using Application.Abstractions.Cache;
using Application.Abstractions.Chat;
using Application.Abstractions.Hub;
using StackExchange.Redis;
using System.Text.Json;

namespace Infrastructure.Hubs;

/// <summary>
/// AppHub 전역 접속자 추적 (Redis 기반).
/// 단일 Hash `app:connections` 에 connectionId → ConnectedUser JSON 으로 기록 (게스트 포함).
/// </summary>
internal sealed class RedisVisitorTracker(IConnectionMultiplexer redis) : IVisitorTracker
{
    private readonly IDatabase _db = redis.GetDatabase();

    private static readonly JsonSerializerOptions _jsonOptions = new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        WriteIndented = false
    };

    public async Task AddAsync(ConnectedUser user)
    {
        var json = JsonSerializer.Serialize(user, _jsonOptions);
        await _db.HashSetAsync(CacheKeys.AppConnections, user.ConnectionId, json);
    }

    public async Task RemoveAsync(string connectionId)
    {
        await _db.HashDeleteAsync(CacheKeys.AppConnections, connectionId);
    }

    public async Task<IReadOnlyList<ConnectedUser>> GetAllAsync()
    {
        var entries = await _db.HashGetAllAsync(CacheKeys.AppConnections);
        if (entries.Length <= 0)
        {
            return [];
        }

        var list = new List<ConnectedUser>(entries.Length);
        foreach (var entry in entries)
        {
            if (!entry.Value.IsNullOrEmpty)
            {
                var user = JsonSerializer.Deserialize<ConnectedUser>((string)entry.Value!, _jsonOptions);
                if (user is not null)
                {
                    list.Add(user);
                }
            }
        }

        return list.AsReadOnly();
    }

    public async Task ClearAllAsync()
    {
        // 서버 시작 시 전체 초기화 (stale 제거) — 단일 키라 SCAN 불필요
        await _db.KeyDeleteAsync(CacheKeys.AppConnections);
    }
}