const fs = require('node:fs')
const path = require('node:path')
const { execFileSync } = require('node:child_process')

// Snapshot only this build, before adding older hashed chunks for open tabs.
function preserveFrontendAssets(root, revision) {
  if (!/^[a-zA-Z0-9-]+$/.test(revision)) throw new Error('Invalid asset revision')
  const assets = path.join(root, 'src/frontend/dist/assets')
  const archive = path.join(root, 'frontend-asset-archives')
  fs.mkdirSync(archive, { recursive: true })
  const previous = fs.readdirSync(archive).filter(name => fs.statSync(path.join(archive, name)).isDirectory())
    .sort((a, b) => fs.statSync(path.join(archive, b)).mtimeMs - fs.statSync(path.join(archive, a)).mtimeMs).slice(0, 3)
  const snapshot = path.join(archive, revision)
  if (fs.existsSync(snapshot)) throw new Error('Asset snapshot already exists')
  fs.cpSync(assets, snapshot, { recursive: true, errorOnExist: true, force: false })
  if (!previous.length) {
    const docker = (...args) => execFileSync('docker', ['--context', 'colima-yawan', ...args], { encoding: 'utf8' }).trim()
    const containers = docker('ps', '-a', '--filter', 'name=yawan-public-frontend', '--format', '{{.Names}}').split('\n').filter(Boolean)
    for (const container of containers) {
      if (!/^yawan-public-frontend(?:-before-[a-zA-Z0-9-]+)?$/.test(container)) continue
      const name = `bootstrap-${container}`
      const destination = path.join(archive, name)
      if (!fs.existsSync(destination)) docker('cp', `${container}:/usr/share/nginx/html/assets`, destination)
      previous.push(name)
    }
  }
  let retained = 0
  for (const name of previous) retained += mergeAssets(path.join(archive, name), assets)
  const now = new Date()
  fs.utimesSync(snapshot, now, now)
  return { retained, previous_builds: previous.length }
}

function mergeAssets(source, destination) {
  let copied = 0
  for (const entry of fs.readdirSync(source, { withFileTypes: true })) {
    const from = path.join(source, entry.name), to = path.join(destination, entry.name)
    if (entry.isSymbolicLink()) throw new Error('Asset symlinks are not supported')
    if (entry.isDirectory()) {
      fs.mkdirSync(to, { recursive: true })
      copied += mergeAssets(from, to)
    } else if (entry.isFile() && !fs.existsSync(to)) {
      fs.copyFileSync(from, to, fs.constants.COPYFILE_EXCL)
      copied++
    }
  }
  return copied
}
module.exports = { preserveFrontendAssets, mergeAssets }