feat: add session capacity waitlist

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

@@ -2,7 +2,6 @@ using Dapper;
 using Npgsql;
 using Telegram.Bot;
 using Telegram.Bot.Types;
-using Telegram.Bot.Types.ReplyMarkups;
 using GmRelay.Shared.Domain;
 using GmRelay.Shared.Rendering;
 
@@ -18,7 +17,7 @@ public sealed record JoinSessionCommand(
     int MessageId);
 
 // DTOs for AOT compilation
-internal sealed record JoinSessionBatchDto(Guid BatchId, string Title);
+internal sealed record JoinSessionBatchDto(Guid BatchId, string Title, int? MaxPlayers);
 
 public sealed class JoinSessionHandler(
     NpgsqlDataSource dataSource,
@@ -29,6 +28,7 @@ public sealed class JoinSessionHandler(
     {
         await using var connection = await dataSource.OpenConnectionAsync(ct);
         await using var transaction = await connection.BeginTransactionAsync(ct);
+        var transactionCommitted = false;
 
         try
         {
@@ -41,12 +41,68 @@ public sealed class JoinSessionHandler(
                 new { TgId = command.TelegramUserId, Name = command.DisplayName, Username = command.TelegramUsername },
                 transaction);
 
-            // 2. Добавляем в участники сессии (статус Pending, так как за 24 часа нужно будет финальное подтверждение)
+            // 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)
-                  VALUES (@SessionId, @PlayerId, false, 'Pending')
+                @"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 { SessionId = command.SessionId, PlayerId = playerId },
+                new
+                {
+                    command.SessionId,
+                    PlayerId = playerId,
+                    Pending = RsvpStatus.Pending,
+                    RegistrationStatus = registrationStatus
+                },
                 transaction);
 
             if (inserted == 0)
@@ -56,26 +112,28 @@ public sealed class JoinSessionHandler(
                 return;
             }
 
-            // 3. Получаем batch_id по session_id
-            var batchInfo = await connection.QuerySingleAsync<JoinSessionBatchDto>(
-                @"SELECT batch_id as BatchId, title as Title FROM sessions WHERE id = @SessionId",
-                new { command.SessionId }, transaction);
-
             // Загружаем весь батч для перерисовки
             var batchSessions = await connection.QueryAsync<SessionBatchDto>(
-                @"SELECT id as SessionId, scheduled_at as ScheduledAt, status as Status FROM sessions WHERE batch_id = @BatchId ORDER BY scheduled_at",
+                @"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 
+                @"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.responded_at ASC, p.created_at ASC",
+                  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());
@@ -88,13 +146,23 @@ public sealed class JoinSessionHandler(
                 replyMarkup: renderResult.Markup,
                 cancellationToken: ct);
 
-            await bot.AnswerCallbackQuery(command.CallbackQueryId, "Вы успешно записаны!", 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");
-            await transaction.RollbackAsync(ct);
-            await bot.AnswerCallbackQuery(command.CallbackQueryId, "Произошла ошибка при регистрации.", cancellationToken: ct);
+            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);
         }
     }
 }