ANTOOZA-BACKEND/Infrastructure/YouTube/YouTubeApiKeyHandler.cs

using Application.Abstractions.YouTube;
using Microsoft.Extensions.Logging;

namespace Infrastructure.YouTube;

/// <summary>
/// YouTube Data API v3 요청에 API Key를 자동으로 추가하는 DelegatingHandler.
/// 실제 캐시/조회는 <see cref="IYouTubeApiKeyProvider"/> 싱글톤에 위임.
/// </summary>
internal sealed class YouTubeApiKeyHandler(
    IYouTubeApiKeyProvider keyProvider,
    ILogger<YouTubeApiKeyHandler> logger
) : DelegatingHandler
{
    protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        var apiKey = await keyProvider.GetAsync(cancellationToken);

        if (!string.IsNullOrEmpty(apiKey) && request.RequestUri is not null)
        {
            // 이미 Authorization 헤더(OAuth)가 있으면 API Key 추가 안 함
            if (request.Headers.Authorization is null)
            {
                var uriStr = request.RequestUri.ToString();
                var separator = uriStr.Contains('?') ? "&" : "?";
                request.RequestUri = new Uri($"{uriStr}{separator}key={Uri.EscapeDataString(apiKey)}");
            }
        }
        else
        {
            logger.LogWarning("[YouTube] API Key가 비어있습니다. DB Config > External > YouTubeApiKeyEnc를 확인하세요.");
        }

        return await base.SendAsync(request, cancellationToken);
    }
}