// Persistent state for dsh-remote: device identity, paired devices (master) or master
// link credentials (slave), sync bookkeeping. One JSON file, written atomically, 0600.
import crypto from 'node:crypto'
import fs from 'node:fs'
import os from 'node:os'
import path from 'node:path'

let PROFILE_DIR = ''

/** Set once from ctx.profileContext.dir at plugin start (authoritative). */
export function setProfileDir(dir) { if (dir) PROFILE_DIR = dir }

export function profileDir() {
  if (PROFILE_DIR) return PROFILE_DIR
  if (process.env.DSH_PROFILE_DIR) return process.env.DSH_PROFILE_DIR
  const home = process.env.DSH_HOME || path.join(os.homedir(), '.dsh')
  return path.join(home, 'profiles', process.env.DSH_PROFILE || 'web')
}

export function stateDir() {
  return path.join(profileDir(), 'dsh-remote')
}

const b64u = (buf) => Buffer.from(buf).toString('base64url')
export const randomId = (bytes = 16) => b64u(crypto.randomBytes(bytes))
export const sha256 = (s) => crypto.createHash('sha256').update(s).digest('hex')

export function safeEqual(a, b) {
  const x = Buffer.from(String(a))
  const y = Buffer.from(String(b))
  return x.length === y.length && crypto.timingSafeEqual(x, y)
}

/** Device id: lowercase slug, safe in URL paths (/r/<id>/). */
export function slug(s) {
  const v = String(s || '').toLowerCase().replace(/[^a-z0-9-]+/g, '-').replace(/^-+|-+$/g, '').slice(0, 40)
  return v || 'device'
}

export class Store {
  constructor(file = path.join(stateDir(), 'state.json')) {
    this.file = file
    this.data = this._load()
  }

  _load() {
    try {
      const v = JSON.parse(fs.readFileSync(this.file, 'utf8'))
      if (v && typeof v === 'object') return v
    } catch { /* first run */ }
    return {}
  }

  save() {
    fs.mkdirSync(path.dirname(this.file), { recursive: true, mode: 0o700 })
    const tmp = `${this.file}.${process.pid}.${Date.now()}.tmp`
    fs.writeFileSync(tmp, JSON.stringify(this.data, null, 2), { mode: 0o600 })
    fs.renameSync(tmp, this.file)
  }

  /** This installation's stable identity. */
  identity(defaultName) {
    if (!this.data.self) {
      const name = defaultName || os.hostname()
      this.data.self = { id: slug(name), name, createdAt: Date.now() }
      this.save()
    }
    return this.data.self
  }

  // ---- master side: paired devices + pairing codes -------------------------
  devices() { return (this.data.devices ||= {}) }

  pairingCodes() { return (this.data.pairing ||= {}) }

  createPairingCode({ ttlMs = 15 * 60 * 1000, label = '' } = {}) {
    // 4 groups of 4 from an unambiguous alphabet: easy to type, ~80 bits.
    const alphabet = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789'
    const raw = crypto.randomBytes(16)
    const code = [...raw].map((b) => alphabet[b % alphabet.length]).join('').replace(/(.{4})(?=.)/g, '$1-')
    this.pairingCodes()[sha256(code)] = { expiresAt: Date.now() + ttlMs, label, createdAt: Date.now() }
    this._prunePairing()
    this.save()
    return { code, expiresAt: Date.now() + ttlMs }
  }

  consumePairingCode(code) {
    this._prunePairing()
    const key = sha256(String(code || '').trim().toUpperCase())
    const rec = this.pairingCodes()[key]
    if (!rec) return null
    delete this.pairingCodes()[key]
    this.save()
    return rec
  }

  _prunePairing() {
    const now = Date.now()
    for (const [k, v] of Object.entries(this.pairingCodes())) if (!v || v.expiresAt < now) delete this.pairingCodes()[k]
  }

  /** Register (or re-register) a device; returns its secret key (shown once). */
  addDevice({ id, name, platform }) {
    const devices = this.devices()
    let devId = slug(id || name)
    // Keep ids unique; a re-pair of the same machine replaces its key.
    const secret = randomId(32)
    devices[devId] = {
      id: devId,
      name: name || devId,
      platform: platform || '',
      keyHash: sha256(secret),
      createdAt: devices[devId]?.createdAt || Date.now(),
      revoked: false,
      sync: devices[devId]?.sync || { enabled: true, allow: [], deny: [], secrets: [] },
    }
    this.save()
    return { id: devId, secret }
  }

  verifyDevice(id, secret) {
    const d = this.devices()[id]
    if (!d || d.revoked) return null
    return safeEqual(d.keyHash, sha256(String(secret || ''))) ? d : null
  }

  revokeDevice(id) {
    const d = this.devices()[id]
    if (!d) return false
    d.revoked = true
    d.revokedAt = Date.now()
    this.save()
    return true
  }

  removeDevice(id) {
    if (!this.devices()[id]) return false
    delete this.devices()[id]
    this.save()
    return true
  }

  // ---- UI-managed node settings ---------------------------------------------
  /** { nodeType?: 'master'|'slave', authMiddleware?: boolean } — set from Settings → Remote devices. */
  settings() { return (this.data.settings ||= {}) }

  setSettings(patch) {
    this.data.settings = { ...this.settings(), ...patch }
    this.save()
    return this.data.settings
  }

  // ---- slave side: link to master ------------------------------------------
  get master() { return this.data.master || null }

  setMaster(m) {
    this.data.master = m
    this.save()
  }
}