/**
 * Autopass payload for HDMS drive sharing (invite → pair → mount).
 * Kept separate from hdms-manager.js for small, Node-testable surface.
 */

import b4a from 'b4a'
import idEnc from 'hypercore-id-encoding'

/** Autopass record key: read-only replica offer (public key only). */
export const HDMS_AUTOPASS_SHARE_KEY = 'bare-os-hdms/pending-share'

/** Autopass record key: read/write replica (public key + writer secret). Legacy peers ignore this key. */
export const HDMS_AUTOPASS_SHARE_RW_KEY = 'bare-os-hdms/pending-share-rw'

/** Expected hex length for a Hypercore Ed25519 secret key (64 bytes). */
export const WRITER_SECRET_HEX_LEN = 128

/**
 * @param {string} hex
 * @returns {string} lowercase hex
 */
export function normalizeWriterSecretHex(hex) {
  if (typeof hex !== 'string') throw new Error('Invalid writer secret')
  const h = hex.trim().toLowerCase()
  if (!/^[0-9a-f]{128}$/.test(h)) {
    throw new Error('writerSecretHex must be 128 hex chars (64 bytes)')
  }
  return h
}

/**
 * @param {string} hex
 * @returns {Uint8Array}
 */
export function writerSecretBytesFromHex(hex) {
  return b4a.from(normalizeWriterSecretHex(hex), 'hex')
}

/** @param {{ remove: (k: string) => Promise<unknown>, member?: { flushed: () => Promise<void> }, base?: { update?: () => Promise<void> } }} ap */
export async function removeBothHdmsShareKeys(ap) {
  for (const k of [HDMS_AUTOPASS_SHARE_KEY, HDMS_AUTOPASS_SHARE_RW_KEY]) {
    try {
      await ap.remove(k)
      if (ap.member) await ap.member.flushed()
      try {
        await ap.base?.update?.()
      } catch (_) {}
    } catch {
      /* no prior offer */
    }
  }
}

/** @param {{ value?: unknown } | null | undefined} offer */
export function decodeShareOffer(offer) {
  if (!offer || offer.value == null) return null
  const v = offer.value
  const raw =
    typeof v === 'string' ? v : b4a.toString(/** @type {Uint8Array} */ (v))
  try {
    const j = JSON.parse(raw)
    if (
      j &&
      typeof j.key === 'string' &&
      typeof j.label === 'string' &&
      j.key.length > 0
    ) {
      return { label: j.label, key: j.key }
    }
  } catch {
    /* ignore */
  }
  return null
}

/**
 * RW payload uses `key` = Hyperdrive public key (manifest id, z32) for discovery/open,
 * and `signerKey` = metadata writer Ed25519 public key (z32) matching `writerSecretHex`.
 * @param {{ value?: unknown } | null | undefined} offer
 * @returns {{ label: string, key: string, signerKey: string, writerSecretHex: string } | null}
 */
export function decodeRwShareOffer(offer) {
  if (!offer || offer.value == null) return null
  const v = offer.value
  const raw =
    typeof v === 'string' ? v : b4a.toString(/** @type {Uint8Array} */ (v))
  try {
    const j = JSON.parse(raw)
    if (
      j &&
      typeof j.key === 'string' &&
      typeof j.label === 'string' &&
      typeof j.signerKey === 'string' &&
      typeof j.writerSecretHex === 'string' &&
      j.key.length > 0 &&
      j.signerKey.length > 0
    ) {
      idEnc.decode(j.signerKey)
      idEnc.decode(j.key)
      return {
        label: j.label,
        key: j.key,
        signerKey: j.signerKey,
        writerSecretHex: normalizeWriterSecretHex(j.writerSecretHex)
      }
    }
  } catch {
    /* ignore */
  }
  return null
}