/**
 * Holesail tunnel manager with optional disk persistence.
 *
 * peardock control plane: HyperDHT + protomux-rpc
 * Data plane tunnels: Holesail L4 TCP/UDP reverse proxy (hs:// keys)
 *
 * Enabled by default. Set ENABLE_HOLESAIL=0 to disable.
 * Package: holesail (AGPL-3.0) — required dependency.
 *
 * @see https://github.com/holesail/holesail
 * @see docs/HOLESAIL.md
 */
import { randomBytes } from 'crypto'
import fs from 'fs'
import path from 'path'
// Static import so bare-pack embeds holesail and Bare resolves it at load time.
// Dynamic createRequire(import.meta.url) fails in standalone bundles (parent URL
// does not match pack resolutions → "package missing").
import HolesailModule from 'holesail'
import logger from '../utils/logger.js'

/** @typedef {{
 *   id: string,
 *   name: string,
 *   host: string,
 *   port: number,
 *   protocol: 'tcp'|'udp',
 *   secure: boolean,
 *   url: string,
 *   key: string,
 *   publicKey?: string,
 *   containerId?: string|null,
 *   containerName?: string|null,
 *   createdAt: string,
 *   state: string,
 *   persist?: boolean,
 * }} TunnelInfo */

const MAX_TUNNELS = Math.max(1, Number(process.env.PEARDOCK_MAX_TUNNELS || 20))
const DEFAULT_HOSTS = new Set(['127.0.0.1', 'localhost', '::1', '0.0.0.0'])

function persistPath() {
  return (
    process.env.PEARDOCK_TUNNELS_PATH || path.join(process.cwd(), 'peardock-tunnels.json')
  )
}

/** @type {Map<string, { instance: any, info: TunnelInfo }>} */
const tunnels = new Map()

/** In-flight create promises keyed by protocol|host|port (coalesce concurrent creates). */
/** @type {Map<string, Promise<TunnelInfo & { existing?: boolean }>>} */
const pendingCreates = new Map()

let HolesailCtor = null
let holesailLoadError = null
let restoreDone = false

/**
 * Normalize host for duplicate matching (localhost ↔ 127.0.0.1).
 * @param {string} host
 */
function normalizeTunnelHost(host) {
  const h = String(host || '127.0.0.1').trim().toLowerCase()
  if (h === 'localhost' || h === '::1' || h === '0.0.0.0' || h === '::') return '127.0.0.1'
  return h
}

/**
 * @param {string} host
 * @param {number} port
 * @param {'tcp'|'udp'} [protocol]
 */
function targetKey(host, port, protocol = 'tcp') {
  return `${protocol === 'udp' ? 'udp' : 'tcp'}|${normalizeTunnelHost(host)}|${Number(port)}`
}

/**
 * Find an active tunnel for the same target (any non-closed state).
 * @param {string} host
 * @param {number} port
 * @param {'tcp'|'udp'} [protocol]
 * @returns {TunnelInfo|null}
 */
export function findTunnelByTarget(host, port, protocol = 'tcp') {
  const key = targetKey(host, port, protocol)
  for (const t of tunnels.values()) {
    if (targetKey(t.info.host, t.info.port, t.info.protocol) === key) {
      return { ...t.info }
    }
  }
  return null
}

function loadHolesail() {
  if (HolesailCtor) return HolesailCtor
  if (holesailLoadError) throw holesailLoadError
  try {
    // CJS interop: module.exports = class Holesail → default under ESM
    const mod = HolesailModule?.default ?? HolesailModule
    if (typeof mod !== 'function') {
      throw new Error(
        `holesail export is not a constructor (got ${typeof mod})`
      )
    }
    HolesailCtor = mod
    return HolesailCtor
  } catch (err) {
    holesailLoadError = err
    logger.error('Failed to load holesail package', {
      error: err?.message || String(err),
      stack: err?.stack,
    })
    throw err
  }
}

/**
 * Holesail tunnels are on by default.
 * Opt out with ENABLE_HOLESAIL=0 / false / off / no.
 */
export function isHolesailEnabled() {
  const v = String(process.env.ENABLE_HOLESAIL ?? '1').trim().toLowerCase()
  if (v === '0' || v === 'false' || v === 'off' || v === 'no') return false
  return true
}

export function isHolesailAvailable() {
  try {
    loadHolesail()
    return true
  } catch {
    return false
  }
}

export function getTunnelsPersistPath() {
  return persistPath()
}

/**
 * @returns {Set<string>}
 */
export function allowedTunnelHosts() {
  const set = new Set(DEFAULT_HOSTS)
  const extra = process.env.PEARDOCK_TUNNEL_HOSTS || ''
  for (const part of extra.split(/[,\s]+/)) {
    const h = part.trim().toLowerCase()
    if (h) set.add(h)
  }
  return set
}

/**
 * @param {string} host
 * @param {number} port
 */
export function assertTunnelTarget(host, port) {
  const h = String(host || '127.0.0.1').trim().toLowerCase()
  const p = Number(port)
  if (!Number.isInteger(p) || p < 1 || p > 65535) {
    throw Object.assign(new Error('port must be an integer 1–65535'), { code: 'INVALID_ARGS' })
  }
  const allowed = allowedTunnelHosts()
  if (!allowed.has(h)) {
    throw Object.assign(
      new Error(
        `Host "${host}" is not allowed for tunnels. Allowed: ${[...allowed].join(', ')}. ` +
          'Extend with PEARDOCK_TUNNEL_HOSTS=host1,host2'
      ),
      { code: 'PERMISSION_DENIED' }
    )
  }
  return { host: h === 'localhost' ? '127.0.0.1' : host, port: p }
}

function newId() {
  return `tnl_${Date.now().toString(36)}_${randomBytes(4).toString('hex')}`
}

/**
 * Persistable definitions (no live sockets). Keys are capabilities — file mode 600.
 * @returns {object[]}
 */
function buildPersistPayload() {
  return [...tunnels.values()]
    .filter((t) => t.info.persist !== false)
    .map((t) => ({
      id: t.info.id,
      name: t.info.name,
      host: t.info.host,
      port: t.info.port,
      protocol: t.info.protocol,
      secure: t.info.secure,
      key: t.info.key,
      containerId: t.info.containerId || null,
      containerName: t.info.containerName || null,
      createdAt: t.info.createdAt,
      persist: true,
    }))
}

export function saveTunnelsToDisk() {
  if (!isHolesailEnabled()) return false
  try {
    const payload = {
      version: 1,
      updatedAt: new Date().toISOString(),
      tunnels: buildPersistPayload(),
    }
    const file = persistPath()
    const tmp = `${file}.${process.pid}.tmp`
    fs.writeFileSync(tmp, JSON.stringify(payload, null, 2), { encoding: 'utf8', mode: 0o600 })
    fs.renameSync(tmp, file)
    try {
      fs.chmodSync(file, 0o600)
    } catch {
      // ignore
    }
    return true
  } catch (err) {
    logger.warn('Failed to persist tunnels', { error: err.message })
    return false
  }
}

/**
 * Read definitions from disk (does not start tunnels).
 * @returns {object[]}
 */
export function loadTunnelDefsFromDisk() {
  try {
    const file = persistPath()
    if (!fs.existsSync(file)) return []
    const raw = JSON.parse(fs.readFileSync(file, 'utf8'))
    const list = Array.isArray(raw?.tunnels) ? raw.tunnels : Array.isArray(raw) ? raw : []
    return list.filter((t) => t && t.port)
  } catch (err) {
    logger.warn('Failed to read tunnel persist file', { error: err.message })
    return []
  }
}

/**
 * Public list shape (includes connection URL — treat as secret capability).
 * @returns {TunnelInfo[]}
 */
export function listTunnels() {
  return [...tunnels.values()].map((t) => ({ ...t.info }))
}

/**
 * @param {string} id
 * @returns {TunnelInfo|null}
 */
export function getTunnel(id) {
  const t = tunnels.get(id)
  return t ? { ...t.info } : null
}

/**
 * Start a Holesail server tunnel to host:port.
 * @param {{
 *   id?: string,
 *   name?: string,
 *   host?: string,
 *   port: number,
 *   protocol?: 'tcp'|'udp',
 *   secure?: boolean,
 *   key?: string,
 *   containerId?: string|null,
 *   containerName?: string|null,
 *   persist?: boolean,
 *   createdAt?: string,
 *   skipPersistWrite?: boolean,
 * }} opts
 * @returns {Promise<TunnelInfo & { existing?: boolean }>}
 */
export async function createTunnel(opts = {}) {
  if (!isHolesailEnabled()) {
    const err = new Error('Holesail tunnels disabled. Remove ENABLE_HOLESAIL=0 to re-enable (on by default).')
    err.code = 'FEATURE_DISABLED'
    throw err
  }

  const protocol = opts.protocol === 'udp' ? 'udp' : 'tcp'
  const { host, port } = assertTunnelTarget(opts.host || '127.0.0.1', opts.port)
  const key = targetKey(host, port, protocol)

  // Idempotent: return existing tunnel for same target (do not start a second Holesail)
  const existing = findTunnelByTarget(host, port, protocol)
  if (existing) {
    logger.info('Tunnel already active — reusing', {
      id: existing.id,
      target: `${protocol}://${host}:${port}`,
    })
    return { ...existing, existing: true }
  }

  // Coalesce concurrent createTunnel calls for the same target
  const inflight = pendingCreates.get(key)
  if (inflight) {
    logger.info('Tunnel create already in flight — joining', { target: `${protocol}://${host}:${port}` })
    const joined = await inflight
    return { ...joined, existing: true }
  }

  if (tunnels.size >= MAX_TUNNELS) {
    throw Object.assign(new Error(`Maximum concurrent tunnels (${MAX_TUNNELS}) reached`), {
      code: 'RATE_LIMIT_EXCEEDED',
    })
  }

  const work = createTunnelUnlocked(opts, { host, port, protocol, key })
  pendingCreates.set(key, work)
  try {
    return await work
  } finally {
    pendingCreates.delete(key)
  }
}

/**
 * @param {object} opts
 * @param {{ host: string, port: number, protocol: 'tcp'|'udp', key: string }} resolved
 * @returns {Promise<TunnelInfo & { existing?: boolean }>}
 */
async function createTunnelUnlocked(opts, resolved) {
  // Re-check after awaiting any prior work / race window
  const again = findTunnelByTarget(resolved.host, resolved.port, resolved.protocol)
  if (again) return { ...again, existing: true }

  if (tunnels.size >= MAX_TUNNELS) {
    throw Object.assign(new Error(`Maximum concurrent tunnels (${MAX_TUNNELS}) reached`), {
      code: 'RATE_LIMIT_EXCEEDED',
    })
  }

  const Holesail = loadHolesail()
  const { host, port, protocol } = resolved
  const secure = opts.secure !== false
  const name =
    String(opts.name || `${protocol}-${host}:${port}`).slice(0, 80) || `tunnel-${port}`
  const persist = opts.persist !== false

  const id = opts.id && String(opts.id).startsWith('tnl_') ? String(opts.id) : newId()
  logger.info('Starting Holesail tunnel', { id, host, port, protocol, secure, persist })

  const ctorOpts = {
    server: true,
    secure,
    port,
    host,
    udp: protocol === 'udp',
    log: false,
  }
  // Reuse connection key so restarts keep the same hs:// URL
  if (opts.key) ctorOpts.key = String(opts.key)

  const instance = new Holesail(ctorOpts)

  try {
    await instance.ready()
  } catch (err) {
    try {
      await instance.close()
    } catch {
      // ignore
    }
    throw Object.assign(new Error(`Failed to start Holesail tunnel: ${err.message || err}`), {
      code: 'DOCKER_ERROR',
      cause: err,
    })
  }

  // Another concurrent path may have registered first
  const raced = findTunnelByTarget(host, port, protocol)
  if (raced) {
    await safeClose(instance)
    return { ...raced, existing: true }
  }

  const raw = instance.info || {}
  /** @type {TunnelInfo} */
  const info = {
    id,
    name,
    host,
    port,
    protocol,
    secure: Boolean(raw.secure ?? secure),
    url: String(raw.url || ''),
    key: String(raw.key || opts.key || ''),
    publicKey: raw.publicKey ? String(raw.publicKey) : undefined,
    containerId: opts.containerId || null,
    containerName: opts.containerName || null,
    createdAt: opts.createdAt || new Date().toISOString(),
    state: String(raw.state || 'listening'),
    persist,
  }

  if (!info.url) {
    await safeClose(instance)
    throw new Error('Holesail started but returned no connection URL')
  }

  tunnels.set(id, { instance, info })
  if (!opts.skipPersistWrite) saveTunnelsToDisk()
  logger.info('Holesail tunnel ready', {
    id,
    name: info.name,
    target: `${protocol}://${host}:${port}`,
    urlPrefix: info.url.slice(0, 12) + '…',
  })
  return { ...info, existing: false }
}

/**
 * @param {string} id
 * @returns {Promise<boolean>}
 */
export async function closeTunnel(id) {
  const entry = tunnels.get(id)
  if (!entry) return false
  tunnels.delete(id)
  await safeClose(entry.instance)
  saveTunnelsToDisk()
  logger.info('Holesail tunnel closed', { id, name: entry.info.name })
  return true
}

export async function closeAllTunnels() {
  const ids = [...tunnels.keys()]
  for (const id of ids) {
    try {
      const entry = tunnels.get(id)
      tunnels.delete(id)
      if (entry) await safeClose(entry.instance)
    } catch (err) {
      logger.warn('Failed to close tunnel on shutdown', { id, error: err.message })
    }
  }
  // Keep persist file so next boot restores
}

/**
 * Recreate tunnels from peardock-tunnels.json (call once at server boot).
 * @returns {Promise<{ restored: number, failed: number }>}
 */
export async function restoreTunnelsFromDisk() {
  if (restoreDone) return { restored: 0, failed: 0 }
  restoreDone = true
  if (!isHolesailEnabled()) return { restored: 0, failed: 0 }

  const defs = loadTunnelDefsFromDisk()
  if (!defs.length) return { restored: 0, failed: 0 }

  let restored = 0
  let failed = 0
  for (const def of defs) {
    try {
      await createTunnel({
        id: def.id,
        name: def.name,
        host: def.host,
        port: def.port,
        protocol: def.protocol,
        secure: def.secure !== false,
        key: def.key,
        containerId: def.containerId,
        containerName: def.containerName,
        createdAt: def.createdAt,
        persist: true,
        skipPersistWrite: true,
      })
      restored += 1
    } catch (err) {
      failed += 1
      logger.warn('Failed to restore tunnel', {
        id: def.id,
        port: def.port,
        error: err.message,
      })
    }
  }
  saveTunnelsToDisk()
  if (restored || failed) {
    logger.info('Holesail tunnel restore complete', { restored, failed })
  }
  return { restored, failed }
}

async function safeClose(instance) {
  if (!instance) return
  try {
    if (typeof instance.close === 'function') await instance.close()
    else if (typeof instance.destroy === 'function') await instance.destroy()
  } catch {
    // ignore
  }
}

export function holesailStatus() {
  const available = isHolesailAvailable()
  return {
    enabled: isHolesailEnabled(),
    available,
    active: tunnels.size,
    max: MAX_TUNNELS,
    allowedHosts: [...allowedTunnelHosts()],
    persistPath: persistPath(),
    /** Present when available === false — helps diagnose bare packing / load issues */
    loadError: available
      ? null
      : holesailLoadError?.message || holesailLoadError
        ? String(holesailLoadError)
        : 'unknown',
  }
}

export default {
  isHolesailEnabled,
  isHolesailAvailable,
  listTunnels,
  getTunnel,
  findTunnelByTarget,
  createTunnel,
  closeTunnel,
  closeAllTunnels,
  restoreTunnelsFromDisk,
  saveTunnelsToDisk,
  loadTunnelDefsFromDisk,
  holesailStatus,
  assertTunnelTarget,
  getTunnelsPersistPath,
}