/**
 * HMAC capability grants + admin seed proof for handshake auth.
 *
 * Pure helpers shared by server and client. Never logs secrets.
 * Uses `b4a` + `crypto` (mapped to bare-crypto under Bare/Pear).
 *
 * Capability token format:
 *   base64url(JSON payload) + "." + base64url(HMAC-SHA256(macKey, payloadBytes))
 *
 * Admin proof (single-round):
 *   mac = HMAC-SHA256(macKey, "peardata-admin-v1" || nonce || peerId || serverPubKey)
 *
 * Invite envelope:
 *   pd1.<base64url JSON { publicKeyHex, capability, role, ... }>
 */
import crypto from 'crypto'
import b4a from 'b4a'
import { Roles } from './protocol.js'

const SALT = b4a.from('peardata-hmac-v1')
const INFO_CAPABILITY = b4a.from('capability')
const ADMIN_PREFIX = b4a.from('peardata-admin-v1')
const VALID_ROLES = new Set([Roles.viewer, Roles.operator, Roles.admin])

export const INVITE_PREFIX = 'pd1.'

function asU8(value) {
  if (value == null) return b4a.alloc(0)
  if (value instanceof Uint8Array) return b4a.from(value)
  return b4a.from(value)
}

/**
 * @param {string|Uint8Array} seedHexOrBuf
 * @returns {Uint8Array}
 */
export function deriveMacKey(seedHexOrBuf) {
  const ikm = toSeedBuffer(seedHexOrBuf)
  if (typeof crypto.hkdfSync === 'function') {
    return asU8(crypto.hkdfSync('sha256', ikm, SALT, INFO_CAPABILITY, 32))
  }
  const prk = crypto.createHmac('sha256', SALT).update(ikm).digest()
  const info = b4a.concat([INFO_CAPABILITY, b4a.from([0x01])])
  return asU8(crypto.createHmac('sha256', prk).update(info).digest())
}

function toSeedBuffer(seedHexOrBuf) {
  if (seedHexOrBuf instanceof Uint8Array) {
    const buf = b4a.from(seedHexOrBuf)
    if (buf.length !== 32) throw new Error('Seed must be 32 bytes')
    return buf
  }
  const hex = String(seedHexOrBuf || '')
    .trim()
    .toLowerCase()
  if (!/^[0-9a-f]{64}$/.test(hex)) {
    throw new Error('Seed must be 64 hex characters (32 bytes)')
  }
  return b4a.from(hex, 'hex')
}

export function b64url(buf) {
  return b4a
    .toString(asU8(buf), 'base64')
    .replace(/\+/g, '-')
    .replace(/\//g, '_')
    .replace(/=+$/, '')
}

export function b64urlDecode(s) {
  const str = String(s || '').replace(/-/g, '+').replace(/_/g, '/')
  const pad = str.length % 4 === 0 ? '' : '='.repeat(4 - (str.length % 4))
  return b4a.from(str + pad, 'base64')
}

export function canonicalizePayload(payload) {
  const ordered = {
    v: payload.v,
    role: payload.role,
    peerId: payload.peerId ?? null,
    exp: payload.exp,
    jti: payload.jti,
    iat: payload.iat,
  }
  return b4a.from(JSON.stringify(ordered))
}

function resolveMacKey(macKeyOrSeed) {
  if (macKeyOrSeed instanceof Uint8Array) {
    const buf = b4a.from(macKeyOrSeed)
    if (buf.length === 32) return buf
    return deriveMacKey(macKeyOrSeed)
  }
  if (typeof macKeyOrSeed === 'string' && /^[0-9a-fA-F]{64}$/.test(macKeyOrSeed.trim())) {
    return deriveMacKey(macKeyOrSeed.trim())
  }
  throw new Error('Invalid mac key or seed')
}

export function safeEqual(a, b) {
  const aa = asU8(a)
  const bb = asU8(b)
  if (aa.length !== bb.length) return false
  return crypto.timingSafeEqual(aa, bb)
}

/**
 * @param {Uint8Array|string} macKeyOrSeed
 * @param {{ role?: string, ttlMs?: number|null, peerId?: string|null, jti?: string, forever?: boolean }} opts
 */
export function signCapability(macKeyOrSeed, opts = {}) {
  const macKey = resolveMacKey(macKeyOrSeed)
  const role = String(opts.role || Roles.operator).toLowerCase()
  if (!VALID_ROLES.has(role)) throw new Error(`Invalid capability role: ${role}`)

  const now = Date.now()
  const rawTtl = opts.ttlMs
  let exp = null
  if (opts.forever === true || rawTtl === 0 || rawTtl === null || rawTtl === undefined) {
    exp = null
  } else {
    const ttlMs = Math.min(
      Math.max(Number(rawTtl) || 72 * 3600 * 1000, 60_000),
      100 * 365 * 24 * 3600 * 1000
    )
    exp = now + ttlMs
  }
  const payload = {
    v: 1,
    role,
    peerId: opts.peerId ? String(opts.peerId).toLowerCase() : null,
    exp,
    jti: opts.jti || b4a.toString(crypto.randomBytes(16), 'hex'),
    iat: now,
  }
  const body = canonicalizePayload(payload)
  const mac = crypto.createHmac('sha256', macKey).update(body).digest()
  return { token: `${b64url(body)}.${b64url(mac)}`, payload }
}

/**
 * @param {Uint8Array|string} macKeyOrSeed
 * @param {string} token
 * @param {{ peerId?: string, now?: number, allowSpentCheck?: (jti: string) => boolean }} [opts]
 */
export function verifyCapability(macKeyOrSeed, token, opts = {}) {
  if (!token || typeof token !== 'string') {
    return { ok: false, error: 'Missing capability token', code: 'CAPABILITY_INVALID' }
  }
  const parts = token.split('.')
  if (parts.length !== 2) {
    return { ok: false, error: 'Malformed capability token', code: 'CAPABILITY_INVALID' }
  }
  let body
  let mac
  try {
    body = b64urlDecode(parts[0])
    mac = b64urlDecode(parts[1])
  } catch {
    return { ok: false, error: 'Malformed capability encoding', code: 'CAPABILITY_INVALID' }
  }
  if (mac.length !== 32) {
    return { ok: false, error: 'Invalid capability MAC length', code: 'CAPABILITY_INVALID' }
  }

  const macKey = resolveMacKey(macKeyOrSeed)
  const expected = crypto.createHmac('sha256', macKey).update(body).digest()
  if (!safeEqual(mac, expected)) {
    return { ok: false, error: 'Capability MAC verification failed', code: 'CAPABILITY_INVALID' }
  }

  let payload
  try {
    payload = JSON.parse(b4a.toString(body, 'utf8'))
  } catch {
    return { ok: false, error: 'Capability payload not JSON', code: 'CAPABILITY_INVALID' }
  }

  if (payload.v !== 1) {
    return { ok: false, error: 'Unsupported capability version', code: 'CAPABILITY_INVALID' }
  }
  if (!VALID_ROLES.has(payload.role)) {
    return { ok: false, error: 'Invalid capability role', code: 'CAPABILITY_INVALID' }
  }

  const now = opts.now ?? Date.now()
  if (payload.exp != null) {
    if (typeof payload.exp !== 'number' || payload.exp < now) {
      return { ok: false, error: 'Capability expired', code: 'CAPABILITY_EXPIRED' }
    }
  }

  if (payload.peerId) {
    const want = String(payload.peerId).toLowerCase()
    const have = String(opts.peerId || '').toLowerCase()
    if (!have || want !== have) {
      return {
        ok: false,
        error: 'Capability bound to a different peer identity',
        code: 'CAPABILITY_PEER_MISMATCH',
      }
    }
  }

  if (typeof opts.allowSpentCheck === 'function' && !opts.allowSpentCheck(payload.jti)) {
    return { ok: false, error: 'Capability already used or revoked', code: 'CAPABILITY_SPENT' }
  }

  return {
    ok: true,
    payload: {
      v: 1,
      role: payload.role,
      peerId: payload.peerId || null,
      exp: payload.exp,
      jti: payload.jti,
      iat: payload.iat,
    },
  }
}

function hmacAdmin(macKey, nonce, peerId, serverPk) {
  return crypto
    .createHmac('sha256', macKey)
    .update(ADMIN_PREFIX)
    .update(b4a.from(nonce))
    .update(b4a.from(peerId))
    .update(b4a.from(serverPk))
    .digest()
}

/**
 * @param {Uint8Array|string} macKeyOrSeed
 * @param {{ nonce?: string, peerId: string, serverPublicKeyHex: string }} opts
 */
export function createAdminProof(macKeyOrSeed, opts) {
  const nonce = String(opts.nonce || b4a.toString(crypto.randomBytes(16), 'hex'))
  if (!/^[0-9a-fA-F]{16,64}$/.test(nonce)) {
    throw new Error('Admin proof nonce must be 16-64 hex characters')
  }
  const peerId = String(opts.peerId || '').toLowerCase()
  const serverPk = String(opts.serverPublicKeyHex || '').toLowerCase()
  if (!/^[0-9a-f]{64}$/.test(peerId)) throw new Error('peerId required for admin proof')
  if (!/^[0-9a-f]{64}$/.test(serverPk)) throw new Error('serverPublicKeyHex required for admin proof')

  const macKey = resolveMacKey(macKeyOrSeed)
  const mac = hmacAdmin(macKey, nonce, peerId, serverPk)
  return { nonce: nonce.toLowerCase(), mac: b4a.toString(asU8(mac), 'hex') }
}

/**
 * @param {Uint8Array|string} macKeyOrSeed
 * @param {{ nonce?: string, mac?: string }|null} proof
 * @param {{ peerId: string, serverPublicKeyHex: string }} ctx
 */
export function verifyAdminProof(macKeyOrSeed, proof, ctx) {
  if (!proof || !proof.nonce || !proof.mac) {
    return { ok: false, error: 'Missing admin proof', code: 'ADMIN_PROOF_FAILED' }
  }
  const nonce = String(proof.nonce).toLowerCase()
  const macHex = String(proof.mac).toLowerCase()
  if (!/^[0-9a-f]{16,64}$/.test(nonce) || !/^[0-9a-f]{64}$/.test(macHex)) {
    return { ok: false, error: 'Malformed admin proof', code: 'ADMIN_PROOF_FAILED' }
  }
  const peerId = String(ctx.peerId || '').toLowerCase()
  const serverPk = String(ctx.serverPublicKeyHex || '').toLowerCase()
  if (!/^[0-9a-f]{64}$/.test(peerId) || !/^[0-9a-f]{64}$/.test(serverPk)) {
    return { ok: false, error: 'Invalid proof context', code: 'ADMIN_PROOF_FAILED' }
  }

  const macKey = resolveMacKey(macKeyOrSeed)
  const expected = hmacAdmin(macKey, nonce, peerId, serverPk)
  const got = b4a.from(macHex, 'hex')
  if (!safeEqual(got, expected)) {
    return { ok: false, error: 'Admin proof verification failed', code: 'ADMIN_PROOF_FAILED' }
  }
  return { ok: true }
}

/**
 * @param {object} pkg
 * @returns {string}
 */
export function encodeInvite(pkg) {
  const body = {
    v: 1,
    publicKeyHex: String(pkg.publicKeyHex || '').toLowerCase(),
    capability: String(pkg.capability || ''),
    role: pkg.role || null,
    jti: pkg.jti || null,
    alias: pkg.alias || null,
    expiresAt: pkg.expiresAt ?? null,
  }
  if (!/^[0-9a-f]{64}$/.test(body.publicKeyHex)) {
    throw new Error('encodeInvite: invalid publicKeyHex')
  }
  if (!body.capability || !body.capability.includes('.')) {
    throw new Error('encodeInvite: invalid capability')
  }
  return `${INVITE_PREFIX}${b64url(b4a.from(JSON.stringify(body)))}`
}

/**
 * @param {string} invite
 * @returns {{ ok: true, package: object } | { ok: false, error: string, code: string }}
 */
export function decodeInvite(invite) {
  const s = String(invite || '').trim()
  if (!s.startsWith(INVITE_PREFIX)) {
    return { ok: false, error: 'Not a pd1 invite', code: 'INVITE_INVALID' }
  }
  try {
    const json = b4a.toString(b64urlDecode(s.slice(INVITE_PREFIX.length)), 'utf8')
    const pkg = JSON.parse(json)
    if (!pkg?.publicKeyHex || !pkg?.capability) {
      return { ok: false, error: 'Invite missing fields', code: 'INVITE_INVALID' }
    }
    return { ok: true, package: pkg }
  } catch {
    return { ok: false, error: 'Malformed invite', code: 'INVITE_INVALID' }
  }
}

/**
 * Classify free-form connection input (public key, invite, capability).
 * @param {string} input
 */
export function classifyConnectionInput(input) {
  const s = String(input || '').trim()
  if (!s) return { kind: 'empty' }
  if (s.startsWith(INVITE_PREFIX)) {
    const dec = decodeInvite(s)
    if (!dec.ok) return { kind: 'invalid', error: dec.error, code: dec.code }
    return {
      kind: 'invite',
      publicKeyHex: dec.package.publicKeyHex,
      capability: dec.package.capability,
      role: dec.package.role,
      alias: dec.package.alias,
    }
  }
  if (/^[0-9a-fA-F]{64}$/.test(s)) {
    return { kind: 'publicKey', publicKeyHex: s.toLowerCase() }
  }
  if (s.includes('.') && s.split('.').length === 2) {
    return { kind: 'capability', capability: s }
  }
  return { kind: 'unknown', error: 'Expected 64-hex public key or pd1. invite' }
}

export function isInsecureOpenAdmin() {
  try {
    const env = typeof process !== 'undefined' ? process.env : null
    const v = String(env?.PEARDATA_INSECURE_OPEN_ADMIN || '').toLowerCase()
    return v === '1' || v === 'true' || v === 'yes'
  } catch {
    return false
  }
}