cthuloid / webui / lib / store.js

// Settings persistence: one JSON file, written atomically (temp + rename) so a
// crash mid-write can never leave a truncated config.
//
// A config that fails to parse is moved aside, never overwritten: otherwise the
// first change after a bad read would replace the user's units and looks with
// defaults.

import fs from 'bare-fs'
import path from 'bare-path'

export class Store {
  constructor (dir) {
    this.dir = dir
    this.file = path.join(dir, 'config.json')
  }

  load () {
    let text
    try {
      text = fs.readFileSync(this.file, 'utf8')
    } catch {
      return {}
    }
    try {
      return JSON.parse(text)
    } catch (err) {
      const aside = this.file + '.bad-' + Date.now()
      fs.renameSync(this.file, aside)
      console.error(JSON.stringify({ msg: 'config unreadable, moved aside', aside, error: err.message }))
      return {}
    }
  }

  save (data) {
    fs.mkdirSync(this.dir, { recursive: true })
    const tmp = this.file + '.tmp'
    fs.writeFileSync(tmp, JSON.stringify(data, null, 2) + '\n')
    fs.renameSync(tmp, this.file)
  }
}