using Discord;
using Discord.WebSocket;
using NodaTime;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace BirthdayBot.UserInterface
{
    internal class ManagerCommands : CommandsCommon
    {
        private delegate Task ConfigSubcommand(string[] param, SocketTextChannel reqChannel);

        private readonly Dictionary<string, ConfigSubcommand> _subcommands;
        private readonly Dictionary<string, CommandHandler> _usercommands;

        public ManagerCommands(BirthdayBot inst, Configuration db, IEnumerable<(string, CommandHandler)> userCommands)
            : base(inst, db)
        {
            _subcommands = new Dictionary<string, ConfigSubcommand>(StringComparer.OrdinalIgnoreCase)
            {
                { "role", ScmdRole },
                { "channel", ScmdChannel },
                { "modrole", ScmdModRole },
                { "message", ScmdAnnounceMsg },
                { "messagepl", ScmdAnnounceMsg },
                { "ping", ScmdPing },
                { "zone", ScmdZone },
                { "block", ScmdBlock },
                { "unblock", ScmdBlock },
                { "moderated", ScmdModerated }
            };

            // Set up local copy of all user commands accessible by the override command
            _usercommands = new Dictionary<string, CommandHandler>(StringComparer.OrdinalIgnoreCase);
            foreach (var item in userCommands) _usercommands.Add(item.Item1, item.Item2);
        }

        public override IEnumerable<(string, CommandHandler)> Commands
            => new List<(string, CommandHandler)>()
            {
                ("config", CmdConfigDispatch),
                ("override", CmdOverride),
                ("status", CmdStatus)
            };

        private async Task CmdConfigDispatch(string[] param, SocketTextChannel reqChannel, SocketGuildUser reqUser)
        {
            // Ignore those without the proper permissions.
            // Requires either the manage guild permission or to be in the moderators role
            if (!Instance.GuildCache[reqUser.Guild.Id].IsUserModerator(reqUser))
            {
                await reqChannel.SendMessageAsync(":x: This command may only be used by bot moderators.");
                return;
            }

            if (param.Length < 2)
            {
                await reqChannel.SendMessageAsync($":x: See `{CommandPrefix}help-config` for information on how to use this command.");
                return;
            }

            // Special case: Restrict 'modrole' to only guild managers
            if (string.Equals(param[1], "modrole", StringComparison.OrdinalIgnoreCase) && !reqUser.GuildPermissions.ManageGuild)
            {
                await reqChannel.SendMessageAsync(":x: This command may only be used by those with the `Manage Server` permission.");
                return;
            }

            // Subcommands get a subset of the parameters, to make things a little easier.
            var confparam = new string[param.Length - 1];
            Array.Copy(param, 1, confparam, 0, param.Length - 1);

            if (_subcommands.TryGetValue(confparam[0], out ConfigSubcommand h))
            {
                await h(confparam, reqChannel);
            }
        }

        #region Configuration sub-commands
        // Birthday role set
        private async Task ScmdRole(string[] param, SocketTextChannel reqChannel)
        {
            if (param.Length != 2)
            {
                await reqChannel.SendMessageAsync(":x: A role name, role mention, or ID value must be specified.");
                return;
            }
            var guild = reqChannel.Guild;
            var role = FindUserInputRole(param[1], guild);

            if (role == null)
            {
                await reqChannel.SendMessageAsync(RoleInputError);
            }
            else if (role.Id == reqChannel.Guild.EveryoneRole.Id)
            {
                await reqChannel.SendMessageAsync(":x: You cannot set that as the birthday role.");
            }
            else
            {
                Instance.GuildCache[guild.Id].UpdateRole(role.Id);
                await reqChannel.SendMessageAsync($":white_check_mark: The birthday role has been set as **{role.Name}**.");
            }
        }

        // Ping setting
        private async Task ScmdPing(string[] param, SocketTextChannel reqChannel)
        {
            const string InputErr = ":x: You must specify either `off` or `on` in this setting.";
            if (param.Length != 2)
            {
                await reqChannel.SendMessageAsync(InputErr);
                return;
            }

            var input = param[1].ToLower();
            bool setting;
            string result;
            if (input == "off")
            {
                setting = false;
                result = ":white_check_mark: Announcement pings are now **off**.";
            }
            else if (input == "on")
            {
                setting = true;
                result = ":white_check_mark: Announcement pings are now **on**.";
            }
            else
            {
                await reqChannel.SendMessageAsync(InputErr);
                return;
            }

            Instance.GuildCache[reqChannel.Guild.Id].UpdateAnnouncePing(setting);
            await reqChannel.SendMessageAsync(result);
        }

        // Announcement channel set
        private async Task ScmdChannel(string[] param, SocketTextChannel reqChannel)
        {
            if (param.Length == 1)
            {
                // No extra parameter. Unset announcement channel.
                var gi = Instance.GuildCache[reqChannel.Guild.Id];

                // Extra detail: Show a unique message if a channel hadn't been set prior.
                if (!gi.AnnounceChannelId.HasValue)
                {
                    await reqChannel.SendMessageAsync(":x: There is no announcement channel set. Nothing to unset.");
                    return;
                }

                gi.UpdateAnnounceChannel(null);
                await reqChannel.SendMessageAsync(":white_check_mark: The announcement channel has been unset.");
            }
            else
            {
                // Determine channel from input
                ulong chId = 0;

                // Try channel mention
                var m = ChannelMention.Match(param[1]);
                if (m.Success)
                {
                    chId = ulong.Parse(m.Groups[1].Value);
                }
                else if (ulong.TryParse(param[1], out chId))
                {
                    // Continue...
                }
                else
                {
                    // Try text-based search
                    var res = reqChannel.Guild.TextChannels
                        .FirstOrDefault(ch => string.Equals(ch.Name, param[1], StringComparison.OrdinalIgnoreCase));
                    if (res != null)
                    {
                        chId = res.Id; // Yep, we're throwing the full result away only to go look for it again later...
                    }
                }

                // Attempt to find channel in guild
                SocketTextChannel chTt = null;
                if (chId != 0) chTt = reqChannel.Guild.GetTextChannel(chId);
                if (chTt == null)
                {
                    await reqChannel.SendMessageAsync(":x: Unable to find the specified channel.");
                    return;
                }

                // Update the value
                Instance.GuildCache[reqChannel.Guild.Id].UpdateAnnounceChannel(chId);

                // Report the success
                await reqChannel.SendMessageAsync($":white_check_mark: The announcement channel is now set to <#{chId}>.");
            }
        }

        // Moderator role set
        private async Task ScmdModRole(string[] param, SocketTextChannel reqChannel)
        {
            if (param.Length != 2)
            {
                await reqChannel.SendMessageAsync(":x: A role name, role mention, or ID value must be specified.");
                return;
            }
            var guild = reqChannel.Guild;
            var role = FindUserInputRole(param[1], guild);

            if (role == null)
            {
                await reqChannel.SendMessageAsync(RoleInputError);
            }
            else
            {
                Instance.GuildCache[guild.Id].UpdateModeratorRole(role.Id);
                await reqChannel.SendMessageAsync($":white_check_mark: The moderator role is now **{role.Name}**.");
            }
        }

        // Guild default time zone set/unset
        private async Task ScmdZone(string[] param, SocketTextChannel reqChannel)
        {
            if (param.Length == 1)
            {
                // No extra parameter. Unset guild default time zone.
                var gi = Instance.GuildCache[reqChannel.Guild.Id];

                // Extra detail: Show a unique message if there is no set zone.
                if (!gi.AnnounceChannelId.HasValue)
                {
                    await reqChannel.SendMessageAsync(":x: A default zone is not set. Nothing to unset.");
                    return;
                }

                gi.UpdateTimeZone(null);
                await reqChannel.SendMessageAsync(":white_check_mark: The default time zone preference has been removed.");
            }
            else
            {
                // Parameter check.
                string zone;
                try
                {
                    zone = ParseTimeZone(param[1]);
                }
                catch (FormatException ex)
                {
                    reqChannel.SendMessageAsync(ex.Message).Wait();
                    return;
                }

                // Update value
                Instance.GuildCache[reqChannel.Guild.Id].UpdateTimeZone(zone);

                // Report the success
                await reqChannel.SendMessageAsync($":white_check_mark: The server's time zone has been set to **{zone}**.");
            }
        }

        // Block/unblock individual non-manager users from using commands.
        private async Task ScmdBlock(string[] param, SocketTextChannel reqChannel)
        {
            if (param.Length != 2)
            {
                await reqChannel.SendMessageAsync(GenericError);
                return;
            }

            bool doBan = param[0].ToLower() == "block"; // true = block, false = unblock

            ulong inputId;
            if (!TryGetUserId(param[1], out inputId))
            {
                await reqChannel.SendMessageAsync(BadUserError);
                return;
            }

            var gi = Instance.GuildCache[reqChannel.Guild.Id];
            var isBanned = await gi.IsUserBlockedAsync(inputId);
            if (doBan)
            {
                if (!isBanned)
                {
                    await gi.BlockUserAsync(inputId);
                    await reqChannel.SendMessageAsync(":white_check_mark: User has been blocked.");
                }
                else
                {
                    await reqChannel.SendMessageAsync(":white_check_mark: User is already blocked.");
                }
            }
            else
            {
                if (isBanned)
                {
                    await gi.UnbanUserAsync(inputId);
                    await reqChannel.SendMessageAsync(":white_check_mark: User is now unblocked.");
                }
                else
                {
                    await reqChannel.SendMessageAsync(":white_check_mark: The specified user has not been blocked.");
                }
            }
        }

        // "moderated on/off" - Sets/unsets moderated mode.
        private async Task ScmdModerated(string[] param, SocketTextChannel reqChannel)
        {
            if (param.Length != 2)
            {
                await reqChannel.SendMessageAsync(GenericError);
                return;
            }

            var parameter = param[1].ToLower();
            bool modSet;
            if (parameter == "on") modSet = true;
            else if (parameter == "off") modSet = false;
            else
            {
                await reqChannel.SendMessageAsync(GenericError);
                return;
            }

            var gi = Instance.GuildCache[reqChannel.Guild.Id];
            var currentSet = gi.IsModerated;
            gi.UpdateModeratedMode(modSet);

            if (currentSet == modSet)
            {
                await reqChannel.SendMessageAsync($":white_check_mark: Moderated mode is already {parameter}.");
            }
            else
            {
                await reqChannel.SendMessageAsync($":white_check_mark: Moderated mode has been turned {parameter}.");
            }
        }

        // Sets/unsets custom announcement message.
        private async Task ScmdAnnounceMsg(string[] param, SocketTextChannel reqChannel)
        {
            var plural = param[0].ToLower().EndsWith("pl");

            string newmsg;
            bool clear;
            if (param.Length == 2)
            {
                newmsg = param[1];
                clear = false;
            }
            else
            {
                newmsg = null;
                clear = true;
            }

            Instance.GuildCache[reqChannel.Guild.Id].UpdateAnnounceMessage(newmsg, plural);
            const string report = ":white_check_mark: The {0} birthday announcement message has been {1}.";
            await reqChannel.SendMessageAsync(string.Format(report, plural ? "plural" : "singular", clear ? "reset" : "updated"));
        }
        #endregion

        // Execute command as another user
        private async Task CmdOverride(string[] param, SocketTextChannel reqChannel, SocketGuildUser reqUser)
        {
            // Moderators only. As with config, silently drop if this check fails.
            if (!Instance.GuildCache[reqUser.Guild.Id].IsUserModerator(reqUser)) return;

            if (param.Length != 3)
            {
                await reqChannel.SendMessageAsync(GenericError);
                return;
            }

            // Second parameter: determine the user to act as
            ulong user = 0;
            if (!TryGetUserId(param[1], out user))
            {
                await reqChannel.SendMessageAsync(BadUserError);
                return;
            }
            var overuser = reqChannel.Guild.GetUser(user);
            if (overuser == null)
            {
                await reqChannel.SendMessageAsync(BadUserError);
                return;
            }

            // Third parameter: determine command to invoke.
            // Reminder that we're only receiving a param array of size 3 at maximum. String must be split again.
            var overparam = param[2].Split(" ", 3, StringSplitOptions.RemoveEmptyEntries);
            var cmdsearch = overparam[0];
            if (cmdsearch.StartsWith(CommandPrefix))
            {
                // Strip command prefix to search for the given command.
                cmdsearch = cmdsearch.Substring(CommandPrefix.Length);
            }
            else
            {
                // Add command prefix to input, just in case.
                overparam[0] = CommandPrefix + overparam[0].ToLower();
            }
            CommandHandler action = null;
            if (!_usercommands.TryGetValue(cmdsearch, out action))
            {
                await reqChannel.SendMessageAsync($":x: `{cmdsearch}` is not an overridable command.");
                return;
            }

            // Preparations complete. Run the command.
            await reqChannel.SendMessageAsync($"Executing `{cmdsearch.ToLower()}` on behalf of {overuser.Nickname ?? overuser.Username}:");
            await action.Invoke(overparam, reqChannel, overuser);
        }

        // Prints a status report useful for troubleshooting operational issues within a guild
        private async Task CmdStatus(string[] param, SocketTextChannel reqChannel, SocketGuildUser reqUser)
        {
            // Moderators only. As with config, silently drop if this check fails.
            if (!Instance.GuildCache[reqUser.Guild.Id].IsUserModerator(reqUser)) return;

            DateTimeOffset optime;
            string optext;
            string zone;
            var gi = Instance.GuildCache[reqChannel.Guild.Id];
            lock (gi)
            {
                var opstat = gi.OperationLog;
                optext = opstat.GetDiagStrings(); // !!! Bulk of output handled by this method
                optime = opstat.Timestamp;
                zone = gi.TimeZone ?? "UTC";
            }
            var shard = Instance.DiscordClient.GetShardIdFor(reqChannel.Guild);

            // Calculate timestamp in current zone
            var zonedTimeInstant = SystemClock.Instance.GetCurrentInstant().InZone(DateTimeZoneProviders.Tzdb.GetZoneOrNull(zone));
            var timeAgoEstimate = DateTimeOffset.UtcNow - optime;

            var result = new EmbedBuilder
            {
                Title = "Background operation status",
                Description = $"Shard: {shard}\n"
                + $"Operation time: {Math.Round(timeAgoEstimate.TotalSeconds)} second(s) ago at {zonedTimeInstant}\n"
                + "Report:\n"
                + optext.TrimEnd()
            };

            await reqChannel.SendMessageAsync(embed: result.Build());
        }

        #region Common/helper methods
        private const string RoleInputError = ":x: Unable to determine the given role.";
        private static readonly Regex RoleMention = new Regex(@"<@?&(?<snowflake>\d+)>", RegexOptions.Compiled);

        private SocketRole FindUserInputRole(string inputStr, SocketGuild guild)
        {
            // Resembles a role mention? Strip it to the pure number
            var input = inputStr;
            var rmatch = RoleMention.Match(input);
            if (rmatch.Success) input = rmatch.Groups["snowflake"].Value;

            // Attempt to get role by ID, or null
            ulong rid;
            if (ulong.TryParse(input, out rid))
            {
                return guild.GetRole(rid);
            }
            else
            {
                // Reset the search value on the off chance there's a role name that actually resembles a role ping.
                input = inputStr;
            }

            // If not already found, attempt to search role by string name
            foreach (var search in guild.Roles)
            {
                if (string.Equals(search.Name, input, StringComparison.OrdinalIgnoreCase)) return search;
            }

            return null;
        }
        #endregion
    }
}