const fs = require('fs')
const path = require('path')

function getBirthTime(dir) {
  let stat = fs.statSync(dir)
  return stat.birthtimeMs
}

function isValid(filename) {
  return filename.startsWith('T')
}

const filesPath = path.join(__dirname, '/mm')
fs.readdir(filesPath, (err, files) => {
  if (!err){
    files.sort((x, y) => {
      let xp = path.join(filesPath, x)
      let yp = path.join(filesPath, y)
      return getBirthTime(yp) - getBirthTime(xp)
    })
    console.log(files)
    let curValidFile
    let curValidName
    let cnt = 1
    files.forEach(f => {
      console.log(f)
      if (isValid(f)){
        curValidName = f
        curValidFile = path.join(filesPath, f)
        cnt = 1
      }else {
        let newname = `${curValidName.slice(0, -4)}--r--${cnt++}.pdf`
        let newpath = path.join(filesPath, newname)
        fs.renameSync(path.join(filesPath, f), newpath)
      }
    })
  }
})