using System;
using System.Linq;
using System.Threading.Tasks;
using Discord;
using Humanizer;
using NodaTime;
using NodaTime.Text;
using NodaTime.TimeZones;

using PluralKit.Bot.CommandSystem;
using PluralKit.Core;

namespace PluralKit.Bot.Commands
{
    public class SystemCommands
    {
        private SystemStore _systems;
        private MemberStore _members;

        private SwitchStore _switches;
        private EmbedService _embeds;

        private ProxyCacheService _proxyCache;

        public SystemCommands(SystemStore systems, MemberStore members, SwitchStore switches, EmbedService embeds, ProxyCacheService proxyCache)
        {
            _systems = systems;
            _members = members;
            _switches = switches;
            _embeds = embeds;
            _proxyCache = proxyCache;
        }
        
        public async Task Query(Context ctx, PKSystem system) {
            if (system == null) throw Errors.NoSystemError;

            await ctx.Reply(embed: await _embeds.CreateSystemEmbed(system));
        }
        
        public async Task New(Context ctx)
        {
            ctx.CheckNoSystem();

            var system = await _systems.Create(ctx.RemainderOrNull());
            await _systems.Link(system, ctx.Author.Id);
            await ctx.Reply($"{Emojis.Success} Your system has been created. Type `pk;system` to view it, and type `pk;help` for more information about commands you can use now.");
        }
        
        public async Task Name(Context ctx)
        {
            ctx.CheckSystem();

            var newSystemName = ctx.RemainderOrNull();
            if (newSystemName != null && newSystemName.Length > Limits.MaxSystemNameLength) throw Errors.SystemNameTooLongError(newSystemName.Length);

            ctx.System.Name = newSystemName;
            await _systems.Save(ctx.System);
            await ctx.Reply($"{Emojis.Success} System name {(newSystemName != null ? "changed" : "cleared")}.");
        }
        
        public async Task Description(Context ctx) {
            ctx.CheckSystem();

            var newDescription = ctx.RemainderOrNull();
            if (newDescription != null && newDescription.Length > Limits.MaxDescriptionLength) throw Errors.DescriptionTooLongError(newDescription.Length);

            ctx.System.Description = newDescription;
            await _systems.Save(ctx.System);
            await ctx.Reply($"{Emojis.Success} System description {(newDescription != null ? "changed" : "cleared")}.");
        }
        
        public async Task Tag(Context ctx)
        {
            ctx.CheckSystem();

            var newTag = ctx.RemainderOrNull();
            ctx.System.Tag = newTag;

            if (newTag != null)
            {
                if (newTag.Length > Limits.MaxSystemTagLength) throw Errors.SystemNameTooLongError(newTag.Length);

                // Check unproxyable messages *after* changing the tag (so it's seen in the method) but *before* we save to DB (so we can cancel)
                var unproxyableMembers = await _members.GetUnproxyableMembers(ctx.System);
                if (unproxyableMembers.Count > 0)
                {
                    var msg = await ctx.Reply(
                        $"{Emojis.Warn} Changing your system tag to '{newTag}' will result in the following members being unproxyable, since the tag would bring their name over {Limits.MaxProxyNameLength} characters:\n**{string.Join(", ", unproxyableMembers.Select((m) => m.Name))}**\nDo you want to continue anyway?");
                    if (!await ctx.PromptYesNo(msg)) throw new PKError("Tag change cancelled.");
                }
            }

            await _systems.Save(ctx.System);
            await ctx.Reply($"{Emojis.Success} System tag {(newTag != null ? "changed" : "cleared")}.");
            
            await _proxyCache.InvalidateResultsForSystem(ctx.System);
        }
        
        public async Task SystemAvatar(Context ctx)
        {
            ctx.CheckSystem();

            var member = await ctx.MatchUser();
            if (member != null)
            {
                if (member.AvatarId == null) throw Errors.UserHasNoAvatar;
                ctx.System.AvatarUrl = member.GetAvatarUrl(ImageFormat.Png, size: 256);
                await _systems.Save(ctx.System);
            
                var embed = new EmbedBuilder().WithImageUrl(ctx.System.AvatarUrl).Build();
                await ctx.Reply(
                    $"{Emojis.Success} System avatar changed to {member.Username}'s avatar! {Emojis.Warn} Please note that if {member.Username} changes their avatar, the system's avatar will need to be re-set.", embed: embed);
            }
            else
            {
                string url = ctx.RemainderOrNull() ?? ctx.Message.Attachments.FirstOrDefault()?.ProxyUrl;
                if (url != null) await ctx.BusyIndicator(() => Utils.VerifyAvatarOrThrow(url));

                ctx.System.AvatarUrl = url;
                await _systems.Save(ctx.System);

                var embed = url != null ? new EmbedBuilder().WithImageUrl(url).Build() : null;
                await ctx.Reply($"{Emojis.Success} System avatar {(url == null ? "cleared" : "changed")}.", embed: embed);
            }
            
            await _proxyCache.InvalidateResultsForSystem(ctx.System);
        }
        
        public async Task Delete(Context ctx) {
            ctx.CheckSystem();

            var msg = await ctx.Reply($"{Emojis.Warn} Are you sure you want to delete your system? If so, reply to this message with your system's ID (`{ctx.System.Hid}`).\n**Note: this action is permanent.**");
            var reply = await ctx.AwaitMessage(ctx.Channel, ctx.Author, timeout: TimeSpan.FromMinutes(1));
            if (reply.Content != ctx.System.Hid) throw new PKError($"System deletion cancelled. Note that you must reply with your system ID (`{ctx.System.Hid}`) *verbatim*.");

            await _systems.Delete(ctx.System);
            await ctx.Reply($"{Emojis.Success} System deleted.");
            
            await _proxyCache.InvalidateResultsForSystem(ctx.System);
        }
        
        public async Task MemberShortList(Context ctx, PKSystem system) {
            if (system == null) throw Errors.NoSystemError;

            var members = await _members.GetBySystem(system);
            var embedTitle = system.Name != null ? $"Members of {system.Name} (`{system.Hid}`)" : $"Members of `{system.Hid}`";
            await ctx.Paginate<PKMember>(
                members.OrderBy(m => m.Name).ToList(),
                25,
                embedTitle,
                (eb, ms) => eb.Description = string.Join("\n", ms.Select((m) => {
                    if (m.HasProxyTags) return $"[`{m.Hid}`] **{m.Name}** *({m.ProxyString})*";
                    return $"[`{m.Hid}`] **{m.Name}**";
                }))
            );
        }

        public async Task MemberLongList(Context ctx, PKSystem system) {
            if (system == null) throw Errors.NoSystemError;

            var members = await _members.GetBySystem(system);
            var embedTitle = system.Name != null ? $"Members of {system.Name} (`{system.Hid}`)" : $"Members of `{system.Hid}`";
            await ctx.Paginate<PKMember>(
                members.OrderBy(m => m.Name).ToList(),
                5,
                embedTitle,
                (eb, ms) => {
                    foreach (var m in ms) {
                        var profile = $"**ID**: {m.Hid}";
                        if (m.Pronouns != null) profile += $"\n**Pronouns**: {m.Pronouns}";
                        if (m.Birthday != null) profile += $"\n**Birthdate**: {m.BirthdayString}";
                        if (m.Prefix != null || m.Suffix != null) profile += $"\n**Proxy tags**: {m.ProxyString}";
                        if (m.Description != null) profile += $"\n\n{m.Description}";
                        eb.AddField(m.Name, profile.Truncate(1024));
                    }
                }
            );
        }
        
        public async Task SystemFronter(Context ctx, PKSystem system)
        {
            if (system == null) throw Errors.NoSystemError;
            
            var sw = await _switches.GetLatestSwitch(system);
            if (sw == null) throw Errors.NoRegisteredSwitches;
            
            await ctx.Reply(embed: await _embeds.CreateFronterEmbed(sw, system.Zone));
        }
        
        public async Task SystemFrontHistory(Context ctx, PKSystem system)
        {
            if (system == null) throw Errors.NoSystemError;

            var sws = (await _switches.GetSwitches(system, 10)).ToList();
            if (sws.Count == 0) throw Errors.NoRegisteredSwitches;
            
            await ctx.Reply(embed: await _embeds.CreateFrontHistoryEmbed(sws, system.Zone));
        }
        
        public async Task SystemFrontPercent(Context ctx, PKSystem system)
        {
            if (system == null) throw Errors.NoSystemError;

            string durationStr = ctx.RemainderOrNull() ?? "30d";
            
            var now = SystemClock.Instance.GetCurrentInstant();

            var rangeStart = PluralKit.Utils.ParseDateTime(durationStr);
            if (rangeStart == null) throw Errors.InvalidDateTime(durationStr);
            if (rangeStart.Value.ToInstant() > now) throw Errors.FrontPercentTimeInFuture;
            
            var frontpercent = await _switches.GetPerMemberSwitchDuration(system, rangeStart.Value.ToInstant(), now);
            await ctx.Reply(embed: await _embeds.CreateFrontPercentEmbed(frontpercent, system.Zone));
        }
        
        public async Task SystemTimezone(Context ctx)
        {
            if (ctx.System == null) throw Errors.NoSystemError;

            var zoneStr = ctx.RemainderOrNull();
            if (zoneStr == null)
            {
                ctx.System.UiTz = "UTC";
                await _systems.Save(ctx.System);
                await ctx.Reply($"{Emojis.Success} System time zone cleared.");
                return;
            }

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

            var currentTime = SystemClock.Instance.GetCurrentInstant().InZone(zone);
            var msg = await ctx.Reply(
                $"This will change the system time zone to {zone.Id}. The current time is {Formats.ZonedDateTimeFormat.Format(currentTime)}. Is this correct?");
            if (!await ctx.PromptYesNo(msg)) throw Errors.TimezoneChangeCancelled;
            ctx.System.UiTz = zone.Id;
            await _systems.Save(ctx.System);

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

        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 = PluralKit.Utils.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}**";
                });
        }
    }
}