using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
using DeukBot4.MessageHandlers.CommandHandler.RequestStructure;
using DeukBot4.MessageHandlers.Permissions;
using DeukBot4.Utilities;
using Discord;
using Discord.WebSocket;

namespace DeukBot4.MessageHandlers.CommandHandler
{
    public static class CommandHandler
    {
        public static Dictionary<string, Command> Commands { get; } = new Dictionary<string, Command>();
        public const char CommandTrigger = '!';

        public static void Build()
        {
            var commandContainers = typeof(CommandHandler).Assembly.GetTypes()
                .Where(x => typeof(CommandContainerBase).IsAssignableFrom(x) && !x.IsAbstract);

            foreach (var commandContainer in commandContainers)
            {
                if (!(Activator.CreateInstance(commandContainer) is CommandContainerBase obj))
                    continue;
                var commands = obj.GetCommands();
                foreach (var command in commands)
                {
                    Commands.Add(command.Name.ToLowerInvariant(), command);
                    foreach (var commandAlternative in command.Alternatives)
                    {
                        Commands.Add(commandAlternative.ToLowerInvariant(), command);
                    }
                }

                Logger.Main.Log(
                    $"Loaded following commands for container {obj.Name}: {commands.Select(x => x.Name).Join(", ")}");

            }

        }

        public static async Task HandleMessage(SocketMessage message)
        {
            if (string.IsNullOrWhiteSpace(message.Content))
                return;

            if (message.Content[0] != CommandTrigger && message.MentionedUsers.All(x => x.Id != Program.BotId))
                return;
            if (message.Content[1] == '!')
                return;

            var req = await CommandRequest.Create(message);
            var resultCode = req.Response;
            switch (resultCode)
            {
                case CommandRequest.RequestCode.Invalid:
                    await Logger.Main.LogError("Invalid content: " + message.Content);
                    return;
                case CommandRequest.RequestCode.InvalidParameters:
                    await Logger.Main.LogError("Invalid parameters: " + message.Content);
                    break;
                case CommandRequest.RequestCode.Forbidden:
                    await Logger.Main.Log(
                        $"Unauthorized user tried to run command: {message.Author.Username} -> {message.Content}");
                    break;
                case CommandRequest.RequestCode.OK:
                    if (!(message.Channel is IGuildChannel) && req.Request.Command.ForbidInPm)
                    {
                        await Logger.Main.Log(
                            $"User is trying to use blocked command in PM: {message.Author.Username}");
                        return;
                    }

                    try
                    {
                        await req.Request.Command.Invoke(req.Request);
                    }
                    catch (Exception e)
                    {
                        await Logger.Main.Log("An error occured: \n" + e);
                    }
                    break;
                case CommandRequest.RequestCode.UnknownCommand:
                    var permission = await PermissionValidator.GetUserPermissionLevel(message);
                    var similar = await GetSimilarCommand(req.CommandName, permission);
                    await message.Channel.SendMessageAsync(
                        $"Unknown command: ``{req.CommandName}``. Did you mean: ``{similar}``? " +
                        $"Alternatively, use ``{CommandTrigger}help`` for a list of all commands");
                    break;
                default:
                    throw new ArgumentOutOfRangeException();
            }
        }

        private static async Task<string> GetSimilarCommand(string command, PermissionLevel permission)
        {
            var closestString = "";
            var similarity = int.MaxValue;
            foreach (var cmd in Commands)
            {
                if (cmd.Value.Permission > permission)
                    continue;
                var distance = Lehvenstein.LevenshteinDistance(command, cmd.Key);
                if (distance >= similarity)
                    continue;
                similarity    = distance;
                closestString = cmd.Key;
            }
            return closestString;
        }

        public static Command GetCommand(string name)
        {
            return Commands.TryGetValue(name.ToLowerInvariant(), out var com) ? com : null;
        }
    }
}