const path = require('path')
const sander = require('sander')
const keygen = require('browser/lib/keygen')
const _ = require('lodash')
const CSON = require('@rokt33r/season')

function migrateFromV5Storage (storagePath) {
  var boostnoteJSONPath = path.join(storagePath, 'boostnote.json')
  return Promise.resolve()
    .then(function readBoostnoteJSON () {
      return sander.readFile(boostnoteJSONPath, {
        encoding: 'utf-8'
      })
    })
    .then(function verifyVersion (rawData) {
      var boostnoteJSONData = JSON.parse(rawData)
      if (boostnoteJSONData.version === '1.0') throw new Error('Target storage seems to be transformed already.')
      if (!_.isArray(boostnoteJSONData.folders)) throw new Error('the value of folders is not an array.')

      return boostnoteJSONData
    })
    .then(function setVersion (boostnoteJSONData) {
      boostnoteJSONData.version = '1.0'
      return sander.writeFile(boostnoteJSONPath, JSON.stringify(boostnoteJSONData))
        .then(() => boostnoteJSONData)
    })
    .then(function fetchNotes (boostnoteJSONData) {
      var fetchNotesFromEachFolder = boostnoteJSONData.folders
        .map(function (folder) {
          const folderDataJSONPath = path.join(storagePath, folder.key, 'data.json')
          return sander
            .readFile(folderDataJSONPath, {
              encoding: 'utf-8'
            })
            .then(function (rawData) {
              var data = JSON.parse(rawData)
              if (!_.isArray(data.notes)) throw new Error('value of notes is not an array.')
              return data.notes
                .map(function setFolderToNote (note) {
                  note.folder = folder.key
                  return note
                })
            })
            .catch(function failedToReadDataJSON (err) {
              console.warn('Failed to fetch notes from ', folderDataJSONPath, err)
              return []
            })
        })

      return Promise.all(fetchNotesFromEachFolder)
        .then(function flatten (folderNotes) {
          return folderNotes
            .reduce(function concatNotes (sum, notes) {
              return sum.concat(notes)
            }, [])
        })
        .then(function saveNotes (notes) {
          notes.forEach(function renewKey (note) {
            var newKey = keygen()
            while (notes.some((_note) => _note.key === newKey)) {
              newKey = keygen()
            }
            note.key = newKey
          })

          const noteDirPath = path.join(storagePath, 'notes')
          notes
            .map(function saveNote (note) {
              CSON.writeFileSync(path.join(noteDirPath, note.key) + '.cson', note)
            })
          return true
        })
        .then(function deleteFolderDir (check) {
          if (check) {
            boostnoteJSONData.folders.forEach((folder) => {
              sander.rimrafSync(path.join(storagePath, folder.key))
            })
          }
          return check
        })
    })
    .catch(function handleError (err) {
      console.warn(err)
      return false
    })
}

module.exports = migrateFromV5Storage