const CommentLikeModel = require('../models/CommentLikeModel')

async function attachCommentLikeFields(comments, viewerId) {
  if (!comments?.length) return comments

  const ids = comments.map((c) => c._id)
  const [likeAgg, userLikes] = await Promise.all([
    CommentLikeModel.aggregate([
      { $match: { commentId: { $in: ids } } },
      { $group: { _id: '$commentId', count: { $sum: 1 } } },
    ]),
    viewerId
      ? CommentLikeModel.find({
          userId: viewerId,
          commentId: { $in: ids },
        })
          .select('commentId')
          .lean()
      : [],
  ])

  const countMap = Object.fromEntries(
    likeAgg.map((row) => [String(row._id), row.count])
  )
  const likedSet = new Set(userLikes.map((l) => String(l.commentId)))

  return comments.map((c) => ({
    ...c,
    likesCount: countMap[String(c._id)] || 0,
    is_liked: likedSet.has(String(c._id)),
  }))
}

module.exports = { attachCommentLikeFields }