GmRelayBot/src/GmRelay.Bot/Features/Sessions/ListSessions/DeleteSessionHandler.cs

using Dapper;
using Npgsql;
using Telegram.Bot;
using GmRelay.Shared.Domain;

namespace GmRelay.Bot.Features.Sessions.ListSessions;

public sealed record DeleteSessionCommand(
    Guid SessionId,
    long TelegramUserId,
    string CallbackQueryId,
    long ChatId,
    int MessageId);

internal sealed record DeleteSessionInfoDto(string Title, Guid BatchId, long GmId, int? ThreadId);

public sealed class DeleteSessionHandler(
    NpgsqlDataSource dataSource,
    ITelegramBotClient bot,
    ILogger<DeleteSessionHandler> logger)
{
    public async Task HandleAsync(DeleteSessionCommand command, CancellationToken ct)
    {
        await using var connection = await dataSource.OpenConnectionAsync(ct);
        await using var transaction = await connection.BeginTransactionAsync(ct);

        // 1. Fetch session and verify GM
        var session = await connection.QuerySingleOrDefaultAsync<DeleteSessionInfoDto>(
            @"SELECT s.title as Title, s.batch_id as BatchId, s.thread_id as ThreadId, g.gm_telegram_id as GmId
              FROM sessions s
              JOIN game_groups g ON s.group_id = g.id
              WHERE s.id = @SessionId",
            new { command.SessionId }, transaction);

        if (session == null)
        {
            await bot.AnswerCallbackQuery(command.CallbackQueryId, "Сессия не найдена.", cancellationToken: ct);
            return;
        }

        if (session.GmId != command.TelegramUserId)
        {
            await bot.AnswerCallbackQuery(command.CallbackQueryId, "Только Мастер Игры (GM) может удалять сессию.", showAlert: true, cancellationToken: ct);
            return;
        }

        // 2. Delete session
        await connection.ExecuteAsync("DELETE FROM sessions WHERE id = @Id", new { Id = command.SessionId }, transaction);

        // 3. Check if any sessions are left in the batch
        var remainingInBatch = await connection.ExecuteScalarAsync<int>(
            "SELECT COUNT(*) FROM sessions WHERE batch_id = @BatchId",
            new { BatchId = session.BatchId }, transaction);

        await transaction.CommitAsync(ct);

        // 4. If no sessions left and we have a forum topic, delete the topic
        if (remainingInBatch == 0 && session.ThreadId.HasValue)
        {
            try
            {
                await bot.DeleteForumTopic(command.ChatId, session.ThreadId.Value, cancellationToken: ct);
                logger.LogInformation("Deleted forum topic {ThreadId} for batch {BatchId} as no sessions remained.", session.ThreadId.Value, session.BatchId);
            }
            catch (Exception ex)
            {
                logger.LogWarning(ex, "Failed to delete forum topic {ThreadId}", session.ThreadId.Value);
            }
        }

        await bot.AnswerCallbackQuery(command.CallbackQueryId, "Сессия удалена!", cancellationToken: ct);

        // 5. Update the /listsessions message (we delete the message or edit it to remove the button)
        // A simple way is to re-render the list:
        await using var readConnection = await dataSource.OpenConnectionAsync(ct);
        var sessions = await readConnection.QueryAsync<SessionListItemDto>(
            @"SELECT s.id as Id, s.title as Title, s.scheduled_at as ScheduledAt, s.status as Status, 
                     COUNT(sp.id) FILTER (WHERE sp.is_gm = false) as PlayerCount,
                     g.gm_telegram_id as GmId
              FROM sessions s
              JOIN game_groups g ON s.group_id = g.id
              LEFT JOIN session_participants sp ON s.id = sp.session_id
              WHERE g.telegram_chat_id = @ChatId AND s.status != @Cancelled AND s.scheduled_at > NOW()
              GROUP BY s.id, s.title, s.scheduled_at, s.status, g.gm_telegram_id
              ORDER BY s.scheduled_at ASC",
            new { ChatId = command.ChatId, Cancelled = SessionStatus.Cancelled });

        var sessionsList = sessions.ToList();

        if (sessionsList.Count == 0)
        {
            try { await bot.EditMessageText(command.ChatId, command.MessageId, "📭 В этой группе нет предстоящих игр.", cancellationToken: ct); } catch {}
            return;
        }

        var text = "📅 <b>Ближайшие игры:</b>\n\n";
        foreach (var s in sessionsList)
        {
            text += $"🔹 <b>{s.ScheduledAt.FormatMoscow()}</b> — {System.Net.WebUtility.HtmlEncode(s.Title)} (Участников: {s.PlayerCount})\n";
        }

        var isGm = command.TelegramUserId == sessionsList.First().GmId;
        var keyboard = isGm 
            ? new Telegram.Bot.Types.ReplyMarkups.InlineKeyboardMarkup(
                sessionsList.Select(s => new[] { Telegram.Bot.Types.ReplyMarkups.InlineKeyboardButton.WithCallbackData($"🗑 Удалить {s.ScheduledAt.FormatMoscowShort()}", $"delete_session:{s.Id}") }))
            : null;

        try
        {
            await bot.EditMessageText(
                command.ChatId,
                command.MessageId,
                text,
                parseMode: Telegram.Bot.Types.Enums.ParseMode.Html,
                replyMarkup: keyboard,
                cancellationToken: ct);
        }
        catch (Exception ex)
        {
            logger.LogWarning(ex, "Failed to edit list sessions message");
        }
    }
}