine(appPaths.LogDirectoryPath, "log_.log"),
                        rollingInterval: RollingInterval.Day,
                        outputTemplate: "[{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz}] [{Level:u3}] {Message}{NewLine}{Exception}"))
                    .Enrich.FromLogContext()
                    .CreateLogger();

                Serilog.Log.Logger.Fatal(ex, "Failed to create/read logger configuration");
            }
        }

        private static IImageEncoder GetImageEncoder(
            IFileSystem fileSystem,
            IApplicationPaths appPaths,
            ILocalizationManager localizationManager)
        {
            try
            {
                return new SkiaEncoder(_loggerFactory, appPaths, fileSystem, localizationManager);
            }
            catch (Exception ex)
            {
                _logger.LogInformation(ex, "Skia not available. Will fallback to NullIMageEncoder. {0}");
            }

            return new NullImageEncoder();
        }

        private static MediaBrowser.Model.System.OperatingSystem GetOperatingSystem()
        {
            switch (Environment.OSVersion.Platform)
            {
                case PlatformID.MacOSX:
                    return MediaBrowser.Model.System.OperatingSystem.OSX;
                case PlatformID.Win32NT:
                    return MediaBrowser.Model.System.OperatingSystem.Windows;
                case PlatformID.Unix:
                default:
                    {
                        string osDescription = RuntimeInformation.OSDescription;
                        if (osDescription.Contains("linux", StringComparison.OrdinalIgnoreCase))
                        {
                            return MediaBrowser.Model.System.OperatingSystem.Linux;
                        }
                        else if (osDescription.Contains("darwin", StringComparison.OrdinalIgnoreCase))
                        {
                            return MediaBrowser.Model.System.OperatingSystem.OSX;
                        }
                        else if (osDescription.Contains("bsd", StringComparison.OrdinalIgnoreCase))
                        {
                            return MediaBrowser.Model.System.OperatingSystem.BSD;
                        }

                        throw new Exception($"Can't resolve OS with description: '{osDescription}'");
                    }
            }
        }

        private static void StartNewInstance(StartupOptions options)
        {
            _logger.LogInformation("Starting new instance");

            string module = options.RestartPath;

            if (string.IsNullOrWhiteSpace(module))
            {
                module = Environment.GetCommandLineArgs().First();
            }

            string commandLineArgsString;

            if (options.RestartArgs != null)
            {
                commandLineArgsString = options.RestartArgs ?? string.Empty;
            }
            else
            {
                commandLineArgsString = string.Join(
                    " ",
                    Environment.GetCommandLineArgs().Skip(1).Select(NormalizeCommandLineArgument));
            }

            _logger.LogInformation("Executable: {0}", module);
            _logger.LogInformation("Arguments: {0}", commandLineArgsString);

            Process.Start(module, commandLineArgsString);
        }

        private static string NormalizeCommandLineArgument(string arg)
        {
            if (!arg.Contains(" ", StringComparison.OrdinalIgnoreCase))
            {
                return arg;
            }

            return "\"" + arg + "\"";
        }
    }
}