using Application.Abstractions.Data;
using Application.Abstractions.YouTube;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

namespace Infrastructure.YouTube;

/// <summary>
/// YouTube API Key 캐시 싱글톤 — 5분 TTL + 수동 Invalidate 지원.
/// DelegatingHandler는 풀링되어 instance 상태 공유가 불안정하므로 별도 싱글톤에 캐시 분리.
/// </summary>
internal sealed class YouTubeApiKeyProvider(
    IServiceProvider serviceProvider,
    ILogger<YouTubeApiKeyProvider> logger
) : IYouTubeApiKeyProvider
{
    private static readonly TimeSpan CacheDuration = TimeSpan.FromMinutes(5);

    private readonly SemaphoreSlim _lock = new(1, 1);
    private string? _cachedApiKey;
    private DateTime _cachedAt = DateTime.MinValue;
    private bool _hasCachedValue;

    public async Task<string?> GetAsync(CancellationToken ct)
    {
        if (_hasCachedValue && DateTime.UtcNow - _cachedAt < CacheDuration)
        {
            return _cachedApiKey;
        }

        await _lock.WaitAsync(ct);
        try
        {
            // double-check after acquiring lock
            if (_hasCachedValue && DateTime.UtcNow - _cachedAt < CacheDuration)
            {
                return _cachedApiKey;
            }

            try
            {
                using var scope = serviceProvider.CreateScope();
                var db = scope.ServiceProvider.GetRequiredService<IAppDbContext>();

                var config = await db.Config.AsNoTracking().FirstOrDefaultAsync(ct);
                _cachedApiKey = config?.External?.YouTubeApiKeyEnc;
                _cachedAt = DateTime.UtcNow;
                _hasCachedValue = true;

                return _cachedApiKey;
            }
            catch (Exception ex)
            {
                logger.LogWarning(ex, "[YouTube] API Key 조회 실패");
                return _cachedApiKey;
            }
        }
        finally
        {
            _lock.Release();
        }
    }

    public void Invalidate()
    {
        _hasCachedValue = false;
        _cachedApiKey = null;
        _cachedAt = DateTime.MinValue;
    }
}