middleware.js

'use strict'
// 3rd
const uuid = require('uuid')
const debug = require('debug')('app:middleware:track')
// 1st
const db = require('../db')
const {isValidUuid, futureDate} = require('../belt')

module.exports = ({cookieKey = 't', interval = 5000} = {}) => {
  debug('initializing track middleware')
  let queue = []

  const clearQueue = () => {
    debug('[clearQueue] queue = %j', queue)
    if (queue.length === 0) {
      return setTimeout(clearQueue, interval)
    }
    const hits = queue.slice(0)
    queue = []

    db.hits.insertHits(hits)
      .then(() => {
        debug(`${hits.length} hits inserted`)
        setTimeout(clearQueue, interval)
      }, (err) => {
        console.error('[track middleware] error inserting hits', err)
        setTimeout(clearQueue, interval)
      })
  }

  // Start loop
  setTimeout(clearQueue, interval)

  return async (ctx, next) => {
    // Skip guests
    if (!ctx.currUser) {
      return next()
    }

    let track

    if (isValidUuid(ctx.cookies.get(cookieKey))) {
      track = ctx.cookies.get(cookieKey)
    } else {
      track = uuid.v4()
      ctx.cookies.set(cookieKey, track, {
        expires: futureDate({ years: 1 })
      })
    }

    // Expose track downstream
    ctx.state.track = track

    await next()

    // Wait til after downstream so that we don't
    // push a hit on errors.
    queue.push({
      user_id: ctx.currUser.id,
      ip_address: ctx.ip,
      track
    })
  }
}