ANTOOZA-BACKEND/Application/Features/Api/Feed/Create/Handler.cs

using Application.Abstractions.Data;
using Application.Abstractions.Hub;
using Application.Abstractions.Messaging;
using Application.Abstractions.Notification;
using Application.Features.Api.Feed.Shared;
using Domain.Entities.Feed;
using Domain.Entities.Notifications.ValueObject;
using Microsoft.EntityFrameworkCore;
using SharedKernel.Results;
using SharedKernel.Storage;

namespace Application.Features.Api.Feed.Create;

public sealed class Handler(
    IAppDbContext db,
    IFileStorage fileStorage,
    IFeedBroadcaster broadcaster,
    INotificationService notificationService
) : ICommandHandler<Command, Result<Response>>
{
    private static readonly string[] AllowedImageExtensions = [".jpg", ".jpeg", ".png", ".gif", ".webp", ".bmp"];
    private const int MaxContentLength = 5000;

    public async Task<Result<Response>> Handle(Command request, CancellationToken ct)
    {
        if (request.MemberID <= 0)
        {
            return Result.Failure<Response>(Error.Problem("Feed.MemberRequired", "로그인이 필요합니다."));
        }

        if (string.IsNullOrWhiteSpace(request.Content))
        {
            return Result.Failure<Response>(Error.Problem("Feed.ContentRequired", "내용을 입력해주세요."));
        }

        var content = request.Content.Trim();
        if (content.Length > MaxContentLength)
        {
            return Result.Failure<Response>(Error.Problem("Feed.ContentTooLong", $"내용은 최대 {MaxContentLength}자까지 입력 가능합니다."));
        }

        var member = await db.Member.AsNoTracking().FirstOrDefaultAsync(m => m.ID == request.MemberID, ct);
        if (member is null)
        {
            return Result.Failure<Response>(Error.NotFound("Feed.MemberNotFound", "회원 정보를 찾을 수 없습니다."));
        }

        // ── FeedPost 본체 저장 ──
        var feedPost = new FeedPost
        {
            MemberID = request.MemberID,
            Content = content
        };

        await db.FeedPost.AddAsync(feedPost, ct);
        await db.SaveChangesAsync(ct);

        var uploadPath = new FileStoragePath(UploadTarget.Upload, UploadFolder.Feed, feedPost.ID);

        // ── 이미지 처리 ──
        string? firstImageUrl = null;
        if (request.Images is { Count: > 0 })
        {
            byte imageCount = 0;

            foreach (var image in request.Images)
            {
                var result = await fileStorage.SaveFileAsync(image, uploadPath, AllowedImageExtensions, ct);
                if (result is null)
                {
                    continue;
                }

                var ext = Path.GetExtension(image.FileName).ToLowerInvariant();

                await db.FeedPostImage.AddAsync(new FeedPostImage
                {
                    FeedPostID = feedPost.ID,
                    FileName = image.FileName,
                    HashedName = result.FileName,
                    Path = uploadPath.ToRelativePath(),
                    Url = result.Url,
                    Extension = ext,
                    ContentType = image.ContentType,
                    Size = result.Size,
                    Width = result.Width,
                    Height = result.Height
                }, ct);

                firstImageUrl ??= result.Url;
                imageCount++;
            }

            feedPost.Images = imageCount;
            if (firstImageUrl is not null)
            {
                feedPost.Thumbnail = firstImageUrl;
            }
        }

        // ── 미디어 URL 처리 ──
        if (request.Medias is { Count: > 0 })
        {
            byte mediaCount = 0;
            foreach (var mediaUrl in request.Medias)
            {
                if (string.IsNullOrWhiteSpace(mediaUrl))
                {
                    continue;
                }

                await db.FeedPostMedia.AddAsync(new FeedPostMedia
                {
                    FeedPostID = feedPost.ID,
                    Url = mediaUrl.Trim()
                }, ct);

                mediaCount++;
            }
            feedPost.Medias = mediaCount;
        }

        // ── 태그 처리: 해시태그 추출 + 요청 태그 병합 ──
        var hashtagsFromContent = FeedContent.ExtractHashtags(content);
        var mergedTags = new List<string>(hashtagsFromContent);
        if (request.Tags is { Count: > 0 })
        {
            foreach (var t in request.Tags)
            {
                if (!string.IsNullOrWhiteSpace(t) && !mergedTags.Any(x => string.Equals(x, t, StringComparison.OrdinalIgnoreCase)))
                {
                    mergedTags.Add(t.Trim());
                }
            }
        }

        byte tagCount = 0;
        foreach (var tagName in mergedTags)
        {
            if (string.IsNullOrWhiteSpace(tagName))
            {
                continue;
            }

            var name = tagName.Trim();
            var slug = name.ToLowerInvariant().Replace(' ', '-');

            var tag = await db.FeedTag.FirstOrDefaultAsync(x => x.Name == name, ct);
            if (tag is null)
            {
                tag = new FeedTag
                {
                    Name = name,
                    Slug = slug
                };
                await db.FeedTag.AddAsync(tag, ct);
                await db.SaveChangesAsync(ct);
            }

            tag.UsageCount++;
            tag.UpdatedAt = DateTime.UtcNow;

            await db.FeedPostTag.AddAsync(new FeedPostTag
            {
                FeedPostID = feedPost.ID,
                FeedTagID = tag.ID
            }, ct);

            tagCount++;
        }
        feedPost.Tags = tagCount;

        // ── 멘션 처리 ──
        var mentionSIDs = FeedContent.ExtractMentions(content);
        var mentionedMemberIDs = new List<int>();
        if (mentionSIDs.Count > 0)
        {
            var mentionedMembers = await db.Member.AsNoTracking()
                .Where(m => mentionSIDs.Contains(m.SID) && m.ID != request.MemberID)
                .Select(m => new { m.ID, m.SID })
                .ToListAsync(ct);

            foreach (var mm in mentionedMembers)
            {
                await db.FeedPostMention.AddAsync(new FeedPostMention
                {
                    FeedPostID = feedPost.ID,
                    MemberID = mm.ID,
                    RawHandle = mm.SID
                }, ct);
                mentionedMemberIDs.Add(mm.ID);
            }
        }

        await db.SaveChangesAsync(ct);

        // ── SignalR 브로드캐스트 + 멘션 알림 ──
        var authorInfo = new
        {
            member.SID,
            member.Name,
            member.Thumb
        };

        var toast = new FeedPostToast(
            PostID: feedPost.ID,
            AuthorSID: authorInfo.SID,
            AuthorName: authorInfo.Name,
            AuthorThumb: authorInfo.Thumb,
            Subject: FeedContent.Excerpt(content, 60),
            Thumbnail: feedPost.Thumbnail,
            CreatedAt: feedPost.CreatedAt
        );

        var followerIDs = await db.MemberFollow.AsNoTracking()
            .Where(f => f.FolloweeMemberID == request.MemberID && !f.IsMuted && f.NotifyOnPost)
            .Select(f => f.FollowerMemberID)
            .ToListAsync(ct);

        if (followerIDs.Count > 0)
        {
            await broadcaster.BroadcastNewPostAsync(followerIDs, toast, ct);
        }

        foreach (var mid in mentionedMemberIDs)
        {
            await notificationService.SendAsync(
                memberID: mid,
                type: NotificationType.NewFeedPost,
                title: "새 멘션",
                message: $"{authorInfo.Name ?? authorInfo.SID}님이 회원님을 언급했습니다.",
                actionUrl: $"/feed/post/{feedPost.ID}",
                relatedType: "FeedPost",
                relatedID: feedPost.ID,
                ct: ct
            );
        }

        return new Response(feedPost.ID);
    }
}