fake-images middleware for local development

fake-images.js

module.exports = function () {
  //
  // [ express middleware ]
  // Generate a /fake/images route for testing images source
  //
  // images service origin:
  //  - PICSUM(https://picsum.photos)
  //      Created by David Marby & Nijiko Yonskai
  //      Having trouble? Poke @DMarby on Twitter
  //      Images from unsplash
  // --------------------------------------------------------------------------------
  // usage:
  //     /fake/images/{width}/{height}/{id:0~999}{?simple}
  // e.g.
  //     /fake/images/320/480/
  //     /fake/images/720-960/480/
  //     /fake/images/720-960/480-540/13
  //     /fake/images/720-960/480-540/13?simple
  //

  const axios = require('axios')

  const PROTOCOL = 'http'
  const VENDORS = {
    picsum: 'picsum.photos'
  }
  const MIN_WIDTH = 100
  const MIN_HEIGHT = 100
  const MAX_WIDTH = 1000
  const MAX_HEIGHT = 1000

  const rand = function (minNum, MaxNum) {
    let len = arguments.length
    if (len === 0) {
      return Math.random()
    } else if (len > 1) {
      return Math.round(Math.random() * (MaxNum - minNum)) + minNum
    }
    return Math.round(Math.random() * minNum)
  }

  return function (req, res, next) {
    let params
    let photoId
    let simple
    let width
    let height
    let widthInfo
    let heightInfo
    let minWidth
    let minHeight
    let maxWidth
    let maxHeight
    let vendorList
    let vendorName
    let source
    if (!/^\/fake\/images(\/.*)?$/.test(req.path)) {
      next()
      return
    }
    params = req.path.replace(/^\/fake\/images\/?/, '').split('/')
    widthInfo = params[0] || null
    heightInfo = params[1] || null
    photoId = params[2] || rand(0, 999)
    simple = (typeof req.query.simple === 'string')
    if (!widthInfo) {
      width = rand(MIN_WIDTH, MAX_WIDTH)
    } else {
      widthInfo = widthInfo.split('-')
      if (widthInfo.length < 2) {
        width = Number(widthInfo[0]) || rand(MIN_WIDTH, MAX_WIDTH)
      } else {
        minWidth = Number(widthInfo[0]) || MIN_WIDTH
        maxWidth = Number(widthInfo[1]) || MIN_WIDTH
        width = rand(minWidth, maxWidth)
      }
    }
    if (!heightInfo) {
      height = rand(MIN_HEIGHT, MAX_HEIGHT)
    } else {
      heightInfo = heightInfo.split('-')
      if (heightInfo.length < 2) {
        height = Number(heightInfo[0]) || rand(MIN_HEIGHT, MAX_HEIGHT)
      } else {
        minHeight = Number(heightInfo[0]) || MIN_HEIGHT
        maxHeight = Number(heightInfo[1]) || MIN_HEIGHT
        height = rand(minHeight, maxHeight)
      }
    }
    vendorList = Object.keys(VENDORS)
    vendorName = (simple || !vendorList.length) ? null : vendorList[rand(0, vendorList.length - 1)]
    switch (vendorName) {
      case 'picsum':
        source = `${PROTOCOL}://${VENDORS[vendorName]}/id/${photoId}/${width}/${height}?random=${Date.now()}`
        break
      default:
        source = `${PROTOCOL}://placehold.jp/${width}x${height}.png`
    }
    if (!source) {
      next()
      return
    }
    axios.get(source, { responseType: 'stream' })
      .then(response => {
        response.data.pipe(res)
      })
      .catch(err => {
        console.log(err)
        next()
      })
  }
}