/**
 * Encrypted-at-rest registry credential vault.
 *
 * AES-256-GCM; key derived from SERVER_SEED (or PEARDOCK_VAULT_KEY).
 * KDF: scrypt when available (Node), else PBKDF2-SHA256 (bare-crypto has no scrypt).
 * File: PEARDOCK_VAULT_PATH (default ./peardock-vault.json)
 */
import fs from 'fs'
import path from 'path'
import crypto from 'crypto'
import logger from '../utils/logger.js'

const SCRYPT_N = 16384
const SCRYPT_R = 8
const SCRYPT_P = 1
const PBKDF2_ITERATIONS = 120_000
const KEY_LEN = 32

function vaultFilePath() {
  return process.env.PEARDOCK_VAULT_PATH || path.join(process.cwd(), 'peardock-vault.json')
}

/** @type {{ key: string, buf: Buffer }|null} */
let cachedKey = null

/**
 * Prefer scrypt on Node; bare-crypto only exposes pbkdf2(Sync).
 * @returns {'scrypt'|'pbkdf2'}
 */
function preferredKdf() {
  return typeof crypto.scryptSync === 'function' ? 'scrypt' : 'pbkdf2'
}

/**
 * @param {string|Buffer} seed
 * @param {string|Buffer} salt
 * @param {'scrypt'|'pbkdf2'} kdf
 * @returns {Buffer}
 */
function deriveKeyMaterial(seed, salt, kdf) {
  const seedBuf = Buffer.isBuffer(seed) ? seed : Buffer.from(String(seed), 'utf8')
  const saltBuf = Buffer.isBuffer(salt) ? salt : Buffer.from(String(salt), 'utf8')

  if (kdf === 'scrypt') {
    if (typeof crypto.scryptSync !== 'function') {
      throw new Error('scryptSync is not available in this runtime')
    }
    return crypto.scryptSync(seedBuf, saltBuf, KEY_LEN, {
      N: SCRYPT_N,
      r: SCRYPT_R,
      p: SCRYPT_P,
    })
  }

  // PBKDF2-SHA256 — supported by Node and bare-crypto
  if (typeof crypto.pbkdf2Sync === 'function') {
    const out = crypto.pbkdf2Sync(seedBuf, saltBuf, PBKDF2_ITERATIONS, KEY_LEN, 'sha256')
    return Buffer.from(out)
  }

  // Last-resort HKDF-style expand via HMAC (createHmac is always present)
  const prk = crypto.createHmac('sha256', saltBuf).update(seedBuf).digest()
  const info = Buffer.concat([Buffer.from('peardock-vault-v1', 'utf8'), Buffer.from([0x01])])
  return crypto.createHmac('sha256', prk).update(info).digest()
}

/**
 * @param {string} [seedHex]
 * @param {'scrypt'|'pbkdf2'} [kdf]
 * @returns {Buffer}
 */
function deriveKey(seedHex, kdf = preferredKdf()) {
  const explicit = process.env.PEARDOCK_VAULT_KEY
  const seed = seedHex || process.env.SERVER_SEED || process.env.SERVER_KEY || 'peardock-dev-vault'
  const salt = process.env.PEARDOCK_VAULT_SALT || 'peardock-vault-v1'
  const cacheKey =
    explicit && /^[0-9a-fA-F]{64}$/.test(explicit)
      ? `k:${explicit}`
      : `s:${kdf}:${seed}:${salt}`
  if (cachedKey?.key === cacheKey) return cachedKey.buf

  let buf
  if (explicit && /^[0-9a-fA-F]{64}$/.test(explicit)) {
    buf = Buffer.from(explicit, 'hex')
  } else {
    buf = deriveKeyMaterial(String(seed), salt, kdf)
  }
  cachedKey = { key: cacheKey, buf }
  return buf
}

/**
 * @param {object} plaintext
 * @param {string} [seedHex]
 */
function encrypt(plaintext, seedHex) {
  const kdf = preferredKdf()
  const key = deriveKey(seedHex, kdf)
  const iv = crypto.randomBytes(12)
  const cipher = crypto.createCipheriv('aes-256-gcm', key, iv)
  const json = Buffer.from(JSON.stringify(plaintext), 'utf8')
  // bare-crypto GCM buffers until final(); Node returns ciphertext from update()
  const part1 = cipher.update(json) || Buffer.alloc(0)
  const part2 = cipher.final() || Buffer.alloc(0)
  const enc = Buffer.concat([
    Buffer.isBuffer(part1) ? part1 : Buffer.from(part1),
    Buffer.isBuffer(part2) ? part2 : Buffer.from(part2),
  ])
  const tag = cipher.getAuthTag()
  return {
    v: 1,
    kdf,
    iv: iv.toString('base64'),
    tag: tag.toString('base64'),
    data: enc.toString('base64'),
  }
}

/**
 * @param {object} blob
 * @param {string} [seedHex]
 * @param {'scrypt'|'pbkdf2'} kdf
 */
function decryptWithKdf(blob, seedHex, kdf) {
  const key = deriveKey(seedHex, kdf)
  const iv = Buffer.from(blob.iv, 'base64')
  const tag = Buffer.from(blob.tag, 'base64')
  const data = Buffer.from(blob.data, 'base64')
  const decipher = crypto.createDecipheriv('aes-256-gcm', key, iv)
  decipher.setAuthTag(tag)
  const part1 = decipher.update(data) || Buffer.alloc(0)
  const part2 = decipher.final() || Buffer.alloc(0)
  const dec = Buffer.concat([
    Buffer.isBuffer(part1) ? part1 : Buffer.from(part1),
    Buffer.isBuffer(part2) ? part2 : Buffer.from(part2),
  ])
  return JSON.parse(dec.toString('utf8'))
}

/**
 * @param {object} blob
 * @param {string} [seedHex]
 */
function decrypt(blob, seedHex) {
  if (!blob?.iv || !blob?.tag || !blob?.data) throw new Error('Corrupt vault blob')

  // Prefer kdf recorded at encrypt time; legacy blobs assumed scrypt (Node-only era)
  const primary =
    blob.kdf === 'pbkdf2' || blob.kdf === 'scrypt'
      ? blob.kdf
      : typeof crypto.scryptSync === 'function'
        ? 'scrypt'
        : 'pbkdf2'
  const fallback = primary === 'scrypt' ? 'pbkdf2' : 'scrypt'

  try {
    return decryptWithKdf(blob, seedHex, primary)
  } catch (err) {
    // Migration / cross-runtime: try the other KDF when possible
    const canFallback =
      (fallback === 'scrypt' && typeof crypto.scryptSync === 'function') ||
      fallback === 'pbkdf2'
    if (!canFallback || blob.kdf) throw err
    try {
      return decryptWithKdf(blob, seedHex, fallback)
    } catch {
      throw err
    }
  }
}

/**
 * @returns {{ credentials: Record<string, object> }}
 */
function loadVault() {
  const VAULT_PATH = vaultFilePath()
  if (!fs.existsSync(VAULT_PATH)) {
    return { credentials: {} }
  }
  try {
    const raw = JSON.parse(fs.readFileSync(VAULT_PATH, 'utf8'))
    if (raw.encrypted) {
      return decrypt(raw.encrypted)
    }
    // Legacy plaintext migration
    if (raw.credentials) {
      saveVault(raw)
      return raw
    }
  } catch (err) {
    logger.warn('vault load failed', { error: err.message })
  }
  return { credentials: {} }
}

/**
 * @param {{ credentials: Record<string, object> }} vault
 */
function saveVault(vault) {
  const VAULT_PATH = vaultFilePath()
  const encrypted = encrypt(vault)
  const out = {
    version: 1,
    updatedAt: new Date().toISOString(),
    encrypted,
  }
  const dir = path.dirname(VAULT_PATH)
  if (!fs.existsSync(dir)) fs.mkdirSync(dir, { recursive: true })
  fs.writeFileSync(VAULT_PATH, JSON.stringify(out, null, 2), { mode: 0o600 })
  try {
    fs.chmodSync(VAULT_PATH, 0o600)
  } catch {
    // ignore
  }
}

/**
 * Store registry credentials.
 * @param {{ id?: string, username: string, password: string, serveraddress?: string, label?: string }} cred
 */
export function storeCredential(cred) {
  const vault = loadVault()
  const id =
    cred.id ||
    crypto
      .createHash('sha256')
      .update(`${cred.serveraddress || 'docker.io'}:${cred.username}:${Date.now()}`)
      .digest('hex')
      .slice(0, 16)
  vault.credentials[id] = {
    id,
    username: String(cred.username),
    password: String(cred.password),
    serveraddress: cred.serveraddress || 'https://index.docker.io/v1/',
    label: cred.label || cred.username,
    createdAt: vault.credentials[id]?.createdAt || new Date().toISOString(),
    updatedAt: new Date().toISOString(),
  }
  saveVault(vault)
  return { id, username: vault.credentials[id].username, serveraddress: vault.credentials[id].serveraddress, label: vault.credentials[id].label }
}

/**
 * @param {string} id
 */
export function deleteCredential(id) {
  const vault = loadVault()
  if (!vault.credentials[id]) throw new Error('Credential not found')
  delete vault.credentials[id]
  saveVault(vault)
  return { success: true, id }
}

/**
 * List credentials without passwords.
 */
export function listCredentials() {
  const vault = loadVault()
  return Object.values(vault.credentials).map((c) => ({
    id: c.id,
    username: c.username,
    serveraddress: c.serveraddress,
    label: c.label,
    createdAt: c.createdAt,
    updatedAt: c.updatedAt,
  }))
}

/**
 * @param {string} id
 * @returns {{ username: string, password: string, serveraddress: string }|null}
 */
export function getCredential(id) {
  const vault = loadVault()
  const c = vault.credentials[id]
  if (!c) return null
  return {
    username: c.username,
    password: c.password,
    serveraddress: c.serveraddress,
  }
}

/**
 * Find a vault credential matching a registry host (best-effort).
 * @param {string} serverHint e.g. ghcr.io or https://index.docker.io/v1/
 * @returns {{ id: string, username: string, password: string, serveraddress: string }|null}
 */
export function findCredentialForServer(serverHint) {
  if (!serverHint) return null
  const hint = String(serverHint).toLowerCase().replace(/\/+$/, '')
  const vault = loadVault()
  const entries = Object.values(vault.credentials)
  // Prefer exact serveraddress match
  for (const c of entries) {
    const sa = String(c.serveraddress || '').toLowerCase().replace(/\/+$/, '')
    if (sa && (sa === hint || sa.includes(hint) || hint.includes(sa))) {
      return {
        id: c.id,
        username: c.username,
        password: c.password,
        serveraddress: c.serveraddress,
      }
    }
  }
  // Host-only match (strip scheme)
  const hostOnly = hint.replace(/^https?:\/\//, '').split('/')[0]
  for (const c of entries) {
    const sa = String(c.serveraddress || '')
      .toLowerCase()
      .replace(/^https?:\/\//, '')
      .split('/')[0]
    if (sa && hostOnly && (sa === hostOnly || sa.endsWith(`.${hostOnly}`) || hostOnly.endsWith(`.${sa}`))) {
      return {
        id: c.id,
        username: c.username,
        password: c.password,
        serveraddress: c.serveraddress,
      }
    }
  }
  return null
}

export function vaultPath() {
  return vaultFilePath()
}