// Per-wallet extra derivation paths — additional account-level BIP32
// paths that this wallet's balance / history scans should look at
// beyond the 6 built-in defaults (BIP44/49/84/86 at DGB coin type, plus
// the 2018-19 breadwallet-mobile m/0' and the Bitcoin-coin-type-under-
// BIP44 m/44'/0'/0' reused-coin-type variant).
//
// Populated from PathSearchPanel — when the recovery sweep finds
// activity on a layout the default scan doesn't cover, the user
// promotes that path here in one click. Stored per wallet by the same
// walletIdHash the SWR scan cache uses, so a phrase moved to a new
// device keeps its identity but a different wallet on the same device
// has its own list.
//
// Cleartext localStorage: the entries are public-derivation metadata
// (an xpath and a script kind), not secrets. Someone reading local
// storage sees which extra paths this wallet asked us to scan, which
// leaks the same information as an on-chain address the user handed
// out. No key material.

import { walletIdHash } from './scan-cache.js';

export type ExtraPathScript = 'p2pkh' | 'p2sh-p2wpkh' | 'p2wpkh';

export interface ExtraPath {
  /** BIP32 path of the account node (e.g. "m/44'/20'/1'"). */
  path: string;
  /** Output script kind for addresses derived under this account. */
  script: ExtraPathScript;
  /** Optional display label; UI synthesizes one if absent. */
  label?: string;
  /** BIP32 master-key HMAC string. Absent = standard "Bitcoin seed". The
   *  2018-19 DigiByte mobile wallets used "DigiByte seed". */
  hmac?: string;
}

/** Identity of an extra path: path + script + hmac. */
export function extraKey(e: { path: string; script: string; hmac?: string }): string {
  return `${e.path}::${e.script}::${e.hmac ?? ''}`;
}

const KEY_PREFIX = 'dgb-wallet:extra-paths:';
const CHANGE_EVENT = 'dgb-wallet:extra-paths-changed';

/** Compute the storage key for a wallet's extras list. Async because
 *  walletIdHash is Web Crypto SHA-256 based. Passphrase, when present,
 *  gives a passphrased wallet its own extras list distinct from the
 *  bare-phrase twin. */
export async function extrasKey(phrase: string, kind: string, passphrase?: string): Promise<string> {
  const id = await walletIdHash(phrase, kind, passphrase);
  return `${KEY_PREFIX}${id}`;
}

export function readExtras(storageKey: string): ExtraPath[] {
  try {
    const raw = localStorage.getItem(storageKey);
    if (!raw) return [];
    const parsed = JSON.parse(raw) as unknown;
    if (!Array.isArray(parsed)) return [];
    // Filter defensively so a corrupt entry can't crash the caller.
    return parsed.filter((e): e is ExtraPath =>
      !!e && typeof (e as ExtraPath).path === 'string' &&
      ['p2pkh', 'p2sh-p2wpkh', 'p2wpkh'].includes((e as ExtraPath).script)
    );
  } catch { return []; }
}

export function writeExtras(storageKey: string, paths: ExtraPath[]): void {
  try {
    if (paths.length === 0) localStorage.removeItem(storageKey);
    else localStorage.setItem(storageKey, JSON.stringify(paths));
    window.dispatchEvent(new CustomEvent(CHANGE_EVENT, { detail: { storageKey } }));
  } catch { /* private mode / quota */ }
}

export function addExtra(storageKey: string, entry: ExtraPath): boolean {
  const existing = readExtras(storageKey);
  if (existing.some((e) => extraKey(e) === extraKey(entry))) return false;
  writeExtras(storageKey, [...existing, entry]);
  return true;
}

export function removeExtra(storageKey: string, path: string, script: ExtraPathScript, hmac?: string): void {
  const k = extraKey({ path, script, hmac });
  writeExtras(storageKey, readExtras(storageKey).filter((e) => extraKey(e) !== k));
}

/** Subscribe to any extras-list change (any wallet). Returns unsubscribe. */
export function subscribeExtras(cb: (storageKey: string | null) => void): () => void {
  const handler = (e: Event): void => {
    const key = (e as CustomEvent<{ storageKey?: string }>).detail?.storageKey ?? null;
    cb(key);
  };
  window.addEventListener(CHANGE_EVENT, handler as EventListener);
  return () => window.removeEventListener(CHANGE_EVENT, handler as EventListener);
}