Search Services Under Business with Population of other services if matches are less than limit

searchController.js

const Service = require('../models/service').model
const Business = require('../models/business').model

exports.search_get = async (req, res) => {
  const { searchQuery } = req.query

  let query = {}

  if (searchQuery) {
    query.name = { $regex: searchQuery, $options: 'i' }
  }

  try {
    let matchServices = await Service.find(query)
      .limit(15)
      .populate([{ path: 'business', select: 'name image address rating' }])
      .lean()

    let matchBusinesses = await Business.find(query)
      .select('name image address rating')
      .limit(15)
      .lean()

    let matchBusinessesIds = matchBusinesses.map(b => b._id)

    console.log(matchBusinessesIds)

    // create list of all businesses linked to services
    let serviceBusinesses = [
      ...new Set(
        matchServices
          .map(s => s.business)
          .filter(b => !matchBusinessesIds.includes(b._id))
      )
    ]

    // merge found businesses and service-linked businesses
    let businesses = [...matchBusinesses, ...serviceBusinesses]
    businesses.forEach(b => (b.services = []))
    let businessesIds = businesses.map(b => b._id)

    // fill all services in respective businesses
    matchServices.forEach(s => {
      let b = s.business._id
      if (businessesIds.indexOf(b) != -1) {
        delete s.business
        businesses[businessesIds.indexOf(b)].services.push(s)
      }
    })

    for (let i = 0; i < businesses.length; i++) {
      // populate empty places with rest of the services
      let diff = 5 - businesses[i].services.length
      if (diff > 0) {
        let existing = businesses[i].services.map(s => s._id)
        let extraServices = await Service.find({
          business: businesses[i]._id,
          _id: {
            $nin: existing
          }
        })
          .limit(diff)
          .lean()

        businesses[i].services = businesses[i].services.concat(extraServices)
      }

      // set business ids on services for handling in cart
      businesses[i].services.forEach(
        s => (s.business = { _id: businesses[i]._id })
      )
    }

    return res.send(businesses)
  } catch (err) {
    console.error(err)
    return res.status(500).send(err)
  }
}