using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Microsoft.EntityFrameworkCore;
using SharedKernel.Results;

namespace Application.Features.Api.Feed.Delete;

public sealed class Handler(IAppDbContext db) : ICommandHandler<Command, Result>
{
    public async Task<Result> Handle(Command request, CancellationToken ct)
    {
        var post = await db.FeedPost.FirstOrDefaultAsync(p => p.ID == request.PostID && !p.IsDeleted, ct);
        if (post is null)
        {
            return Result.Failure(Error.NotFound("Feed.PostNotFound", "게시글을 찾을 수 없습니다."));
        }

        if (post.MemberID != request.MemberID)
        {
            return Result.Failure(Error.Forbidden("Feed.NotOwner", "삭제 권한이 없습니다."));
        }

        // 소프트 삭제
        post.IsDeleted = true;
        post.DeletedAt = DateTime.UtcNow;

        // 태그 UsageCount 차감
        var tagLinks = await db.FeedPostTag.Where(pt => pt.FeedPostID == post.ID).Select(pt => pt.FeedTagID).ToListAsync(ct);
        if (tagLinks.Count > 0)
        {
            var tags = await db.FeedTag.Where(t => tagLinks.Contains(t.ID)).ToListAsync(ct);
            foreach (var tag in tags)
            {
                tag.UsageCount = tag.UsageCount > 0 ? tag.UsageCount - 1 : 0;
                tag.UpdatedAt = DateTime.UtcNow;
            }
        }

        await db.SaveChangesAsync(ct);

        return Result.Success();
    }
}