// 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 System.Text.RegularExpressions;
using Catalogger.Backend.Cache.InMemoryCache;
using Catalogger.Backend.Database;
using Catalogger.Backend.Database.Models;
using Catalogger.Backend.Database.Queries;
using Catalogger.Backend.Extensions;
using Catalogger.Backend.Services;
using Humanizer;
using Remora.Discord.API.Abstractions.Gateway.Events;
using Remora.Discord.Gateway.Responders;
using Remora.Results;

namespace Catalogger.Backend.Bot.Responders.Messages;

public class MessageCreateResponder(
    ILogger logger,
    Config config,
    DatabaseContext db,
    MessageRepository messageRepository,
    UserCache userCache,
    PkMessageHandler pkMessageHandler
) : IResponder<IMessageCreate>
{
    private readonly ILogger _logger = logger.ForContext<MessageCreateResponder>();

    public async Task<Result> RespondAsync(IMessageCreate msg, CancellationToken ct = default)
    {
        userCache.UpdateUser(msg.Author);
        CataloggerMetrics.MessagesReceived.Inc();

        if (!msg.GuildID.IsDefined())
        {
            _logger.Debug(
                "Received message create event for message {MessageId} despite it not being in a guild",
                msg.ID
            );
            return Result.Success;
        }

        var guild = await db.GetGuildAsync(msg.GuildID, ct);
        // The guild needs to have enabled at least one of the message logging events,
        // and the channel must not be ignored, to store the message.
        if (guild.IsMessageIgnored(msg.ChannelID, msg.Author.ID))
        {
            db.IgnoredMessages.Add(new IgnoredMessage(msg.ID.ToUlong()));
            await db.SaveChangesAsync(ct);
            return Result.Success;
        }

        if (msg.Author.ID == DiscordUtils.PkUserId)
            _ = pkMessageHandler.HandlePkMessageAsync(msg);
        if (msg.ApplicationID.Is(DiscordUtils.PkUserId))
            _ = pkMessageHandler.HandleProxiedMessageAsync(msg.ID.Value);
        else if (msg.ApplicationID.HasValue && msg.ApplicationID.Is(config.Discord.ApplicationId))
        {
            db.IgnoredMessages.Add(new IgnoredMessage(msg.ID.Value));
            await db.SaveChangesAsync(ct);
            return Result.Success;
        }

        await messageRepository.SaveMessageAsync(msg, ct);
        return Result.Success;
    }
}

public partial class PkMessageHandler(ILogger logger, IServiceProvider services)
{
    private readonly ILogger _logger = logger.ForContext<PkMessageHandler>();

    [GeneratedRegex(
        @"^System ID: (\w{5,6}) \| Member ID: (\w{5,6}) \| Sender: .+ \((\d+)\) \| Message ID: (\d+) \| Original Message ID: (\d+)$"
    )]
    private static partial Regex FooterRegex();

    [GeneratedRegex(@"^https:\/\/discord.com\/channels\/\d+\/(\d+)\/\d+$")]
    private static partial Regex LinkRegex();

    public async Task HandlePkMessageAsync(IMessageCreate msg)
    {
        _logger.Debug("Received PluralKit message");

        await Task.Delay(500.Milliseconds());

        _logger.Debug("Starting handling PluralKit message");

        // Check if the content matches a Discord link--if not, it's not a log message (we already check if this is a PluralKit message earlier)
        if (!LinkRegex().IsMatch(msg.Content))
        {
            _logger.Debug("PluralKit message is not a log message because content is not a link");
            return;
        }

        // The first (only, I think always?) embed's footer must match the expected format
        var firstEmbed = msg.Embeds.FirstOrDefault();
        if (
            firstEmbed == null
            || !firstEmbed.Footer.TryGet(out var footer)
            || !FooterRegex().IsMatch(footer.Text)
        )
        {
            _logger.Debug(
                "PK message is not a log message because there is no first embed or its footer doesn't match the regex"
            );
            return;
        }

        var match = FooterRegex().Match(footer.Text);

        if (!ulong.TryParse(match.Groups[3].Value, out var authorId))
        {
            _logger.Debug(
                "Author ID in PluralKit log {LogMessageId} was not a valid snowflake",
                msg.ID
            );
            return;
        }

        if (!ulong.TryParse(match.Groups[4].Value, out var msgId))
        {
            _logger.Debug(
                "Message ID in PluralKit log {LogMessageId} was not a valid snowflake",
                msg.ID
            );
            return;
        }

        if (!ulong.TryParse(match.Groups[5].Value, out var originalId))
        {
            _logger.Debug(
                "Original ID in PluralKit log {LogMessageId} was not a valid snowflake",
                msg.ID
            );
            return;
        }

        await using var scope = services.CreateAsyncScope();
        await using var db = scope.ServiceProvider.GetRequiredService<DatabaseContext>();
        var messageRepository = scope.ServiceProvider.GetRequiredService<MessageRepository>();

        await messageRepository.SetProxiedMessageDataAsync(
            msgId,
            originalId,
            authorId,
            systemId: match.Groups[1].Value,
            memberId: match.Groups[2].Value
        );

        db.IgnoredMessages.Add(new IgnoredMessage(originalId));
        await db.SaveChangesAsync();
    }

    public async Task HandleProxiedMessageAsync(ulong msgId)
    {
        await Task.Delay(3.Seconds());

        await using var scope = services.CreateAsyncScope();
        await using var db = scope.ServiceProvider.GetRequiredService<DatabaseContext>();
        var messageRepository = scope.ServiceProvider.GetRequiredService<MessageRepository>();
        var pluralkitApi = scope.ServiceProvider.GetRequiredService<PluralkitApiService>();

        var (isStored, hasProxyInfo) = await messageRepository.HasProxyInfoAsync(msgId);
        if (!isStored)
        {
            _logger.Debug("Message with ID {MessageId} is not stored in the database", msgId);
            return;
        }

        if (hasProxyInfo)
            return;

        var pkMessage = await pluralkitApi.GetPluralKitMessageAsync(msgId);
        if (pkMessage == null)
        {
            _logger.Debug(
                "Message with ID {MessageId} was proxied by PluralKit, but API returned 404",
                msgId
            );
            return;
        }

        await messageRepository.SetProxiedMessageDataAsync(
            msgId,
            pkMessage.Original,
            pkMessage.Sender,
            pkMessage.System?.Id,
            pkMessage.Member?.Id
        );

        db.IgnoredMessages.Add(new IgnoredMessage(pkMessage.Original));
        await db.SaveChangesAsync();
    }
}