ANTOOZA-BACKEND/Application/Features/Api/YouTube/PubSubNotify/Handler.cs

using Application.Abstractions.Data;
using Application.Abstractions.Hub;
using Application.Abstractions.Messaging;
using Application.Abstractions.YouTube;
using Domain.Entities.Members;
using Domain.Entities.Members.ValueObject;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;

namespace Application.Features.Api.YouTube.PubSubNotify;

internal sealed class Handler(
    IAppDbContext db,
    IYouTubeApiService youTubeApi,
    IYouTubeLiveChatService liveChatService,
    IYouTubeLiveStateStore liveStateStore,
    IYouTubePubSubService pubSubService,
    IChannelStatusBroadcaster statusBroadcaster,
    ILogger<Handler> logger
) : ICommandHandler<Command>
{
    public async Task Handle(Command request, CancellationToken ct)
    {
        if (string.IsNullOrWhiteSpace(request.VideoID) || string.IsNullOrWhiteSpace(request.YouTubeChannelID))
        {
            logger.LogWarning("[PubSub] Missing videoId or channelId");
            return;
        }

        // 중복 처리 방지
        var firstTime = await pubSubService.TryMarkProcessedAsync(request.VideoID, ct);
        if (!firstTime)
        {
            logger.LogDebug("[PubSub] Duplicate notify ignored: videoId={VideoId}", request.VideoID);
            return;
        }

        // 라이브 정보 조회
        var liveInfo = await youTubeApi.GetLiveStreamInfoAsync(request.VideoID, ct);
        if (liveInfo is null)
        {
            logger.LogInformation("[PubSub] Video not found (may be private/deleted): videoId={VideoId}", request.VideoID);
            return;
        }

        // 라이브 방송이 아니면 종료 (VOD/upcoming 무시 — actualStartTime 필수)
        if (!liveInfo.IsLive || liveInfo.ActualStartTime is null)
        {
            logger.LogDebug(
                "[PubSub] Skip — not live: videoId={VideoId}, content={Content}",
                request.VideoID, liveInfo.LiveBroadcastContent
            );
            return;
        }

        // 내부 Channel 조회 (YouTube channel ID → 내부 Channel.ID)
        var channel = await db.Channel
            .FirstOrDefaultAsync(c => c.YouTubeChannelID == request.YouTubeChannelID && c.IsActive, ct);

        if (channel is null)
        {
            logger.LogWarning("[PubSub] Internal channel not found for YouTubeChannelID={YtChannelId}", request.YouTubeChannelID);
            return;
        }

        // 중복 BroadcastSession 체크
        var existing = await db.BroadcastSession
            .FirstOrDefaultAsync(b => b.Platform == BroadcastPlatform.YouTube && b.VideoID == request.VideoID, ct);

        if (existing is null)
        {
            var session = BroadcastSession.Create(channel.ID, BroadcastPlatform.YouTube, request.VideoID);
            session.UpdateStats(liveInfo.Title, liveInfo.ActualStartTime, null, 0, 0);
            db.BroadcastSession.Add(session);
            await db.SaveChangesAsync(ct);

            logger.LogInformation(
                "[PubSub] BroadcastSession created: channelID={ChannelId}, videoId={VideoId}, title={Title}",
                channel.ID, request.VideoID, liveInfo.Title
            );
        }
        else
        {
            logger.LogDebug("[PubSub] BroadcastSession already exists: videoId={VideoId}", request.VideoID);
        }

        // Redis 라이브 상태 저장 (watch 페이지에서 조회용)
        await liveStateStore.SetLiveAsync(request.YouTubeChannelID, liveInfo);

        // SignalR 브로드캐스트 — ChannelSidebar / WatchView 가 실시간 반영
        await statusBroadcaster.BroadcastAsync(channel.SID, isLive: true, viewerCount: 0, videoId: request.VideoID, ct);

        // ⚠️ liveChatMessages.list = 5 unit/call (가장 비싼 일반 read). 5초 폴링 시 시간당 3,600 unit → 라이브 3시간이면 일일 quota 10K 다 소모.
        // antooza 채팅은 YouTube iframe 으로 대체되어 backend 채팅 메시지 수집 불필요.
        // quota 증액 승인 후 재활성화 (memory: plan_dpot_chat_reactivate_after_quota.md).
        // 강제 활성화하려면 환경변수 등으로 toggle 추가 필요.
        // await liveChatService.StartAsync(request.VideoID, ct);
        _ = liveChatService;  // 의존성은 유지 (DI 깨지지 않게)

        // Feed Polling 중복 감지 방지 — "마지막 처리된 videoId" 기록
        await pubSubService.SetLastProcessedVideoIdAsync(request.YouTubeChannelID, request.VideoID, ct);
    }
}