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

using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Domain.Entities.Feed;
using Microsoft.EntityFrameworkCore;
using SharedKernel.Results;

namespace Application.Features.Api.Feed.ToggleLike;

public sealed class Handler(IAppDbContext db) : ICommandHandler<Command, Result<Response>>
{
    public async Task<Result<Response>> 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<Response>(Error.NotFound("Feed.PostNotFound", "게시글을 찾을 수 없습니다."));
        }

        var existing = await db.FeedLike.FirstOrDefaultAsync(l => l.FeedPostID == request.PostID && l.MemberID == request.MemberID, ct);

        bool hasLike;

        if (existing is null)
        {
            await db.FeedLike.AddAsync(new FeedLike
            {
                FeedPostID = request.PostID,
                MemberID = request.MemberID
            }, ct);
            post.Likes++;
            hasLike = true;
        }
        else
        {
            db.FeedLike.Remove(existing);
            post.Likes = post.Likes > 0 ? post.Likes - 1 : 0;
            hasLike = false;
        }

        await db.SaveChangesAsync(ct);

        return new Response(hasLike, post.Likes);
    }
}