import { generateMnemonic, mnemonicToSeedSync, validateMnemonic } from '@scure/bip39';
import { wordlist } from '@scure/bip39/wordlists/english';
import { HDKey } from '@scure/bip32';

/**
 * NIP-06: Basic key derivation from mnemonic seed phrase
 * https://github.com/nostr-protocol/nips/blob/master/06.md
 * 
 * Uses BIP39 for mnemonic generation and BIP32 for key derivation
 * Derivation path: m/44'/1237'/account'/0/0
 */

export const NIP06_PATH = "m/44'/1237'/0'/0/0";

/**
 * Generate a new mnemonic seed phrase
 * @param strength - 128 for 12 words, 256 for 24 words (default: 128)
 * @returns 12 or 24 word mnemonic phrase
 */
export function generateMnemonicPhrase(strength: 128 | 256 = 128): string {
  return generateMnemonic(wordlist, strength);
}

/**
 * Validate a mnemonic seed phrase
 * @param mnemonic - Space-separated words
 * @returns true if valid, false otherwise
 */
export function validateMnemonicPhrase(mnemonic: string): boolean {
  try {
    return validateMnemonic(mnemonic, wordlist);
  } catch {
    return false;
  }
}

/**
 * Derive a private key from a mnemonic phrase using NIP-06
 * @param mnemonic - Space-separated mnemonic phrase
 * @param account - Account index (default: 0)
 * @returns 32-byte private key as Uint8Array
 */
export function privateKeyFromMnemonic(mnemonic: string, account: number = 0): Uint8Array {
  if (!validateMnemonicPhrase(mnemonic)) {
    throw new Error('Invalid mnemonic phrase');
  }

  // Generate seed from mnemonic
  const seed = mnemonicToSeedSync(mnemonic);

  // Derive key using NIP-06 path
  const path = account === 0 ? NIP06_PATH : `m/44'/1237'/${account}'/0/0`;
  const hdKey = HDKey.fromMasterSeed(seed);
  const derivedKey = hdKey.derive(path);

  if (!derivedKey.privateKey) {
    throw new Error('Failed to derive private key');
  }

  return derivedKey.privateKey;
}

/**
 * Derive multiple accounts from a single mnemonic
 * @param mnemonic - Space-separated mnemonic phrase
 * @param count - Number of accounts to derive (default: 1)
 * @returns Array of 32-byte private keys
 */
export function deriveMultipleAccounts(mnemonic: string, count: number = 1): Uint8Array[] {
  const accounts: Uint8Array[] = [];
  
  for (let i = 0; i < count; i++) {
    accounts.push(privateKeyFromMnemonic(mnemonic, i));
  }
  
  return accounts;
}

/**
 * Normalize mnemonic phrase (trim, lowercase, normalize whitespace)
 * @param mnemonic - Raw mnemonic input
 * @returns Normalized mnemonic
 */
export function normalizeMnemonic(mnemonic: string): string {
  return mnemonic
    .trim()
    .toLowerCase()
    .replace(/\s+/g, ' '); // Normalize whitespace to single spaces
}

/**
 * Split mnemonic into word array
 * @param mnemonic - Space-separated mnemonic phrase
 * @returns Array of words
 */
export function mnemonicToWords(mnemonic: string): string[] {
  return normalizeMnemonic(mnemonic).split(' ');
}

/**
 * Join word array into mnemonic string
 * @param words - Array of mnemonic words
 * @returns Space-separated mnemonic phrase
 */
export function wordsToMnemonic(words: string[]): string {
  return words.join(' ');
}