GmRelayBot/src/GmRelay.Bot/Features/Sessions/CreateSession/JoinSessionHandler.cs

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

namespace GmRelay.Bot.Features.Sessions.CreateSession;

public sealed record JoinSessionCommand(
    Guid SessionId,
    long TelegramUserId,
    string DisplayName,
    string? TelegramUsername,
    string CallbackQueryId,
    long ChatId,
    int MessageId);

// DTOs for AOT compilation
internal sealed record JoinSessionBatchDto(Guid BatchId, string Title, int? MaxPlayers);

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

        try
        {
            // 1. Убеждаемся, что игрок есть в базе
            var playerId = await connection.ExecuteScalarAsync<Guid>(
                @"INSERT INTO players (telegram_id, display_name, telegram_username) 
                  VALUES (@TgId, @Name, @Username)
                  ON CONFLICT (telegram_id) DO UPDATE SET display_name = EXCLUDED.display_name, telegram_username = EXCLUDED.telegram_username
                  RETURNING id;",
                new { TgId = command.TelegramUserId, Name = command.DisplayName, Username = command.TelegramUsername },
                transaction);

            // 2. Блокируем сессию на время расчета мест, чтобы параллельные нажатия не переполнили состав.
            var batchInfo = await connection.QuerySingleOrDefaultAsync<JoinSessionBatchDto>(
                @"SELECT batch_id as BatchId, title as Title, max_players as MaxPlayers
                  FROM sessions
                  WHERE id = @SessionId
                  FOR UPDATE",
                new { command.SessionId },
                transaction);

            if (batchInfo is null)
            {
                await transaction.RollbackAsync(ct);
                await bot.AnswerCallbackQuery(command.CallbackQueryId, "Сессия не найдена.", cancellationToken: ct);
                return;
            }

            var existingRegistrationStatus = await connection.ExecuteScalarAsync<string?>(
                """
                SELECT sp.registration_status
                FROM session_participants sp
                WHERE sp.session_id = @SessionId
                  AND sp.player_id = @PlayerId
                  AND sp.is_gm = false
                """,
                new { command.SessionId, PlayerId = playerId },
                transaction);

            if (existingRegistrationStatus is not null)
            {
                await transaction.RollbackAsync(ct);
                var alreadyText = existingRegistrationStatus == ParticipantRegistrationStatus.Waitlisted
                    ? "Вы уже в листе ожидания!"
                    : "Вы уже записаны!";
                await bot.AnswerCallbackQuery(command.CallbackQueryId, alreadyText, cancellationToken: ct);
                return;
            }

            var activeParticipants = await connection.ExecuteScalarAsync<int>(
                """
                SELECT COUNT(*)
                FROM session_participants
                WHERE session_id = @SessionId
                  AND is_gm = false
                  AND registration_status = @Active
                """,
                new { command.SessionId, Active = ParticipantRegistrationStatus.Active },
                transaction);

            var registrationStatus = SessionCapacityRules.DecideJoinStatus(batchInfo.MaxPlayers, activeParticipants);

            // 3. Добавляем в основной состав или лист ожидания. RSVP остается Pending до финального подтверждения.
            var inserted = await connection.ExecuteAsync(
                @"INSERT INTO session_participants (session_id, player_id, is_gm, rsvp_status, registration_status)
                  VALUES (@SessionId, @PlayerId, false, @Pending, @RegistrationStatus)
                  ON CONFLICT (session_id, player_id) DO NOTHING;",
                new
                {
                    command.SessionId,
                    PlayerId = playerId,
                    Pending = RsvpStatus.Pending,
                    RegistrationStatus = registrationStatus
                },
                transaction);

            if (inserted == 0)
            {
                await transaction.RollbackAsync(ct);
                await bot.AnswerCallbackQuery(command.CallbackQueryId, "Вы уже записаны!", cancellationToken: ct);
                return;
            }

            // Загружаем весь батч для перерисовки
            var batchSessions = await connection.QueryAsync<SessionBatchDto>(
                @"SELECT id as SessionId, scheduled_at as ScheduledAt, status as Status, max_players as MaxPlayers
                  FROM sessions
                  WHERE batch_id = @BatchId
                  ORDER BY scheduled_at",
                new { BatchId = batchInfo.BatchId }, transaction);

            var batchParticipants = await connection.QueryAsync<ParticipantBatchDto>(
                @"SELECT sp.session_id as SessionId,
                         p.display_name as DisplayName,
                         p.telegram_username as TelegramUsername,
                         sp.registration_status as RegistrationStatus
                  FROM session_participants sp
                  JOIN players p ON sp.player_id = p.id
                  JOIN sessions s ON sp.session_id = s.id
                  WHERE s.batch_id = @BatchId AND sp.is_gm = false
                  ORDER BY sp.registration_status ASC, sp.created_at ASC, sp.responded_at ASC, p.created_at ASC",
                new { BatchId = batchInfo.BatchId }, transaction);

            await transaction.CommitAsync(ct);
            transactionCommitted = true;

            // 4. Перерисовываем сообщение
            var renderResult = SessionBatchRenderer.Render(batchInfo.Title, batchSessions.ToList(), batchParticipants.ToList());

            await bot.EditMessageText(
                chatId: command.ChatId,
                messageId: command.MessageId,
                text: renderResult.Text,
                parseMode: Telegram.Bot.Types.Enums.ParseMode.Html,
                replyMarkup: renderResult.Markup,
                cancellationToken: ct);

            var callbackText = registrationStatus == ParticipantRegistrationStatus.Waitlisted
                ? "Основной состав заполнен. Вы добавлены в лист ожидания."
                : "Вы успешно записаны!";
            await bot.AnswerCallbackQuery(command.CallbackQueryId, callbackText, cancellationToken: ct);
        }
        catch (Exception ex)
        {
            logger.LogError(ex, "Ошибка при добавлении игрока к сессии");
            if (!transactionCommitted)
            {
                await transaction.RollbackAsync(ct);
            }

            var errorText = transactionCommitted
                ? "Регистрация сохранена, но не удалось обновить сообщение расписания."
                : "Произошла ошибка при регистрации.";
            await bot.AnswerCallbackQuery(command.CallbackQueryId, errorText, cancellationToken: ct);
        }
    }
}