storage.js

const Datastore = require('nedb')
const crypto = require('crypto')

const SECOND = 1000
const HOUR = 60 * SECOND
const DAY = 24 * HOUR

const CompactionTimeout = 10 * SECOND

const sha256 = (x) =>
  crypto.createHash('sha256').update(x, 'utf8').digest('hex')

const now = () => new Date().getTime()

class Storage {
  constructor(filename = './storage.db', autoload = true) {
    this._db = new Datastore({ filename, autoload })
  }

  async close() {
    this._db.persistence.compactDatafile()

    return new Promise((resolve) => {
      this._db.on('compaction.done', () => {
        this._db.removeAllListeners('compaction.done')
        resolve()
      })

      setTimeout(() => {
        resolve()
      }, CompactionTimeout)
    })
  }

  async isValid(username, addr, limit = 2, span = DAY) {
    username = sha256(username)
    addr = sha256(addr)

    const totalUsername = await this._query(username, span)
    const totalAddr = await this._query(addr, span)

    if (totalUsername < limit && totalAddr < limit) {
      return true
    }

    return false
  }

  async saveData(username, addr) {
    username = sha256(username)
    addr = sha256(addr)

    await this._insert(username)
    await this._insert(addr)
    return true
  }

  async _insert(item) {
    const timestamp = now()

    return new Promise((resolve, reject) => {
      this._db.insert({ item, timestamp }, (err) => {
        if (err) reject(err)
        resolve()
      })
    })
  }

  async _query(item, span) {
    const timestamp = now()

    const query = {
      $and: [{ item }, { timestamp: { $gt: timestamp - span } }],
    }

    return new Promise((resolve, reject) => {
      this._db.find(query, (err, docs) => {
        if (err) reject()
        resolve(docs.length)
      })
    })
  }
}

module.exports = Storage