PlotDirector/PlotLine/Hubs/WordCompanionFollowHub.cs

using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.SignalR;
using PlotLine.Models;
using PlotLine.Services;
using System.Security.Claims;

namespace PlotLine.Hubs;

[Authorize]
public sealed class WordCompanionFollowHub(IWordCompanionPresenceService presence) : Hub
{
    public override async Task OnConnectedAsync()
    {
        if (TryGetUserId(out var userId))
        {
            await Groups.AddToGroupAsync(Context.ConnectionId, PresenceGroup(userId));
        }

        await base.OnConnectedAsync();
    }

    public async Task<WordCompanionPresenceStatus> WatchCompanionPresence()
    {
        var userId = RequireUserId();
        await Groups.AddToGroupAsync(Context.ConnectionId, PresenceGroup(userId));
        return await presence.GetStatusAsync(userId);
    }

    public async Task<WordCompanionPresenceStatus> RegisterCompanion(WordCompanionPresenceRegistration registration)
    {
        var userId = RequireUserId();
        if (registration.UserID.HasValue && registration.UserID.Value != userId)
        {
            throw new HubException("The Companion is signed in as a different user.");
        }

        var status = await presence.RegisterAsync(userId, Context.ConnectionId, registration);
        await Clients.Group(PresenceGroup(userId)).SendAsync("WordCompanionPresenceChanged", status);
        return status;
    }

    public async Task<WordCompanionPresenceStatus> CompanionHeartbeat(WordCompanionPresenceHeartbeat heartbeat)
    {
        var userId = RequireUserId();
        var status = await presence.HeartbeatAsync(userId, Context.ConnectionId, heartbeat);
        await Clients.Group(PresenceGroup(userId)).SendAsync("WordCompanionPresenceChanged", status);
        return status;
    }

    public override async Task OnDisconnectedAsync(Exception? exception)
    {
        var status = await presence.DisconnectAsync(Context.ConnectionId);
        if (status is not null)
        {
            await Clients.Group(PresenceGroup(status.UserID)).SendAsync("WordCompanionPresenceChanged", status);
        }

        await base.OnDisconnectedAsync(exception);
    }

    private int RequireUserId()
        => TryGetUserId(out var userId) ? userId : throw new HubException("Sign in to use the Word Companion.");

    private bool TryGetUserId(out int userId)
        => int.TryParse(Context.User?.FindFirstValue(ClaimTypes.NameIdentifier), out userId);

    private static string PresenceGroup(int userId) => $"word-companion-presence:{userId}";
}