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import { encoder, concat, uint32be, lengthAndInput, concatKdf } from '../lib/buffer_utils.ts'import crypto, { isCryptoKey } from './webcrypto.ts'import { checkEncCryptoKey } from '../lib/crypto_key.ts'import invalidKeyInput from '../lib/invalid_key_input.ts'import { types } from './is_key_like.ts'
export async function deriveKey(  publicKey: unknown,  privateKey: unknown,  algorithm: string,  keyLength: number,  apu: Uint8Array = new Uint8Array(0),  apv: Uint8Array = new Uint8Array(0),) {  if (!isCryptoKey(publicKey)) {    throw new TypeError(invalidKeyInput(publicKey, ...types))  }  checkEncCryptoKey(publicKey, 'ECDH')  if (!isCryptoKey(privateKey)) {    throw new TypeError(invalidKeyInput(privateKey, ...types))  }  checkEncCryptoKey(privateKey, 'ECDH', 'deriveBits')
  const value = concat(    lengthAndInput(encoder.encode(algorithm)),    lengthAndInput(apu),    lengthAndInput(apv),    uint32be(keyLength),  )
  let length: number  if (publicKey.algorithm.name === 'X25519') {    length = 256  } else if (publicKey.algorithm.name === 'X448') {    length = 448  } else {    length =      Math.ceil(parseInt((<EcKeyAlgorithm>publicKey.algorithm).namedCurve.substr(-3), 10) / 8) << 3  }
  const sharedSecret = new Uint8Array(    await crypto.subtle.deriveBits(      {        name: publicKey.algorithm.name,        public: publicKey,      },      privateKey,      length,    ),  )
  return concatKdf(sharedSecret, keyLength, value)}
export async function generateEpk(key: unknown) {  if (!isCryptoKey(key)) {    throw new TypeError(invalidKeyInput(key, ...types))  }
  return crypto.subtle.generateKey(<EcKeyAlgorithm>key.algorithm, true, ['deriveBits'])}
export function ecdhAllowed(key: unknown) {  if (!isCryptoKey(key)) {    throw new TypeError(invalidKeyInput(key, ...types))  }  return (    ['P-256', 'P-384', 'P-521'].includes((<EcKeyAlgorithm>key.algorithm).namedCurve) ||    key.algorithm.name === 'X25519' ||    key.algorithm.name === 'X448'  )}