ANTOOZA-BACKEND/Application/Features/Api/MyPage/UnlinkYouTube/Handler.cs

using Application.Abstractions.Crypto;
using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Application.Abstractions.YouTube;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using SharedKernel.Results;

namespace Application.Features.Api.MyPage.UnlinkYouTube;

/// <summary>
/// YouTube 연동 해제 처리:
///  1. 회원의 MemberOAuthToken (Google provider) revoke + DB row 삭제
///  2. 회원의 Channel.WipeYouTubeData() 호출 — YT 출처 필드 모두 null·0
///  3. Redis YouTubeChannel:{channelID} 캐시 삭제
///
/// 회원 본인 또는 Google Security 설정에서 권한 회수 시 호출됨.
/// 탈퇴 Handler 와 동일한 wipe 절차, member.Withdraw() 호출만 제외.
/// </summary>
internal sealed class Handler(
    IAppDbContext db,
    IGoogleOAuthService oauthService,
    IYouTubeChannelCache youTubeChannelCache,
    IFieldEncryptor fieldEncryptor,
    ILogger<Handler> logger
) : ICommandHandler<Command, Result>
{
    public async Task<Result> Handle(Command request, CancellationToken ct)
    {
        var memberExists = await db.Member.AnyAsync(m => m.ID == request.MemberID, ct);
        if (!memberExists)
        {
            return Result.Failure(Error.NotFound("MyPage.MemberNotFound", "회원 정보를 찾을 수 없습니다."));
        }

        var oauthTokens = await db.MemberOAuthToken.Where(t => t.MemberID == request.MemberID).ToListAsync(ct);
        var purgedChannelIds = new List<string>();

        foreach (var token in oauthTokens)
        {
            var encrypted = token.RefreshTokenEnc ?? token.AccessTokenEnc;
            if (!string.IsNullOrEmpty(encrypted))
            {
                try
                {
                    var plaintext = fieldEncryptor.Decrypt(encrypted, 1);
                    if (!string.IsNullOrEmpty(plaintext))
                    {
                        await oauthService.RevokeTokenAsync(plaintext, ct);
                    }
                }
                catch (Exception ex)
                {
                    logger.LogWarning(ex, "[UnlinkYouTube] OAuth revoke 실패 (memberID={MemberID}) — row 삭제는 진행", request.MemberID);
                }
            }

            db.MemberOAuthToken.Remove(token);
        }

        var channels = await db.Channel.Where(c => c.MemberID == request.MemberID).ToListAsync(ct);
        foreach (var channel in channels)
        {
            if (!string.IsNullOrEmpty(channel.YouTubeChannelID))
            {
                purgedChannelIds.Add(channel.YouTubeChannelID);
            }
            channel.WipeYouTubeData();
        }

        if (oauthTokens.Count == 0 && channels.Count == 0)
        {
            return Result.Success();
        }

        await db.SaveChangesAsync(ct);

        foreach (var channelID in purgedChannelIds)
        {
            try
            {
                await youTubeChannelCache.RemoveAsync(channelID);
            }
            catch (Exception ex)
            {
                logger.LogWarning(ex, "[UnlinkYouTube] Redis YouTube 캐시 제거 실패 (channelID={ChannelID})", channelID);
            }
        }

        logger.LogInformation(
            "[UnlinkYouTube] memberID={MemberID} — tokens={Tokens}, channels={Channels}, cache={Cache}",
            request.MemberID, oauthTokens.Count, channels.Count, purgedChannelIds.Count
        );

        return Result.Success();
    }
}