@polkadot/util-crypto/mnemonic/toLegacySeed.js

// Copyright 2017-2022 @polkadot/util-crypto authors & contributors
// SPDX-License-Identifier: Apache-2.0
import { hasBigInt } from '@polkadot/util';
import { bip39ToSeed, isReady } from '@polkadot/wasm-crypto';
import { mnemonicToSeedSync } from "./bip39.js";
import { mnemonicValidate } from "./validate.js";
/**
 * @name mnemonicToLegacySeed
 * @summary Creates a valid Ethereum/Bitcoin-compatible seed from a mnemonic input
 * @example
 * <BR>
 *
 * ```javascript
 * import { mnemonicGenerate, mnemonicToLegacySeed, mnemonicValidate } from '@polkadot/util-crypto';
 *
 * const mnemonic = mnemonicGenerate(); // => string
 * const isValidMnemonic = mnemonicValidate(mnemonic); // => boolean
 *
 * if (isValidMnemonic) {
 *   console.log(`Seed generated from mnemonic: ${mnemonicToLegacySeed(mnemonic)}`); => u8a
 * }
 * ```
 */

export function mnemonicToLegacySeed(mnemonic, password = '', onlyJs, byteLength = 32) {
  if (!mnemonicValidate(mnemonic)) {
    throw new Error('Invalid bip39 mnemonic specified');
  } else if (![32, 64].includes(byteLength)) {
    throw new Error(`Invalid seed length ${byteLength}, expected 32 or 64`);
  }

  return byteLength === 32 ? !hasBigInt || !onlyJs && isReady() ? bip39ToSeed(mnemonic, password) : mnemonicToSeedSync(mnemonic, password).subarray(0, 32) : mnemonicToSeedSync(mnemonic, password);
}