const fs = require('fs')
const path = require('path')
const rollbacksDir = path.join(__dirname, '..', 'rollbacks')

function ensureDir() {
  if (!fs.existsSync(rollbacksDir)) fs.mkdirSync(rollbacksDir, { recursive: true })
}

function snapshot(providerName, _candidateContentIgnored) {
  ensureDir()
  const servicesDir = path.join(__dirname, '..', 'services')
  const servicePath = path.join(servicesDir, `${providerName}Service.js`)
  if (!fs.existsSync(servicePath)) return null
  const originalCode = fs.readFileSync(servicePath, 'utf-8')
  const filePath = path.join(rollbacksDir, `rollback_${providerName}_${Date.now()}.js.bak`)
  fs.writeFileSync(filePath, originalCode, 'utf-8')
  return filePath
}

function getActiveSnapshot(providerName) {
  ensureDir()
  const files = fs.readdirSync(rollbacksDir)
    .filter(f => f.startsWith(`rollback_${providerName}_`) && f.endsWith('.js.bak'))
    .sort()
  if (files.length === 0) return null
  return path.join(rollbacksDir, files[files.length - 1])
}

function restore(providerName, snapshotPath) {
  const servicesDir = path.join(__dirname, '..', 'services')
  const targetPath = path.join(servicesDir, `${providerName}Service.js`)
  fs.copyFileSync(snapshotPath, targetPath)
}

function clearSnapshots(providerName) {
  ensureDir()
  const files = fs.readdirSync(rollbacksDir)
    .filter(f => f.startsWith(`rollback_${providerName}_`))
  for (const f of files) {
    fs.unlinkSync(path.join(rollbacksDir, f))
  }
}

module.exports = {
  snapshot,
  getActiveSnapshot,
  restore,
  clearSnapshots,
}