using Discord;
using Discord.WebSocket;
using System;
using System.Threading.Tasks;

namespace Kerobot
{
    /// <summary>
    /// Program startup class.
    /// </summary>
    class Program
    {
        /// <summary>
        /// Timestamp specifying the date and time that the program began running.
        /// </summary> 
        public static DateTimeOffset StartTime { get; private set; }

        static Kerobot _main;
        
        /// <summary>
        /// Entry point. Loads options, initializes all components, then connects to Discord.
        /// </summary>
        static async Task Main(string[] args)
        {
            StartTime = DateTimeOffset.UtcNow;
            Console.WriteLine("Bot start time: " + StartTime.ToString("u"));

            // Get instance configuration from file and parameters
            var opts = Options.ParseOptions(args); // Program can exit here.
            InstanceConfig cfg;
            try
            {
                cfg = new InstanceConfig(opts);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                Environment.ExitCode = 1;
                return;
            }

            // Quick test of database configuration
            try
            {
                using (var d = new Npgsql.NpgsqlConnection(cfg.PostgresConnString))
                {
                    await d.OpenAsync();
                    d.Close();
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine("Could not establish a database connection! Check your settings and try again.");
                Console.WriteLine($"Error: {ex.GetType().FullName}: {ex.Message}");
                Environment.Exit(1);
            }

            // Configure Discord client
            var client = new DiscordSocketClient(new DiscordSocketConfig()
            {
                DefaultRetryMode = RetryMode.AlwaysRetry,
                MessageCacheSize = 0, // using our own
                LogLevel = LogSeverity.Info
            });

            // Kerobot class initialization - will set up services and modules
            _main = new Kerobot(cfg, client);

            // Set up application close handler
            Console.CancelKeyPress += Console_CancelKeyPress;

            // TODO Set up unhandled exception handler
            // send error notification to instance log channel, if possible

            // And off we go.
            await _main.DiscordClient.LoginAsync(TokenType.Bot, cfg.BotToken);
            await _main.DiscordClient.StartAsync();
            await Task.Delay(-1);
        }

        private static void Console_CancelKeyPress(object sender, ConsoleCancelEventArgs e)
        {
            e.Cancel = true;

            _main.InstanceLogAsync(true, "Kerobot", "Shutting down. Reason: Interrupt signal.");

            // 5 seconds of leeway - any currently running tasks will need time to finish executing
            var leeway = Task.Delay(5000);

            // TODO periodic task service: stop processing, wait for all tasks to finish
            // TODO notify services of shutdown

            leeway.Wait();
            
            bool success = _main.DiscordClient.StopAsync().Wait(1000);
            if (!success) _main.InstanceLogAsync(false, "Kerobot",
                "Failed to disconnect cleanly from Discord. Will force shut down.").Wait();
            Environment.Exit(0);
        }
    }
}