// Copyright (C) 2021-present sam (starshines.gay)
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

using Catalogger.Backend.Cache.InMemoryCache;
using Catalogger.Backend.Database;
using Catalogger.Backend.Database.Queries;
using Catalogger.Backend.Extensions;
using Catalogger.Backend.Services;
using Remora.Discord.API;
using Remora.Discord.API.Abstractions.Gateway.Events;
using Remora.Discord.API.Abstractions.Objects;
using Remora.Discord.Extensions.Embeds;
using Remora.Discord.Gateway.Responders;
using Remora.Results;

namespace Catalogger.Backend.Bot.Responders.Guilds;

public class GuildEmojisUpdateResponder(
    ILogger logger,
    DatabaseContext db,
    EmojiCache emojiCache,
    WebhookExecutorService webhookExecutor
) : IResponder<IGuildEmojisUpdate>
{
    private readonly ILogger _logger = logger.ForContext<GuildEmojisUpdateResponder>();

    public async Task<Result> RespondAsync(IGuildEmojisUpdate evt, CancellationToken ct = default)
    {
        try
        {
            if (!emojiCache.TryGet(evt.GuildID, out var oldEmoji))
            {
                _logger.Information(
                    "Previous emoji for {GuildId} were not in cache, ignoring event",
                    evt.GuildID
                );
                return Result.Success;
            }

            IEmbed embed;

            // As far as I know, only one emoji can be added or removed at once.
            var added = evt.Emojis.FirstOrDefault(e => oldEmoji.All(o => o.ID != e.ID));
            var removed = oldEmoji.FirstOrDefault(o => evt.Emojis.All(e => o.ID != e.ID));
            var updated = evt.Emojis.FirstOrDefault(e =>
                oldEmoji.Any(o => o.ID == e.ID && o.Name != e.Name)
            );
            if (added != null)
            {
                var url = CDN.GetEmojiUrl(added).GetOrThrow().ToString();
                embed = new EmbedBuilder()
                    .WithTitle("Emoji created")
                    .WithDescription($"{FormatEmoji(added)} [{added.Name}]({url})")
                    .WithThumbnailUrl(url)
                    .WithFooter($"ID: {added.ID}")
                    .WithColour(DiscordUtils.Green)
                    .WithCurrentTimestamp()
                    .Build()
                    .GetOrThrow();
            }
            else if (removed != null)
            {
                var url = CDN.GetEmojiUrl(removed).GetOrThrow().ToString();
                embed = new EmbedBuilder()
                    .WithTitle("Emoji removed")
                    .WithDescription($"[{removed.Name}]({url})")
                    .WithThumbnailUrl(url)
                    .WithFooter($"ID: {removed.ID}")
                    .WithColour(DiscordUtils.Red)
                    .WithCurrentTimestamp()
                    .Build()
                    .GetOrThrow();
            }
            else if (updated != null)
            {
                var url = CDN.GetEmojiUrl(updated).GetOrThrow().ToString();
                var previous = oldEmoji.First(o => o.ID == updated.ID);
                embed = new EmbedBuilder()
                    .WithTitle("Emoji renamed")
                    .WithDescription(
                        $"""
                        {FormatEmoji(updated)} [{updated.Name}]({url})
                        {previous.Name} → {updated.Name}
                        """
                    )
                    .WithThumbnailUrl(url)
                    .WithFooter($"ID: {updated.ID}")
                    .WithColour(DiscordUtils.Green)
                    .WithCurrentTimestamp()
                    .Build()
                    .GetOrThrow();
            }
            else
            {
                _logger.Warning(
                    "Received emoji update event for {GuildId} but all emoji were identical, not logging",
                    evt.GuildID
                );
                return Result.Success;
            }

            var guildConfig = await db.GetGuildAsync(evt.GuildID, false, ct);
            webhookExecutor.QueueLog(guildConfig, LogChannelType.GuildEmojisUpdate, embed);
            return Result.Success;
        }
        finally
        {
            emojiCache.Set(evt.GuildID, evt.Emojis);
        }
    }

    private static string FormatEmoji(IEmoji emoji) =>
        emoji.IsAnimated.OrDefault(false)
            ? $"<a:{emoji.Name}:{emoji.ID}>"
            : $"<:{emoji.Name}:{emoji.ID}>";
}