using Discord;
using Discord.WebSocket;
using Newtonsoft.Json.Linq;
using Noikoio.RegexBot.ConfigItem;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace Noikoio.RegexBot.Module.ModCommands.Commands
{
    /// <summary>
    /// Base class for a command within the module.
    /// After implementing, don't forget to add a reference to
    /// <see cref="CreateInstance(ModCommands, JProperty)"/>.
    /// </summary>
    [DebuggerDisplay("Command def: {Label}")]
    abstract class Command
    {
        private readonly ModCommands _mod;
        private readonly string _label;
        private readonly string _command;

        protected ModCommands Module => _mod;
        public string Label => _label;
        public string Trigger => _command;

        public Command(ModCommands l, string label, JObject conf)
        {
            _mod = l;
            _label = label;
            _command = conf["command"].Value<string>();
        }

        public abstract Task Invoke(SocketGuild g, SocketMessage msg);

        protected Task Log(string text)
        {
            return _mod.Log($"{Label}: {text}");
        }

        #region Config loading
        private static readonly ReadOnlyDictionary<string, Type> _commands =
            new ReadOnlyDictionary<string, Type>(
            new Dictionary<string, Type>(StringComparer.OrdinalIgnoreCase)
            {
                // Define all command types and their corresponding Types here
                { "ban",        typeof(Ban) },
                { "confreload", typeof(ConfReload) },
                { "kick",       typeof(Kick) },
                { "say",        typeof(Say) },
                { "unban",      typeof(Unban) },
                { "addrole",    typeof(RoleAdd) },
                { "delrole",    typeof(RoleDel) }
            });

        public static Command CreateInstance(ModCommands root, JProperty def)
        {
            string label = def.Name;
            if (string.IsNullOrWhiteSpace(label)) throw new RuleImportException("Label cannot be blank.");

            var definition = (JObject)def.Value;
            string cmdinvoke = definition["command"]?.Value<string>();
            if (string.IsNullOrWhiteSpace(cmdinvoke))
                throw new RuleImportException($"{label}: 'command' value was not specified.");
            if (cmdinvoke.Contains(" "))
                throw new RuleImportException($"{label}: 'command' must not contain spaces.");

            string ctypestr = definition["type"]?.Value<string>();
            if (string.IsNullOrWhiteSpace(ctypestr))
                throw new RuleImportException($"Value 'type' must be specified in definition for '{label}'.");
            if (_commands.TryGetValue(ctypestr, out Type ctype))
            {
                try
                {
                    return (Command)Activator.CreateInstance(ctype, root, label, definition);
                }
                catch (TargetInvocationException ex)
                {
                    if (ex.InnerException is RuleImportException)
                        throw new RuleImportException($"Error in configuration for command '{label}': {ex.InnerException.Message}");
                    else throw;
                }
            }
            else
            {
                throw new RuleImportException($"The given 'type' value is invalid in definition for '{label}'.");
            }
        }
        #endregion

        #region Helper methods and common values
        protected static readonly Regex UserMention = new Regex(@"<@!?(?<snowflake>\d+)>", RegexOptions.Compiled);
        protected static readonly Regex RoleMention = new Regex(@"<@&(?<snowflake>\d+)>", RegexOptions.Compiled);
        protected static readonly Regex ChannelMention = new Regex(@"<#(?<snowflake>\d+)>", RegexOptions.Compiled);
        protected static readonly Regex EmojiMatch = new Regex(@"<:(?<name>[A-Za-z0-9_]{2,}):(?<ID>\d+)>", RegexOptions.Compiled);
        protected const string Fail403 = "I do not have the required permissions to perform that action.";
        protected const string FailDefault = "An unknown error occurred. Notify the bot operator.";

        protected string DefaultUsageMsg { get; set; }
        /// <summary>
        /// Sends out the default usage message (<see cref="DefaultUsageMsg"/>) within an embed. 
        /// An optional message can be included, for uses such as notifying users of incorrect usage.
        /// </summary>
        /// <param name="target">Target channel for sending the message.</param>
        /// <param name="message">The message to send alongside the default usage message.</param>
        protected async Task SendUsageMessageAsync(ISocketMessageChannel target, string message = null)
        {
            if (DefaultUsageMsg == null)
                throw new InvalidOperationException("DefaultUsage was not defined.");

            var usageEmbed = new EmbedBuilder()
            {
                Title = "Usage",
                Description = DefaultUsageMsg
            };
            await target.SendMessageAsync(message ?? "", embed: usageEmbed);
        }

        /// <summary>
        /// Helper method for turning input into user data. Only returns the first cache result.
        /// </summary>
        /// <returns>
        /// First value: 0 for no data, 1 for no data + exception.
        /// May return a partial result: a valid ulong value but no CacheUser.
        /// </returns>
        protected async Task<(ulong, EntityCache.CacheUser)> GetUserDataFromString(ulong guild, string input)
        {
            ulong uid;
            EntityCache.CacheUser cdata = null;

            // If input is a mention, isolate the ID value
            Match m = UserMention.Match(input);
            if (m.Success) input = m.Groups["snowflake"].Value;

            // Attempt to turn the input into a ulong
            try { uid = ulong.Parse(input); }
            catch (FormatException) { uid = 0; }

            // EntityCache lookup
            try
            {
                cdata = (await EntityCache.EntityCache.QueryUserAsync(guild, input))
                    .FirstOrDefault();
                if (cdata != null) uid = cdata.UserId;
            }
            catch (Npgsql.NpgsqlException ex)
            {
                await Log("A databasae error occurred during user lookup: " + ex.Message);
                if (uid == 0) uid = 1;
            }

            return (uid, cdata);
        }
        #endregion
    }
}