using System;
using System.Linq;
using System.Threading.Tasks;

using DSharpPlus.Entities;

using NodaTime;
using NodaTime.Text;
using NodaTime.TimeZones;

using PluralKit.Core;

namespace PluralKit.Bot
{
    public class SystemEdit
    {
        private readonly IDatabase _db;
        private readonly ModelRepository _repo;

        public SystemEdit(IDatabase db, ModelRepository repo)
        {
            _db = db;
            _repo = repo;
        }

        public async Task Name(Context ctx)
        {
            ctx.CheckSystem();

            if (await ctx.MatchClear("your system's name"))
            {
                var clearPatch = new SystemPatch {Name = null};
                await _db.Execute(conn => _repo.UpdateSystem(conn, ctx.System.Id, clearPatch));

                await ctx.Reply($"{Emojis.Success} System name cleared.");
                return;
            }

            var newSystemName = ctx.RemainderOrNull();
            if (newSystemName == null)
            {
                if (ctx.System.Name != null)
                    await ctx.Reply($"Your system's name is currently **{ctx.System.Name}**. Type `pk;system name -clear` to clear it.");
                else
                    await ctx.Reply("Your system currently does not have a name. Type `pk;system name <name>` to set one.");
                return;
            }
            
            if (newSystemName != null && newSystemName.Length > Limits.MaxSystemNameLength)
                throw Errors.SystemNameTooLongError(newSystemName.Length);
            
            var patch = new SystemPatch {Name = newSystemName};
            await _db.Execute(conn => _repo.UpdateSystem(conn, ctx.System.Id, patch));
            
            await ctx.Reply($"{Emojis.Success} System name changed.");
        }
        
        public async Task Description(Context ctx) {
            ctx.CheckSystem();

            if (await ctx.MatchClear("your system's description"))
            {
                var patch = new SystemPatch {Description = null};
                await _db.Execute(conn => _repo.UpdateSystem(conn, ctx.System.Id, patch));
                
                await ctx.Reply($"{Emojis.Success} System description cleared.");
                return;
            }
            
            var newDescription = ctx.RemainderOrNull()?.NormalizeLineEndSpacing();
            if (newDescription == null)
            {
                if (ctx.System.Description == null)
                    await ctx.Reply("Your system does not have a description set. To set one, type `pk;s description <description>`.");
                else if (ctx.MatchFlag("r", "raw"))
                    await ctx.Reply($"```\n{ctx.System.Description}\n```");
                else
                    await ctx.Reply(embed: new DiscordEmbedBuilder()
                        .WithTitle("System description")
                        .WithDescription(ctx.System.Description)
                        .WithFooter("To print the description with formatting, type `pk;s description -raw`. To clear it, type `pk;s description -clear`. To change it, type `pk;s description <new description>`.")
                        .Build());
            }
            else
            {
                if (newDescription.Length > Limits.MaxDescriptionLength) throw Errors.DescriptionTooLongError(newDescription.Length);
                
                var patch = new SystemPatch {Description = newDescription};
                await _db.Execute(conn => _repo.UpdateSystem(conn, ctx.System.Id, patch));
                
                await ctx.Reply($"{Emojis.Success} System description changed.");
            }
        }
        
        public async Task Tag(Context ctx)
        {
            ctx.CheckSystem();

            if (await ctx.MatchClear("your system's tag"))
            {
                var patch = new SystemPatch {Tag = null};
                await _db.Execute(conn => _repo.UpdateSystem(conn, ctx.System.Id, patch));
                
                await ctx.Reply($"{Emojis.Success} System tag cleared.");
            } else if (!ctx.HasNext(skipFlags: false))
            {
                if (ctx.System.Tag == null)
                    await ctx.Reply($"You currently have no system tag. To set one, type `pk;s tag <tag>`.");
                else
                    await ctx.Reply($"Your current system tag is {ctx.System.Tag.AsCode()}. To change it, type `pk;s tag <tag>`. To clear it, type `pk;s tag -clear`.");
            }
            else
            {
                var newTag = ctx.RemainderOrNull(skipFlags: false);
                if (newTag != null)
                    if (newTag.Length > Limits.MaxSystemTagLength)
                        throw Errors.SystemNameTooLongError(newTag.Length);
                
                var patch = new SystemPatch {Tag = newTag};
                await _db.Execute(conn => _repo.UpdateSystem(conn, ctx.System.Id, patch));
                
                await ctx.Reply($"{Emojis.Success} System tag changed. Member names will now end with {newTag.AsCode()} when proxied.");
            }
        }
        
        public async Task Avatar(Context ctx)
        {
            ctx.CheckSystem();

            async Task ClearIcon()
            {
                await _db.Execute(c => _repo.UpdateSystem(c, ctx.System.Id, new SystemPatch {AvatarUrl = null}));
                await ctx.Reply($"{Emojis.Success} System icon cleared.");
            }

            async Task SetIcon(ParsedImage img)
            {
                await AvatarUtils.VerifyAvatarOrThrow(img.Url);

                await _db.Execute(c => _repo.UpdateSystem(c, ctx.System.Id, new SystemPatch {AvatarUrl = img.Url}));
            
                var msg = img.Source switch
                {
                    AvatarSource.User => $"{Emojis.Success} System icon changed to {img.SourceUser?.Username}'s avatar!\n{Emojis.Warn} If {img.SourceUser?.Username} changes their avatar, the system icon will need to be re-set.",
                    AvatarSource.Url => $"{Emojis.Success} System icon changed to the image at the given URL.",
                    AvatarSource.Attachment => $"{Emojis.Success} System icon changed to attached image.\n{Emojis.Warn} If you delete the message containing the attachment, the system icon will stop working.",
                    _ => throw new ArgumentOutOfRangeException()
                };
            
                // The attachment's already right there, no need to preview it.
                var hasEmbed = img.Source != AvatarSource.Attachment;
                await (hasEmbed 
                    ? ctx.Reply(msg, embed: new DiscordEmbedBuilder().WithImageUrl(img.Url).Build()) 
                    : ctx.Reply(msg));
            }

            async Task ShowIcon()
            {
                if ((ctx.System.AvatarUrl?.Trim() ?? "").Length > 0)
                {
                    var eb = new DiscordEmbedBuilder()
                        .WithTitle("System icon")
                        .WithImageUrl(ctx.System.AvatarUrl)
                        .WithDescription("To clear, use `pk;system icon clear`.");
                    await ctx.Reply(embed: eb.Build());
                }
                else
                    throw new PKSyntaxError("This system does not have an icon set. Set one by attaching an image to this command, or by passing an image URL or @mention.");
            }

            if (await ctx.MatchClear("your system's icon"))
                await ClearIcon();
            else if (await ctx.MatchImage() is {} img)
                await SetIcon(img);
            else
                await ShowIcon();
        }
        
        public async Task Delete(Context ctx) {
            ctx.CheckSystem();

            await ctx.Reply($"{Emojis.Warn} Are you sure you want to delete your system? If so, reply to this message with your system's ID (`{ctx.System.Hid}`).\n**Note: this action is permanent.**");
            if (!await ctx.ConfirmWithReply(ctx.System.Hid))
                throw new PKError($"System deletion cancelled. Note that you must reply with your system ID (`{ctx.System.Hid}`) *verbatim*.");

            await _db.Execute(conn => _repo.DeleteSystem(conn, ctx.System.Id));
            
            await ctx.Reply($"{Emojis.Success} System deleted.");
        }
        
        public async Task SystemProxy(Context ctx)
        {
            ctx.CheckSystem().CheckGuildContext();
            var gs = await _db.Execute(c => _repo.GetSystemGuild(c, ctx.GuildNew.Id, ctx.System.Id));

            bool newValue;
            if (ctx.Match("on", "enabled", "true", "yes")) newValue = true;
            else if (ctx.Match("off", "disabled", "false", "no")) newValue = false;
            else if (ctx.HasNext()) throw new PKSyntaxError("You must pass either \"on\" or \"off\".");
            else
            {
                if (gs.ProxyEnabled)
                    await ctx.Reply("Proxying in this server is currently **enabled** for your system. To disable it, type `pk;system proxy off`.");
                else
                    await ctx.Reply("Proxying in this server is currently **disabled** for your system. To enable it, type `pk;system proxy on`.");
                return;
            }

            var patch = new SystemGuildPatch {ProxyEnabled = newValue};
            await _db.Execute(conn => _repo.UpsertSystemGuild(conn, ctx.System.Id, ctx.GuildNew.Id, patch));

            if (newValue)
                await ctx.Reply($"Message proxying in this server ({ctx.GuildNew.Name.EscapeMarkdown()}) is now **enabled** for your system.");
            else
                await ctx.Reply($"Message proxying in this server ({ctx.GuildNew.Name.EscapeMarkdown()}) is now **disabled** for your system.");
        }
        
         public async Task SystemTimezone(Context ctx)
        {
            if (ctx.System == null) throw Errors.NoSystemError;

            if (await ctx.MatchClear())
            {
                var clearPatch = new SystemPatch {UiTz = "UTC"};
                await _db.Execute(conn => _repo.UpdateSystem(conn, ctx.System.Id, clearPatch));

                await ctx.Reply($"{Emojis.Success} System time zone cleared (set to UTC).");
                return;
            }
            
            var zoneStr = ctx.RemainderOrNull();
            if (zoneStr == null)
            {
                await ctx.Reply(
                    $"Your current system time zone is set to **{ctx.System.UiTz}**. It is currently **{SystemClock.Instance.GetCurrentInstant().FormatZoned(ctx.System)}** in that time zone. To change your system time zone, type `pk;s tz <zone>`.");
                return;
            }

            var zone = await FindTimeZone(ctx, zoneStr);
            if (zone == null) throw Errors.InvalidTimeZone(zoneStr);

            var currentTime = SystemClock.Instance.GetCurrentInstant().InZone(zone);
            var msg = $"This will change the system time zone to **{zone.Id}**. The current time is **{currentTime.FormatZoned()}**. Is this correct?";
            if (!await ctx.PromptYesNo(msg)) throw Errors.TimezoneChangeCancelled;
            
            var patch = new SystemPatch {UiTz = zone.Id};
            await _db.Execute(conn => _repo.UpdateSystem(conn, ctx.System.Id, patch));

            await ctx.Reply($"System time zone changed to **{zone.Id}**.");
        }

        public async Task SystemPrivacy(Context ctx)
        {
            ctx.CheckSystem();

            Task PrintEmbed()
            {
                var eb = new DiscordEmbedBuilder()
                    .WithTitle("Current privacy settings for your system")
                    .AddField("Description", ctx.System.DescriptionPrivacy.Explanation())
                    .AddField("Member list", ctx.System.MemberListPrivacy.Explanation())
                    .AddField("Group list", ctx.System.GroupListPrivacy.Explanation())
                    .AddField("Current fronter(s)", ctx.System.FrontPrivacy.Explanation())
                    .AddField("Front/switch history", ctx.System.FrontHistoryPrivacy.Explanation())
                    .WithDescription("To edit privacy settings, use the command:\n`pk;system privacy <subject> <level>`\n\n- `subject` is one of `description`, `list`, `front`, `fronthistory`, `groups`, or `all` \n- `level` is either `public` or `private`.");
                return ctx.Reply(embed: eb.Build());
            }

            async Task SetLevel(SystemPrivacySubject subject, PrivacyLevel level)
            {
                await _db.Execute(conn => _repo.UpdateSystem(conn, ctx.System.Id, new SystemPatch().WithPrivacy(subject, level)));

                var levelExplanation = level switch
                {
                    PrivacyLevel.Public => "be able to query",
                    PrivacyLevel.Private => "*not* be able to query",
                    _ => ""
                };

                var subjectStr = subject switch
                {
                    SystemPrivacySubject.Description => "description",
                    SystemPrivacySubject.Front => "front",
                    SystemPrivacySubject.FrontHistory => "front history",
                    SystemPrivacySubject.MemberList => "member list",
                    SystemPrivacySubject.GroupList => "group list",
                    _ => ""
                };

                var msg = $"System {subjectStr} privacy has been set to **{level.LevelName()}**. Other accounts will now {levelExplanation} your system {subjectStr}.";
                await ctx.Reply($"{Emojis.Success} {msg}");
            }

            async Task SetAll(PrivacyLevel level)
            {
                await _db.Execute(conn => _repo.UpdateSystem(conn, ctx.System.Id, new SystemPatch().WithAllPrivacy(level)));

                var msg = level switch
                {
                    PrivacyLevel.Private => $"All system privacy settings have been set to **{level.LevelName()}**. Other accounts will now not be able to view your member list, group list, front history, or system description.",
                    PrivacyLevel.Public => $"All system privacy settings have been set to **{level.LevelName()}**. Other accounts will now be able to view everything.",
                    _ => ""
                };

                await ctx.Reply($"{Emojis.Success} {msg}");
            }

            if (!ctx.HasNext())
                await PrintEmbed();
            else if (ctx.Match("all"))
                await SetAll(ctx.PopPrivacyLevel());
            else
                await SetLevel(ctx.PopSystemPrivacySubject(), ctx.PopPrivacyLevel());
        }

        public async Task SystemPing(Context ctx) 
	    {
	        ctx.CheckSystem();

	        if (!ctx.HasNext()) 
	        {
		        if (ctx.System.PingsEnabled) {await ctx.Reply("Reaction pings are currently **enabled** for your system. To disable reaction pings, type `pk;s ping disable`.");}
		        else {await ctx.Reply("Reaction pings are currently **disabled** for your system. To enable reaction pings, type `pk;s ping enable`.");}
	        }
            else {
                if (ctx.Match("on", "enable")) {
                    var patch = new SystemPatch {PingsEnabled = true};
                    await _db.Execute(conn => _repo.UpdateSystem(conn, ctx.System.Id, patch));
                    
                    await ctx.Reply("Reaction pings have now been enabled.");
                }
                if (ctx.Match("off", "disable")) {
                    var patch = new SystemPatch {PingsEnabled = false};
                    await _db.Execute(conn => _repo.UpdateSystem(conn, ctx.System.Id, patch));
                    
                    await ctx.Reply("Reaction pings have now been disabled.");
                }
            }
	    }

        public async Task<DateTimeZone> FindTimeZone(Context ctx, string zoneStr) {
            // First, if we're given a flag emoji, we extract the flag emoji code from it.
            zoneStr = Core.StringUtils.ExtractCountryFlag(zoneStr) ?? zoneStr;
            
            // Then, we find all *locations* matching either the given country code or the country name.
            var locations = TzdbDateTimeZoneSource.Default.Zone1970Locations;
            var matchingLocations = locations.Where(l => l.Countries.Any(c =>
                string.Equals(c.Code, zoneStr, StringComparison.InvariantCultureIgnoreCase) ||
                string.Equals(c.Name, zoneStr, StringComparison.InvariantCultureIgnoreCase)));
            
            // Then, we find all (unique) time zone IDs that match.
            var matchingZones = matchingLocations.Select(l => DateTimeZoneProviders.Tzdb.GetZoneOrNull(l.ZoneId))
                .Distinct().ToList();
            
            // If the set of matching zones is empty (ie. we didn't find anything), we try a few other things.
            if (matchingZones.Count == 0)
            {
                // First, we try to just find the time zone given directly and return that.
                var givenZone = DateTimeZoneProviders.Tzdb.GetZoneOrNull(zoneStr);
                if (givenZone != null) return givenZone;

                // If we didn't find anything there either, we try parsing the string as an offset, then
                // find all possible zones that match that offset. For an offset like UTC+2, this doesn't *quite*
                // work, since there are 57(!) matching zones (as of 2019-06-13) - but for less populated time zones
                // this could work nicely.
                var inputWithoutUtc = zoneStr.Replace("UTC", "").Replace("GMT", "");

                var res = OffsetPattern.CreateWithInvariantCulture("+H").Parse(inputWithoutUtc);
                if (!res.Success) res = OffsetPattern.CreateWithInvariantCulture("+H:mm").Parse(inputWithoutUtc);

                // If *this* didn't parse correctly, fuck it, bail.
                if (!res.Success) return null;
                var offset = res.Value;

                // To try to reduce the count, we go by locations from the 1970+ database instead of just the full database
                // This elides regions that have been identical since 1970, omitting small distinctions due to Ancient History(tm).
                var allZones = TzdbDateTimeZoneSource.Default.Zone1970Locations.Select(l => l.ZoneId).Distinct();
                matchingZones = allZones.Select(z => DateTimeZoneProviders.Tzdb.GetZoneOrNull(z))
                    .Where(z => z.GetUtcOffset(SystemClock.Instance.GetCurrentInstant()) == offset).ToList();
            }
            
            // If we have a list of viable time zones, we ask the user which is correct.
            
            // If we only have one, return that one.
            if (matchingZones.Count == 1)
                return matchingZones.First();
            
            // Otherwise, prompt and return!
            return await ctx.Choose("There were multiple matches for your time zone query. Please select the region that matches you the closest:", matchingZones,
                z =>
                {
                    if (TzdbDateTimeZoneSource.Default.Aliases.Contains(z.Id))
                        return $"**{z.Id}**, {string.Join(", ", TzdbDateTimeZoneSource.Default.Aliases[z.Id])}";

                    return $"**{z.Id}**";
                });
        }
    }
}