/**
 * Peer connection roster cache.
 *
 * Primary path (desktop / Pear):
 *   ~/.config/peardock/cache/peers.json
 *
 * Falls back to localStorage when the filesystem is unavailable
 * (pure browser / restricted environments).
 */

import fs from 'fs'
import path from 'path'
import os from 'os'

export const PEERS_CACHE_VERSION = 1
export const LOCALSTORAGE_KEY = 'peardock_connections'
export const LOCALSTORAGE_FLAG = 'peardock_use_localstorage'
/** Last UI-selected active peer id (12-char prefix) */
export const ACTIVE_PEER_KEY = 'peardock_active_peer_id'

/**
 * Absolute path to the peers cache file.
 * @returns {string}
 */
export function getPeersCachePath() {
  const home =
    process.env.PEARDOCK_HOME ||
    process.env.HOME ||
    process.env.USERPROFILE ||
    (typeof os.homedir === 'function' ? os.homedir() : '') ||
    ''
  return path.join(home, '.config', 'peardock', 'cache', 'peers.json')
}

/**
 * Directory containing peers.json
 * @returns {string}
 */
export function getPeersCacheDir() {
  return path.dirname(getPeersCachePath())
}

/**
 * Normalize optional SERVER_SEED for admin reconnect (64 hex only).
 * @param {unknown} raw
 * @returns {string|null}
 */
export function normalizeAdminSeed(raw) {
  if (raw == null || raw === '') return null
  const seed = String(raw).trim().toLowerCase()
  return /^[0-9a-f]{64}$/.test(seed) ? seed : null
}

/**
 * Normalize one peer entry.
 * @param {object|string} value
 * @param {string} [idHint]
 * @returns {{ id: string, publicKeyHex: string, alias: string|null, inviteToken: string|null, capability: string|null, adminSeed: string|null }|null}
 */
export function normalizePeerEntry(value, idHint = '') {
  if (!value) return null
  if (typeof value === 'string') {
    const publicKeyHex = value.trim().toLowerCase()
    if (!/^[0-9a-f]{64}$/.test(publicKeyHex)) return null
    return {
      id: publicKeyHex.slice(0, 12),
      publicKeyHex,
      alias: null,
      inviteToken: null,
      capability: null,
      adminSeed: null,
    }
  }
  const publicKeyHex = String(
    value.publicKeyHex || value.topicHex || value.topic || ''
  )
    .trim()
    .toLowerCase()
  if (!/^[0-9a-f]{64}$/.test(publicKeyHex)) return null
  const id = String(idHint || value.id || publicKeyHex.slice(0, 12)).slice(0, 12)
  // Prefer capability; migrate inviteToken if it looks like an HMAC grant
  let capability = value.capability || null
  let inviteToken = value.inviteToken || null
  if (!capability && inviteToken && String(inviteToken).includes('.')) {
    capability = inviteToken
    inviteToken = null
  }
  return {
    id,
    publicKeyHex,
    alias: value.alias || null,
    inviteToken,
    capability,
    // Persist for auto-reconnect as admin (file mode 0600)
    adminSeed: normalizeAdminSeed(value.adminSeed),
  }
}

/**
 * Parse raw JSON (file or localStorage) into an id → peer map.
 * Accepts:
 *  - { version, peers: { id: {...} } }
 *  - flat { id: {...} } (legacy)
 * @param {string|object} raw
 * @returns {Record<string, { publicKeyHex: string, alias: string|null, inviteToken: string|null }>}
 */
export function parsePeersPayload(raw) {
  let parsed = raw
  if (typeof raw === 'string') {
    try {
      parsed = JSON.parse(raw)
    } catch {
      return {}
    }
  }
  if (!parsed || typeof parsed !== 'object') return {}

  const source =
    parsed.peers && typeof parsed.peers === 'object' && !Array.isArray(parsed.peers)
      ? parsed.peers
      : parsed

  /** @type {Record<string, { publicKeyHex: string, alias: string|null, inviteToken: string|null, capability: string|null, adminSeed: string|null }>} */
  const out = {}
  for (const [key, value] of Object.entries(source)) {
    // Skip meta keys if someone stored a flat object with version
    if (key === 'version' || key === 'updatedAt' || key === 'peers' || key === 'activePeerId') continue
    const entry = normalizePeerEntry(value, key)
    if (!entry) continue
    out[entry.id] = {
      publicKeyHex: entry.publicKeyHex,
      alias: entry.alias,
      inviteToken: entry.inviteToken,
      capability: entry.capability,
      adminSeed: entry.adminSeed,
    }
  }
  return out
}

/**
 * Build on-disk payload.
 * @param {Record<string, { publicKeyHex?: string, topicHex?: string, alias?: string|null, inviteToken?: string|null, capability?: string|null, adminSeed?: string|null }>} peersMap
 * @param {{ activePeerId?: string|null }} [opts]
 */
export function buildPeersPayload(peersMap, opts = {}) {
  const peers = {}
  for (const [id, value] of Object.entries(peersMap || {})) {
    const entry = normalizePeerEntry(value, id)
    if (!entry) continue
    const row = {
      publicKeyHex: entry.publicKeyHex,
      alias: entry.alias,
      inviteToken: entry.inviteToken,
      capability: entry.capability,
    }
    // Only write seed when present (omit null to avoid empty secret fields)
    if (entry.adminSeed) row.adminSeed = entry.adminSeed
    peers[entry.id] = row
  }
  const payload = {
    version: PEERS_CACHE_VERSION,
    updatedAt: new Date().toISOString(),
    peers,
  }
  if (Object.prototype.hasOwnProperty.call(opts, 'activePeerId')) {
    if (opts.activePeerId != null && opts.activePeerId !== '') {
      payload.activePeerId = String(opts.activePeerId).slice(0, 12)
    }
    // null/'' → omit (clear)
  } else {
    // preserve existing disk active id when not provided
    const existing = readActivePeerIdFromFile()
    if (existing) payload.activePeerId = existing
  }
  return payload
}

/**
 * @returns {string|null}
 */
function readActivePeerIdFromFile() {
  const file = getPeersCachePath()
  try {
    if (!fs.existsSync(file)) return null
    const raw = JSON.parse(fs.readFileSync(file, 'utf8'))
    const id = raw?.activePeerId
    return id ? String(id).slice(0, 12) : null
  } catch {
    return null
  }
}

/**
 * Last known active peer id (file first, then localStorage).
 * @returns {string|null}
 */
export function getLastActivePeerId() {
  const fromFile = readActivePeerIdFromFile()
  if (fromFile) return fromFile
  try {
    if (typeof localStorage !== 'undefined') {
      const id = localStorage.getItem(ACTIVE_PEER_KEY)
      return id ? String(id).slice(0, 12) : null
    }
  } catch {
    // ignore
  }
  return null
}

/**
 * Persist last active peer id (localStorage + peers.json meta when possible).
 * @param {string|null} id
 */
export function setLastActivePeerId(id) {
  const next = id ? String(id).slice(0, 12) : null
  try {
    if (typeof localStorage !== 'undefined') {
      if (next) localStorage.setItem(ACTIVE_PEER_KEY, next)
      else localStorage.removeItem(ACTIVE_PEER_KEY)
    }
  } catch {
    // ignore
  }
  // Merge into peers.json without rewriting peer entries
  try {
    const peers = loadPeers()
    if (Object.keys(peers).length === 0 && !next) return
    writePeersToFile(peers, { activePeerId: next })
  } catch {
    // ignore
  }
}

function ensureCacheDir() {
  const dir = getPeersCacheDir()
  fs.mkdirSync(dir, { recursive: true })
  return dir
}

/**
 * Read peers from ~/.config/peardock/cache/peers.json
 * @returns {Record<string, { publicKeyHex: string, alias: string|null, inviteToken: string|null }>}
 */
export function readPeersFromFile() {
  const file = getPeersCachePath()
  try {
    if (!fs.existsSync(file)) return {}
    const raw = fs.readFileSync(file, 'utf8')
    return parsePeersPayload(raw)
  } catch (err) {
    console.warn('[WARN] peerCache: failed to read file', err?.message || err)
    return {}
  }
}

/**
 * Write peers to ~/.config/peardock/cache/peers.json (atomic replace).
 * @param {Record<string, object>} peersMap
 * @param {{ activePeerId?: string|null }} [opts]
 * @returns {boolean}
 */
export function writePeersToFile(peersMap, opts = {}) {
  const file = getPeersCachePath()
  const payload = buildPeersPayload(peersMap, opts)
  const json = JSON.stringify(payload, null, 2)
  try {
    ensureCacheDir()
    const tmp = `${file}.${process.pid}.${Date.now()}.tmp`
    fs.writeFileSync(tmp, json, { encoding: 'utf8', mode: 0o600 })
    fs.renameSync(tmp, file)
    try {
      fs.chmodSync(file, 0o600)
    } catch {
      // ignore chmod failures on some platforms
    }
    return true
  } catch (err) {
    console.error('[ERROR] peerCache: failed to write file', err?.message || err)
    // Best-effort cleanup of temp files is ignored
    return false
  }
}

/**
 * Remove the peers cache file (and leave empty dir).
 * @returns {boolean}
 */
export function clearPeersFile() {
  try {
    const file = getPeersCachePath()
    if (fs.existsSync(file)) fs.unlinkSync(file)
    return true
  } catch (err) {
    console.warn('[WARN] peerCache: failed to clear file', err?.message || err)
    return false
  }
}

/**
 * Read peers: file first, then migrate from localStorage if file empty.
 * @returns {Record<string, { publicKeyHex: string, alias: string|null, inviteToken: string|null }>}
 */
export function loadPeers() {
  let peers = readPeersFromFile()
  if (Object.keys(peers).length > 0) return peers

  // Migrate legacy browser storage once
  try {
    if (typeof localStorage !== 'undefined') {
      const raw = localStorage.getItem(LOCALSTORAGE_KEY)
      if (raw) {
        peers = parsePeersPayload(raw)
        if (Object.keys(peers).length > 0) {
          writePeersToFile(peers)
          console.log(
            '[INFO] peerCache: migrated',
            Object.keys(peers).length,
            'peer(s) from localStorage →',
            getPeersCachePath()
          )
        }
      }
    }
  } catch {
    // ignore
  }
  return peers
}

/**
 * Persist peers to file (+ mirror localStorage as secondary cache).
 * @param {Record<string, object>} peersMap
 * @param {{ activePeerId?: string|null }} [opts]
 * @returns {{ ok: boolean, path: string, count: number }}
 */
export function savePeers(peersMap, opts = {}) {
  const payload = buildPeersPayload(peersMap, opts)
  // Pass through only when caller set activePeerId; otherwise preserve on disk
  const writeOpts = Object.prototype.hasOwnProperty.call(opts, 'activePeerId')
    ? { activePeerId: opts.activePeerId }
    : {}
  const ok = writePeersToFile(payload.peers, writeOpts)

  // Mirror for quick in-session reads / legacy code paths
  try {
    if (typeof localStorage !== 'undefined') {
      // Keep flat map for older readers
      localStorage.setItem(LOCALSTORAGE_KEY, JSON.stringify(payload.peers))
      localStorage.setItem(LOCALSTORAGE_FLAG, '1')
      if (payload.activePeerId) {
        localStorage.setItem(ACTIVE_PEER_KEY, payload.activePeerId)
      }
    }
  } catch {
    // ignore
  }

  return {
    ok,
    path: getPeersCachePath(),
    count: Object.keys(payload.peers).length,
  }
}

/**
 * Clear file + localStorage peer roster.
 */
export function clearPeers() {
  clearPeersFile()
  try {
    if (typeof localStorage !== 'undefined') {
      localStorage.removeItem(LOCALSTORAGE_KEY)
      localStorage.removeItem(LOCALSTORAGE_FLAG)
    }
  } catch {
    // ignore
  }
}

/**
 * List form used by ConnectionManager.loadSaved()
 * @returns {Array<{ id: string, publicKeyHex: string, alias: string|null, inviteToken: string|null, capability: string|null, adminSeed: string|null }>}
 */
export function listSavedPeers() {
  const map = loadPeers()
  return Object.entries(map).map(([id, value]) => ({
    id,
    publicKeyHex: value.publicKeyHex,
    alias: value.alias || null,
    inviteToken: value.inviteToken || null,
    capability: value.capability || null,
    adminSeed: value.adminSeed || null,
  }))
}

export default {
  getPeersCachePath,
  getPeersCacheDir,
  loadPeers,
  savePeers,
  clearPeers,
  listSavedPeers,
  parsePeersPayload,
  buildPeersPayload,
  normalizePeerEntry,
  normalizeAdminSeed,
  readPeersFromFile,
  writePeersToFile,
  getLastActivePeerId,
  setLastActivePeerId,
}