ponytars.js

'use strict'

const path = require(`path`)
const glob = require(`glob`)
const ponytars = glob.sync(`.bin/semipublic/ponytars/*.png`)

// app.get('/ponytar/:hash.png', getPonytar)

function getPonytar(req, res) {
  const { hash } = req.params
  const seed = seedFromHash(hash)
  const random = randomFromSeed(seed)
  const index = Math.floor(random() * ponytars.length)
  const ponytar = ponytars[index]

  res.sendFile(path.resolve(ponytar))
}

function randomFromSeed(seed) {
  return () => {
    const x = Math.sin(seed++) * 1000
    return x - Math.floor(x)
  }
}

function seedFromHash(hash) {
  const rnotation = /[.e+]/g
  const integer = parseInt(hash, 16).toString()
  const seed = integer.toString().replace(rnotation, ``)
  return seed / 100000
}

module.exports = getPonytar