using System;
using System.Collections.Concurrent;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.SignalR;
using Microsoft.Extensions.Logging;

namespace FinlyticBackend.Hubs;

/// <summary>
/// SignalR Hub streaming real-time stock prices & daily % growth updates for favorite assets every 10 seconds.
/// </summary>
[Authorize]
public class FavoritesPriceHub : Hub
{
    private readonly ILogger<FavoritesPriceHub> _logger;

    // Speichert thread-sicher, wie viele aktive Verbindungen ein User hat (UserId -> ConnectionCount)
    private static readonly ConcurrentDictionary<string, int> ActiveUserConnections = new();

    public FavoritesPriceHub(ILogger<FavoritesPriceHub> logger)
    {
        _logger = logger;
    }

    /// <summary>
    /// Liefert eine Übersicht aller aktuell mit dem Hub verbundenen User-IDs.
    /// </summary>
    public static string[] GetActiveUserIds() => [.. ActiveUserConnections.Keys];

    public override async Task OnConnectedAsync()
    {
        var userId = Context.UserIdentifier;

        if (!string.IsNullOrEmpty(userId))
        {
            // Füge die Verbindung der benutzerspezifischen Gruppe hinzu
            await Groups.AddToGroupAsync(Context.ConnectionId, GetGroupName(userId));

            ActiveUserConnections.AddOrUpdate(userId, 1, (_, count) => count + 1);

            _logger.LogInformation("[FavoritesPriceHub] User '{UserId}' connected (ConnectionId={ConnectionId}). Active connections for user: {Count}",
                userId, Context.ConnectionId, ActiveUserConnections[userId]);
        }
        else
        {
            _logger.LogWarning("[FavoritesPriceHub] Anonymous SignalR client connected without UserIdentifier: ConnectionId={ConnectionId}", Context.ConnectionId);
        }

        await base.OnConnectedAsync();
    }

    public override async Task OnDisconnectedAsync(Exception? exception)
    {
        var userId = Context.UserIdentifier;

        if (!string.IsNullOrEmpty(userId))
        {
            await Groups.RemoveFromGroupAsync(Context.ConnectionId, GetGroupName(userId));

            ActiveUserConnections.AddOrUpdate(userId, 0, (_, count) =>
            {
                var newCount = count - 1;
                return newCount < 0 ? 0 : newCount;
            });

            // Wenn keine aktiven Verbindungen mehr bestehen, aus Dictionary entfernen
            if (ActiveUserConnections.TryGetValue(userId, out var remainingCount) && remainingCount <= 0)
            {
                ActiveUserConnections.TryRemove(userId, out _);
            }

            _logger.LogInformation("[FavoritesPriceHub] User '{UserId}' disconnected (ConnectionId={ConnectionId})", userId, Context.ConnectionId);
        }

        await base.OnDisconnectedAsync(exception);
    }

    public static string GetGroupName(string userId) => $"User_{userId.Trim()}";
}