const UserFollowModel = require('../models/UserFollowModel')
const UserModel = require('../models/UserModel')

async function getFollowCounts (userId) {
  const [followersCount, followingCount] = await Promise.all([
    UserFollowModel.countDocuments({ followingId: userId }),
    UserFollowModel.countDocuments({ followerId: userId })
  ])
  return { followersCount, followingCount }
}

async function mapFollowUsers (ids, viewerId) {
  if (!ids.length) return []
  const users = await UserModel.find({ _id: { $in: ids } })
    .select('_id user_name first_name last_name profile_image is_verified verify_badge account_status')
    .lean()
  const byId = Object.fromEntries(users.map((u) => [String(u._id), u]))

  let followingSet = new Set()
  if (viewerId) {
    const rows = await UserFollowModel.find({
      followerId: viewerId,
      followingId: { $in: ids }
    }).select('followingId').lean()
    followingSet = new Set(rows.map((r) => String(r.followingId)))
  }

  return ids
    .map((id) => byId[String(id)])
    .filter(Boolean)
    .map((u) => ({
      _id: String(u._id),
      user_name: u.user_name || '',
      first_name: u.first_name || '',
      last_name: u.last_name || '',
      profile_image: u.profile_image || '',
      is_verified: u.is_verified || 'none',
      verify_badge: u.verify_badge || 'none',
      is_following: followingSet.has(String(u._id))
    }))
}

module.exports = {
  getFollowCounts,
  mapFollowUsers
}