bitforum-backend/Web.Api/Hubs/ChatHub.cs

using Application.Abstractions.Chat;
using Application.Abstractions.Data;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.SignalR;
using Microsoft.EntityFrameworkCore;
using Microsoft.IdentityModel.JsonWebTokens;
using System.Collections.Concurrent;

namespace Web.Api.Hubs;

[Authorize]
public sealed class ChatHub(IChatMessageStore messageStore, IServiceScopeFactory scopeFactory) : Hub<IChatHubClient>
{
    private static readonly ConcurrentDictionary<string, DateTime> _lastMessageTime = new();

    public override async Task OnConnectedAsync()
    {
        var messages = await messageStore.GetRecentMessagesAsync(ChatSettings.MaxMessages);
        await Clients.Caller.ReceiveHistory(messages);

        var memberName = GetMemberName();
        if (!string.IsNullOrEmpty(memberName))
        {
            await Clients.Others.ReceiveSystemMessage($"{memberName}님이 입장했습니다.");
        }

        await base.OnConnectedAsync();
    }

    public override async Task OnDisconnectedAsync(Exception? exception)
    {
        _lastMessageTime.TryRemove(Context.ConnectionId, out _);

        var memberName = GetMemberName();
        if (!string.IsNullOrEmpty(memberName))
        {
            await Clients.Others.ReceiveSystemMessage($"{memberName}님이 퇴장했습니다.");
        }

        await base.OnDisconnectedAsync(exception);
    }

    public async Task SendMessage(string content)
    {
        if (string.IsNullOrWhiteSpace(content))
        {
            return;
        }

        content = content.Trim();

        if (content.Length > ChatSettings.MaxContentLength)
        {
            return;
        }

        var now = DateTime.UtcNow;
        if (_lastMessageTime.TryGetValue(Context.ConnectionId, out var lastTime))
        {
            if ((now - lastTime).TotalSeconds < ChatSettings.RateLimitSeconds)
            {
                return;
            }
        }
        _lastMessageTime[Context.ConnectionId] = now;

        var memberID = GetMemberID();
        if (memberID is null)
        {
            return;
        }

        using var scope = scopeFactory.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<IAppDbContext>();
        var member = await db.Member.AsNoTracking().Where(x => x.ID == memberID.Value).Select(x => new { x.SID, x.Name }).FirstOrDefaultAsync();

        if (member is null)
        {
            return;
        }

        var message = new ChatMessage(
            memberID.Value,
            member.SID,
            member.Name ?? "익명",
            content,
            now
        );

        // 채팅 기록 저장
        await messageStore.AddMessageAsync(message);

        // 모든 클라이언트에게 메시지 전송
        await Clients.All.ReceiveMessage(message);
    }

    private int? GetMemberID()
    {
        var sub = Context.User?.FindFirst(JwtRegisteredClaimNames.Sub)?.Value;

        if (int.TryParse(sub, out var memberID))
        {
            return memberID;
        }

        return null;
    }

    private string? GetMemberName()
    {
        return Context.User?.FindFirst(JwtRegisteredClaimNames.Name)?.Value;
    }
}