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function unusable(name: string | number, prop = 'algorithm.name') {  return new TypeError(`CryptoKey does not support this operation, its ${prop} must be ${name}`)}
function isAlgorithm<T extends KeyAlgorithm>(  algorithm: KeyAlgorithm,  name: string,): algorithm is T {  return algorithm.name === name}
function getHashLength(hash: KeyAlgorithm) {  return parseInt(hash.name.slice(4), 10)}
function getNamedCurve(alg: string) {  switch (alg) {    case 'ES256':      return 'P-256'    case 'ES384':      return 'P-384'    case 'ES512':      return 'P-521'    default:      throw new Error('unreachable')  }}
function checkUsage(key: CryptoKey, usages: KeyUsage[]) {  if (usages.length && !usages.some((expected) => key.usages.includes(expected))) {    let msg = 'CryptoKey does not support this operation, its usages must include '    if (usages.length > 2) {      const last = usages.pop()      msg += `one of ${usages.join(', ')}, or ${last}.`    } else if (usages.length === 2) {      msg += `one of ${usages[0]} or ${usages[1]}.`    } else {      msg += `${usages[0]}.`    }
    throw new TypeError(msg)  }}
export function checkSigCryptoKey(key: CryptoKey, alg: string, ...usages: KeyUsage[]) {  switch (alg) {    case 'HS256':    case 'HS384':    case 'HS512': {      if (!isAlgorithm<HmacKeyAlgorithm>(key.algorithm, 'HMAC')) throw unusable('HMAC')      const expected = parseInt(alg.slice(2), 10)      const actual = getHashLength(key.algorithm.hash)      if (actual !== expected) throw unusable(`SHA-${expected}`, 'algorithm.hash')      break    }    case 'RS256':    case 'RS384':    case 'RS512': {      if (!isAlgorithm<RsaHashedKeyAlgorithm>(key.algorithm, 'RSASSA-PKCS1-v1_5'))        throw unusable('RSASSA-PKCS1-v1_5')      const expected = parseInt(alg.slice(2), 10)      const actual = getHashLength(key.algorithm.hash)      if (actual !== expected) throw unusable(`SHA-${expected}`, 'algorithm.hash')      break    }    case 'PS256':    case 'PS384':    case 'PS512': {      if (!isAlgorithm<RsaHashedKeyAlgorithm>(key.algorithm, 'RSA-PSS')) throw unusable('RSA-PSS')      const expected = parseInt(alg.slice(2), 10)      const actual = getHashLength(key.algorithm.hash)      if (actual !== expected) throw unusable(`SHA-${expected}`, 'algorithm.hash')      break    }    case 'EdDSA': {      if (key.algorithm.name !== 'Ed25519' && key.algorithm.name !== 'Ed448') {        throw unusable('Ed25519 or Ed448')      }      break    }    case 'ES256':    case 'ES384':    case 'ES512': {      if (!isAlgorithm<EcKeyAlgorithm>(key.algorithm, 'ECDSA')) throw unusable('ECDSA')      const expected = getNamedCurve(alg)      const actual = key.algorithm.namedCurve      if (actual !== expected) throw unusable(expected, 'algorithm.namedCurve')      break    }    default:      throw new TypeError('CryptoKey does not support this operation')  }
  checkUsage(key, usages)}
export function checkEncCryptoKey(key: CryptoKey, alg: string, ...usages: KeyUsage[]) {  switch (alg) {    case 'A128GCM':    case 'A192GCM':    case 'A256GCM': {      if (!isAlgorithm<AesKeyAlgorithm>(key.algorithm, 'AES-GCM')) throw unusable('AES-GCM')      const expected = parseInt(alg.slice(1, 4), 10)      const actual = key.algorithm.length      if (actual !== expected) throw unusable(expected, 'algorithm.length')      break    }    case 'A128KW':    case 'A192KW':    case 'A256KW': {      if (!isAlgorithm<AesKeyAlgorithm>(key.algorithm, 'AES-KW')) throw unusable('AES-KW')      const expected = parseInt(alg.slice(1, 4), 10)      const actual = key.algorithm.length      if (actual !== expected) throw unusable(expected, 'algorithm.length')      break    }    case 'ECDH': {      switch (key.algorithm.name) {        case 'ECDH':        case 'X25519':        case 'X448':          break        default:          throw unusable('ECDH, X25519, or X448')      }      break    }    case 'PBES2-HS256+A128KW':    case 'PBES2-HS384+A192KW':    case 'PBES2-HS512+A256KW':      if (!isAlgorithm(key.algorithm, 'PBKDF2')) throw unusable('PBKDF2')      break    case 'RSA-OAEP':    case 'RSA-OAEP-256':    case 'RSA-OAEP-384':    case 'RSA-OAEP-512': {      if (!isAlgorithm<RsaHashedKeyAlgorithm>(key.algorithm, 'RSA-OAEP')) throw unusable('RSA-OAEP')      const expected = parseInt(alg.slice(9), 10) || 1      const actual = getHashLength(key.algorithm.hash)      if (actual !== expected) throw unusable(`SHA-${expected}`, 'algorithm.hash')      break    }    default:      throw new TypeError('CryptoKey does not support this operation')  }
  checkUsage(key, usages)}